/*
 * TI HECC (CAN) device driver
 *
 * This driver supports TI's HECC (High End CAN Controller module) and the
 * specs for the same is available at <http://www.ti.com>
 *
 * Copyright (C) 2009 Texas Instruments Incorporated - http://www.ti.com/
 * Copyright (C) 2019 Jeroen Hofstee <jhofstee@victronenergy.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation version 2.
 *
 * This program is distributed as is WITHOUT ANY WARRANTY of any
 * kind, whether express or implied; without even the implied warranty
 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/interrupt.h>
#include <linux/errno.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/platform_device.h>
#include <linux/clk.h>
#include <linux/io.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/regulator/consumer.h>

#include <linux/can/dev.h>
#include <linux/can/error.h>
#include <linux/can/led.h>
#include <linux/can/rx-offload.h>

#define DRV_NAME "ti_hecc"
#define HECC_MODULE_VERSION     "0.7"
MODULE_VERSION(HECC_MODULE_VERSION);
#define DRV_DESC "TI High End CAN Controller Driver " HECC_MODULE_VERSION

/* TX / RX Mailbox Configuration */
#define HECC_MAX_MAILBOXES      32      /* hardware mailboxes - do not change */
#define MAX_TX_PRIO             0x3F    /* hardware value - do not change */

/* Important Note: TX mailbox configuration
 * TX mailboxes should be restricted to the number of SKB buffers to avoid
 * maintaining SKB buffers separately. TX mailboxes should be a power of 2
 * for the mailbox logic to work.  Top mailbox numbers are reserved for RX
 * and lower mailboxes for TX.
 *
 * HECC_MAX_TX_MBOX     HECC_MB_TX_SHIFT
 * 4 (default)          2
 * 8                    3
 * 16                   4
 */
#define HECC_MB_TX_SHIFT        2 /* as per table above */
#define HECC_MAX_TX_MBOX        BIT(HECC_MB_TX_SHIFT)

#define HECC_TX_PRIO_SHIFT      (HECC_MB_TX_SHIFT)
#define HECC_TX_PRIO_MASK       (MAX_TX_PRIO << HECC_MB_TX_SHIFT)
#define HECC_TX_MB_MASK         (HECC_MAX_TX_MBOX - 1)
#define HECC_TX_MASK            ((HECC_MAX_TX_MBOX - 1) | HECC_TX_PRIO_MASK)

/* RX mailbox configuration
 *
 * The remaining mailboxes are used for reception and are delivered
 * based on their timestamp, to avoid a hardware race when CANME is
 * changed while CAN-bus traffic is being received.
 */
#define HECC_MAX_RX_MBOX        (HECC_MAX_MAILBOXES - HECC_MAX_TX_MBOX)
#define HECC_RX_FIRST_MBOX      (HECC_MAX_MAILBOXES - 1)
#define HECC_RX_LAST_MBOX       (HECC_MAX_TX_MBOX)

/* TI HECC module registers */
#define HECC_CANME              0x0     /* Mailbox enable */
#define HECC_CANMD              0x4     /* Mailbox direction */
#define HECC_CANTRS             0x8     /* Transmit request set */
#define HECC_CANTRR             0xC     /* Transmit request */
#define HECC_CANTA              0x10    /* Transmission acknowledge */
#define HECC_CANAA              0x14    /* Abort acknowledge */
#define HECC_CANRMP             0x18    /* Receive message pending */
#define HECC_CANRML             0x1C    /* Receive message lost */
#define HECC_CANRFP             0x20    /* Remote frame pending */
#define HECC_CANGAM             0x24    /* SECC only:Global acceptance mask */
#define HECC_CANMC              0x28    /* Master control */
#define HECC_CANBTC             0x2C    /* Bit timing configuration */
#define HECC_CANES              0x30    /* Error and status */
#define HECC_CANTEC             0x34    /* Transmit error counter */
#define HECC_CANREC             0x38    /* Receive error counter */
#define HECC_CANGIF0            0x3C    /* Global interrupt flag 0 */
#define HECC_CANGIM             0x40    /* Global interrupt mask */
#define HECC_CANGIF1            0x44    /* Global interrupt flag 1 */
#define HECC_CANMIM             0x48    /* Mailbox interrupt mask */
#define HECC_CANMIL             0x4C    /* Mailbox interrupt level */
#define HECC_CANOPC             0x50    /* Overwrite protection control */
#define HECC_CANTIOC            0x54    /* Transmit I/O control */
#define HECC_CANRIOC            0x58    /* Receive I/O control */
#define HECC_CANLNT             0x5C    /* HECC only: Local network time */
#define HECC_CANTOC             0x60    /* HECC only: Time-out control */
#define HECC_CANTOS             0x64    /* HECC only: Time-out status */
#define HECC_CANTIOCE           0x68    /* SCC only:Enhanced TX I/O control */
#define HECC_CANRIOCE           0x6C    /* SCC only:Enhanced RX I/O control */

