/*
 * Copyright © 2014 Red Hat
 *
 * Permission to use, copy, modify, distribute, and sell this software and its
 * documentation for any purpose is hereby granted without fee, provided that
 * the above copyright notice appear in all copies and that both that copyright
 * notice and this permission notice appear in supporting documentation, and
 * that the name of the copyright holders not be used in advertising or
 * publicity pertaining to distribution of the software without specific,
 * written prior permission.  The copyright holders make no representations
 * about the suitability of this software for any purpose.  It is provided "as
 * is" without express or implied warranty.
 *
 * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
 * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
 * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
 * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
 * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
 * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
 * OF THIS SOFTWARE.
 */

#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/seq_file.h>
#include <linux/i2c.h>
#include <drm/drm_dp_mst_helper.h>
#include <drm/drmP.h>

#include <drm/drm_fixed.h>
#include <drm/drm_atomic.h>
#include <drm/drm_atomic_helper.h>

/**
 * DOC: dp mst helper
 *
 * These functions contain parts of the DisplayPort 1.2a MultiStream Transport
 * protocol. The helpers contain a topology manager and bandwidth manager.
 * The helpers encapsulate the sending and received of sideband msgs.
 */
static bool dump_dp_payload_table(struct drm_dp_mst_topology_mgr *mgr,
                                  char *buf);
static int test_calc_pbn_mode(void);

static void drm_dp_put_port(struct drm_dp_mst_port *port);

static int drm_dp_dpcd_write_payload(struct drm_dp_mst_topology_mgr *mgr,
                                     int id,
                                     struct drm_dp_payload *payload);

static int drm_dp_send_dpcd_write(struct drm_dp_mst_topology_mgr *mgr,
                                  struct drm_dp_mst_port *port,
                                  int offset, int size, u8 *bytes);

static void drm_dp_send_link_address(struct drm_dp_mst_topology_mgr *mgr,
                                     struct drm_dp_mst_branch *mstb);
static int drm_dp_send_enum_path_resources(struct drm_dp_mst_topology_mgr *mgr,
                                           struct drm_dp_mst_branch *mstb,
                                           struct drm_dp_mst_port *port);
static bool drm_dp_validate_guid(struct drm_dp_mst_topology_mgr *mgr,
                                 u8 *guid);

static int drm_dp_mst_register_i2c_bus(struct drm_dp_aux *aux);
static void drm_dp_mst_unregister_i2c_bus(struct drm_dp_aux *aux);
static void drm_dp_mst_kick_tx(struct drm_dp_mst_topology_mgr *mgr);
/* sideband msg handling */
static u8 drm_dp_msg_header_crc4(const uint8_t *data, size_t num_nibbles)
{
        u8 bitmask = 0x80;
        u8 bitshift = 7;
        u8 array_index = 0;
        int number_of_bits = num_nibbles * 4;
        u8 remainder = 0;

        while (number_of_bits != 0) {
                number_of_bits--;
                remainder <<= 1;
                remainder |= (data[array_index] & bitmask) >> bitshift;
                bitmask >>= 1;
                bitshift--;
                if (bitmask == 0) {
                        bitmask = 0x80;
                        bitshift = 7;
                        array_index++;
                }
                if ((remainder & 0x10) == 0x10)
                        remainder ^= 0x13;
        }

        number_of_bits = 4;
        while (number_of_bits != 0) {
                number_of_bits--;
                remainder <<= 1;
                if ((remainder & 0x10) != 0)
                        remainder ^= 0x13;
        }

        return remainder;
}

static u8 drm_dp_msg_data_crc4(const uint8_t *data, u8 number_of_bytes)
{
        u8 bitmask = 0x80;
        u8 bitshift = 7;
        u8 array_index = 0;
        int number_of_bits = number_of_bytes * 8;
        u16 remainder = 0;

        while (number_of_bits != 0) {
                number_of_bits--;
                remainder <<= 1;
                remainder |= (data[array_index] & bitmask) >> bitshift;
                bitmask >>= 1;
                bitshift--;
                if (bitmask == 0) {
                        bitmask = 0x80;
                        bitshift = 7;
                        array_index++;
                }
                if ((remainder & 0x100) == 0x100)
                        remainder ^= 0xd5;
        }

        number_of_bits = 8;
        while (number_of_bits != 0) {
                number_of_bits--;
                remainder <<= 1;
                if ((remainder & 0x100) != 0)
                        remainder ^= 0xd5;
        }

        return remainder & 0xff;
}
static inline u8 drm_dp_calc_sb_hdr_size(struct drm_dp_sideband_msg_hdr *hdr)
{
        u8 size = 3;
        size += (hdr->lct / 2);
        return size;
}

static void drm_dp_encode_sideband_msg_hdr(struct drm_dp_sideband_msg_hdr *hdr,
                                           u8 *buf, int *len)
{
        int idx = 0;
        int i;
        u8 crc4;
        buf[idx++] = ((hdr->lct & 0xf) << 4) | (hdr->lcr & 0xf);
        for (i = 0; i < (hdr->lct / 2); i++)
                buf[idx++] = hdr->rad[i];
        buf[idx++] = (hdr->broadcast << 7) | (hdr->path_msg << 6) |
                (hdr->msg_len & 0x3f);
        buf[idx++] = (hdr->somt << 7) | (hdr->eomt << 6) | (hdr->seqno << 4);

        crc4 = drm_dp_msg_header_crc4(buf, (idx * 2) - 1);
        buf[idx - 1] |= (crc4 & 0xf);

        *len = idx;
}

static bool drm_dp_decode_sideband_msg_hdr(struct drm_dp_sideband_msg_hdr *hdr,
                                           u8 *buf, int buflen, u8 *hdrlen)
{
        u8 crc4;
        u8 len;
        int i;
        u8 idx;
        if (buf[0] == 0)
                return false;
        len = 3;
        len += ((buf[0] & 0xf0) >> 4) / 2;
        if (len > buflen)
                return false;
        crc4 = drm_dp_msg_header_crc4(buf, (len * 2) - 1);

        if ((crc4 & 0xf) != (buf[len - 1] & 0xf)) {
                DRM_DEBUG_KMS("crc4 mismatch 0x%x 0x%x\n", crc4, buf[len - 1]);
                return false;
        }

        hdr->lct = (buf[0] & 0xf0) >> 4;
        hdr->lcr = (buf[0] & 0xf);
        idx = 1;
        for (i = 0; i < (hdr->lct / 2); i++)
                hdr->rad[i] = buf[idx++];
        hdr->broadcast = (buf[idx] >> 7) & 0x1;
        hdr->path_msg = (buf[idx] >> 6) & 0x1;
        hdr->msg_len = buf[idx] & 0x3f;
        idx++;
        hdr->somt = (buf[idx] >> 7) & 0x1;
        hdr->eomt = (buf[idx] >> 6) & 0x1;
        hdr->seqno = (buf[idx] >> 4) & 0x1;
        idx++;
        *hdrlen = idx;
        return true;
}

static void drm_dp_encode_sideband_req(struct drm_dp_sideband_msg_req_body *req,
                                       struct drm_dp_sideband_msg_tx *raw)
{
        int idx = 0;
        int i;
        u8 *buf = raw->msg;
        buf[idx++] = req->req_type & 0x7f;

        switch (req->req_type) {
        case DP_ENUM_PATH_RESOURCES:
                buf[idx] = (req->u.port_num.port_number & 0xf) << 4;
                idx++;
                break;
        case DP_ALLOCATE_PAYLOAD:
                buf[idx] = (req->u.allocate_payload.port_number & 0xf) << 4 |
                        (req->u.allocate_payload.number_sdp_streams & 0xf);
                idx++;
                buf[idx] = (req->u.allocate_payload.vcpi & 0x7f);
                idx++;
                buf[idx] = (req->u.allocate_payload.pbn >> 8);
                idx++;
                buf[idx] = (req->u.allocate_payload.pbn & 0xff);
                idx++;
                for (i = 0; i < req->u.allocate_payload.number_sdp_streams / 2; i++) {
                        buf[idx] = ((req->u.allocate_payload.sdp_stream_sink[i * 2] & 0xf) << 4) |
                                (req->u.allocate_payload.sdp_stream_sink[i * 2 + 1] & 0xf);
                        idx++;
                }
                if (req->u.allocate_payload.number_sdp_streams & 1) {
                        i = req->u.allocate_payload.number_sdp_streams - 1;
                        buf[idx] = (req->u.allocate_payload.sdp_stream_sink[i] & 0xf) << 4;
                        idx++;
                }
                break;
        case DP_QUERY_PAYLOAD:
                buf[idx] = (req->u.query_payload.port_number & 0xf) << 4;
                idx++;
                buf[idx] = (req->u.query_payload.vcpi & 0x7f);
                idx++;
                break;
        case DP_REMOTE_DPCD_READ:
                buf[idx] = (req->u.dpcd_read.port_number & 0xf) << 4;
                buf[idx] |= ((req->u.dpcd_read.dpcd_address & 0xf0000) >> 16) & 0xf;
                idx++;
                buf[idx] = (req->u.dpcd_read.dpcd_address & 0xff00) >> 8;
                idx++;
                buf[idx] = (req->u.dpcd_read.dpcd_address & 0xff);
                idx++;
                buf[idx] = (req->u.dpcd_read.num_bytes);
                idx++;
                break;

        case DP_REMOTE_DPCD_WRITE:
                buf[idx] = (req->u.dpcd_write.port_number & 0xf) << 4;
                buf[idx] |= ((req->u.dpcd_write.dpcd_address & 0xf0000) >> 16) & 0xf;
                idx++;
                buf[idx] = (req->u.dpcd_write.dpcd_address & 0xff00) >> 8;
                idx++;
                buf[idx] = (req->u.dpcd_write.dpcd_address & 0xff);
                idx++;
                buf[idx] = (req->u.dpcd_write.num_bytes);
                idx++;
                memcpy(&buf[idx], req->u.dpcd_write.bytes, req->u.dpcd_write.num_bytes);
                idx += req->u.dpcd_write.num_bytes;
                break;
        case DP_REMOTE_I2C_READ:
                buf[idx] = (req->u.i2c_read.port_number & 0xf) << 4;
                buf[idx] |= (req->u.i2c_read.num_transactions & 0x3);
                idx++;
                for (i = 0; i < (req->u.i2c_read.num_transactions & 0x3); i++) {
                        buf[idx] = req->u.i2c_read.transactions[i].i2c_dev_id & 0x7f;
                        idx++;
                        buf[idx] = req->u.i2c_read.transactions[i].num_bytes;
                        idx++;
                        memcpy(&buf[idx], req->u.i2c_read.transactions[i].bytes, req->u.i2c_read.transactions[i].num_bytes);
                        idx += req->u.i2c_read.transactions[i].num_bytes;

                        buf[idx] = (req->u.i2c_read.transactions[i].no_stop_bit & 0x1) << 5;
                        buf[idx] |= (req->u.i2c_read.transactions[i].i2c_transaction_delay & 0xf);
                        idx++;
                }
                buf[idx] = (req->u.i2c_read.read_i2c_device_id) & 0x7f;
                idx++;
                buf[idx] = (req->u.i2c_read.num_bytes_read);
                idx++;
                break;

        case DP_REMOTE_I2C_WRITE:
                buf[idx] = (req->u.i2c_write.port_number & 0xf) << 4;
                idx++;
                buf[idx] = (req->u.i2c_write.write_i2c_device_id) & 0x7f;
                idx++;
                buf[idx] = (req->u.i2c_write.num_bytes);
                idx++;
                memcpy(&buf[idx], req->u.i2c_write.bytes, req->u.i2c_write.num_bytes);
                idx += req->u.i2c_write.num_bytes;
                break;

        case DP_POWER_DOWN_PHY:
        case DP_POWER_UP_PHY:
                buf[idx] = (req->u.port_num.port_number & 0xf) << 4;
                idx++;
                break;
        }
        raw->cur_len = idx;
}

static void drm_dp_crc_sideband_chunk_req(u8 *msg, u8 len)
{
        u8 crc4;
        crc4 = drm_dp_msg_data_crc4(msg, len);
        msg[len] = crc4;
}

static void drm_dp_encode_sideband_reply(struct drm_dp_sideband_msg_reply_body *rep,
                                         struct drm_dp_sideband_msg_tx *raw)
{
        int idx = 0;
        u8 *buf = raw->msg;

        buf[idx++] = (rep->reply_type & 0x1) << 7 | (rep->req_type & 0x7f);

        raw->cur_len = idx;
}

/* this adds a chunk of msg to the builder to get the final msg */
static bool drm_dp_sideband_msg_build(struct drm_dp_sideband_msg_rx *msg,
                                      u8 *replybuf, u8 replybuflen, bool hdr)
{
        int ret;
        u8 crc4;

        if (hdr) {
                u8 hdrlen;
                struct drm_dp_sideband_msg_hdr recv_hdr;
                ret = drm_dp_decode_sideband_msg_hdr(&recv_hdr, replybuf, replybuflen, &hdrlen);
                if (ret == false) {
                        print_hex_dump(KERN_DEBUG, "failed hdr", DUMP_PREFIX_NONE, 16, 1, replybuf, replybuflen, false);
                        return false;
                }

                /*
                 * ignore out-of-order messages or messages that are part of a
                 * failed transaction
                 */
                if (!recv_hdr.somt && !msg->have_somt)
                        return false;

                /* get length contained in this portion */
                msg->curchunk_len = recv_hdr.msg_len;
                msg->curchunk_hdrlen = hdrlen;

                /* we have already gotten an somt - don't bother parsing */
                if (recv_hdr.somt && msg->have_somt)
                        return false;

                if (recv_hdr.somt) {
                        memcpy(&msg->initial_hdr, &recv_hdr, sizeof(struct drm_dp_sideband_msg_hdr));
                        msg->have_somt = true;
                }
                if (recv_hdr.eomt)
                        msg->have_eomt = true;

                /* copy the bytes for the remainder of this header chunk */
                msg->curchunk_idx = min(msg->curchunk_len, (u8)(replybuflen - hdrlen));
                memcpy(&msg->chunk[0], replybuf + hdrlen, msg->curchunk_idx);
        } else {
                memcpy(&msg->chunk[msg->curchunk_idx], replybuf, replybuflen);
                msg->curchunk_idx += replybuflen;
        }

        if (msg->curchunk_idx >= msg->curchunk_len) {
                /* do CRC */
                crc4 = drm_dp_msg_data_crc4(msg->chunk, msg->curchunk_len - 1);
                /* copy chunk into bigger msg */
                memcpy(&msg->msg[msg->curlen], msg->chunk, msg->curchunk_len - 1);
                msg->curlen += msg->curchunk_len - 1;
        }
        return true;
}

static bool drm_dp_sideband_parse_link_address(struct drm_dp_sideband_msg_rx *raw,
                                               struct drm_dp_sideband_msg_reply_body *repmsg)
{
        int idx = 1;
        int i;
        memcpy(repmsg->u.link_addr.guid, &raw->msg[idx], 16);
        idx += 16;
        repmsg->u.link_addr.nports = raw->msg[idx] & 0xf;
        idx++;
        if (idx > raw->curlen)
                goto fail_len;
        for (i = 0; i < repmsg->u.link_addr.nports; i++) {
                if (raw->msg[idx] & 0x80)
                        repmsg->u.link_addr.ports[i].input_port = 1;

                repmsg->u.link_addr.ports[i].peer_device_type = (raw->msg[idx] >> 4) & 0x7;
                repmsg->u.link_addr.ports[i].port_number = (raw->msg[idx] & 0xf);

                idx++;
                if (idx > raw->curlen)
                        goto fail_len;
                repmsg->u.link_addr.ports[i].mcs = (raw->msg[idx] >> 7) & 0x1;
                repmsg->u.link_addr.ports[i].ddps = (raw->msg[idx] >> 6) & 0x1;
                if (repmsg->u.link_addr.ports[i].input_port == 0)
                        repmsg->u.link_addr.ports[i].legacy_device_plug_status = (raw->msg[idx] >> 5) & 0x1;
                idx++;
                if (idx > raw->curlen)
                        goto fail_len;
                if (repmsg->u.link_addr.ports[i].input_port == 0) {
                        repmsg->u.link_addr.ports[i].dpcd_revision = (raw->msg[idx]);
                        idx++;
                        if (idx > raw->curlen)
                                goto fail_len;
                        memcpy(repmsg->u.link_addr.ports[i].peer_guid, &raw->msg[idx], 16);
                        idx += 16;
                        if (idx > raw->curlen)
                                goto fail_len;
                        repmsg->u.link_addr.ports[i].num_sdp_streams = (raw->msg[idx] >> 4) & 0xf;
                        repmsg->u.link_addr.ports[i].num_sdp_stream_sinks = (raw->msg[idx] & 0xf);
                        idx++;

