// SPDX-License-Identifier: GPL-2.0
#include <linux/types.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/console.h>
#include <asm/hvsi.h>

#include "hvc_console.h"

static int hvsi_send_packet(struct hvsi_priv *pv, struct hvsi_header *packet)
{
        packet->seqno = cpu_to_be16(atomic_inc_return(&pv->seqno));

        /* Assumes that always succeeds, works in practice */
        return pv->put_chars(pv->termno, (u8 *)packet, packet->len);
}

static void hvsi_start_handshake(struct hvsi_priv *pv)
{
        struct hvsi_query q;

        /* Reset state */
        pv->established = 0;
        atomic_set(&pv->seqno, 0);

        pr_devel("HVSI@%x: Handshaking started\n", pv->termno);

        /* Send version query */
        q.hdr.type = VS_QUERY_PACKET_HEADER;
        q.hdr.len = sizeof(struct hvsi_query);
        q.verb = cpu_to_be16(VSV_SEND_VERSION_NUMBER);
        hvsi_send_packet(pv, &q.hdr);
}

static int hvsi_send_close(struct hvsi_priv *pv)
{
        struct hvsi_control ctrl;

        pv->established = 0;

        ctrl.hdr.type = VS_CONTROL_PACKET_HEADER;
        ctrl.hdr.len = sizeof(struct hvsi_control);
        ctrl.verb = cpu_to_be16(VSV_CLOSE_PROTOCOL);
        return hvsi_send_packet(pv, &ctrl.hdr);
}

static void hvsi_cd_change(struct hvsi_priv *pv, int cd)
{
        if (cd)
                pv->mctrl |= TIOCM_CD;
        else {
                pv->mctrl &= ~TIOCM_CD;

                /* We copy the existing hvsi driver semantics
                 * here which are to trigger a hangup when
                 * we get a carrier loss.
                 * Closing our connection to the server will
                 * do just that.
                 */
                if (!pv->is_console && pv->opened) {
                        pr_devel("HVSI@%x Carrier lost, hanging up !\n",
                                 pv->termno);
                        hvsi_send_close(pv);
                }
        }
}

static void hvsi_got_control(struct hvsi_priv *pv)
{
        struct hvsi_control *pkt = (struct hvsi_control *)pv->inbuf;

        switch (be16_to_cpu(pkt->verb)) {
        case VSV_CLOSE_PROTOCOL:
                /* We restart the handshaking */
                hvsi_start_handshake(pv);
                break;
        case VSV_MODEM_CTL_UPDATE:
                /* Transition of carrier detect */
                hvsi_cd_change(pv, be32_to_cpu(pkt->word) & HVSI_TSCD);
                break;
        }
}

static void hvsi_got_query(struct hvsi_priv *pv)
{
        struct hvsi_query *pkt = (struct hvsi_query *)pv->inbuf;
        struct hvsi_query_response r;

        /* We only handle version queries */
        if (be16_to_cpu(pkt->verb) != VSV_SEND_VERSION_NUMBER)
                return;

        pr_devel("HVSI@%x: Got version query, sending response...\n",
                 pv->termno);

        /* Send version response */
        r.hdr.type = VS_QUERY_RESPONSE_PACKET_HEADER;
        r.hdr.len = sizeof(struct hvsi_query_response);
        r.verb = cpu_to_be16(VSV_SEND_VERSION_NUMBER);
        r.u.version = HVSI_VERSION;
        r.query_seqno = pkt->hdr.seqno;
        hvsi_send_packet(pv, &r.hdr);

        /* Assume protocol is open now */
        pv->established = 1;
}

static void hvsi_got_response(struct hvsi_priv *pv)
{
        struct hvsi_query_response *r =
                (struct hvsi_query_response *)pv->inbuf;

        switch(r->verb) {
        case VSV_SEND_MODEM_CTL_STATUS:
                hvsi_cd_change(pv, be32_to_cpu(r->u.mctrl_word) & HVSI_TSCD);
                pv->mctrl_update = 1;
                break;
        }
}

static int hvsi_check_packet(struct hvsi_priv *pv)
{
        u8 len, type;

        /* Check header validity. If it's invalid, we ditch
         * the whole buffer and hope we eventually resync
         */
        if (pv->inbuf[0] < 0xfc) {
                pv->inbuf_len = pv->inbuf_pktlen = 0;
                return 0;
        }
        type = pv->inbuf[0];
        len = pv->inbuf[1];

        /* Packet incomplete ? */
        if (pv->inbuf_len < len)
                return 0;

        pr_devel("HVSI@%x: Got packet type %x len %d bytes:\n",
                 pv->termno, type, len);