/* TI HECC RAM registers */
#define HECC_CANMOTS            0x80    /* Message object time stamp */

/* Mailbox registers */
#define HECC_CANMID             0x0
#define HECC_CANMCF             0x4
#define HECC_CANMDL             0x8
#define HECC_CANMDH             0xC

#define HECC_SET_REG            0xFFFFFFFF
#define HECC_CANID_MASK         0x3FF   /* 18 bits mask for extended id's */
#define HECC_CCE_WAIT_COUNT     100     /* Wait for ~1 sec for CCE bit */

#define HECC_CANMC_SCM          BIT(13) /* SCC compat mode */
#define HECC_CANMC_CCR          BIT(12) /* Change config request */
#define HECC_CANMC_PDR          BIT(11) /* Local Power down - for sleep mode */
#define HECC_CANMC_ABO          BIT(7)  /* Auto Bus On */
#define HECC_CANMC_STM          BIT(6)  /* Self test mode - loopback */
#define HECC_CANMC_SRES         BIT(5)  /* Software reset */

#define HECC_CANTIOC_EN         BIT(3)  /* Enable CAN TX I/O pin */
#define HECC_CANRIOC_EN         BIT(3)  /* Enable CAN RX I/O pin */

#define HECC_CANMID_IDE         BIT(31) /* Extended frame format */
#define HECC_CANMID_AME         BIT(30) /* Acceptance mask enable */
#define HECC_CANMID_AAM         BIT(29) /* Auto answer mode */

#define HECC_CANES_FE           BIT(24) /* form error */
#define HECC_CANES_BE           BIT(23) /* bit error */
#define HECC_CANES_SA1          BIT(22) /* stuck at dominant error */
#define HECC_CANES_CRCE         BIT(21) /* CRC error */
#define HECC_CANES_SE           BIT(20) /* stuff bit error */
#define HECC_CANES_ACKE         BIT(19) /* ack error */
#define HECC_CANES_BO           BIT(18) /* Bus off status */
#define HECC_CANES_EP           BIT(17) /* Error passive status */
#define HECC_CANES_EW           BIT(16) /* Error warning status */
#define HECC_CANES_SMA          BIT(5)  /* suspend mode ack */
#define HECC_CANES_CCE          BIT(4)  /* Change config enabled */
#define HECC_CANES_PDA          BIT(3)  /* Power down mode ack */

#define HECC_CANBTC_SAM         BIT(7)  /* sample points */

#define HECC_BUS_ERROR          (HECC_CANES_FE | HECC_CANES_BE |\
                                HECC_CANES_CRCE | HECC_CANES_SE |\
                                HECC_CANES_ACKE)
#define HECC_CANES_FLAGS        (HECC_BUS_ERROR | HECC_CANES_BO |\
                                HECC_CANES_EP | HECC_CANES_EW)

#define HECC_CANMCF_RTR         BIT(4)  /* Remote transmit request */

#define HECC_CANGIF_MAIF        BIT(17) /* Message alarm interrupt */
#define HECC_CANGIF_TCOIF       BIT(16) /* Timer counter overflow int */
#define HECC_CANGIF_GMIF        BIT(15) /* Global mailbox interrupt */
#define HECC_CANGIF_AAIF        BIT(14) /* Abort ack interrupt */
#define HECC_CANGIF_WDIF        BIT(13) /* Write denied interrupt */
#define HECC_CANGIF_WUIF        BIT(12) /* Wake up interrupt */
#define HECC_CANGIF_RMLIF       BIT(11) /* Receive message lost interrupt */
#define HECC_CANGIF_BOIF        BIT(10) /* Bus off interrupt */
#define HECC_CANGIF_EPIF        BIT(9)  /* Error passive interrupt */
#define HECC_CANGIF_WLIF        BIT(8)  /* Warning level interrupt */
#define HECC_CANGIF_MBOX_MASK   0x1F    /* Mailbox number mask */
#define HECC_CANGIM_I1EN        BIT(1)  /* Int line 1 enable */
#define HECC_CANGIM_I0EN        BIT(0)  /* Int line 0 enable */
#define HECC_CANGIM_DEF_MASK    0x700   /* only busoff/warning/passive */
#define HECC_CANGIM_SIL         BIT(2)  /* system interrupts to int line 1 */