                }
                if (idx > raw->curlen)
                        goto fail_len;
        }

        return true;
fail_len:
        DRM_DEBUG_KMS("link address reply parse length fail %d %d\n", idx, raw->curlen);
        return false;
}

static bool drm_dp_sideband_parse_remote_dpcd_read(struct drm_dp_sideband_msg_rx *raw,
                                                   struct drm_dp_sideband_msg_reply_body *repmsg)
{
        int idx = 1;
        repmsg->u.remote_dpcd_read_ack.port_number = raw->msg[idx] & 0xf;
        idx++;
        if (idx > raw->curlen)
                goto fail_len;
        repmsg->u.remote_dpcd_read_ack.num_bytes = raw->msg[idx];
        idx++;
        if (idx > raw->curlen)
                goto fail_len;

        memcpy(repmsg->u.remote_dpcd_read_ack.bytes, &raw->msg[idx], repmsg->u.remote_dpcd_read_ack.num_bytes);
        return true;
fail_len:
        DRM_DEBUG_KMS("link address reply parse length fail %d %d\n", idx, raw->curlen);
        return false;
}

static bool drm_dp_sideband_parse_remote_dpcd_write(struct drm_dp_sideband_msg_rx *raw,
                                                      struct drm_dp_sideband_msg_reply_body *repmsg)
{
        int idx = 1;
        repmsg->u.remote_dpcd_write_ack.port_number = raw->msg[idx] & 0xf;
        idx++;
        if (idx > raw->curlen)
                goto fail_len;
        return true;
fail_len:
        DRM_DEBUG_KMS("parse length fail %d %d\n", idx, raw->curlen);
        return false;
}

static bool drm_dp_sideband_parse_remote_i2c_read_ack(struct drm_dp_sideband_msg_rx *raw,
                                                      struct drm_dp_sideband_msg_reply_body *repmsg)
{
        int idx = 1;

        repmsg->u.remote_i2c_read_ack.port_number = (raw->msg[idx] & 0xf);
        idx++;
        if (idx > raw->curlen)
                goto fail_len;
        repmsg->u.remote_i2c_read_ack.num_bytes = raw->msg[idx];
        idx++;
        /* TODO check */
        memcpy(repmsg->u.remote_i2c_read_ack.bytes, &raw->msg[idx], repmsg->u.remote_i2c_read_ack.num_bytes);
        return true;
fail_len:
        DRM_DEBUG_KMS("remote i2c reply parse length fail %d %d\n", idx, raw->curlen);
        return false;
}

static bool drm_dp_sideband_parse_enum_path_resources_ack(struct drm_dp_sideband_msg_rx *raw,
                                                          struct drm_dp_sideband_msg_reply_body *repmsg)
{
        int idx = 1;
        repmsg->u.path_resources.port_number = (raw->msg[idx] >> 4) & 0xf;
        idx++;
        if (idx > raw->curlen)
                goto fail_len;
        repmsg->u.path_resources.full_payload_bw_number = (raw->msg[idx] << 8) | (raw->msg[idx+1]);
        idx += 2;
        if (idx > raw->curlen)
                goto fail_len;
        repmsg->u.path_resources.avail_payload_bw_number = (raw->msg[idx] << 8) | (raw->msg[idx+1]);
        idx += 2;
        if (idx > raw->curlen)
                goto fail_len;
        return true;
fail_len:
        DRM_DEBUG_KMS("enum resource parse length fail %d %d\n", idx, raw->curlen);
        return false;
}

static bool drm_dp_sideband_parse_allocate_payload_ack(struct drm_dp_sideband_msg_rx *raw,
                                                          struct drm_dp_sideband_msg_reply_body *repmsg)
{
        int idx = 1;
        repmsg->u.allocate_payload.port_number = (raw->msg[idx] >> 4) & 0xf;
        idx++;
        if (idx > raw->curlen)
                goto fail_len;
        repmsg->u.allocate_payload.vcpi = raw->msg[idx];
        idx++;
        if (idx > raw->curlen)
                goto fail_len;
        repmsg->u.allocate_payload.allocated_pbn = (raw->msg[idx] << 8) | (raw->msg[idx+1]);
        idx += 2;
        if (idx > raw->curlen)
                goto fail_len;
        return true;
fail_len:
        DRM_DEBUG_KMS("allocate payload parse length fail %d %d\n", idx, raw->curlen);
        return false;
}

static bool drm_dp_sideband_parse_query_payload_ack(struct drm_dp_sideband_msg_rx *raw,
                                                    struct drm_dp_sideband_msg_reply_body *repmsg)
{
        int idx = 1;
        repmsg->u.query_payload.port_number = (raw->msg[idx] >> 4) & 0xf;
        idx++;
        if (idx > raw->curlen)
                goto fail_len;
        repmsg->u.query_payload.allocated_pbn = (raw->msg[idx] << 8) | (raw->msg[idx + 1]);
        idx += 2;
        if (idx > raw->curlen)
                goto fail_len;
        return true;
fail_len:
        DRM_DEBUG_KMS("query payload parse length fail %d %d\n", idx, raw->curlen);
        return false;
}

static bool drm_dp_sideband_parse_power_updown_phy_ack(struct drm_dp_sideband_msg_rx *raw,
                                                       struct drm_dp_sideband_msg_reply_body *repmsg)
{
        int idx = 1;

        repmsg->u.port_number.port_number = (raw->msg[idx] >> 4) & 0xf;
        idx++;
        if (idx > raw->curlen) {
                DRM_DEBUG_KMS("power up/down phy parse length fail %d %d\n",
                              idx, raw->curlen);
                return false;
        }
        return true;
}

static bool drm_dp_sideband_parse_reply(struct drm_dp_sideband_msg_rx *raw,
                                        struct drm_dp_sideband_msg_reply_body *msg)
{
        memset(msg, 0, sizeof(*msg));
        msg->reply_type = (raw->msg[0] & 0x80) >> 7;
        msg->req_type = (raw->msg[0] & 0x7f);

        if (msg->reply_type) {
                memcpy(msg->u.nak.guid, &raw->msg[1], 16);
                msg->u.nak.reason = raw->msg[17];
                msg->u.nak.nak_data = raw->msg[18];
                return false;
        }

        switch (msg->req_type) {
        case DP_LINK_ADDRESS:
                return drm_dp_sideband_parse_link_address(raw, msg);
        case DP_QUERY_PAYLOAD:
                return drm_dp_sideband_parse_query_payload_ack(raw, msg);
        case DP_REMOTE_DPCD_READ:
                return drm_dp_sideband_parse_remote_dpcd_read(raw, msg);
        case DP_REMOTE_DPCD_WRITE:
                return drm_dp_sideband_parse_remote_dpcd_write(raw, msg);
        case DP_REMOTE_I2C_READ:
                return drm_dp_sideband_parse_remote_i2c_read_ack(raw, msg);
        case DP_ENUM_PATH_RESOURCES:
                return drm_dp_sideband_parse_enum_path_resources_ack(raw, msg);
        case DP_ALLOCATE_PAYLOAD:
                return drm_dp_sideband_parse_allocate_payload_ack(raw, msg);
        case DP_POWER_DOWN_PHY:
        case DP_POWER_UP_PHY:
                return drm_dp_sideband_parse_power_updown_phy_ack(raw, msg);
        default:
                DRM_ERROR("Got unknown reply 0x%02x\n", msg->req_type);
                return false;
        }
}

static bool drm_dp_sideband_parse_connection_status_notify(struct drm_dp_sideband_msg_rx *raw,
                                                           struct drm_dp_sideband_msg_req_body *msg)
{
        int idx = 1;

        msg->u.conn_stat.port_number = (raw->msg[idx] & 0xf0) >> 4;
        idx++;
        if (idx > raw->curlen)
                goto fail_len;

        memcpy(msg->u.conn_stat.guid, &raw->msg[idx], 16);
        idx += 16;
        if (idx > raw->curlen)
                goto fail_len;

        msg->u.conn_stat.legacy_device_plug_status = (raw->msg[idx] >> 6) & 0x1;
        msg->u.conn_stat.displayport_device_plug_status = (raw->msg[idx] >> 5) & 0x1;
        msg->u.conn_stat.message_capability_status = (raw->msg[idx] >> 4) & 0x1;
        msg->u.conn_stat.input_port = (raw->msg[idx] >> 3) & 0x1;
        msg->u.conn_stat.peer_device_type = (raw->msg[idx] & 0x7);
        idx++;
        return true;
fail_len:
        DRM_DEBUG_KMS("connection status reply parse length fail %d %d\n", idx, raw->curlen);
        return false;
}

static bool drm_dp_sideband_parse_resource_status_notify(struct drm_dp_sideband_msg_rx *raw,
                                                           struct drm_dp_sideband_msg_req_body *msg)
{
        int idx = 1;

        msg->u.resource_stat.port_number = (raw->msg[idx] & 0xf0) >> 4;
        idx++;
        if (idx > raw->curlen)
                goto fail_len;

        memcpy(msg->u.resource_stat.guid, &raw->msg[idx], 16);
        idx += 16;
        if (idx > raw->curlen)
                goto fail_len;

        msg->u.resource_stat.available_pbn = (raw->msg[idx] << 8) | (raw->msg[idx + 1]);
        idx++;
        return true;
fail_len:
        DRM_DEBUG_KMS("resource status reply parse length fail %d %d\n", idx, raw->curlen);
        return false;
}

static bool drm_dp_sideband_parse_req(struct drm_dp_sideband_msg_rx *raw,
                                      struct drm_dp_sideband_msg_req_body *msg)
{
        memset(msg, 0, sizeof(*msg));
        msg->req_type = (raw->msg[0] & 0x7f);

        switch (msg->req_type) {
        case DP_CONNECTION_STATUS_NOTIFY:
                return drm_dp_sideband_parse_connection_status_notify(raw, msg);
        case DP_RESOURCE_STATUS_NOTIFY:
                return drm_dp_sideband_parse_resource_status_notify(raw, msg);
        default:
                DRM_ERROR("Got unknown request 0x%02x\n", msg->req_type);
                return false;
        }
}

static int build_dpcd_write(struct drm_dp_sideband_msg_tx *msg, u8 port_num, u32 offset, u8 num_bytes, u8 *bytes)
{
        struct drm_dp_sideband_msg_req_body req;

        req.req_type = DP_REMOTE_DPCD_WRITE;
        req.u.dpcd_write.port_number = port_num;
        req.u.dpcd_write.dpcd_address = offset;
        req.u.dpcd_write.num_bytes = num_bytes;
        req.u.dpcd_write.bytes = bytes;
        drm_dp_encode_sideband_req(&req, msg);

        return 0;
}

static int build_link_address(struct drm_dp_sideband_msg_tx *msg)
{
        struct drm_dp_sideband_msg_req_body req;

        req.req_type = DP_LINK_ADDRESS;
        drm_dp_encode_sideband_req(&req, msg);
        return 0;
}

static int build_enum_path_resources(struct drm_dp_sideband_msg_tx *msg, int port_num)
{
        struct drm_dp_sideband_msg_req_body req;

        req.req_type = DP_ENUM_PATH_RESOURCES;
        req.u.port_num.port_number = port_num;
        drm_dp_encode_sideband_req(&req, msg);
        msg->path_msg = true;
        return 0;
}

static int build_allocate_payload(struct drm_dp_sideband_msg_tx *msg, int port_num,
                                  u8 vcpi, uint16_t pbn,
                                  u8 number_sdp_streams,
                                  u8 *sdp_stream_sink)
{
        struct drm_dp_sideband_msg_req_body req;
        memset(&req, 0, sizeof(req));
        req.req_type = DP_ALLOCATE_PAYLOAD;
        req.u.allocate_payload.port_number = port_num;
        req.u.allocate_payload.vcpi = vcpi;
        req.u.allocate_payload.pbn = pbn;
        req.u.allocate_payload.number_sdp_streams = number_sdp_streams;
        memcpy(req.u.allocate_payload.sdp_stream_sink, sdp_stream_sink,
                   number_sdp_streams);
        drm_dp_encode_sideband_req(&req, msg);
        msg->path_msg = true;
        return 0;
}

static int build_power_updown_phy(struct drm_dp_sideband_msg_tx *msg,
                                  int port_num, bool power_up)
{
        struct drm_dp_sideband_msg_req_body req;

        if (power_up)
                req.req_type = DP_POWER_UP_PHY;
        else
                req.req_type = DP_POWER_DOWN_PHY;

        req.u.port_num.port_number = port_num;
        drm_dp_encode_sideband_req(&req, msg);
        msg->path_msg = true;
        return 0;
}

static int drm_dp_mst_assign_payload_id(struct drm_dp_mst_topology_mgr *mgr,
                                        struct drm_dp_vcpi *vcpi)
{
        int ret, vcpi_ret;

        mutex_lock(&mgr->payload_lock);
        ret = find_first_zero_bit(&mgr->payload_mask, mgr->max_payloads + 1);
        if (ret > mgr->max_payloads) {
                ret = -EINVAL;
                DRM_DEBUG_KMS("out of payload ids %d\n", ret);
                goto out_unlock;
        }

        vcpi_ret = find_first_zero_bit(&mgr->vcpi_mask, mgr->max_payloads + 1);
        if (vcpi_ret > mgr->max_payloads) {
                ret = -EINVAL;
                DRM_DEBUG_KMS("out of vcpi ids %d\n", ret);
                goto out_unlock;
        }

        set_bit(ret, &mgr->payload_mask);
        set_bit(vcpi_ret, &mgr->vcpi_mask);
        vcpi->vcpi = vcpi_ret + 1;
        mgr->proposed_vcpis[ret - 1] = vcpi;
out_unlock:
        mutex_unlock(&mgr->payload_lock);
        return ret;
}

static void drm_dp_mst_put_payload_id(struct drm_dp_mst_topology_mgr *mgr,
                                      int vcpi)
{
        int i;
        if (vcpi == 0)
                return;

        mutex_lock(&mgr->payload_lock);
        DRM_DEBUG_KMS("putting payload %d\n", vcpi);
        clear_bit(vcpi - 1, &mgr->vcpi_mask);

        for (i = 0; i < mgr->max_payloads; i++) {
                if (mgr->proposed_vcpis[i])
                        if (mgr->proposed_vcpis[i]->vcpi == vcpi) {
                                mgr->proposed_vcpis[i] = NULL;
                                clear_bit(i + 1, &mgr->payload_mask);
                        }
        }
        mutex_unlock(&mgr->payload_lock);
}

static bool check_txmsg_state(struct drm_dp_mst_topology_mgr *mgr,
                              struct drm_dp_sideband_msg_tx *txmsg)
{
        unsigned int state;

