// SPDX-License-Identifier: GPL-2.0-only
/*
 * CAN bus driver for the alone generic (as possible as) MSCAN controller.
 *
 * Copyright (C) 2005-2006 Andrey Volkov <avolkov@varma-el.com>,
 *                         Varma Electronics Oy
 * Copyright (C) 2008-2009 Wolfgang Grandegger <wg@grandegger.com>
 * Copyright (C) 2008-2009 Pengutronix <kernel@pengutronix.de>
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/delay.h>
#include <linux/netdevice.h>
#include <linux/if_arp.h>
#include <linux/if_ether.h>
#include <linux/list.h>
#include <linux/can/dev.h>
#include <linux/can/error.h>
#include <linux/io.h>

#include "mscan.h"

static const struct can_bittiming_const mscan_bittiming_const = {
        .name = "mscan",
        .tseg1_min = 4,
        .tseg1_max = 16,
        .tseg2_min = 2,
        .tseg2_max = 8,
        .sjw_max = 4,
        .brp_min = 1,
        .brp_max = 64,
        .brp_inc = 1,
};

static enum can_state state_map[] = {
        CAN_STATE_ERROR_ACTIVE,
        CAN_STATE_ERROR_WARNING,
        CAN_STATE_ERROR_PASSIVE,
        CAN_STATE_BUS_OFF
};

static int mscan_set_mode(struct net_device *dev, u8 mode)
{
        struct mscan_priv *priv = netdev_priv(dev);
        struct mscan_regs __iomem *regs = priv->reg_base;
        int ret = 0;
        int i;
        u8 canctl1;

        if (mode != MSCAN_NORMAL_MODE) {
                if (priv->tx_active) {
                        /* Abort transfers before going to sleep */#
                        out_8(&regs->cantarq, priv->tx_active);
                        /* Suppress TX done interrupts */
                        out_8(&regs->cantier, 0);
                }

                canctl1 = in_8(&regs->canctl1);
                if ((mode & MSCAN_SLPRQ) && !(canctl1 & MSCAN_SLPAK)) {
                        setbits8(&regs->canctl0, MSCAN_SLPRQ);
                        for (i = 0; i < MSCAN_SET_MODE_RETRIES; i++) {
                                if (in_8(&regs->canctl1) & MSCAN_SLPAK)
                                        break;
                                udelay(100);
                        }
                        /*
                         * The mscan controller will fail to enter sleep mode,
                         * while there are irregular activities on bus, like
                         * somebody keeps retransmitting. This behavior is
                         * undocumented and seems to differ between mscan built
                         * in mpc5200b and mpc5200. We proceed in that case,
                         * since otherwise the slprq will be kept set and the
                         * controller will get stuck. NOTE: INITRQ or CSWAI
                         * will abort all active transmit actions, if still
                         * any, at once.
                         */
                        if (i >= MSCAN_SET_MODE_RETRIES)
                                netdev_dbg(dev,
                                           "device failed to enter sleep mode. "
                                           "We proceed anyhow.\n");
                        else
                                priv->can.state = CAN_STATE_SLEEPING;
                }

                if ((mode & MSCAN_INITRQ) && !(canctl1 & MSCAN_INITAK)) {
                        setbits8(&regs->canctl0, MSCAN_INITRQ);
                        for (i = 0; i < MSCAN_SET_MODE_RETRIES; i++) {
                                if (in_8(&regs->canctl1) & MSCAN_INITAK)
                                        break;
                        }
                        if (i >= MSCAN_SET_MODE_RETRIES)
                                ret = -ENODEV;
                }
                if (!ret)
                        priv->can.state = CAN_STATE_STOPPED;

                if (mode & MSCAN_CSWAI)
                        setbits8(&regs->canctl0, MSCAN_CSWAI);