/* CAN Bittiming constants as per HECC specs */
static const struct can_bittiming_const ti_hecc_bittiming_const = {
        .name = DRV_NAME,
        .tseg1_min = 1,
        .tseg1_max = 16,
        .tseg2_min = 1,
        .tseg2_max = 8,
        .sjw_max = 4,
        .brp_min = 1,
        .brp_max = 256,
        .brp_inc = 1,
};

struct ti_hecc_priv {
        struct can_priv can;    /* MUST be first member/field */
        struct can_rx_offload offload;
        struct net_device *ndev;
        struct clk *clk;
        void __iomem *base;
        void __iomem *hecc_ram;
        void __iomem *mbx;
        bool use_hecc1int;
        spinlock_t mbx_lock; /* CANME register needs protection */
        u32 tx_head;
        u32 tx_tail;
        struct regulator *reg_xceiver;
};

static inline int get_tx_head_mb(struct ti_hecc_priv *priv)
{
        return priv->tx_head & HECC_TX_MB_MASK;
}

static inline int get_tx_tail_mb(struct ti_hecc_priv *priv)
{
        return priv->tx_tail & HECC_TX_MB_MASK;
}

static inline int get_tx_head_prio(struct ti_hecc_priv *priv)
{
        return (priv->tx_head >> HECC_TX_PRIO_SHIFT) & MAX_TX_PRIO;
}

static inline void hecc_write_lam(struct ti_hecc_priv *priv, u32 mbxno, u32 val)
{
        __raw_writel(val, priv->hecc_ram + mbxno * 4);
}

static inline u32 hecc_read_stamp(struct ti_hecc_priv *priv, u32 mbxno)
{
        return __raw_readl(priv->hecc_ram + HECC_CANMOTS + mbxno * 4);
}

static inline void hecc_write_mbx(struct ti_hecc_priv *priv, u32 mbxno,
                                  u32 reg, u32 val)
{
        __raw_writel(val, priv->mbx + mbxno * 0x10 + reg);
}

static inline u32 hecc_read_mbx(struct ti_hecc_priv *priv, u32 mbxno, u32 reg)
{
        return __raw_readl(priv->mbx + mbxno * 0x10 + reg);
}

static inline void hecc_write(struct ti_hecc_priv *priv, u32 reg, u32 val)
{
        __raw_writel(val, priv->base + reg);
}

static inline u32 hecc_read(struct ti_hecc_priv *priv, int reg)
{
        return __raw_readl(priv->base + reg);
}

static inline void hecc_set_bit(struct ti_hecc_priv *priv, int reg,
                                u32 bit_mask)
{
        hecc_write(priv, reg, hecc_read(priv, reg) | bit_mask);
}

static inline void hecc_clear_bit(struct ti_hecc_priv *priv, int reg,
                                  u32 bit_mask)
{
        hecc_write(priv, reg, hecc_read(priv, reg) & ~bit_mask);
}

static inline u32 hecc_get_bit(struct ti_hecc_priv *priv, int reg, u32 bit_mask)
{
        return (hecc_read(priv, reg) & bit_mask) ? 1 : 0;
}

static int ti_hecc_set_btc(struct ti_hecc_priv *priv)
{
        struct can_bittiming *bit_timing = &priv->can.bittiming;
        u32 can_btc;

        can_btc = (bit_timing->phase_seg2 - 1) & 0x7;
        can_btc |= ((bit_timing->phase_seg1 + bit_timing->prop_seg - 1)
                        & 0xF) << 3;
        if (priv->can.ctrlmode & CAN_CTRLMODE_3_SAMPLES) {
                if (bit_timing->brp > 4)
                        can_btc |= HECC_CANBTC_SAM;
                else
                        netdev_warn(priv->ndev,
                                    "WARN: Triple sampling not set due to h/w limitations");
        }
        can_btc |= ((bit_timing->sjw - 1) & 0x3) << 8;
        can_btc |= ((bit_timing->brp - 1) & 0xFF) << 16;