        /*
         * All updates to txmsg->state are protected by mgr->qlock, and the two
         * cases we check here are terminal states. For those the barriers
         * provided by the wake_up/wait_event pair are enough.
         */
        state = READ_ONCE(txmsg->state);
        return (state == DRM_DP_SIDEBAND_TX_RX ||
                state == DRM_DP_SIDEBAND_TX_TIMEOUT);
}

static int drm_dp_mst_wait_tx_reply(struct drm_dp_mst_branch *mstb,
                                    struct drm_dp_sideband_msg_tx *txmsg)
{
        struct drm_dp_mst_topology_mgr *mgr = mstb->mgr;
        int ret;

        ret = wait_event_timeout(mgr->tx_waitq,
                                 check_txmsg_state(mgr, txmsg),
                                 (4 * HZ));
        mutex_lock(&mstb->mgr->qlock);
        if (ret > 0) {
                if (txmsg->state == DRM_DP_SIDEBAND_TX_TIMEOUT) {
                        ret = -EIO;
                        goto out;
                }
        } else {
                DRM_DEBUG_KMS("timedout msg send %p %d %d\n", txmsg, txmsg->state, txmsg->seqno);

                /* dump some state */
                ret = -EIO;

                /* remove from q */
                if (txmsg->state == DRM_DP_SIDEBAND_TX_QUEUED ||
                    txmsg->state == DRM_DP_SIDEBAND_TX_START_SEND) {
                        list_del(&txmsg->next);
                }

                if (txmsg->state == DRM_DP_SIDEBAND_TX_START_SEND ||
                    txmsg->state == DRM_DP_SIDEBAND_TX_SENT) {
                        mstb->tx_slots[txmsg->seqno] = NULL;
                }
        }
out:
        mutex_unlock(&mgr->qlock);

        return ret;
}

static struct drm_dp_mst_branch *drm_dp_add_mst_branch_device(u8 lct, u8 *rad)
{
        struct drm_dp_mst_branch *mstb;

        mstb = kzalloc(sizeof(*mstb), GFP_KERNEL);
        if (!mstb)
                return NULL;

        mstb->lct = lct;
        if (lct > 1)
                memcpy(mstb->rad, rad, lct / 2);
        INIT_LIST_HEAD(&mstb->ports);
        kref_init(&mstb->kref);
        return mstb;
}

static void drm_dp_free_mst_port(struct kref *kref);

static void drm_dp_free_mst_branch_device(struct kref *kref)
{
        struct drm_dp_mst_branch *mstb = container_of(kref, struct drm_dp_mst_branch, kref);
        if (mstb->port_parent) {
                if (list_empty(&mstb->port_parent->next))
                        kref_put(&mstb->port_parent->kref, drm_dp_free_mst_port);
        }
        kfree(mstb);
}

static void drm_dp_destroy_mst_branch_device(struct kref *kref)
{
        struct drm_dp_mst_branch *mstb = container_of(kref, struct drm_dp_mst_branch, kref);
        struct drm_dp_mst_port *port, *tmp;
        bool wake_tx = false;

        /*
         * init kref again to be used by ports to remove mst branch when it is
         * not needed anymore
         */
        kref_init(kref);

        if (mstb->port_parent && list_empty(&mstb->port_parent->next))
                kref_get(&mstb->port_parent->kref);

        /*
         * destroy all ports - don't need lock
         * as there are no more references to the mst branch
         * device at this point.
         */
        list_for_each_entry_safe(port, tmp, &mstb->ports, next) {
                list_del(&port->next);
                drm_dp_put_port(port);
        }

        /* drop any tx slots msg */
        mutex_lock(&mstb->mgr->qlock);
        if (mstb->tx_slots[0]) {
                mstb->tx_slots[0]->state = DRM_DP_SIDEBAND_TX_TIMEOUT;
                mstb->tx_slots[0] = NULL;
                wake_tx = true;
        }
        if (mstb->tx_slots[1]) {
                mstb->tx_slots[1]->state = DRM_DP_SIDEBAND_TX_TIMEOUT;
                mstb->tx_slots[1] = NULL;
                wake_tx = true;
        }
        mutex_unlock(&mstb->mgr->qlock);

        if (wake_tx)
                wake_up_all(&mstb->mgr->tx_waitq);

        kref_put(kref, drm_dp_free_mst_branch_device);
}

static void drm_dp_put_mst_branch_device(struct drm_dp_mst_branch *mstb)
{
        kref_put(&mstb->kref, drm_dp_destroy_mst_branch_device);
}


static void drm_dp_port_teardown_pdt(struct drm_dp_mst_port *port, int old_pdt)
{
        struct drm_dp_mst_branch *mstb;

        switch (old_pdt) {
        case DP_PEER_DEVICE_DP_LEGACY_CONV:
        case DP_PEER_DEVICE_SST_SINK:
                /* remove i2c over sideband */
                drm_dp_mst_unregister_i2c_bus(&port->aux);
                break;
        case DP_PEER_DEVICE_MST_BRANCHING:
                mstb = port->mstb;
                port->mstb = NULL;
                drm_dp_put_mst_branch_device(mstb);
                break;
        }
}

static void drm_dp_destroy_port(struct kref *kref)
{
        struct drm_dp_mst_port *port = container_of(kref, struct drm_dp_mst_port, kref);
        struct drm_dp_mst_topology_mgr *mgr = port->mgr;

        if (!port->input) {
                port->vcpi.num_slots = 0;

                kfree(port->cached_edid);

                /*
                 * The only time we don't have a connector
                 * on an output port is if the connector init
                 * fails.
                 */
                if (port->connector) {
                        /* we can't destroy the connector here, as
                         * we might be holding the mode_config.mutex
                         * from an EDID retrieval */

                        mutex_lock(&mgr->destroy_connector_lock);
                        kref_get(&port->parent->kref);
                        list_add(&port->next, &mgr->destroy_connector_list);
                        mutex_unlock(&mgr->destroy_connector_lock);
                        schedule_work(&mgr->destroy_connector_work);
                        return;
                }
                /* no need to clean up vcpi
                 * as if we have no connector we never setup a vcpi */
                drm_dp_port_teardown_pdt(port, port->pdt);
                port->pdt = DP_PEER_DEVICE_NONE;
        }
        kfree(port);
}

static void drm_dp_put_port(struct drm_dp_mst_port *port)
{
        kref_put(&port->kref, drm_dp_destroy_port);
}

static struct drm_dp_mst_branch *drm_dp_mst_get_validated_mstb_ref_locked(struct drm_dp_mst_branch *mstb, struct drm_dp_mst_branch *to_find)
{
        struct drm_dp_mst_port *port;
        struct drm_dp_mst_branch *rmstb;
        if (to_find == mstb) {
                kref_get(&mstb->kref);
                return mstb;
        }
        list_for_each_entry(port, &mstb->ports, next) {
                if (port->mstb) {
                        rmstb = drm_dp_mst_get_validated_mstb_ref_locked(port->mstb, to_find);
                        if (rmstb)
                                return rmstb;
                }
        }
        return NULL;
}

static struct drm_dp_mst_branch *drm_dp_get_validated_mstb_ref(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_branch *mstb)
{
        struct drm_dp_mst_branch *rmstb = NULL;
        mutex_lock(&mgr->lock);
        if (mgr->mst_primary)
                rmstb = drm_dp_mst_get_validated_mstb_ref_locked(mgr->mst_primary, mstb);
        mutex_unlock(&mgr->lock);
        return rmstb;
}

static struct drm_dp_mst_port *drm_dp_mst_get_port_ref_locked(struct drm_dp_mst_branch *mstb, struct drm_dp_mst_port *to_find)
{
        struct drm_dp_mst_port *port, *mport;

        list_for_each_entry(port, &mstb->ports, next) {
                if (port == to_find) {
                        kref_get(&port->kref);
                        return port;
                }
                if (port->mstb) {
                        mport = drm_dp_mst_get_port_ref_locked(port->mstb, to_find);
                        if (mport)
                                return mport;
                }
        }
        return NULL;
}

static struct drm_dp_mst_port *drm_dp_get_validated_port_ref(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_port *port)
{
        struct drm_dp_mst_port *rport = NULL;
        mutex_lock(&mgr->lock);
        if (mgr->mst_primary)
                rport = drm_dp_mst_get_port_ref_locked(mgr->mst_primary, port);
        mutex_unlock(&mgr->lock);
        return rport;
}

static struct drm_dp_mst_port *drm_dp_get_port(struct drm_dp_mst_branch *mstb, u8 port_num)
{
        struct drm_dp_mst_port *port;

        list_for_each_entry(port, &mstb->ports, next) {
                if (port->port_num == port_num) {
                        kref_get(&port->kref);
                        return port;
                }
        }

        return NULL;
}

/*
 * calculate a new RAD for this MST branch device
 * if parent has an LCT of 2 then it has 1 nibble of RAD,
 * if parent has an LCT of 3 then it has 2 nibbles of RAD,
 */
static u8 drm_dp_calculate_rad(struct drm_dp_mst_port *port,
                                 u8 *rad)
{
        int parent_lct = port->parent->lct;
        int shift = 4;
        int idx = (parent_lct - 1) / 2;
        if (parent_lct > 1) {
                memcpy(rad, port->parent->rad, idx + 1);
                shift = (parent_lct % 2) ? 4 : 0;
        } else
                rad[0] = 0;

        rad[idx] |= port->port_num << shift;
        return parent_lct + 1;
}

/*
 * return sends link address for new mstb
 */
static bool drm_dp_port_setup_pdt(struct drm_dp_mst_port *port)
{
        int ret;
        u8 rad[6], lct;
        bool send_link = false;
        switch (port->pdt) {
        case DP_PEER_DEVICE_DP_LEGACY_CONV:
        case DP_PEER_DEVICE_SST_SINK:
                /* add i2c over sideband */
                ret = drm_dp_mst_register_i2c_bus(&port->aux);
                break;
        case DP_PEER_DEVICE_MST_BRANCHING:
                lct = drm_dp_calculate_rad(port, rad);

                port->mstb = drm_dp_add_mst_branch_device(lct, rad);
                if (port->mstb) {
                        port->mstb->mgr = port->mgr;
                        port->mstb->port_parent = port;

                        send_link = true;
                }
                break;
        }
        return send_link;
}

static void drm_dp_check_mstb_guid(struct drm_dp_mst_branch *mstb, u8 *guid)
{
        int ret;

        memcpy(mstb->guid, guid, 16);

        if (!drm_dp_validate_guid(mstb->mgr, mstb->guid)) {
                if (mstb->port_parent) {
                        ret = drm_dp_send_dpcd_write(
                                        mstb->mgr,
                                        mstb->port_parent,
                                        DP_GUID,
                                        16,
                                        mstb->guid);
                } else {

                        ret = drm_dp_dpcd_write(
                                        mstb->mgr->aux,
                                        DP_GUID,
                                        mstb->guid,
                                        16);
                }
        }
}

static void build_mst_prop_path(const struct drm_dp_mst_branch *mstb,
                                int pnum,
                                char *proppath,
                                size_t proppath_size)
{
        int i;
        char temp[8];
        snprintf(proppath, proppath_size, "mst:%d", mstb->mgr->conn_base_id);
        for (i = 0; i < (mstb->lct - 1); i++) {
                int shift = (i % 2) ? 0 : 4;
                int port_num = (mstb->rad[i / 2] >> shift) & 0xf;
                snprintf(temp, sizeof(temp), "-%d", port_num);
                strlcat(proppath, temp, proppath_size);
        }
        snprintf(temp, sizeof(temp), "-%d", pnum);
        strlcat(proppath, temp, proppath_size);
}

static void drm_dp_add_port(struct drm_dp_mst_branch *mstb,
                            struct drm_device *dev,
                            struct drm_dp_link_addr_reply_port *port_msg)
{
        struct drm_dp_mst_port *port;
        bool ret;
        bool created = false;
        int old_pdt = 0;
        int old_ddps = 0;
        port = drm_dp_get_port(mstb, port_msg->port_number);
        if (!port) {
                port = kzalloc(sizeof(*port), GFP_KERNEL);
                if (!port)
                        return;
                kref_init(&port->kref);
                port->parent = mstb;
                port->port_num = port_msg->port_number;
                port->mgr = mstb->mgr;
                port->aux.name = "DPMST";
                port->aux.dev = dev->dev;
                created = true;
        } else {
                old_pdt = port->pdt;
                old_ddps = port->ddps;
        }

        port->pdt = port_msg->peer_device_type;
        port->input = port_msg->input_port;
        port->mcs = port_msg->mcs;
        port->ddps = port_msg->ddps;
        port->ldps = port_msg->legacy_device_plug_status;
        port->dpcd_rev = port_msg->dpcd_revision;
        port->num_sdp_streams = port_msg->num_sdp_streams;
        port->num_sdp_stream_sinks = port_msg->num_sdp_stream_sinks;

        /* manage mstb port lists with mgr lock - take a reference
           for this list */
        if (created) {
                mutex_lock(&mstb->mgr->lock);
                kref_get(&port->kref);
                list_add(&port->next, &mstb->ports);
                mutex_unlock(&mstb->mgr->lock);
        }

        if (old_ddps != port->ddps) {
                if (port->ddps) {
                        if (!port->input)
                                drm_dp_send_enum_path_resources(mstb->mgr, mstb, port);
                } else {
                        port->available_pbn = 0;
                        }
        }

        if (old_pdt != port->pdt && !port->input) {
                drm_dp_port_teardown_pdt(port, old_pdt);

                ret = drm_dp_port_setup_pdt(port);
                if (ret == true)
                        drm_dp_send_link_address(mstb->mgr, port->mstb);
        }

        if (created && !port->input) {
                char proppath[255];

                build_mst_prop_path(mstb, port->port_num, proppath, sizeof(proppath));
                port->connector = (*mstb->mgr->cbs->add_connector)(mstb->mgr, port, proppath);
                if (!port->connector) {
                        /* remove it from the port list */
                        mutex_lock(&mstb->mgr->lock);
                        list_del(&port->next);
                        mutex_unlock(&mstb->mgr->lock);
                        /* drop port list reference */
                        drm_dp_put_port(port);
                        goto out;
                }
                if ((port->pdt == DP_PEER_DEVICE_DP_LEGACY_CONV ||
                     port->pdt == DP_PEER_DEVICE_SST_SINK) &&
                    port->port_num >= DP_MST_LOGICAL_PORT_0) {
                        port->cached_edid = drm_get_edid(port->connector, &port->aux.ddc);
                        drm_connector_set_tile_property(port->connector);
                }
                (*mstb->mgr->cbs->register_connector)(port->connector);
        }

out:
        /* put reference to this port */
        drm_dp_put_port(port);
}

static void drm_dp_update_port(struct drm_dp_mst_branch *mstb,
                               struct drm_dp_connection_status_notify *conn_stat)
{
        struct drm_dp_mst_port *port;
        int old_pdt;
        int old_ddps;
        bool dowork = false;
        port = drm_dp_get_port(mstb, conn_stat->port_number);
        if (!port)
                return;

        old_ddps = port->ddps;
        old_pdt = port->pdt;
        port->pdt = conn_stat->peer_device_type;
        port->mcs = conn_stat->message_capability_status;
        port->ldps = conn_stat->legacy_device_plug_status;
        port->ddps = conn_stat->displayport_device_plug_status;

        if (old_ddps != port->ddps) {
                if (port->ddps) {
                        dowork = true;
                } else {
                        port->available_pbn = 0;
                }
        }
        if (old_pdt != port->pdt && !port->input) {
                drm_dp_port_teardown_pdt(port, old_pdt);

                if (drm_dp_port_setup_pdt(port))
                        dowork = true;
        }

        drm_dp_put_port(port);
        if (dowork)
                queue_work(system_long_wq, &mstb->mgr->work);