        } else {
                canctl1 = in_8(&regs->canctl1);
                if (canctl1 & (MSCAN_SLPAK | MSCAN_INITAK)) {
                        clrbits8(&regs->canctl0, MSCAN_SLPRQ | MSCAN_INITRQ);
                        for (i = 0; i < MSCAN_SET_MODE_RETRIES; i++) {
                                canctl1 = in_8(&regs->canctl1);
                                if (!(canctl1 & (MSCAN_INITAK | MSCAN_SLPAK)))
                                        break;
                        }
                        if (i >= MSCAN_SET_MODE_RETRIES)
                                ret = -ENODEV;
                        else
                                priv->can.state = CAN_STATE_ERROR_ACTIVE;
                }
        }
        return ret;
}

static int mscan_start(struct net_device *dev)
{
        struct mscan_priv *priv = netdev_priv(dev);
        struct mscan_regs __iomem *regs = priv->reg_base;
        u8 canrflg;
        int err;

        out_8(&regs->canrier, 0);

        INIT_LIST_HEAD(&priv->tx_head);
        priv->prev_buf_id = 0;
        priv->cur_pri = 0;
        priv->tx_active = 0;
        priv->shadow_canrier = 0;
        priv->flags = 0;

        if (priv->type == MSCAN_TYPE_MPC5121) {
                /* Clear pending bus-off condition */
                if (in_8(&regs->canmisc) & MSCAN_BOHOLD)
                        out_8(&regs->canmisc, MSCAN_BOHOLD);
        }

        err = mscan_set_mode(dev, MSCAN_NORMAL_MODE);
        if (err)
                return err;

        canrflg = in_8(&regs->canrflg);
        priv->shadow_statflg = canrflg & MSCAN_STAT_MSK;
        priv->can.state = state_map[max(MSCAN_STATE_RX(canrflg),
                                    MSCAN_STATE_TX(canrflg))];
        out_8(&regs->cantier, 0);

        /* Enable receive interrupts. */
        out_8(&regs->canrier, MSCAN_RX_INTS_ENABLE);

        return 0;
}

static int mscan_restart(struct net_device *dev)
{
        struct mscan_priv *priv = netdev_priv(dev);

        if (priv->type == MSCAN_TYPE_MPC5121) {
                struct mscan_regs __iomem *regs = priv->reg_base;

                priv->can.state = CAN_STATE_ERROR_ACTIVE;
                WARN(!(in_8(&regs->canmisc) & MSCAN_BOHOLD),
                     "bus-off state expected\n");
                out_8(&regs->canmisc, MSCAN_BOHOLD);
                /* Re-enable receive interrupts. */
                out_8(&regs->canrier, MSCAN_RX_INTS_ENABLE);
        } else {
                if (priv->can.state <= CAN_STATE_BUS_OFF)
                        mscan_set_mode(dev, MSCAN_INIT_MODE);
                return mscan_start(dev);
        }

        return 0;
}

static netdev_tx_t mscan_start_xmit(struct sk_buff *skb, struct net_device *dev)
{
        struct can_frame *frame = (struct can_frame *)skb->data;
        struct mscan_priv *priv = netdev_priv(dev);
        struct mscan_regs __iomem *regs = priv->reg_base;
        int i, rtr, buf_id;
        u32 can_id;

        if (can_dev_dropped_skb(dev, skb))
                return NETDEV_TX_OK;

        out_8(&regs->cantier, 0);

        i = ~priv->tx_active & MSCAN_TXE;
        buf_id = ffs(i) - 1;
        switch (hweight8(i)) {
        case 0:
                netif_stop_queue(dev);
                netdev_err(dev, "Tx Ring full when queue awake!\n");
                return NETDEV_TX_BUSY;
        case 1:
                /*
                 * if buf_id < 3, then current frame will be send out of order,
                 * since buffer with lower id have higher priority (hell..)
                 */
                netif_stop_queue(dev);
                fallthrough;
        case 2:
                if (buf_id < priv->prev_buf_id) {
                        priv->cur_pri++;
                        if (priv->cur_pri == 0xff) {
                                set_bit(F_TX_WAIT_ALL, &priv->flags);
                                netif_stop_queue(dev);
                        }
                }
                set_bit(F_TX_PROGRESS, &priv->flags);
                break;
        }
        priv->prev_buf_id = buf_id;
        out_8(&regs->cantbsel, i);

        rtr = frame->can_id & CAN_RTR_FLAG;