        /* We have a packet, yay ! Handle it */
        switch(type) {
        case VS_DATA_PACKET_HEADER:
                pv->inbuf_pktlen = len - 4;
                pv->inbuf_cur = 4;
                return 1;
        case VS_CONTROL_PACKET_HEADER:
                hvsi_got_control(pv);
                break;
        case VS_QUERY_PACKET_HEADER:
                hvsi_got_query(pv);
                break;
        case VS_QUERY_RESPONSE_PACKET_HEADER:
                hvsi_got_response(pv);
                break;
        }

        /* Swallow packet and retry */
        pv->inbuf_len -= len;
        memmove(pv->inbuf, &pv->inbuf[len], pv->inbuf_len);
        return 1;
}

static int hvsi_get_packet(struct hvsi_priv *pv)
{
        /* If we have room in the buffer, ask HV for more */
        if (pv->inbuf_len < HVSI_INBUF_SIZE)
                pv->inbuf_len += pv->get_chars(pv->termno,
                                             &pv->inbuf[pv->inbuf_len],
                                             HVSI_INBUF_SIZE - pv->inbuf_len);
        /*
         * If we have at least 4 bytes in the buffer, check for
         * a full packet and retry
         */
        if (pv->inbuf_len >= 4)
                return hvsi_check_packet(pv);
        return 0;
}

ssize_t hvsilib_get_chars(struct hvsi_priv *pv, u8 *buf, size_t count)
{
        unsigned int tries;
        size_t read = 0;

        if (WARN_ON(!pv))
                return -ENXIO;

        /* If we aren't open, don't do anything in order to avoid races
         * with connection establishment. The hvc core will call this
         * before we have returned from notifier_add(), and we need to
         * avoid multiple users playing with the receive buffer
         */
        if (!pv->opened)
                return 0;

        /* We try twice, once with what data we have and once more
         * after we try to fetch some more from the hypervisor
         */
        for (tries = 1; count && tries < 2; tries++) {
                /* Consume existing data packet */
                if (pv->inbuf_pktlen) {
                        size_t l = min(count, pv->inbuf_pktlen);
                        memcpy(&buf[read], &pv->inbuf[pv->inbuf_cur], l);
                        pv->inbuf_cur += l;
                        pv->inbuf_pktlen -= l;
                        count -= l;
                        read += l;
                }
                if (count == 0)
                        break;

                /* Data packet fully consumed, move down remaning data */
                if (pv->inbuf_cur) {
                        pv->inbuf_len -= pv->inbuf_cur;
                        memmove(pv->inbuf, &pv->inbuf[pv->inbuf_cur],
                                pv->inbuf_len);
                        pv->inbuf_cur = 0;
                }

                /* Try to get another packet */
                if (hvsi_get_packet(pv))
                        tries--;
        }
        if (!pv->established) {
                pr_devel("HVSI@%x: returning -EPIPE\n", pv->termno);
                return -EPIPE;
        }
        return read;
}

ssize_t hvsilib_put_chars(struct hvsi_priv *pv, const u8 *buf, size_t count)
{
        struct hvsi_data dp;
        size_t adjcount = min_t(size_t, count, HVSI_MAX_OUTGOING_DATA);
        int rc;

        if (WARN_ON(!pv))
                return -ENODEV;

        dp.hdr.type = VS_DATA_PACKET_HEADER;
        dp.hdr.len = adjcount + sizeof(struct hvsi_header);
        memcpy(dp.data, buf, adjcount);
        rc = hvsi_send_packet(pv, &dp.hdr);
        if (rc <= 0)
                return rc;
        return adjcount;
}

static void maybe_msleep(unsigned long ms)
{
        /* During early boot, IRQs are disabled, use mdelay */
        if (irqs_disabled())
                mdelay(ms);
        else
                msleep(ms);
}

int hvsilib_read_mctrl(struct hvsi_priv *pv)
{
        struct hvsi_query q;
        int rc, timeout;

        pr_devel("HVSI@%x: Querying modem control status...\n",
                 pv->termno);

        pv->mctrl_update = 0;
        q.hdr.type = VS_QUERY_PACKET_HEADER;
        q.hdr.len = sizeof(struct hvsi_query);
        q.verb = cpu_to_be16(VSV_SEND_MODEM_CTL_STATUS);
        rc = hvsi_send_packet(pv, &q.hdr);
        if (rc <= 0) {
                pr_devel("HVSI@%x: Error %d...\n", pv->termno, rc);
                return rc;
        }