}

static struct drm_dp_mst_branch *drm_dp_get_mst_branch_device(struct drm_dp_mst_topology_mgr *mgr,
                                                               u8 lct, u8 *rad)
{
        struct drm_dp_mst_branch *mstb;
        struct drm_dp_mst_port *port;
        int i;
        /* find the port by iterating down */

        mutex_lock(&mgr->lock);
        mstb = mgr->mst_primary;

        if (!mstb)
                goto out;

        for (i = 0; i < lct - 1; i++) {
                int shift = (i % 2) ? 0 : 4;
                int port_num = (rad[i / 2] >> shift) & 0xf;

                list_for_each_entry(port, &mstb->ports, next) {
                        if (port->port_num == port_num) {
                                mstb = port->mstb;
                                if (!mstb) {
                                        DRM_ERROR("failed to lookup MSTB with lct %d, rad %02x\n", lct, rad[0]);
                                        goto out;
                                }

                                break;
                        }
                }
        }
        kref_get(&mstb->kref);
out:
        mutex_unlock(&mgr->lock);
        return mstb;
}

static struct drm_dp_mst_branch *get_mst_branch_device_by_guid_helper(
        struct drm_dp_mst_branch *mstb,
        uint8_t *guid)
{
        struct drm_dp_mst_branch *found_mstb;
        struct drm_dp_mst_port *port;

        if (memcmp(mstb->guid, guid, 16) == 0)
                return mstb;


        list_for_each_entry(port, &mstb->ports, next) {
                if (!port->mstb)
                        continue;

                found_mstb = get_mst_branch_device_by_guid_helper(port->mstb, guid);

                if (found_mstb)
                        return found_mstb;
        }

        return NULL;
}

static struct drm_dp_mst_branch *drm_dp_get_mst_branch_device_by_guid(
        struct drm_dp_mst_topology_mgr *mgr,
        uint8_t *guid)
{
        struct drm_dp_mst_branch *mstb;

        /* find the port by iterating down */
        mutex_lock(&mgr->lock);

        mstb = get_mst_branch_device_by_guid_helper(mgr->mst_primary, guid);

        if (mstb)
                kref_get(&mstb->kref);

        mutex_unlock(&mgr->lock);
        return mstb;
}

static void drm_dp_check_and_send_link_address(struct drm_dp_mst_topology_mgr *mgr,
                                               struct drm_dp_mst_branch *mstb)
{
        struct drm_dp_mst_port *port;
        struct drm_dp_mst_branch *mstb_child;
        if (!mstb->link_address_sent)
                drm_dp_send_link_address(mgr, mstb);

        list_for_each_entry(port, &mstb->ports, next) {
                if (port->input)
                        continue;

                if (!port->ddps)
                        continue;

                if (!port->available_pbn)
                        drm_dp_send_enum_path_resources(mgr, mstb, port);

                if (port->mstb) {
                        mstb_child = drm_dp_get_validated_mstb_ref(mgr, port->mstb);
                        if (mstb_child) {
                                drm_dp_check_and_send_link_address(mgr, mstb_child);
                                drm_dp_put_mst_branch_device(mstb_child);
                        }
                }
        }
}

static void drm_dp_mst_link_probe_work(struct work_struct *work)
{
        struct drm_dp_mst_topology_mgr *mgr = container_of(work, struct drm_dp_mst_topology_mgr, work);
        struct drm_dp_mst_branch *mstb;

        mutex_lock(&mgr->lock);
        mstb = mgr->mst_primary;
        if (mstb) {
                kref_get(&mstb->kref);
        }
        mutex_unlock(&mgr->lock);
        if (mstb) {
                drm_dp_check_and_send_link_address(mgr, mstb);
                drm_dp_put_mst_branch_device(mstb);
        }
}

static bool drm_dp_validate_guid(struct drm_dp_mst_topology_mgr *mgr,
                                 u8 *guid)
{
        u64 salt;

        if (memchr_inv(guid, 0, 16))
                return true;

        salt = get_jiffies_64();

        memcpy(&guid[0], &salt, sizeof(u64));
        memcpy(&guid[8], &salt, sizeof(u64));

        return false;
}

#if 0
static int build_dpcd_read(struct drm_dp_sideband_msg_tx *msg, u8 port_num, u32 offset, u8 num_bytes)
{
        struct drm_dp_sideband_msg_req_body req;

        req.req_type = DP_REMOTE_DPCD_READ;
        req.u.dpcd_read.port_number = port_num;
        req.u.dpcd_read.dpcd_address = offset;
        req.u.dpcd_read.num_bytes = num_bytes;
        drm_dp_encode_sideband_req(&req, msg);

        return 0;
}
#endif

static int drm_dp_send_sideband_msg(struct drm_dp_mst_topology_mgr *mgr,
                                    bool up, u8 *msg, int len)
{
        int ret;
        int regbase = up ? DP_SIDEBAND_MSG_UP_REP_BASE : DP_SIDEBAND_MSG_DOWN_REQ_BASE;
        int tosend, total, offset;
        int retries = 0;

retry:
        total = len;
        offset = 0;
        do {
                tosend = min3(mgr->max_dpcd_transaction_bytes, 16, total);

                ret = drm_dp_dpcd_write(mgr->aux, regbase + offset,
                                        &msg[offset],
                                        tosend);
                if (ret != tosend) {
                        if (ret == -EIO && retries < 5) {
                                retries++;
                                goto retry;
                        }
                        DRM_DEBUG_KMS("failed to dpcd write %d %d\n", tosend, ret);

                        return -EIO;
                }
                offset += tosend;
                total -= tosend;
        } while (total > 0);
        return 0;
}

static int set_hdr_from_dst_qlock(struct drm_dp_sideband_msg_hdr *hdr,
                                  struct drm_dp_sideband_msg_tx *txmsg)
{
        struct drm_dp_mst_branch *mstb = txmsg->dst;
        u8 req_type;

        /* both msg slots are full */
        if (txmsg->seqno == -1) {
                if (mstb->tx_slots[0] && mstb->tx_slots[1]) {
                        DRM_DEBUG_KMS("%s: failed to find slot\n", __func__);
                        return -EAGAIN;
                }
                if (mstb->tx_slots[0] == NULL && mstb->tx_slots[1] == NULL) {
                        txmsg->seqno = mstb->last_seqno;
                        mstb->last_seqno ^= 1;
                } else if (mstb->tx_slots[0] == NULL)
                        txmsg->seqno = 0;
                else
                        txmsg->seqno = 1;
                mstb->tx_slots[txmsg->seqno] = txmsg;
        }

        req_type = txmsg->msg[0] & 0x7f;
        if (req_type == DP_CONNECTION_STATUS_NOTIFY ||
                req_type == DP_RESOURCE_STATUS_NOTIFY)
                hdr->broadcast = 1;
        else
                hdr->broadcast = 0;
        hdr->path_msg = txmsg->path_msg;
        hdr->lct = mstb->lct;
        hdr->lcr = mstb->lct - 1;
        if (mstb->lct > 1)
                memcpy(hdr->rad, mstb->rad, mstb->lct / 2);
        hdr->seqno = txmsg->seqno;
        return 0;
}
/*
 * process a single block of the next message in the sideband queue
 */
static int process_single_tx_qlock(struct drm_dp_mst_topology_mgr *mgr,
                                   struct drm_dp_sideband_msg_tx *txmsg,
                                   bool up)
{
        u8 chunk[48];
        struct drm_dp_sideband_msg_hdr hdr;
        int len, space, idx, tosend;
        int ret;

        memset(&hdr, 0, sizeof(struct drm_dp_sideband_msg_hdr));

        if (txmsg->state == DRM_DP_SIDEBAND_TX_QUEUED) {
                txmsg->seqno = -1;
                txmsg->state = DRM_DP_SIDEBAND_TX_START_SEND;
        }

        /* make hdr from dst mst - for replies use seqno
           otherwise assign one */
        ret = set_hdr_from_dst_qlock(&hdr, txmsg);
        if (ret < 0)
                return ret;

        /* amount left to send in this message */
        len = txmsg->cur_len - txmsg->cur_offset;

        /* 48 - sideband msg size - 1 byte for data CRC, x header bytes */
        space = 48 - 1 - drm_dp_calc_sb_hdr_size(&hdr);

        tosend = min(len, space);
        if (len == txmsg->cur_len)
                hdr.somt = 1;
        if (space >= len)
                hdr.eomt = 1;


        hdr.msg_len = tosend + 1;
        drm_dp_encode_sideband_msg_hdr(&hdr, chunk, &idx);
        memcpy(&chunk[idx], &txmsg->msg[txmsg->cur_offset], tosend);
        /* add crc at end */
        drm_dp_crc_sideband_chunk_req(&chunk[idx], tosend);
        idx += tosend + 1;

        ret = drm_dp_send_sideband_msg(mgr, up, chunk, idx);
        if (ret) {
                DRM_DEBUG_KMS("sideband msg failed to send\n");
                return ret;
        }

        txmsg->cur_offset += tosend;
        if (txmsg->cur_offset == txmsg->cur_len) {
                txmsg->state = DRM_DP_SIDEBAND_TX_SENT;
                return 1;
        }
        return 0;
}

static void process_single_down_tx_qlock(struct drm_dp_mst_topology_mgr *mgr)
{
        struct drm_dp_sideband_msg_tx *txmsg;
        int ret;

        WARN_ON(!mutex_is_locked(&mgr->qlock));

        /* construct a chunk from the first msg in the tx_msg queue */
        if (list_empty(&mgr->tx_msg_downq))
                return;

        txmsg = list_first_entry(&mgr->tx_msg_downq, struct drm_dp_sideband_msg_tx, next);
        ret = process_single_tx_qlock(mgr, txmsg, false);
        if (ret == 1) {
                /* txmsg is sent it should be in the slots now */
                list_del(&txmsg->next);
        } else if (ret) {
                DRM_DEBUG_KMS("failed to send msg in q %d\n", ret);
                list_del(&txmsg->next);
                if (txmsg->seqno != -1)
                        txmsg->dst->tx_slots[txmsg->seqno] = NULL;
                txmsg->state = DRM_DP_SIDEBAND_TX_TIMEOUT;
                wake_up_all(&mgr->tx_waitq);
        }
}

/* called holding qlock */
static void process_single_up_tx_qlock(struct drm_dp_mst_topology_mgr *mgr,
                                       struct drm_dp_sideband_msg_tx *txmsg)
{
        int ret;

        /* construct a chunk from the first msg in the tx_msg queue */
        ret = process_single_tx_qlock(mgr, txmsg, true);

        if (ret != 1)
                DRM_DEBUG_KMS("failed to send msg in q %d\n", ret);

        txmsg->dst->tx_slots[txmsg->seqno] = NULL;
}

static void drm_dp_queue_down_tx(struct drm_dp_mst_topology_mgr *mgr,
                                 struct drm_dp_sideband_msg_tx *txmsg)
{
        mutex_lock(&mgr->qlock);
        list_add_tail(&txmsg->next, &mgr->tx_msg_downq);
        if (list_is_singular(&mgr->tx_msg_downq))
                process_single_down_tx_qlock(mgr);
        mutex_unlock(&mgr->qlock);
}

static void drm_dp_send_link_address(struct drm_dp_mst_topology_mgr *mgr,
                                     struct drm_dp_mst_branch *mstb)
{
        int len;
        struct drm_dp_sideband_msg_tx *txmsg;
        int ret;

        txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL);
        if (!txmsg)
                return;

        txmsg->dst = mstb;
        len = build_link_address(txmsg);

        mstb->link_address_sent = true;
        drm_dp_queue_down_tx(mgr, txmsg);

        ret = drm_dp_mst_wait_tx_reply(mstb, txmsg);
        if (ret > 0) {
                int i;

                if (txmsg->reply.reply_type == 1)
                        DRM_DEBUG_KMS("link address nak received\n");
                else {
                        DRM_DEBUG_KMS("link address reply: %d\n", txmsg->reply.u.link_addr.nports);
                        for (i = 0; i < txmsg->reply.u.link_addr.nports; i++) {
                                DRM_DEBUG_KMS("port %d: input %d, pdt: %d, pn: %d, dpcd_rev: %02x, mcs: %d, ddps: %d, ldps %d, sdp %d/%d\n", i,
                                       txmsg->reply.u.link_addr.ports[i].input_port,
                                       txmsg->reply.u.link_addr.ports[i].peer_device_type,
                                       txmsg->reply.u.link_addr.ports[i].port_number,
                                       txmsg->reply.u.link_addr.ports[i].dpcd_revision,
                                       txmsg->reply.u.link_addr.ports[i].mcs,
                                       txmsg->reply.u.link_addr.ports[i].ddps,
                                       txmsg->reply.u.link_addr.ports[i].legacy_device_plug_status,
                                       txmsg->reply.u.link_addr.ports[i].num_sdp_streams,
                                       txmsg->reply.u.link_addr.ports[i].num_sdp_stream_sinks);
                        }

                        drm_dp_check_mstb_guid(mstb, txmsg->reply.u.link_addr.guid);