        /* RTR is always the lowest bit of interest, then IDs follow */
        if (frame->can_id & CAN_EFF_FLAG) {
                can_id = (frame->can_id & CAN_EFF_MASK)
                         << (MSCAN_EFF_RTR_SHIFT + 1);
                if (rtr)
                        can_id |= 1 << MSCAN_EFF_RTR_SHIFT;
                out_be16(&regs->tx.idr3_2, can_id);

                can_id >>= 16;
                /* EFF_FLAGS are between the IDs :( */
                can_id = (can_id & 0x7) | ((can_id << 2) & 0xffe0)
                         | MSCAN_EFF_FLAGS;
        } else {
                can_id = (frame->can_id & CAN_SFF_MASK)
                         << (MSCAN_SFF_RTR_SHIFT + 1);
                if (rtr)
                        can_id |= 1 << MSCAN_SFF_RTR_SHIFT;
        }
        out_be16(&regs->tx.idr1_0, can_id);

        if (!rtr) {
                void __iomem *data = &regs->tx.dsr1_0;
                u16 *payload = (u16 *)frame->data;

                for (i = 0; i < frame->len / 2; i++) {
                        out_be16(data, *payload++);
                        data += 2 + _MSCAN_RESERVED_DSR_SIZE;
                }
                /* write remaining byte if necessary */
                if (frame->len & 1)
                        out_8(data, frame->data[frame->len - 1]);
        }

        out_8(&regs->tx.dlr, frame->len);
        out_8(&regs->tx.tbpr, priv->cur_pri);

        /* Start transmission. */
        out_8(&regs->cantflg, 1 << buf_id);

        if (!test_bit(F_TX_PROGRESS, &priv->flags))
                netif_trans_update(dev);

        list_add_tail(&priv->tx_queue[buf_id].list, &priv->tx_head);

        can_put_echo_skb(skb, dev, buf_id, 0);

        /* Enable interrupt. */
        priv->tx_active |= 1 << buf_id;
        out_8(&regs->cantier, priv->tx_active);

        return NETDEV_TX_OK;
}

static enum can_state get_new_state(struct net_device *dev, u8 canrflg)
{
        struct mscan_priv *priv = netdev_priv(dev);

        if (unlikely(canrflg & MSCAN_CSCIF))
                return state_map[max(MSCAN_STATE_RX(canrflg),
                                 MSCAN_STATE_TX(canrflg))];

        return priv->can.state;
}

static void mscan_get_rx_frame(struct net_device *dev, struct can_frame *frame)
{
        struct mscan_priv *priv = netdev_priv(dev);
        struct mscan_regs __iomem *regs = priv->reg_base;
        u32 can_id;
        int i;

        can_id = in_be16(&regs->rx.idr1_0);
        if (can_id & (1 << 3)) {
                frame->can_id = CAN_EFF_FLAG;
                can_id = ((can_id << 16) | in_be16(&regs->rx.idr3_2));
                can_id = ((can_id & 0xffe00000) |
                          ((can_id & 0x7ffff) << 2)) >> 2;
        } else {
                can_id >>= 4;
                frame->can_id = 0;
        }

        frame->can_id |= can_id >> 1;
        if (can_id & 1)
                frame->can_id |= CAN_RTR_FLAG;

        frame->len = can_cc_dlc2len(in_8(&regs->rx.dlr) & 0xf);

        if (!(frame->can_id & CAN_RTR_FLAG)) {
                void __iomem *data = &regs->rx.dsr1_0;
                u16 *payload = (u16 *)frame->data;

                for (i = 0; i < frame->len / 2; i++) {
                        *payload++ = in_be16(data);
                        data += 2 + _MSCAN_RESERVED_DSR_SIZE;
                }
                /* read remaining byte if necessary */
                if (frame->len & 1)
                        frame->data[frame->len - 1] = in_8(data);
        }

        out_8(&regs->canrflg, MSCAN_RXF);
}

static void mscan_get_err_frame(struct net_device *dev, struct can_frame *frame,
                                u8 canrflg)
{
        struct mscan_priv *priv = netdev_priv(dev);
        struct mscan_regs __iomem *regs = priv->reg_base;
        struct net_device_stats *stats = &dev->stats;
        enum can_state new_state;

        netdev_dbg(dev, "error interrupt (canrflg=%#x)\n", canrflg);
        frame->can_id = CAN_ERR_FLAG;