        /* ERM being set to 0 by default meaning resync at falling edge */

        hecc_write(priv, HECC_CANBTC, can_btc);
        netdev_info(priv->ndev, "setting CANBTC=%#x\n", can_btc);

        return 0;
}

static int ti_hecc_transceiver_switch(const struct ti_hecc_priv *priv,
                                      int on)
{
        if (!priv->reg_xceiver)
                return 0;

        if (on)
                return regulator_enable(priv->reg_xceiver);
        else
                return regulator_disable(priv->reg_xceiver);
}

static void ti_hecc_reset(struct net_device *ndev)
{
        u32 cnt;
        struct ti_hecc_priv *priv = netdev_priv(ndev);

        netdev_dbg(ndev, "resetting hecc ...\n");
        hecc_set_bit(priv, HECC_CANMC, HECC_CANMC_SRES);

        /* Set change control request and wait till enabled */
        hecc_set_bit(priv, HECC_CANMC, HECC_CANMC_CCR);

        /* INFO: It has been observed that at times CCE bit may not be
         * set and hw seems to be ok even if this bit is not set so
         * timing out with a timing of 1ms to respect the specs
         */
        cnt = HECC_CCE_WAIT_COUNT;
        while (!hecc_get_bit(priv, HECC_CANES, HECC_CANES_CCE) && cnt != 0) {
                --cnt;
                udelay(10);
        }

        /* Note: On HECC, BTC can be programmed only in initialization mode, so
         * it is expected that the can bittiming parameters are set via ip
         * utility before the device is opened
         */
        ti_hecc_set_btc(priv);

        /* Clear CCR (and CANMC register) and wait for CCE = 0 enable */
        hecc_write(priv, HECC_CANMC, 0);

        /* INFO: CAN net stack handles bus off and hence disabling auto-bus-on
         * hecc_set_bit(priv, HECC_CANMC, HECC_CANMC_ABO);
         */

        /* INFO: It has been observed that at times CCE bit may not be
         * set and hw seems to be ok even if this bit is not set so
         */
        cnt = HECC_CCE_WAIT_COUNT;
        while (hecc_get_bit(priv, HECC_CANES, HECC_CANES_CCE) && cnt != 0) {
                --cnt;
                udelay(10);
        }

        /* Enable TX and RX I/O Control pins */
        hecc_write(priv, HECC_CANTIOC, HECC_CANTIOC_EN);
        hecc_write(priv, HECC_CANRIOC, HECC_CANRIOC_EN);

        /* Clear registers for clean operation */
        hecc_write(priv, HECC_CANTA, HECC_SET_REG);
        hecc_write(priv, HECC_CANRMP, HECC_SET_REG);
        hecc_write(priv, HECC_CANGIF0, HECC_SET_REG);
        hecc_write(priv, HECC_CANGIF1, HECC_SET_REG);
        hecc_write(priv, HECC_CANME, 0);
        hecc_write(priv, HECC_CANMD, 0);

        /* SCC compat mode NOT supported (and not needed too) */
        hecc_set_bit(priv, HECC_CANMC, HECC_CANMC_SCM);
}

static void ti_hecc_start(struct net_device *ndev)
{
        struct ti_hecc_priv *priv = netdev_priv(ndev);
        u32 cnt, mbxno, mbx_mask;

        /* put HECC in initialization mode and set btc */
        ti_hecc_reset(ndev);

        priv->tx_head = HECC_TX_MASK;
        priv->tx_tail = HECC_TX_MASK;

        /* Enable local and global acceptance mask registers */
        hecc_write(priv, HECC_CANGAM, HECC_SET_REG);

        /* Prepare configured mailboxes to receive messages */
        for (cnt = 0; cnt < HECC_MAX_RX_MBOX; cnt++) {
                mbxno = HECC_MAX_MAILBOXES - 1 - cnt;
                mbx_mask = BIT(mbxno);
                hecc_clear_bit(priv, HECC_CANME, mbx_mask);
                hecc_write_mbx(priv, mbxno, HECC_CANMID, HECC_CANMID_AME);
                hecc_write_lam(priv, mbxno, HECC_SET_REG);
                hecc_set_bit(priv, HECC_CANMD, mbx_mask);
                hecc_set_bit(priv, HECC_CANME, mbx_mask);
                hecc_set_bit(priv, HECC_CANMIM, mbx_mask);
        }