                        for (i = 0; i < txmsg->reply.u.link_addr.nports; i++) {
                                drm_dp_add_port(mstb, mgr->dev, &txmsg->reply.u.link_addr.ports[i]);
                        }
                        (*mgr->cbs->hotplug)(mgr);
                }
        } else {
                mstb->link_address_sent = false;
                DRM_DEBUG_KMS("link address failed %d\n", ret);
        }

        kfree(txmsg);
}

static int drm_dp_send_enum_path_resources(struct drm_dp_mst_topology_mgr *mgr,
                                           struct drm_dp_mst_branch *mstb,
                                           struct drm_dp_mst_port *port)
{
        int len;
        struct drm_dp_sideband_msg_tx *txmsg;
        int ret;

        txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL);
        if (!txmsg)
                return -ENOMEM;

        txmsg->dst = mstb;
        len = build_enum_path_resources(txmsg, port->port_num);

        drm_dp_queue_down_tx(mgr, txmsg);

        ret = drm_dp_mst_wait_tx_reply(mstb, txmsg);
        if (ret > 0) {
                if (txmsg->reply.reply_type == 1)
                        DRM_DEBUG_KMS("enum path resources nak received\n");
                else {
                        if (port->port_num != txmsg->reply.u.path_resources.port_number)
                                DRM_ERROR("got incorrect port in response\n");
                        DRM_DEBUG_KMS("enum path resources %d: %d %d\n", txmsg->reply.u.path_resources.port_number, txmsg->reply.u.path_resources.full_payload_bw_number,
                               txmsg->reply.u.path_resources.avail_payload_bw_number);
                        port->available_pbn = txmsg->reply.u.path_resources.avail_payload_bw_number;
                }
        }

        kfree(txmsg);
        return 0;
}

static struct drm_dp_mst_port *drm_dp_get_last_connected_port_to_mstb(struct drm_dp_mst_branch *mstb)
{
        if (!mstb->port_parent)
                return NULL;

        if (mstb->port_parent->mstb != mstb)
                return mstb->port_parent;

        return drm_dp_get_last_connected_port_to_mstb(mstb->port_parent->parent);
}

static struct drm_dp_mst_branch *drm_dp_get_last_connected_port_and_mstb(struct drm_dp_mst_topology_mgr *mgr,
                                                                         struct drm_dp_mst_branch *mstb,
                                                                         int *port_num)
{
        struct drm_dp_mst_branch *rmstb = NULL;
        struct drm_dp_mst_port *found_port;
        mutex_lock(&mgr->lock);
        if (mgr->mst_primary) {
                found_port = drm_dp_get_last_connected_port_to_mstb(mstb);

                if (found_port) {
                        rmstb = found_port->parent;
                        kref_get(&rmstb->kref);
                        *port_num = found_port->port_num;
                }
        }
        mutex_unlock(&mgr->lock);
        return rmstb;
}

static int drm_dp_payload_send_msg(struct drm_dp_mst_topology_mgr *mgr,
                                   struct drm_dp_mst_port *port,
                                   int id,
                                   int pbn)
{
        struct drm_dp_sideband_msg_tx *txmsg;
        struct drm_dp_mst_branch *mstb;
        int len, ret, port_num;
        u8 sinks[DRM_DP_MAX_SDP_STREAMS];
        int i;

        port = drm_dp_get_validated_port_ref(mgr, port);
        if (!port)
                return -EINVAL;

        port_num = port->port_num;
        mstb = drm_dp_get_validated_mstb_ref(mgr, port->parent);
        if (!mstb) {
                mstb = drm_dp_get_last_connected_port_and_mstb(mgr, port->parent, &port_num);

                if (!mstb) {
                        drm_dp_put_port(port);
                        return -EINVAL;
                }
        }

        txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL);
        if (!txmsg) {
                ret = -ENOMEM;
                goto fail_put;
        }

        for (i = 0; i < port->num_sdp_streams; i++)
                sinks[i] = i;

        txmsg->dst = mstb;
        len = build_allocate_payload(txmsg, port_num,
                                     id,
                                     pbn, port->num_sdp_streams, sinks);

        drm_dp_queue_down_tx(mgr, txmsg);

        ret = drm_dp_mst_wait_tx_reply(mstb, txmsg);
        if (ret > 0) {
                if (txmsg->reply.reply_type == 1) {
                        ret = -EINVAL;
                } else
                        ret = 0;
        }
        kfree(txmsg);
fail_put:
        drm_dp_put_mst_branch_device(mstb);
        drm_dp_put_port(port);
        return ret;
}

int drm_dp_send_power_updown_phy(struct drm_dp_mst_topology_mgr *mgr,
                                 struct drm_dp_mst_port *port, bool power_up)
{
        struct drm_dp_sideband_msg_tx *txmsg;
        int len, ret;

        port = drm_dp_get_validated_port_ref(mgr, port);
        if (!port)
                return -EINVAL;

        txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL);
        if (!txmsg) {
                drm_dp_put_port(port);
                return -ENOMEM;
        }

        txmsg->dst = port->parent;
        len = build_power_updown_phy(txmsg, port->port_num, power_up);
        drm_dp_queue_down_tx(mgr, txmsg);

        ret = drm_dp_mst_wait_tx_reply(port->parent, txmsg);
        if (ret > 0) {
                if (txmsg->reply.reply_type == 1)
                        ret = -EINVAL;
                else
                        ret = 0;
        }
        kfree(txmsg);
        drm_dp_put_port(port);

        return ret;
}
EXPORT_SYMBOL(drm_dp_send_power_updown_phy);

static int drm_dp_create_payload_step1(struct drm_dp_mst_topology_mgr *mgr,
                                       int id,
                                       struct drm_dp_payload *payload)
{
        int ret;

        ret = drm_dp_dpcd_write_payload(mgr, id, payload);
        if (ret < 0) {
                payload->payload_state = 0;
                return ret;
        }
        payload->payload_state = DP_PAYLOAD_LOCAL;
        return 0;
}

static int drm_dp_create_payload_step2(struct drm_dp_mst_topology_mgr *mgr,
                                       struct drm_dp_mst_port *port,
                                       int id,
                                       struct drm_dp_payload *payload)
{
        int ret;
        ret = drm_dp_payload_send_msg(mgr, port, id, port->vcpi.pbn);
        if (ret < 0)
                return ret;
        payload->payload_state = DP_PAYLOAD_REMOTE;
        return ret;
}

static int drm_dp_destroy_payload_step1(struct drm_dp_mst_topology_mgr *mgr,
                                        struct drm_dp_mst_port *port,
                                        int id,
                                        struct drm_dp_payload *payload)
{
        DRM_DEBUG_KMS("\n");
        /* its okay for these to fail */
        if (port) {
                drm_dp_payload_send_msg(mgr, port, id, 0);
        }

        drm_dp_dpcd_write_payload(mgr, id, payload);
        payload->payload_state = DP_PAYLOAD_DELETE_LOCAL;
        return 0;
}

static int drm_dp_destroy_payload_step2(struct drm_dp_mst_topology_mgr *mgr,
                                        int id,
                                        struct drm_dp_payload *payload)
{
        payload->payload_state = 0;
        return 0;
}

/**
 * drm_dp_update_payload_part1() - Execute payload update part 1
 * @mgr: manager to use.
 *
 * This iterates over all proposed virtual channels, and tries to
 * allocate space in the link for them. For 0->slots transitions,
 * this step just writes the VCPI to the MST device. For slots->0
 * transitions, this writes the updated VCPIs and removes the
 * remote VC payloads.
 *
 * after calling this the driver should generate ACT and payload
 * packets.
 */
int drm_dp_update_payload_part1(struct drm_dp_mst_topology_mgr *mgr)
{
        int i, j;
        int cur_slots = 1;
        struct drm_dp_payload req_payload;
        struct drm_dp_mst_port *port;

        mutex_lock(&mgr->payload_lock);
        for (i = 0; i < mgr->max_payloads; i++) {
                /* solve the current payloads - compare to the hw ones
                   - update the hw view */
                req_payload.start_slot = cur_slots;
                if (mgr->proposed_vcpis[i]) {
                        port = container_of(mgr->proposed_vcpis[i], struct drm_dp_mst_port, vcpi);
                        port = drm_dp_get_validated_port_ref(mgr, port);
                        if (!port) {
                                mutex_unlock(&mgr->payload_lock);
                                return -EINVAL;
                        }
                        req_payload.num_slots = mgr->proposed_vcpis[i]->num_slots;
                        req_payload.vcpi = mgr->proposed_vcpis[i]->vcpi;
                } else {
                        port = NULL;
                        req_payload.num_slots = 0;
                }

                if (mgr->payloads[i].start_slot != req_payload.start_slot) {
                        mgr->payloads[i].start_slot = req_payload.start_slot;
                }
                /* work out what is required to happen with this payload */
                if (mgr->payloads[i].num_slots != req_payload.num_slots) {

                        /* need to push an update for this payload */
                        if (req_payload.num_slots) {
                                drm_dp_create_payload_step1(mgr, mgr->proposed_vcpis[i]->vcpi, &req_payload);
                                mgr->payloads[i].num_slots = req_payload.num_slots;
                                mgr->payloads[i].vcpi = req_payload.vcpi;
                        } else if (mgr->payloads[i].num_slots) {
                                mgr->payloads[i].num_slots = 0;
                                drm_dp_destroy_payload_step1(mgr, port, mgr->payloads[i].vcpi, &mgr->payloads[i]);
                                req_payload.payload_state = mgr->payloads[i].payload_state;
                                mgr->payloads[i].start_slot = 0;
                        }
                        mgr->payloads[i].payload_state = req_payload.payload_state;
                }
                cur_slots += req_payload.num_slots;

                if (port)
                        drm_dp_put_port(port);
        }

        for (i = 0; i < mgr->max_payloads; i++) {
                if (mgr->payloads[i].payload_state == DP_PAYLOAD_DELETE_LOCAL) {
                        DRM_DEBUG_KMS("removing payload %d\n", i);
                        for (j = i; j < mgr->max_payloads - 1; j++) {
                                memcpy(&mgr->payloads[j], &mgr->payloads[j + 1], sizeof(struct drm_dp_payload));
                                mgr->proposed_vcpis[j] = mgr->proposed_vcpis[j + 1];
                                if (mgr->proposed_vcpis[j] && mgr->proposed_vcpis[j]->num_slots) {
                                        set_bit(j + 1, &mgr->payload_mask);
                                } else {
                                        clear_bit(j + 1, &mgr->payload_mask);
                                }
                        }
                        memset(&mgr->payloads[mgr->max_payloads - 1], 0, sizeof(struct drm_dp_payload));
                        mgr->proposed_vcpis[mgr->max_payloads - 1] = NULL;
                        clear_bit(mgr->max_payloads, &mgr->payload_mask);

                }
        }
        mutex_unlock(&mgr->payload_lock);

        return 0;
}
EXPORT_SYMBOL(drm_dp_update_payload_part1);

/**
 * drm_dp_update_payload_part2() - Execute payload update part 2
 * @mgr: manager to use.
 *
 * This iterates over all proposed virtual channels, and tries to
 * allocate space in the link for them. For 0->slots transitions,
 * this step writes the remote VC payload commands. For slots->0
 * this just resets some internal state.
 */
int drm_dp_update_payload_part2(struct drm_dp_mst_topology_mgr *mgr)
{
        struct drm_dp_mst_port *port;
        int i;
        int ret = 0;
        mutex_lock(&mgr->payload_lock);
        for (i = 0; i < mgr->max_payloads; i++) {

                if (!mgr->proposed_vcpis[i])
                        continue;

                port = container_of(mgr->proposed_vcpis[i], struct drm_dp_mst_port, vcpi);

                DRM_DEBUG_KMS("payload %d %d\n", i, mgr->payloads[i].payload_state);
                if (mgr->payloads[i].payload_state == DP_PAYLOAD_LOCAL) {
                        ret = drm_dp_create_payload_step2(mgr, port, mgr->proposed_vcpis[i]->vcpi, &mgr->payloads[i]);
                } else if (mgr->payloads[i].payload_state == DP_PAYLOAD_DELETE_LOCAL) {
                        ret = drm_dp_destroy_payload_step2(mgr, mgr->proposed_vcpis[i]->vcpi, &mgr->payloads[i]);
                }
                if (ret) {
                        mutex_unlock(&mgr->payload_lock);
                        return ret;
                }
        }
        mutex_unlock(&mgr->payload_lock);
        return 0;
}
EXPORT_SYMBOL(drm_dp_update_payload_part2);

#if 0 /* unused as of yet */
static int drm_dp_send_dpcd_read(struct drm_dp_mst_topology_mgr *mgr,
                                 struct drm_dp_mst_port *port,
                                 int offset, int size)
{
        int len;
        struct drm_dp_sideband_msg_tx *txmsg;

        txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL);
        if (!txmsg)
                return -ENOMEM;

        len = build_dpcd_read(txmsg, port->port_num, 0, 8);
        txmsg->dst = port->parent;

        drm_dp_queue_down_tx(mgr, txmsg);

        return 0;
}
#endif

static int drm_dp_send_dpcd_write(struct drm_dp_mst_topology_mgr *mgr,
                                  struct drm_dp_mst_port *port,
                                  int offset, int size, u8 *bytes)
{
        int len;
        int ret;
        struct drm_dp_sideband_msg_tx *txmsg;
        struct drm_dp_mst_branch *mstb;

        mstb = drm_dp_get_validated_mstb_ref(mgr, port->parent);
        if (!mstb)
                return -EINVAL;

        txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL);
        if (!txmsg) {
                ret = -ENOMEM;
                goto fail_put;
        }

        len = build_dpcd_write(txmsg, port->port_num, offset, size, bytes);
        txmsg->dst = mstb;

        drm_dp_queue_down_tx(mgr, txmsg);

        ret = drm_dp_mst_wait_tx_reply(mstb, txmsg);
        if (ret > 0) {
                if (txmsg->reply.reply_type == 1) {
                        ret = -EINVAL;
                } else
                        ret = 0;
        }
        kfree(txmsg);
fail_put:
        drm_dp_put_mst_branch_device(mstb);
        return ret;
}

static int drm_dp_encode_up_ack_reply(struct drm_dp_sideband_msg_tx *msg, u8 req_type)
{
        struct drm_dp_sideband_msg_reply_body reply;

        reply.reply_type = 0;
        reply.req_type = req_type;
        drm_dp_encode_sideband_reply(&reply, msg);
        return 0;
}

static int drm_dp_send_up_ack_reply(struct drm_dp_mst_topology_mgr *mgr,
                                    struct drm_dp_mst_branch *mstb,
                                    int req_type, int seqno, bool broadcast)
{
        struct drm_dp_sideband_msg_tx *txmsg;

        txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL);
        if (!txmsg)
                return -ENOMEM;

        txmsg->dst = mstb;
        txmsg->seqno = seqno;
        drm_dp_encode_up_ack_reply(txmsg, req_type);

        mutex_lock(&mgr->qlock);

        process_single_up_tx_qlock(mgr, txmsg);

        mutex_unlock(&mgr->qlock);

        kfree(txmsg);
        return 0;
}

static bool drm_dp_get_vc_payload_bw(int dp_link_bw,
                                     int dp_link_count,
                                     int *out)
{
        switch (dp_link_bw) {
        default:
                DRM_DEBUG_KMS("invalid link bandwidth in DPCD: %x (link count: %d)\n",
                              dp_link_bw, dp_link_count);
                return false;

        case DP_LINK_BW_1_62:
                *out = 3 * dp_link_count;
                break;
        case DP_LINK_BW_2_7:
                *out = 5 * dp_link_count;
                break;
        case DP_LINK_BW_5_4:
                *out = 10 * dp_link_count;
                break;
        case DP_LINK_BW_8_1:
                *out = 15 * dp_link_count;
                break;
        }
        return true;
}

/**
 * drm_dp_mst_topology_mgr_set_mst() - Set the MST state for a topology manager
 * @mgr: manager to set state for
 * @mst_state: true to enable MST on this connector - false to disable.
 *
 * This is called by the driver when it detects an MST capable device plugged
 * into a DP MST capable port, or when a DP MST capable device is unplugged.
 */
int drm_dp_mst_topology_mgr_set_mst(struct drm_dp_mst_topology_mgr *mgr, bool mst_state)
{
        int ret = 0;
        struct drm_dp_mst_branch *mstb = NULL;

        mutex_lock(&mgr->lock);
        if (mst_state == mgr->mst_state)
                goto out_unlock;

        mgr->mst_state = mst_state;
        /* set the device into MST mode */
        if (mst_state) {
                WARN_ON(mgr->mst_primary);

                /* get dpcd info */
                ret = drm_dp_dpcd_read(mgr->aux, DP_DPCD_REV, mgr->dpcd, DP_RECEIVER_CAP_SIZE);
                if (ret != DP_RECEIVER_CAP_SIZE) {
                        DRM_DEBUG_KMS("failed to read DPCD\n");
                        goto out_unlock;
                }

                if (!drm_dp_get_vc_payload_bw(mgr->dpcd[1],
                                              mgr->dpcd[2] & DP_MAX_LANE_COUNT_MASK,
                                              &mgr->pbn_div)) {
                        ret = -EINVAL;
                        goto out_unlock;
                }

                /* add initial branch device at LCT 1 */
                mstb = drm_dp_add_mst_branch_device(1, NULL);
                if (mstb == NULL) {
                        ret = -ENOMEM;
                        goto out_unlock;
                }
                mstb->mgr = mgr;