        if (canrflg & MSCAN_OVRIF) {
                frame->can_id |= CAN_ERR_CRTL;
                frame->data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
                stats->rx_over_errors++;
                stats->rx_errors++;
        } else {
                frame->data[1] = 0;
        }

        new_state = get_new_state(dev, canrflg);
        if (new_state != priv->can.state) {
                can_change_state(dev, frame,
                                 state_map[MSCAN_STATE_TX(canrflg)],
                                 state_map[MSCAN_STATE_RX(canrflg)]);

                if (priv->can.state == CAN_STATE_BUS_OFF) {
                        /*
                         * The MSCAN on the MPC5200 does recover from bus-off
                         * automatically. To avoid that we stop the chip doing
                         * a light-weight stop (we are in irq-context).
                         */
                        if (priv->type != MSCAN_TYPE_MPC5121) {
                                out_8(&regs->cantier, 0);
                                out_8(&regs->canrier, 0);
                                setbits8(&regs->canctl0,
                                         MSCAN_SLPRQ | MSCAN_INITRQ);
                        }
                        can_bus_off(dev);
                }
        }
        priv->shadow_statflg = canrflg & MSCAN_STAT_MSK;
        frame->len = CAN_ERR_DLC;
        out_8(&regs->canrflg, MSCAN_ERR_IF);
}

static int mscan_rx_poll(struct napi_struct *napi, int quota)
{
        struct mscan_priv *priv = container_of(napi, struct mscan_priv, napi);
        struct net_device *dev = napi->dev;
        struct mscan_regs __iomem *regs = priv->reg_base;
        struct net_device_stats *stats = &dev->stats;
        int work_done = 0;
        struct sk_buff *skb;
        struct can_frame *frame;
        u8 canrflg;

        while (work_done < quota) {
                canrflg = in_8(&regs->canrflg);
                if (!(canrflg & (MSCAN_RXF | MSCAN_ERR_IF)))
                        break;

                skb = alloc_can_skb(dev, &frame);
                if (!skb) {
                        if (printk_ratelimit())
                                netdev_notice(dev, "packet dropped\n");
                        stats->rx_dropped++;
                        out_8(&regs->canrflg, canrflg);
                        continue;
                }

                if (canrflg & MSCAN_RXF) {
                        mscan_get_rx_frame(dev, frame);
                        stats->rx_packets++;
                        if (!(frame->can_id & CAN_RTR_FLAG))
                                stats->rx_bytes += frame->len;
                } else if (canrflg & MSCAN_ERR_IF) {
                        mscan_get_err_frame(dev, frame, canrflg);
                }

                work_done++;
                netif_receive_skb(skb);
        }

        if (work_done < quota) {
                if (likely(napi_complete_done(&priv->napi, work_done))) {
                        clear_bit(F_RX_PROGRESS, &priv->flags);
                        if (priv->can.state < CAN_STATE_BUS_OFF)
                                out_8(&regs->canrier, priv->shadow_canrier);
                }
        }
        return work_done;
}

static irqreturn_t mscan_isr(int irq, void *dev_id)
{
        struct net_device *dev = (struct net_device *)dev_id;
        struct mscan_priv *priv = netdev_priv(dev);
        struct mscan_regs __iomem *regs = priv->reg_base;
        struct net_device_stats *stats = &dev->stats;
        u8 cantier, cantflg, canrflg;
        irqreturn_t ret = IRQ_NONE;

        cantier = in_8(&regs->cantier) & MSCAN_TXE;
        cantflg = in_8(&regs->cantflg) & cantier;

        if (cantier && cantflg) {
                struct list_head *tmp, *pos;

                list_for_each_safe(pos, tmp, &priv->tx_head) {
                        struct tx_queue_entry *entry =
                            list_entry(pos, struct tx_queue_entry, list);
                        u8 mask = entry->mask;

                        if (!(cantflg & mask))
                                continue;