        /* Enable tx interrupts */
        hecc_set_bit(priv, HECC_CANMIM, BIT(HECC_MAX_TX_MBOX) - 1);

        /* Prevent message over-write to create a rx fifo, but not for
         * the lowest priority mailbox, since that allows detecting
         * overflows instead of the hardware silently dropping the
         * messages.
         */
        mbx_mask = ~BIT(HECC_RX_LAST_MBOX);
        hecc_write(priv, HECC_CANOPC, mbx_mask);

        /* Enable interrupts */
        if (priv->use_hecc1int) {
                hecc_write(priv, HECC_CANMIL, HECC_SET_REG);
                hecc_write(priv, HECC_CANGIM, HECC_CANGIM_DEF_MASK |
                        HECC_CANGIM_I1EN | HECC_CANGIM_SIL);
        } else {
                hecc_write(priv, HECC_CANMIL, 0);
                hecc_write(priv, HECC_CANGIM,
                           HECC_CANGIM_DEF_MASK | HECC_CANGIM_I0EN);
        }
        priv->can.state = CAN_STATE_ERROR_ACTIVE;
}

static void ti_hecc_stop(struct net_device *ndev)
{
        struct ti_hecc_priv *priv = netdev_priv(ndev);

        /* Disable the CPK; stop sending, erroring and acking */
        hecc_set_bit(priv, HECC_CANMC, HECC_CANMC_CCR);

        /* Disable interrupts and disable mailboxes */
        hecc_write(priv, HECC_CANGIM, 0);
        hecc_write(priv, HECC_CANMIM, 0);
        hecc_write(priv, HECC_CANME, 0);
        priv->can.state = CAN_STATE_STOPPED;
}

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

        switch (mode) {
        case CAN_MODE_START:
                ti_hecc_start(ndev);
                netif_wake_queue(ndev);
                break;
        default:
                ret = -EOPNOTSUPP;
                break;
        }

        return ret;
}

static int ti_hecc_get_berr_counter(const struct net_device *ndev,
                                    struct can_berr_counter *bec)
{
        struct ti_hecc_priv *priv = netdev_priv(ndev);

        bec->txerr = hecc_read(priv, HECC_CANTEC);
        bec->rxerr = hecc_read(priv, HECC_CANREC);

        return 0;
}

/* ti_hecc_xmit: HECC Transmit
 *
 * The transmit mailboxes start from 0 to HECC_MAX_TX_MBOX. In HECC the
 * priority of the mailbox for transmission is dependent upon priority setting
 * field in mailbox registers. The mailbox with highest value in priority field
 * is transmitted first. Only when two mailboxes have the same value in
 * priority field the highest numbered mailbox is transmitted first.
 *
 * To utilize the HECC priority feature as described above we start with the
 * highest numbered mailbox with highest priority level and move on to the next
 * mailbox with the same priority level and so on. Once we loop through all the
 * transmit mailboxes we choose the next priority level (lower) and so on
 * until we reach the lowest priority level on the lowest numbered mailbox
 * when we stop transmission until all mailboxes are transmitted and then
 * restart at highest numbered mailbox with highest priority.
 *
 * Two counters (head and tail) are used to track the next mailbox to transmit
 * and to track the echo buffer for already transmitted mailbox. The queue
 * is stopped when all the mailboxes are busy or when there is a priority
 * value roll-over happens.
 */
static netdev_tx_t ti_hecc_xmit(struct sk_buff *skb, struct net_device *ndev)
{
        struct ti_hecc_priv *priv = netdev_priv(ndev);
        struct can_frame *cf = (struct can_frame *)skb->data;
        u32 mbxno, mbx_mask, data;
        unsigned long flags;

        if (can_dropped_invalid_skb(ndev, skb))
                return NETDEV_TX_OK;

        mbxno = get_tx_head_mb(priv);
        mbx_mask = BIT(mbxno);
        spin_lock_irqsave(&priv->mbx_lock, flags);
        if (unlikely(hecc_read(priv, HECC_CANME) & mbx_mask)) {
                spin_unlock_irqrestore(&priv->mbx_lock, flags);
                netif_stop_queue(ndev);
                netdev_err(priv->ndev,
                           "BUG: TX mbx not ready tx_head=%08X, tx_tail=%08X\n",
                           priv->tx_head, priv->tx_tail);
                return NETDEV_TX_BUSY;
        }
        spin_unlock_irqrestore(&priv->mbx_lock, flags);