                /* give this the main reference */
                mgr->mst_primary = mstb;
                kref_get(&mgr->mst_primary->kref);

                ret = drm_dp_dpcd_writeb(mgr->aux, DP_MSTM_CTRL,
                                                         DP_MST_EN | DP_UP_REQ_EN | DP_UPSTREAM_IS_SRC);
                if (ret < 0) {
                        goto out_unlock;
                }

                {
                        struct drm_dp_payload reset_pay;
                        reset_pay.start_slot = 0;
                        reset_pay.num_slots = 0x3f;
                        drm_dp_dpcd_write_payload(mgr, 0, &reset_pay);
                }

                queue_work(system_long_wq, &mgr->work);

                ret = 0;
        } else {
                /* disable MST on the device */
                mstb = mgr->mst_primary;
                mgr->mst_primary = NULL;
                /* this can fail if the device is gone */
                drm_dp_dpcd_writeb(mgr->aux, DP_MSTM_CTRL, 0);
                ret = 0;
                memset(mgr->payloads, 0, mgr->max_payloads * sizeof(struct drm_dp_payload));
                mgr->payload_mask = 0;
                set_bit(0, &mgr->payload_mask);
                mgr->vcpi_mask = 0;
        }

out_unlock:
        mutex_unlock(&mgr->lock);
        if (mstb)
                drm_dp_put_mst_branch_device(mstb);
        return ret;

}
EXPORT_SYMBOL(drm_dp_mst_topology_mgr_set_mst);

/**
 * drm_dp_mst_topology_mgr_suspend() - suspend the MST manager
 * @mgr: manager to suspend
 *
 * This function tells the MST device that we can't handle UP messages
 * anymore. This should stop it from sending any since we are suspended.
 */
void drm_dp_mst_topology_mgr_suspend(struct drm_dp_mst_topology_mgr *mgr)
{
        mutex_lock(&mgr->lock);
        drm_dp_dpcd_writeb(mgr->aux, DP_MSTM_CTRL,
                           DP_MST_EN | DP_UPSTREAM_IS_SRC);
        mutex_unlock(&mgr->lock);
        flush_work(&mgr->work);
        flush_work(&mgr->destroy_connector_work);
}
EXPORT_SYMBOL(drm_dp_mst_topology_mgr_suspend);

/**
 * drm_dp_mst_topology_mgr_resume() - resume the MST manager
 * @mgr: manager to resume
 *
 * This will fetch DPCD and see if the device is still there,
 * if it is, it will rewrite the MSTM control bits, and return.
 *
 * if the device fails this returns -1, and the driver should do
 * a full MST reprobe, in case we were undocked.
 */
int drm_dp_mst_topology_mgr_resume(struct drm_dp_mst_topology_mgr *mgr)
{
        int ret = 0;

        mutex_lock(&mgr->lock);

        if (mgr->mst_primary) {
                int sret;
                u8 guid[16];

                sret = drm_dp_dpcd_read(mgr->aux, DP_DPCD_REV, mgr->dpcd, DP_RECEIVER_CAP_SIZE);
                if (sret != DP_RECEIVER_CAP_SIZE) {
                        DRM_DEBUG_KMS("dpcd read failed - undocked during suspend?\n");
                        ret = -1;
                        goto out_unlock;
                }

                ret = drm_dp_dpcd_writeb(mgr->aux, DP_MSTM_CTRL,
                                         DP_MST_EN | DP_UP_REQ_EN | DP_UPSTREAM_IS_SRC);
                if (ret < 0) {
                        DRM_DEBUG_KMS("mst write failed - undocked during suspend?\n");
                        ret = -1;
                        goto out_unlock;
                }

                /* Some hubs forget their guids after they resume */
                sret = drm_dp_dpcd_read(mgr->aux, DP_GUID, guid, 16);
                if (sret != 16) {
                        DRM_DEBUG_KMS("dpcd read failed - undocked during suspend?\n");
                        ret = -1;
                        goto out_unlock;
                }
                drm_dp_check_mstb_guid(mgr->mst_primary, guid);

                ret = 0;
        } else
                ret = -1;

out_unlock:
        mutex_unlock(&mgr->lock);
        return ret;
}
EXPORT_SYMBOL(drm_dp_mst_topology_mgr_resume);

static bool drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up)
{
        int len;
        u8 replyblock[32];
        int replylen, origlen, curreply;
        int ret;
        struct drm_dp_sideband_msg_rx *msg;
        int basereg = up ? DP_SIDEBAND_MSG_UP_REQ_BASE : DP_SIDEBAND_MSG_DOWN_REP_BASE;
        msg = up ? &mgr->up_req_recv : &mgr->down_rep_recv;

        len = min(mgr->max_dpcd_transaction_bytes, 16);
        ret = drm_dp_dpcd_read(mgr->aux, basereg,
                               replyblock, len);
        if (ret != len) {
                DRM_DEBUG_KMS("failed to read DPCD down rep %d %d\n", len, ret);
                return false;
        }
        ret = drm_dp_sideband_msg_build(msg, replyblock, len, true);
        if (!ret) {
                DRM_DEBUG_KMS("sideband msg build failed %d\n", replyblock[0]);
                return false;
        }
        replylen = msg->curchunk_len + msg->curchunk_hdrlen;

        origlen = replylen;
        replylen -= len;
        curreply = len;
        while (replylen > 0) {
                len = min3(replylen, mgr->max_dpcd_transaction_bytes, 16);
                ret = drm_dp_dpcd_read(mgr->aux, basereg + curreply,
                                    replyblock, len);
                if (ret != len) {
                        DRM_DEBUG_KMS("failed to read a chunk (len %d, ret %d)\n",
                                      len, ret);
                        return false;
                }

                ret = drm_dp_sideband_msg_build(msg, replyblock, len, false);
                if (!ret) {
                        DRM_DEBUG_KMS("failed to build sideband msg\n");
                        return false;
                }

                curreply += len;
                replylen -= len;
        }
        return true;
}

static int drm_dp_mst_handle_down_rep(struct drm_dp_mst_topology_mgr *mgr)
{
        int ret = 0;

        if (!drm_dp_get_one_sb_msg(mgr, false)) {
                memset(&mgr->down_rep_recv, 0,
                       sizeof(struct drm_dp_sideband_msg_rx));
                return 0;
        }

        if (mgr->down_rep_recv.have_eomt) {
                struct drm_dp_sideband_msg_tx *txmsg;
                struct drm_dp_mst_branch *mstb;
                int slot = -1;
                mstb = drm_dp_get_mst_branch_device(mgr,
                                                    mgr->down_rep_recv.initial_hdr.lct,
                                                    mgr->down_rep_recv.initial_hdr.rad);

                if (!mstb) {
                        DRM_DEBUG_KMS("Got MST reply from unknown device %d\n", mgr->down_rep_recv.initial_hdr.lct);
                        memset(&mgr->down_rep_recv, 0, sizeof(struct drm_dp_sideband_msg_rx));
                        return 0;
                }

                /* find the message */
                slot = mgr->down_rep_recv.initial_hdr.seqno;
                mutex_lock(&mgr->qlock);
                txmsg = mstb->tx_slots[slot];
                /* remove from slots */
                mutex_unlock(&mgr->qlock);

                if (!txmsg) {
                        DRM_DEBUG_KMS("Got MST reply with no msg %p %d %d %02x %02x\n",
                               mstb,
                               mgr->down_rep_recv.initial_hdr.seqno,
                               mgr->down_rep_recv.initial_hdr.lct,
                                      mgr->down_rep_recv.initial_hdr.rad[0],
                                      mgr->down_rep_recv.msg[0]);
                        drm_dp_put_mst_branch_device(mstb);
                        memset(&mgr->down_rep_recv, 0, sizeof(struct drm_dp_sideband_msg_rx));
                        return 0;
                }

                drm_dp_sideband_parse_reply(&mgr->down_rep_recv, &txmsg->reply);
                if (txmsg->reply.reply_type == 1) {
                        DRM_DEBUG_KMS("Got NAK reply: req 0x%02x, reason 0x%02x, nak data 0x%02x\n", txmsg->reply.req_type, txmsg->reply.u.nak.reason, txmsg->reply.u.nak.nak_data);
                }

                memset(&mgr->down_rep_recv, 0, sizeof(struct drm_dp_sideband_msg_rx));
                drm_dp_put_mst_branch_device(mstb);

                mutex_lock(&mgr->qlock);
                txmsg->state = DRM_DP_SIDEBAND_TX_RX;
                mstb->tx_slots[slot] = NULL;
                mutex_unlock(&mgr->qlock);

                wake_up_all(&mgr->tx_waitq);
        }
        return ret;
}

static int drm_dp_mst_handle_up_req(struct drm_dp_mst_topology_mgr *mgr)
{
        int ret = 0;

        if (!drm_dp_get_one_sb_msg(mgr, true)) {
                memset(&mgr->up_req_recv, 0,
                       sizeof(struct drm_dp_sideband_msg_rx));
                return 0;
        }

        if (mgr->up_req_recv.have_eomt) {
                struct drm_dp_sideband_msg_req_body msg;
                struct drm_dp_mst_branch *mstb = NULL;
                bool seqno;

                if (!mgr->up_req_recv.initial_hdr.broadcast) {
                        mstb = drm_dp_get_mst_branch_device(mgr,
                                                            mgr->up_req_recv.initial_hdr.lct,
                                                            mgr->up_req_recv.initial_hdr.rad);
                        if (!mstb) {
                                DRM_DEBUG_KMS("Got MST reply from unknown device %d\n", mgr->up_req_recv.initial_hdr.lct);
                                memset(&mgr->up_req_recv, 0, sizeof(struct drm_dp_sideband_msg_rx));
                                return 0;
                        }
                }

                seqno = mgr->up_req_recv.initial_hdr.seqno;
                drm_dp_sideband_parse_req(&mgr->up_req_recv, &msg);

                if (msg.req_type == DP_CONNECTION_STATUS_NOTIFY) {
                        drm_dp_send_up_ack_reply(mgr, mgr->mst_primary, msg.req_type, seqno, false);

                        if (!mstb)
                                mstb = drm_dp_get_mst_branch_device_by_guid(mgr, msg.u.conn_stat.guid);

                        if (!mstb) {
                                DRM_DEBUG_KMS("Got MST reply from unknown device %d\n", mgr->up_req_recv.initial_hdr.lct);
                                memset(&mgr->up_req_recv, 0, sizeof(struct drm_dp_sideband_msg_rx));
                                return 0;
                        }

                        drm_dp_update_port(mstb, &msg.u.conn_stat);

                        DRM_DEBUG_KMS("Got CSN: pn: %d ldps:%d ddps: %d mcs: %d ip: %d pdt: %d\n", msg.u.conn_stat.port_number, msg.u.conn_stat.legacy_device_plug_status, msg.u.conn_stat.displayport_device_plug_status, msg.u.conn_stat.message_capability_status, msg.u.conn_stat.input_port, msg.u.conn_stat.peer_device_type);
                        (*mgr->cbs->hotplug)(mgr);

                } else if (msg.req_type == DP_RESOURCE_STATUS_NOTIFY) {
                        drm_dp_send_up_ack_reply(mgr, mgr->mst_primary, msg.req_type, seqno, false);
                        if (!mstb)
                                mstb = drm_dp_get_mst_branch_device_by_guid(mgr, msg.u.resource_stat.guid);

                        if (!mstb) {
                                DRM_DEBUG_KMS("Got MST reply from unknown device %d\n", mgr->up_req_recv.initial_hdr.lct);
                                memset(&mgr->up_req_recv, 0, sizeof(struct drm_dp_sideband_msg_rx));
                                return 0;
                        }

                        DRM_DEBUG_KMS("Got RSN: pn: %d avail_pbn %d\n", msg.u.resource_stat.port_number, msg.u.resource_stat.available_pbn);
                }

                if (mstb)
                        drm_dp_put_mst_branch_device(mstb);

                memset(&mgr->up_req_recv, 0, sizeof(struct drm_dp_sideband_msg_rx));
        }
        return ret;
}

/**
 * drm_dp_mst_hpd_irq() - MST hotplug IRQ notify
 * @mgr: manager to notify irq for.
 * @esi: 4 bytes from SINK_COUNT_ESI
 * @handled: whether the hpd interrupt was consumed or not
 *
 * This should be called from the driver when it detects a short IRQ,
 * along with the value of the DEVICE_SERVICE_IRQ_VECTOR_ESI0. The
 * topology manager will process the sideband messages received as a result
 * of this.
 */
int drm_dp_mst_hpd_irq(struct drm_dp_mst_topology_mgr *mgr, u8 *esi, bool *handled)
{
        int ret = 0;
        int sc;
        *handled = false;
        sc = esi[0] & 0x3f;

        if (sc != mgr->sink_count) {
                mgr->sink_count = sc;
                *handled = true;
        }

        if (esi[1] & DP_DOWN_REP_MSG_RDY) {
                ret = drm_dp_mst_handle_down_rep(mgr);
                *handled = true;
        }

        if (esi[1] & DP_UP_REQ_MSG_RDY) {
                ret |= drm_dp_mst_handle_up_req(mgr);
                *handled = true;
        }

        drm_dp_mst_kick_tx(mgr);
        return ret;
}
EXPORT_SYMBOL(drm_dp_mst_hpd_irq);

/**
 * drm_dp_mst_detect_port() - get connection status for an MST port
 * @connector: DRM connector for this port
 * @mgr: manager for this port
 * @port: unverified pointer to a port
 *
 * This returns the current connection state for a port. It validates the
 * port pointer still exists so the caller doesn't require a reference
 */
enum drm_connector_status drm_dp_mst_detect_port(struct drm_connector *connector,
                                                 struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_port *port)
{
        enum drm_connector_status status = connector_status_disconnected;

        /* we need to search for the port in the mgr in case its gone */
        port = drm_dp_get_validated_port_ref(mgr, port);
        if (!port)
                return connector_status_disconnected;

        if (!port->ddps)
                goto out;

        switch (port->pdt) {
        case DP_PEER_DEVICE_NONE:
        case DP_PEER_DEVICE_MST_BRANCHING:
                break;

        case DP_PEER_DEVICE_SST_SINK:
                status = connector_status_connected;
                /* for logical ports - cache the EDID */
                if (port->port_num >= 8 && !port->cached_edid) {
                        port->cached_edid = drm_get_edid(connector, &port->aux.ddc);
                }
                break;
        case DP_PEER_DEVICE_DP_LEGACY_CONV:
                if (port->ldps)
                        status = connector_status_connected;
                break;
        }
out:
        drm_dp_put_port(port);
        return status;
}
EXPORT_SYMBOL(drm_dp_mst_detect_port);

/**
 * drm_dp_mst_port_has_audio() - Check whether port has audio capability or not
 * @mgr: manager for this port
 * @port: unverified pointer to a port.
 *
 * This returns whether the port supports audio or not.
 */
bool drm_dp_mst_port_has_audio(struct drm_dp_mst_topology_mgr *mgr,
                                        struct drm_dp_mst_port *port)
{
        bool ret = false;

        port = drm_dp_get_validated_port_ref(mgr, port);
        if (!port)
                return ret;
        ret = port->has_audio;
        drm_dp_put_port(port);
        return ret;
}
EXPORT_SYMBOL(drm_dp_mst_port_has_audio);

/**
 * drm_dp_mst_get_edid() - get EDID for an MST port
 * @connector: toplevel connector to get EDID for
 * @mgr: manager for this port
 * @port: unverified pointer to a port.
 *
 * This returns an EDID for the port connected to a connector,
 * It validates the pointer still exists so the caller doesn't require a
 * reference.
 */
struct edid *drm_dp_mst_get_edid(struct drm_connector *connector, struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_port *port)
{
        struct edid *edid = NULL;