                        out_8(&regs->cantbsel, mask);
                        stats->tx_bytes += can_get_echo_skb(dev, entry->id,
                                                            NULL);
                        stats->tx_packets++;
                        priv->tx_active &= ~mask;
                        list_del(pos);
                }

                if (list_empty(&priv->tx_head)) {
                        clear_bit(F_TX_WAIT_ALL, &priv->flags);
                        clear_bit(F_TX_PROGRESS, &priv->flags);
                        priv->cur_pri = 0;
                } else {
                        netif_trans_update(dev);
                }

                if (!test_bit(F_TX_WAIT_ALL, &priv->flags))
                        netif_wake_queue(dev);

                out_8(&regs->cantier, priv->tx_active);
                ret = IRQ_HANDLED;
        }

        canrflg = in_8(&regs->canrflg);
        if ((canrflg & ~MSCAN_STAT_MSK) &&
            !test_and_set_bit(F_RX_PROGRESS, &priv->flags)) {
                if (canrflg & ~MSCAN_STAT_MSK) {
                        priv->shadow_canrier = in_8(&regs->canrier);
                        out_8(&regs->canrier, 0);
                        napi_schedule(&priv->napi);
                        ret = IRQ_HANDLED;
                } else {
                        clear_bit(F_RX_PROGRESS, &priv->flags);
                }
        }
        return ret;
}

static int mscan_do_set_mode(struct net_device *dev, enum can_mode mode)
{
        int ret = 0;

        switch (mode) {
        case CAN_MODE_START:
                ret = mscan_restart(dev);
                if (ret)
                        break;
                if (netif_queue_stopped(dev))
                        netif_wake_queue(dev);
                break;

        default:
                ret = -EOPNOTSUPP;
                break;
        }
        return ret;
}

static int mscan_do_set_bittiming(struct net_device *dev)
{
        struct mscan_priv *priv = netdev_priv(dev);
        struct mscan_regs __iomem *regs = priv->reg_base;
        struct can_bittiming *bt = &priv->can.bittiming;
        u8 btr0, btr1;

        btr0 = BTR0_SET_BRP(bt->brp) | BTR0_SET_SJW(bt->sjw);
        btr1 = (BTR1_SET_TSEG1(bt->prop_seg + bt->phase_seg1) |
                BTR1_SET_TSEG2(bt->phase_seg2) |
                BTR1_SET_SAM(priv->can.ctrlmode & CAN_CTRLMODE_3_SAMPLES));

        netdev_info(dev, "setting BTR0=0x%02x BTR1=0x%02x\n", btr0, btr1);

        out_8(&regs->canbtr0, btr0);
        out_8(&regs->canbtr1, btr1);

        return 0;
}

static int mscan_get_berr_counter(const struct net_device *dev,
                                  struct can_berr_counter *bec)
{
        struct mscan_priv *priv = netdev_priv(dev);
        struct mscan_regs __iomem *regs = priv->reg_base;

        bec->txerr = in_8(&regs->cantxerr);
        bec->rxerr = in_8(&regs->canrxerr);

        return 0;
}

static int mscan_open(struct net_device *dev)
{
        int ret;
        struct mscan_priv *priv = netdev_priv(dev);
        struct mscan_regs __iomem *regs = priv->reg_base;

        ret = clk_prepare_enable(priv->clk_ipg);
        if (ret)
                goto exit_retcode;
        ret = clk_prepare_enable(priv->clk_can);
        if (ret)
                goto exit_dis_ipg_clock;

        /* common open */
        ret = open_candev(dev);
        if (ret)
                goto exit_dis_can_clock;

        napi_enable(&priv->napi);

        ret = request_irq(dev->irq, mscan_isr, 0, dev->name, dev);
        if (ret < 0) {
                netdev_err(dev, "failed to attach interrupt\n");
                goto exit_napi_disable;
        }

        if (priv->can.ctrlmode & CAN_CTRLMODE_LISTENONLY)
                setbits8(&regs->canctl1, MSCAN_LISTEN);
        else
                clrbits8(&regs->canctl1, MSCAN_LISTEN);

        ret = mscan_start(dev);
        if (ret)
                goto exit_free_irq;

        netif_start_queue(dev);

        return 0;

exit_free_irq:
        free_irq(dev->irq, dev);
exit_napi_disable:
        napi_disable(&priv->napi);
        close_candev(dev);
exit_dis_can_clock:
        clk_disable_unprepare(priv->clk_can);
exit_dis_ipg_clock:
        clk_disable_unprepare(priv->clk_ipg);
exit_retcode:
        return ret;
}