        /* Try for up to 200ms */
        for (timeout = 0; timeout < 20; timeout++) {
                if (!pv->established)
                        return -ENXIO;
                if (pv->mctrl_update)
                        return 0;
                if (!hvsi_get_packet(pv))
                        maybe_msleep(10);
        }
        return -EIO;
}

int hvsilib_write_mctrl(struct hvsi_priv *pv, int dtr)
{
        struct hvsi_control ctrl;
        unsigned short mctrl;

        mctrl = pv->mctrl;
        if (dtr)
                mctrl |= TIOCM_DTR;
        else
                mctrl &= ~TIOCM_DTR;
        if (mctrl == pv->mctrl)
                return 0;
        pv->mctrl = mctrl;

        pr_devel("HVSI@%x: %s DTR...\n", pv->termno,
                 dtr ? "Setting" : "Clearing");

        ctrl.hdr.type = VS_CONTROL_PACKET_HEADER;
        ctrl.hdr.len = sizeof(struct hvsi_control);
        ctrl.verb = cpu_to_be16(VSV_SET_MODEM_CTL);
        ctrl.mask = cpu_to_be32(HVSI_TSDTR);
        ctrl.word = cpu_to_be32(dtr ? HVSI_TSDTR : 0);
        return hvsi_send_packet(pv, &ctrl.hdr);
}

void hvsilib_establish(struct hvsi_priv *pv)
{
        int timeout;

        pr_devel("HVSI@%x: Establishing...\n", pv->termno);

        /* Try for up to 200ms, there can be a packet to
         * start the process waiting for us...
         */
        for (timeout = 0; timeout < 20; timeout++) {
                if (pv->established)
                        goto established;
                if (!hvsi_get_packet(pv))
                        maybe_msleep(10);
        }

        /* Failed, send a close connection packet just
         * in case
         */
        pr_devel("HVSI@%x:   ... sending close\n", pv->termno);

        hvsi_send_close(pv);

        /* Then restart handshake */

        pr_devel("HVSI@%x:   ... restarting handshake\n", pv->termno);

        hvsi_start_handshake(pv);

        pr_devel("HVSI@%x:   ... waiting handshake\n", pv->termno);

        /* Try for up to 400ms */
        for (timeout = 0; timeout < 40; timeout++) {
                if (pv->established)
                        goto established;
                if (!hvsi_get_packet(pv))
                        maybe_msleep(10);
        }

        if (!pv->established) {
                pr_devel("HVSI@%x: Timeout handshaking, giving up !\n",
                         pv->termno);
                return;
        }
 established:
        /* Query modem control lines */

        pr_devel("HVSI@%x:   ... established, reading mctrl\n", pv->termno);

        hvsilib_read_mctrl(pv);

        /* Set our own DTR */

        pr_devel("HVSI@%x:   ... setting mctrl\n", pv->termno);

        hvsilib_write_mctrl(pv, 1);

        /* Set the opened flag so reads are allowed */
        wmb();
        pv->opened = 1;
}

int hvsilib_open(struct hvsi_priv *pv, struct hvc_struct *hp)
{
        pr_devel("HVSI@%x: open !\n", pv->termno);

        /* Keep track of the tty data structure */
        pv->tty = tty_port_tty_get(&hp->port);

        hvsilib_establish(pv);

        return 0;
}

void hvsilib_close(struct hvsi_priv *pv, struct hvc_struct *hp)
{
        unsigned long flags;

        pr_devel("HVSI@%x: close !\n", pv->termno);

        if (!pv->is_console) {
                pr_devel("HVSI@%x: Not a console, tearing down\n",
                         pv->termno);

                /* Clear opened, synchronize with khvcd */
                spin_lock_irqsave(&hp->lock, flags);
                pv->opened = 0;
                spin_unlock_irqrestore(&hp->lock, flags);

                /* Clear our own DTR */
                if (!pv->tty || (pv->tty->termios.c_cflag & HUPCL))
                        hvsilib_write_mctrl(pv, 0);

                /* Tear down the connection */
                hvsi_send_close(pv);
        }

        tty_kref_put(pv->tty);
        pv->tty = NULL;
}

void hvsilib_init(struct hvsi_priv *pv,
                  ssize_t (*get_chars)(uint32_t termno, u8 *buf, size_t count),
                  ssize_t (*put_chars)(uint32_t termno, const u8 *buf,
                                       size_t count),
                  int termno, int is_console)
{
        memset(pv, 0, sizeof(*pv));
        pv->get_chars = get_chars;
        pv->put_chars = put_chars;
        pv->termno = termno;
        pv->is_console = is_console;
}