        /* we need to search for the port in the mgr in case its gone */
        port = drm_dp_get_validated_port_ref(mgr, port);
        if (!port)
                return NULL;

        if (port->cached_edid)
                edid = drm_edid_duplicate(port->cached_edid);
        else {
                edid = drm_get_edid(connector, &port->aux.ddc);
                drm_connector_set_tile_property(connector);
        }
        port->has_audio = drm_detect_monitor_audio(edid);
        drm_dp_put_port(port);
        return edid;
}
EXPORT_SYMBOL(drm_dp_mst_get_edid);

/**
 * drm_dp_find_vcpi_slots() - find slots for this PBN value
 * @mgr: manager to use
 * @pbn: payload bandwidth to convert into slots.
 */
int drm_dp_find_vcpi_slots(struct drm_dp_mst_topology_mgr *mgr,
                           int pbn)
{
        int num_slots;

        num_slots = DIV_ROUND_UP(pbn, mgr->pbn_div);

        /* max. time slots - one slot for MTP header */
        if (num_slots > 63)
                return -ENOSPC;
        return num_slots;
}
EXPORT_SYMBOL(drm_dp_find_vcpi_slots);

static int drm_dp_init_vcpi(struct drm_dp_mst_topology_mgr *mgr,
                            struct drm_dp_vcpi *vcpi, int pbn, int slots)
{
        int ret;

        /* max. time slots - one slot for MTP header */
        if (slots > 63)
                return -ENOSPC;

        vcpi->pbn = pbn;
        vcpi->aligned_pbn = slots * mgr->pbn_div;
        vcpi->num_slots = slots;

        ret = drm_dp_mst_assign_payload_id(mgr, vcpi);
        if (ret < 0)
                return ret;
        return 0;
}

/**
 * drm_dp_atomic_find_vcpi_slots() - Find and add vcpi slots to the state
 * @state: global atomic state
 * @mgr: MST topology manager for the port
 * @port: port to find vcpi slots for
 * @pbn: bandwidth required for the mode in PBN
 *
 * RETURNS:
 * Total slots in the atomic state assigned for this port or error
 */
int drm_dp_atomic_find_vcpi_slots(struct drm_atomic_state *state,
                                  struct drm_dp_mst_topology_mgr *mgr,
                                  struct drm_dp_mst_port *port, int pbn)
{
        struct drm_dp_mst_topology_state *topology_state;
        int req_slots;

        topology_state = drm_atomic_get_mst_topology_state(state, mgr);
        if (IS_ERR(topology_state))
                return PTR_ERR(topology_state);

        port = drm_dp_get_validated_port_ref(mgr, port);
        if (port == NULL)
                return -EINVAL;
        req_slots = DIV_ROUND_UP(pbn, mgr->pbn_div);
        DRM_DEBUG_KMS("vcpi slots req=%d, avail=%d\n",
                        req_slots, topology_state->avail_slots);

        if (req_slots > topology_state->avail_slots) {
                drm_dp_put_port(port);
                return -ENOSPC;
        }

        topology_state->avail_slots -= req_slots;
        DRM_DEBUG_KMS("vcpi slots avail=%d", topology_state->avail_slots);

        drm_dp_put_port(port);
        return req_slots;
}
EXPORT_SYMBOL(drm_dp_atomic_find_vcpi_slots);

/**
 * drm_dp_atomic_release_vcpi_slots() - Release allocated vcpi slots
 * @state: global atomic state
 * @mgr: MST topology manager for the port
 * @slots: number of vcpi slots to release
 *
 * RETURNS:
 * 0 if @slots were added back to &drm_dp_mst_topology_state->avail_slots or
 * negative error code
 */
int drm_dp_atomic_release_vcpi_slots(struct drm_atomic_state *state,
                                     struct drm_dp_mst_topology_mgr *mgr,
                                     int slots)
{
        struct drm_dp_mst_topology_state *topology_state;

        topology_state = drm_atomic_get_mst_topology_state(state, mgr);
        if (IS_ERR(topology_state))
                return PTR_ERR(topology_state);

        /* We cannot rely on port->vcpi.num_slots to update
         * topology_state->avail_slots as the port may not exist if the parent
         * branch device was unplugged. This should be fixed by tracking
         * per-port slot allocation in drm_dp_mst_topology_state instead of
         * depending on the caller to tell us how many slots to release.
         */
        topology_state->avail_slots += slots;
        DRM_DEBUG_KMS("vcpi slots released=%d, avail=%d\n",
                        slots, topology_state->avail_slots);

        return 0;
}
EXPORT_SYMBOL(drm_dp_atomic_release_vcpi_slots);

/**
 * drm_dp_mst_allocate_vcpi() - Allocate a virtual channel
 * @mgr: manager for this port
 * @port: port to allocate a virtual channel for.
 * @pbn: payload bandwidth number to request
 * @slots: returned number of slots for this PBN.
 */
bool drm_dp_mst_allocate_vcpi(struct drm_dp_mst_topology_mgr *mgr,
                              struct drm_dp_mst_port *port, int pbn, int slots)
{
        int ret;

        port = drm_dp_get_validated_port_ref(mgr, port);
        if (!port)
                return false;

        if (slots < 0)
                return false;

        if (port->vcpi.vcpi > 0) {
                DRM_DEBUG_KMS("payload: vcpi %d already allocated for pbn %d - requested pbn %d\n", port->vcpi.vcpi, port->vcpi.pbn, pbn);
                if (pbn == port->vcpi.pbn) {
                        drm_dp_put_port(port);
                        return true;
                }
        }

        ret = drm_dp_init_vcpi(mgr, &port->vcpi, pbn, slots);
        if (ret) {
                DRM_DEBUG_KMS("failed to init vcpi slots=%d max=63 ret=%d\n",
                                DIV_ROUND_UP(pbn, mgr->pbn_div), ret);
                goto out;
        }
        DRM_DEBUG_KMS("initing vcpi for pbn=%d slots=%d\n",
                        pbn, port->vcpi.num_slots);

        drm_dp_put_port(port);
        return true;
out:
        return false;
}
EXPORT_SYMBOL(drm_dp_mst_allocate_vcpi);

int drm_dp_mst_get_vcpi_slots(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_port *port)
{
        int slots = 0;
        port = drm_dp_get_validated_port_ref(mgr, port);
        if (!port)
                return slots;

        slots = port->vcpi.num_slots;
        drm_dp_put_port(port);
        return slots;
}
EXPORT_SYMBOL(drm_dp_mst_get_vcpi_slots);

/**
 * drm_dp_mst_reset_vcpi_slots() - Reset number of slots to 0 for VCPI
 * @mgr: manager for this port
 * @port: unverified pointer to a port.
 *
 * This just resets the number of slots for the ports VCPI for later programming.
 */
void drm_dp_mst_reset_vcpi_slots(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_port *port)
{
        port = drm_dp_get_validated_port_ref(mgr, port);
        if (!port)
                return;
        port->vcpi.num_slots = 0;
        drm_dp_put_port(port);
}
EXPORT_SYMBOL(drm_dp_mst_reset_vcpi_slots);

/**
 * drm_dp_mst_deallocate_vcpi() - deallocate a VCPI
 * @mgr: manager for this port
 * @port: unverified port to deallocate vcpi for
 */
void drm_dp_mst_deallocate_vcpi(struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_port *port)
{
        port = drm_dp_get_validated_port_ref(mgr, port);
        if (!port)
                return;

        drm_dp_mst_put_payload_id(mgr, port->vcpi.vcpi);
        port->vcpi.num_slots = 0;
        port->vcpi.pbn = 0;
        port->vcpi.aligned_pbn = 0;
        port->vcpi.vcpi = 0;
        drm_dp_put_port(port);
}
EXPORT_SYMBOL(drm_dp_mst_deallocate_vcpi);

static int drm_dp_dpcd_write_payload(struct drm_dp_mst_topology_mgr *mgr,
                                     int id, struct drm_dp_payload *payload)
{
        u8 payload_alloc[3], status;
        int ret;
        int retries = 0;

        drm_dp_dpcd_writeb(mgr->aux, DP_PAYLOAD_TABLE_UPDATE_STATUS,
                           DP_PAYLOAD_TABLE_UPDATED);

        payload_alloc[0] = id;
        payload_alloc[1] = payload->start_slot;
        payload_alloc[2] = payload->num_slots;

        ret = drm_dp_dpcd_write(mgr->aux, DP_PAYLOAD_ALLOCATE_SET, payload_alloc, 3);
        if (ret != 3) {
                DRM_DEBUG_KMS("failed to write payload allocation %d\n", ret);
                goto fail;
        }

retry:
        ret = drm_dp_dpcd_readb(mgr->aux, DP_PAYLOAD_TABLE_UPDATE_STATUS, &status);
        if (ret < 0) {
                DRM_DEBUG_KMS("failed to read payload table status %d\n", ret);
                goto fail;
        }

        if (!(status & DP_PAYLOAD_TABLE_UPDATED)) {
                retries++;
                if (retries < 20) {
                        usleep_range(10000, 20000);
                        goto retry;
                }
                DRM_DEBUG_KMS("status not set after read payload table status %d\n", status);
                ret = -EINVAL;
                goto fail;
        }
        ret = 0;
fail:
        return ret;
}


/**
 * drm_dp_check_act_status() - Check ACT handled status.
 * @mgr: manager to use
 *
 * Check the payload status bits in the DPCD for ACT handled completion.
 */
int drm_dp_check_act_status(struct drm_dp_mst_topology_mgr *mgr)
{
#if 0
        /*
         * There doesn't seem to be any recommended retry count or timeout in
         * the MST specification. Since some hubs have been observed to take
         * over 1 second to update their payload allocations under certain
         * conditions, we use a rather large timeout value.
         */
        const int timeout_ms = 3000;
        int ret, status;

        ret = readx_poll_timeout(do_get_act_status, mgr->aux, status,
                                 status & DP_PAYLOAD_ACT_HANDLED || status < 0,
                                 200, timeout_ms * USEC_PER_MSEC);
        if (ret < 0 && status >= 0) {
                DRM_DEBUG_KMS("Failed to get ACT after %dms, last status: %02x\n",
                              timeout_ms, status);
                return -EINVAL;
        } else if (status < 0) {
                DRM_DEBUG_KMS("Failed to read payload table status: %d\n",
                              status);
                return status;
        }

        return 0;
#else /* taken from FreeBSD */
        u8 status;
        int ret;
        int count = 0;

        do {
                ret = drm_dp_dpcd_readb(mgr->aux, DP_PAYLOAD_TABLE_UPDATE_STATUS, &status);

                if (ret < 0) {
                        DRM_DEBUG_KMS("failed to read payload table status %d\n", ret);
                        goto fail;
                }

                if (status & DP_PAYLOAD_ACT_HANDLED)
                        break;
                count++;
                udelay(100);

        } while (count < 30);

        if (!(status & DP_PAYLOAD_ACT_HANDLED)) {
                DRM_DEBUG_KMS("failed to get ACT bit %d after %d retries\n", status, count);
                ret = -EINVAL;
                goto fail;
        }
        return 0;
fail:
        return ret;
#endif
}
EXPORT_SYMBOL(drm_dp_check_act_status);

/**
 * drm_dp_calc_pbn_mode() - Calculate the PBN for a mode.
 * @clock: dot clock for the mode
 * @bpp: bpp for the mode.
 *
 * This uses the formula in the spec to calculate the PBN value for a mode.
 */
int drm_dp_calc_pbn_mode(int clock, int bpp)
{
        u64 kbps;
        s64 peak_kbps;
        u32 numerator;
        u32 denominator;

        kbps = clock * bpp;

        /*
         * margin 5300ppm + 300ppm ~ 0.6% as per spec, factor is 1.006
         * The unit of 54/64Mbytes/sec is an arbitrary unit chosen based on
         * common multiplier to render an integer PBN for all link rate/lane
         * counts combinations
         * calculate
         * peak_kbps *= (1006/1000)
         * peak_kbps *= (64/54)
         * peak_kbps *= 8    convert to bytes
         */

        numerator = 64 * 1006;
        denominator = 54 * 8 * 1000 * 1000;

        kbps *= numerator;
        peak_kbps = drm_fixp_from_fraction(kbps, denominator);

        return drm_fixp2int_ceil(peak_kbps);
}
EXPORT_SYMBOL(drm_dp_calc_pbn_mode);

static int test_calc_pbn_mode(void)
{
        int ret;
        ret = drm_dp_calc_pbn_mode(154000, 30);
        if (ret != 689) {
                DRM_ERROR("PBN calculation test failed - clock %d, bpp %d, expected PBN %d, actual PBN %d.\n",
                                154000, 30, 689, ret);
                return -EINVAL;
        }
        ret = drm_dp_calc_pbn_mode(234000, 30);
        if (ret != 1047) {
                DRM_ERROR("PBN calculation test failed - clock %d, bpp %d, expected PBN %d, actual PBN %d.\n",
                                234000, 30, 1047, ret);
                return -EINVAL;
        }
        ret = drm_dp_calc_pbn_mode(297000, 24);
        if (ret != 1063) {
                DRM_ERROR("PBN calculation test failed - clock %d, bpp %d, expected PBN %d, actual PBN %d.\n",
                                297000, 24, 1063, ret);
                return -EINVAL;
        }
        return 0;
}

/* we want to kick the TX after we've ack the up/down IRQs. */
static void drm_dp_mst_kick_tx(struct drm_dp_mst_topology_mgr *mgr)
{
        queue_work(system_long_wq, &mgr->tx_work);
}

static void drm_dp_mst_dump_mstb(struct seq_file *m,
                                 struct drm_dp_mst_branch *mstb)
{
        struct drm_dp_mst_port *port;
        int tabs = mstb->lct;
        char prefix[10];
        int i;

        for (i = 0; i < tabs; i++)
                prefix[i] = '\t';
        prefix[i] = '\0';

        seq_printf(m, "%smst: %p, %d\n", prefix, mstb, mstb->num_ports);
        list_for_each_entry(port, &mstb->ports, next) {
                seq_printf(m, "%sport: %d: input: %d: pdt: %d, ddps: %d ldps: %d, sdp: %d/%d, %p, conn: %p\n", prefix, port->port_num, port->input, port->pdt, port->ddps, port->ldps, port->num_sdp_streams, port->num_sdp_stream_sinks, port, port->connector);
                if (port->mstb)
                        drm_dp_mst_dump_mstb(m, port->mstb);
        }
}

#define DP_PAYLOAD_TABLE_SIZE           64

static bool dump_dp_payload_table(struct drm_dp_mst_topology_mgr *mgr,
                                  char *buf)
{
        int i;

        for (i = 0; i < DP_PAYLOAD_TABLE_SIZE; i += 16) {
                if (drm_dp_dpcd_read(mgr->aux,
                                     DP_PAYLOAD_TABLE_UPDATE_STATUS + i,
                                     &buf[i], 16) != 16)
                        return false;
        }
        return true;
}

static void fetch_monitor_name(struct drm_dp_mst_topology_mgr *mgr,
                               struct drm_dp_mst_port *port, char *name,
                               int namelen)
{
        struct edid *mst_edid;

        mst_edid = drm_dp_mst_get_edid(port->connector, mgr, port);
        drm_edid_get_monitor_name(mst_edid, name, namelen);
}