static int mscan_close(struct net_device *dev)
{
        struct mscan_priv *priv = netdev_priv(dev);
        struct mscan_regs __iomem *regs = priv->reg_base;

        netif_stop_queue(dev);
        napi_disable(&priv->napi);

        out_8(&regs->cantier, 0);
        out_8(&regs->canrier, 0);
        mscan_set_mode(dev, MSCAN_INIT_MODE);
        close_candev(dev);
        free_irq(dev->irq, dev);

        clk_disable_unprepare(priv->clk_can);
        clk_disable_unprepare(priv->clk_ipg);

        return 0;
}

static const struct net_device_ops mscan_netdev_ops = {
        .ndo_open       = mscan_open,
        .ndo_stop       = mscan_close,
        .ndo_start_xmit = mscan_start_xmit,
};

static const struct ethtool_ops mscan_ethtool_ops = {
        .get_ts_info = ethtool_op_get_ts_info,
};

int register_mscandev(struct net_device *dev, int mscan_clksrc)
{
        struct mscan_priv *priv = netdev_priv(dev);
        struct mscan_regs __iomem *regs = priv->reg_base;
        u8 ctl1;

        ctl1 = in_8(&regs->canctl1);
        if (mscan_clksrc)
                ctl1 |= MSCAN_CLKSRC;
        else
                ctl1 &= ~MSCAN_CLKSRC;

        if (priv->type == MSCAN_TYPE_MPC5121) {
                priv->can.do_get_berr_counter = mscan_get_berr_counter;
                ctl1 |= MSCAN_BORM; /* bus-off recovery upon request */
        }

        ctl1 |= MSCAN_CANE;
        out_8(&regs->canctl1, ctl1);
        udelay(100);

        /* acceptance mask/acceptance code (accept everything) */
        out_be16(&regs->canidar1_0, 0);
        out_be16(&regs->canidar3_2, 0);
        out_be16(&regs->canidar5_4, 0);
        out_be16(&regs->canidar7_6, 0);

        out_be16(&regs->canidmr1_0, 0xffff);
        out_be16(&regs->canidmr3_2, 0xffff);
        out_be16(&regs->canidmr5_4, 0xffff);
        out_be16(&regs->canidmr7_6, 0xffff);
        /* Two 32 bit Acceptance Filters */
        out_8(&regs->canidac, MSCAN_AF_32BIT);

        mscan_set_mode(dev, MSCAN_INIT_MODE);

        return register_candev(dev);
}

void unregister_mscandev(struct net_device *dev)
{
        struct mscan_priv *priv = netdev_priv(dev);
        struct mscan_regs __iomem *regs = priv->reg_base;
        mscan_set_mode(dev, MSCAN_INIT_MODE);
        clrbits8(&regs->canctl1, MSCAN_CANE);
        unregister_candev(dev);
}

struct net_device *alloc_mscandev(void)
{
        struct net_device *dev;
        struct mscan_priv *priv;
        int i;

        dev = alloc_candev(sizeof(struct mscan_priv), MSCAN_ECHO_SKB_MAX);
        if (!dev)
                return NULL;
        priv = netdev_priv(dev);

        dev->netdev_ops = &mscan_netdev_ops;
        dev->ethtool_ops = &mscan_ethtool_ops;

        dev->flags |= IFF_ECHO; /* we support local echo */

        netif_napi_add_weight(dev, &priv->napi, mscan_rx_poll, 8);

        priv->can.bittiming_const = &mscan_bittiming_const;
        priv->can.do_set_bittiming = mscan_do_set_bittiming;
        priv->can.do_set_mode = mscan_do_set_mode;
        priv->can.ctrlmode_supported = CAN_CTRLMODE_3_SAMPLES |
                CAN_CTRLMODE_LISTENONLY;

        for (i = 0; i < TX_QUEUE_SIZE; i++) {
                priv->tx_queue[i].id = i;
                priv->tx_queue[i].mask = 1 << i;
        }

        return dev;
}

MODULE_AUTHOR("Andrey Volkov <avolkov@varma-el.com>");
MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("CAN port driver for a MSCAN based chips");