/**
 * drm_dp_mst_dump_topology(): dump topology to seq file.
 * @m: seq_file to dump output to
 * @mgr: manager to dump current topology for.
 *
 * helper to dump MST topology to a seq file for debugfs.
 */
void drm_dp_mst_dump_topology(struct seq_file *m,
                              struct drm_dp_mst_topology_mgr *mgr)
{
        int i;
        struct drm_dp_mst_port *port;

        mutex_lock(&mgr->lock);
        if (mgr->mst_primary)
                drm_dp_mst_dump_mstb(m, mgr->mst_primary);

        /* dump VCPIs */
        mutex_unlock(&mgr->lock);

        mutex_lock(&mgr->payload_lock);
        seq_printf(m, "vcpi: %lx %lx %d\n", mgr->payload_mask, mgr->vcpi_mask,
                mgr->max_payloads);

        for (i = 0; i < mgr->max_payloads; i++) {
                if (mgr->proposed_vcpis[i]) {
                        char name[14];

                        port = container_of(mgr->proposed_vcpis[i], struct drm_dp_mst_port, vcpi);
                        fetch_monitor_name(mgr, port, name, sizeof(name));
                        seq_printf(m, "vcpi %d: %d %d %d sink name: %s\n", i,
                                   port->port_num, port->vcpi.vcpi,
                                   port->vcpi.num_slots,
                                   (*name != 0) ? name :  "Unknown");
                } else
                        seq_printf(m, "vcpi %d:unused\n", i);
        }
        for (i = 0; i < mgr->max_payloads; i++) {
                seq_printf(m, "payload %d: %d, %d, %d\n",
                           i,
                           mgr->payloads[i].payload_state,
                           mgr->payloads[i].start_slot,
                           mgr->payloads[i].num_slots);


        }
        mutex_unlock(&mgr->payload_lock);

        mutex_lock(&mgr->lock);
        if (mgr->mst_primary) {
                u8 buf[DP_PAYLOAD_TABLE_SIZE];
                int ret;

                ret = drm_dp_dpcd_read(mgr->aux, DP_DPCD_REV, buf, DP_RECEIVER_CAP_SIZE);
                seq_printf(m, "dpcd: %*ph\n", DP_RECEIVER_CAP_SIZE, buf);
                ret = drm_dp_dpcd_read(mgr->aux, DP_FAUX_CAP, buf, 2);
                seq_printf(m, "faux/mst: %*ph\n", 2, buf);
                ret = drm_dp_dpcd_read(mgr->aux, DP_MSTM_CTRL, buf, 1);
                seq_printf(m, "mst ctrl: %*ph\n", 1, buf);

                /* dump the standard OUI branch header */
                ret = drm_dp_dpcd_read(mgr->aux, DP_BRANCH_OUI, buf, DP_BRANCH_OUI_HEADER_SIZE);
                seq_printf(m, "branch oui: %*phN devid: ", 3, buf);
                for (i = 0x3; i < 0x8 && buf[i]; i++)
                        seq_printf(m, "%c", buf[i]);
                seq_printf(m, " revision: hw: %x.%x sw: %x.%x\n",
                           buf[0x9] >> 4, buf[0x9] & 0xf, buf[0xa], buf[0xb]);
                if (dump_dp_payload_table(mgr, buf))
                        seq_printf(m, "payload table: %*ph\n", DP_PAYLOAD_TABLE_SIZE, buf);
        }

        mutex_unlock(&mgr->lock);

}
EXPORT_SYMBOL(drm_dp_mst_dump_topology);

static void drm_dp_tx_work(struct work_struct *work)
{
        struct drm_dp_mst_topology_mgr *mgr = container_of(work, struct drm_dp_mst_topology_mgr, tx_work);

        mutex_lock(&mgr->qlock);
        if (!list_empty(&mgr->tx_msg_downq))
                process_single_down_tx_qlock(mgr);
        mutex_unlock(&mgr->qlock);
}

static void drm_dp_free_mst_port(struct kref *kref)
{
        struct drm_dp_mst_port *port = container_of(kref, struct drm_dp_mst_port, kref);
        kref_put(&port->parent->kref, drm_dp_free_mst_branch_device);
        kfree(port);
}

static void drm_dp_destroy_connector_work(struct work_struct *work)
{
        struct drm_dp_mst_topology_mgr *mgr = container_of(work, struct drm_dp_mst_topology_mgr, destroy_connector_work);
        struct drm_dp_mst_port *port;
        bool send_hotplug = false;
        /*
         * Not a regular list traverse as we have to drop the destroy
         * connector lock before destroying the connector, to avoid AB->BA
         * ordering between this lock and the config mutex.
         */
        for (;;) {
                mutex_lock(&mgr->destroy_connector_lock);
                port = list_first_entry_or_null(&mgr->destroy_connector_list, struct drm_dp_mst_port, next);
                if (!port) {
                        mutex_unlock(&mgr->destroy_connector_lock);
                        break;
                }
                list_del(&port->next);
                mutex_unlock(&mgr->destroy_connector_lock);

                kref_init(&port->kref);
                INIT_LIST_HEAD(&port->next);

                mgr->cbs->destroy_connector(mgr, port->connector);

                drm_dp_port_teardown_pdt(port, port->pdt);
                port->pdt = DP_PEER_DEVICE_NONE;

                if (!port->input && port->vcpi.vcpi > 0) {
                        drm_dp_mst_reset_vcpi_slots(mgr, port);
                        drm_dp_update_payload_part1(mgr);
                        drm_dp_mst_put_payload_id(mgr, port->vcpi.vcpi);
                }

                kref_put(&port->kref, drm_dp_free_mst_port);
                send_hotplug = true;
        }
        if (send_hotplug)
                (*mgr->cbs->hotplug)(mgr);
}

static struct drm_private_state *
drm_dp_mst_duplicate_state(struct drm_private_obj *obj)
{
        struct drm_dp_mst_topology_state *state;

        state = kmemdup(obj->state, sizeof(*state), GFP_KERNEL);
        if (!state)
                return NULL;

        __drm_atomic_helper_private_obj_duplicate_state(obj, &state->base);

        return &state->base;
}

static void drm_dp_mst_destroy_state(struct drm_private_obj *obj,
                                     struct drm_private_state *state)
{
        struct drm_dp_mst_topology_state *mst_state =
                to_dp_mst_topology_state(state);

        kfree(mst_state);
}

static const struct drm_private_state_funcs mst_state_funcs = {
        .atomic_duplicate_state = drm_dp_mst_duplicate_state,
        .atomic_destroy_state = drm_dp_mst_destroy_state,
};

/**
 * drm_atomic_get_mst_topology_state: get MST topology state
 *
 * @state: global atomic state
 * @mgr: MST topology manager, also the private object in this case
 *
 * This function wraps drm_atomic_get_priv_obj_state() passing in the MST atomic
 * state vtable so that the private object state returned is that of a MST
 * topology object. Also, drm_atomic_get_private_obj_state() expects the caller
 * to care of the locking, so warn if don't hold the connection_mutex.
 *
 * RETURNS:
 *
 * The MST topology state or error pointer.
 */
struct drm_dp_mst_topology_state *drm_atomic_get_mst_topology_state(struct drm_atomic_state *state,
                                                                    struct drm_dp_mst_topology_mgr *mgr)
{
        struct drm_device *dev = mgr->dev;

        WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex));
        return to_dp_mst_topology_state(drm_atomic_get_private_obj_state(state, &mgr->base));
}
EXPORT_SYMBOL(drm_atomic_get_mst_topology_state);

/**
 * drm_dp_mst_topology_mgr_init - initialise a topology manager
 * @mgr: manager struct to initialise
 * @dev: device providing this structure - for i2c addition.
 * @aux: DP helper aux channel to talk to this device
 * @max_dpcd_transaction_bytes: hw specific DPCD transaction limit
 * @max_payloads: maximum number of payloads this GPU can source
 * @conn_base_id: the connector object ID the MST device is connected to.
 *
 * Return 0 for success, or negative error code on failure
 */
int drm_dp_mst_topology_mgr_init(struct drm_dp_mst_topology_mgr *mgr,
                                 struct drm_device *dev, struct drm_dp_aux *aux,
                                 int max_dpcd_transaction_bytes,
                                 int max_payloads, int conn_base_id)
{
        struct drm_dp_mst_topology_state *mst_state;

        lockinit(&mgr->lock, "drmml", 0, LK_CANRECURSE);
        lockinit(&mgr->qlock, "drmmql", 0, LK_CANRECURSE);
        lockinit(&mgr->payload_lock, "drmmpl", 0, LK_CANRECURSE);
        lockinit(&mgr->destroy_connector_lock, "drmmdcl", 0, LK_CANRECURSE);
        INIT_LIST_HEAD(&mgr->tx_msg_downq);
        INIT_LIST_HEAD(&mgr->destroy_connector_list);
        INIT_WORK(&mgr->work, drm_dp_mst_link_probe_work);
        INIT_WORK(&mgr->tx_work, drm_dp_tx_work);
        INIT_WORK(&mgr->destroy_connector_work, drm_dp_destroy_connector_work);
        init_waitqueue_head(&mgr->tx_waitq);
        mgr->dev = dev;
        mgr->aux = aux;
        mgr->max_dpcd_transaction_bytes = max_dpcd_transaction_bytes;
        mgr->max_payloads = max_payloads;
        mgr->conn_base_id = conn_base_id;
        if (max_payloads + 1 > sizeof(mgr->payload_mask) * 8 ||
            max_payloads + 1 > sizeof(mgr->vcpi_mask) * 8)
                return -EINVAL;
        mgr->payloads = kcalloc(max_payloads, sizeof(struct drm_dp_payload), GFP_KERNEL);
        if (!mgr->payloads)
                return -ENOMEM;
        mgr->proposed_vcpis = kcalloc(max_payloads, sizeof(struct drm_dp_vcpi *), GFP_KERNEL);
        if (!mgr->proposed_vcpis)
                return -ENOMEM;
        set_bit(0, &mgr->payload_mask);
        if (test_calc_pbn_mode() < 0)
                DRM_ERROR("MST PBN self-test failed\n");

        mst_state = kzalloc(sizeof(*mst_state), GFP_KERNEL);
        if (mst_state == NULL)
                return -ENOMEM;

        mst_state->mgr = mgr;

        /* max. time slots - one slot for MTP header */
        mst_state->avail_slots = 63;

        drm_atomic_private_obj_init(&mgr->base,
                                    &mst_state->base,
                                    &mst_state_funcs);

        return 0;
}
EXPORT_SYMBOL(drm_dp_mst_topology_mgr_init);

/**
 * drm_dp_mst_topology_mgr_destroy() - destroy topology manager.
 * @mgr: manager to destroy
 */
void drm_dp_mst_topology_mgr_destroy(struct drm_dp_mst_topology_mgr *mgr)
{
        flush_work(&mgr->work);
        flush_work(&mgr->destroy_connector_work);
        mutex_lock(&mgr->payload_lock);
        kfree(mgr->payloads);
        mgr->payloads = NULL;
        kfree(mgr->proposed_vcpis);
        mgr->proposed_vcpis = NULL;
        mutex_unlock(&mgr->payload_lock);
        mgr->dev = NULL;
        mgr->aux = NULL;
        drm_atomic_private_obj_fini(&mgr->base);
        mgr->funcs = NULL;
}
EXPORT_SYMBOL(drm_dp_mst_topology_mgr_destroy);

/* I2C device */
static int drm_dp_mst_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs,
                               int num)
{
        struct drm_dp_aux *aux = adapter->algo_data;
        struct drm_dp_mst_port *port = container_of(aux, struct drm_dp_mst_port, aux);
        struct drm_dp_mst_branch *mstb;
        struct drm_dp_mst_topology_mgr *mgr = port->mgr;
        unsigned int i;
        bool reading = false;
        struct drm_dp_sideband_msg_req_body msg;
        struct drm_dp_sideband_msg_tx *txmsg = NULL;
        int ret;

        mstb = drm_dp_get_validated_mstb_ref(mgr, port->parent);
        if (!mstb)
                return -EREMOTEIO;

        /* construct i2c msg */
        /* see if last msg is a read */
        if (msgs[num - 1].flags & I2C_M_RD)
                reading = true;

        if (!reading || (num - 1 > DP_REMOTE_I2C_READ_MAX_TRANSACTIONS)) {
                DRM_DEBUG_KMS("Unsupported I2C transaction for MST device\n");
                ret = -EIO;
                goto out;
        }

        memset(&msg, 0, sizeof(msg));
        msg.req_type = DP_REMOTE_I2C_READ;
        msg.u.i2c_read.num_transactions = num - 1;
        msg.u.i2c_read.port_number = port->port_num;
        for (i = 0; i < num - 1; i++) {
                msg.u.i2c_read.transactions[i].i2c_dev_id = msgs[i].addr;
                msg.u.i2c_read.transactions[i].num_bytes = msgs[i].len;
                msg.u.i2c_read.transactions[i].bytes = msgs[i].buf;
        }
        msg.u.i2c_read.read_i2c_device_id = msgs[num - 1].addr;
        msg.u.i2c_read.num_bytes_read = msgs[num - 1].len;

        txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL);
        if (!txmsg) {
                ret = -ENOMEM;
                goto out;
        }

        txmsg->dst = mstb;
        drm_dp_encode_sideband_req(&msg, txmsg);

        drm_dp_queue_down_tx(mgr, txmsg);

        ret = drm_dp_mst_wait_tx_reply(mstb, txmsg);
        if (ret > 0) {

                if (txmsg->reply.reply_type == 1) { /* got a NAK back */
                        ret = -EREMOTEIO;
                        goto out;
                }
                if (txmsg->reply.u.remote_i2c_read_ack.num_bytes != msgs[num - 1].len) {
                        ret = -EIO;
                        goto out;
                }
                memcpy(msgs[num - 1].buf, txmsg->reply.u.remote_i2c_read_ack.bytes, msgs[num - 1].len);
                ret = num;
        }
out:
        kfree(txmsg);
        drm_dp_put_mst_branch_device(mstb);
        return ret;
}

static u32 drm_dp_mst_i2c_functionality(struct i2c_adapter *adapter)
{
        return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |
               I2C_FUNC_SMBUS_READ_BLOCK_DATA |
               I2C_FUNC_SMBUS_BLOCK_PROC_CALL |
               I2C_FUNC_10BIT_ADDR;
}

static const struct i2c_algorithm drm_dp_mst_i2c_algo = {
        .functionality = drm_dp_mst_i2c_functionality,
        .master_xfer = drm_dp_mst_i2c_xfer,
};

/**
 * drm_dp_mst_register_i2c_bus() - register an I2C adapter for I2C-over-AUX
 * @aux: DisplayPort AUX channel
 *
 * Returns 0 on success or a negative error code on failure.
 */
static int drm_dp_mst_register_i2c_bus(struct drm_dp_aux *aux)
{
        aux->ddc.algo = &drm_dp_mst_i2c_algo;
        aux->ddc.algo_data = aux;
        aux->ddc.retries = 3;

#if 0
        aux->ddc.class = I2C_CLASS_DDC;
        aux->ddc.owner = THIS_MODULE;
#endif
        aux->ddc.dev.parent = aux->dev;
#if 0
        aux->ddc.dev.of_node = aux->dev->of_node;
#endif

        strlcpy(aux->ddc.name, aux->name ? aux->name : dev_name(aux->dev),
                sizeof(aux->ddc.name));

        return i2c_add_adapter(&aux->ddc);
}

/**
 * drm_dp_mst_unregister_i2c_bus() - unregister an I2C-over-AUX adapter
 * @aux: DisplayPort AUX channel
 */
static void drm_dp_mst_unregister_i2c_bus(struct drm_dp_aux *aux)
{
        i2c_del_adapter(&aux->ddc);
}