        /* Prepare mailbox for transmission */
        data = cf->len | (get_tx_head_prio(priv) << 8);
        if (cf->can_id & CAN_RTR_FLAG) /* Remote transmission request */
                data |= HECC_CANMCF_RTR;
        hecc_write_mbx(priv, mbxno, HECC_CANMCF, data);

        if (cf->can_id & CAN_EFF_FLAG) /* Extended frame format */
                data = (cf->can_id & CAN_EFF_MASK) | HECC_CANMID_IDE;
        else /* Standard frame format */
                data = (cf->can_id & CAN_SFF_MASK) << 18;
        hecc_write_mbx(priv, mbxno, HECC_CANMID, data);
        hecc_write_mbx(priv, mbxno, HECC_CANMDL,
                       be32_to_cpu(*(__be32 *)(cf->data)));
        if (cf->len > 4)
                hecc_write_mbx(priv, mbxno, HECC_CANMDH,
                               be32_to_cpu(*(__be32 *)(cf->data + 4)));
        else
                *(u32 *)(cf->data + 4) = 0;
        can_put_echo_skb(skb, ndev, mbxno, 0);

        spin_lock_irqsave(&priv->mbx_lock, flags);
        --priv->tx_head;
        if ((hecc_read(priv, HECC_CANME) & BIT(get_tx_head_mb(priv))) ||
            (priv->tx_head & HECC_TX_MASK) == HECC_TX_MASK) {
                netif_stop_queue(ndev);
        }
        hecc_set_bit(priv, HECC_CANME, mbx_mask);
        spin_unlock_irqrestore(&priv->mbx_lock, flags);

        hecc_write(priv, HECC_CANTRS, mbx_mask);

        return NETDEV_TX_OK;
}

static inline
struct ti_hecc_priv *rx_offload_to_priv(struct can_rx_offload *offload)
{
        return container_of(offload, struct ti_hecc_priv, offload);
}

static struct sk_buff *ti_hecc_mailbox_read(struct can_rx_offload *offload,
                                            unsigned int mbxno, u32 *timestamp,
                                            bool drop)
{
        struct ti_hecc_priv *priv = rx_offload_to_priv(offload);
        struct sk_buff *skb;
        struct can_frame *cf;
        u32 data, mbx_mask;

        mbx_mask = BIT(mbxno);

        if (unlikely(drop)) {
                skb = ERR_PTR(-ENOBUFS);
                goto mark_as_read;
        }

        skb = alloc_can_skb(offload->dev, &cf);
        if (unlikely(!skb)) {
                skb = ERR_PTR(-ENOMEM);
                goto mark_as_read;
        }

        data = hecc_read_mbx(priv, mbxno, HECC_CANMID);
        if (data & HECC_CANMID_IDE)
                cf->can_id = (data & CAN_EFF_MASK) | CAN_EFF_FLAG;
        else
                cf->can_id = (data >> 18) & CAN_SFF_MASK;

        data = hecc_read_mbx(priv, mbxno, HECC_CANMCF);
        if (data & HECC_CANMCF_RTR)
                cf->can_id |= CAN_RTR_FLAG;
        cf->len = can_cc_dlc2len(data & 0xF);

        data = hecc_read_mbx(priv, mbxno, HECC_CANMDL);
        *(__be32 *)(cf->data) = cpu_to_be32(data);
        if (cf->len > 4) {
                data = hecc_read_mbx(priv, mbxno, HECC_CANMDH);
                *(__be32 *)(cf->data + 4) = cpu_to_be32(data);
        }

        *timestamp = hecc_read_stamp(priv, mbxno);

        /* Check for FIFO overrun.
         *
         * All but the last RX mailbox have activated overwrite
         * protection. So skip check for overrun, if we're not
         * handling the last RX mailbox.
         *
         * As the overwrite protection for the last RX mailbox is
         * disabled, the CAN core might update while we're reading
         * it. This means the skb might be inconsistent.
         *
         * Return an error to let rx-offload discard this CAN frame.
         */
        if (unlikely(mbxno == HECC_RX_LAST_MBOX &&
                     hecc_read(priv, HECC_CANRML) & mbx_mask))
                skb = ERR_PTR(-ENOBUFS);

 mark_as_read:
        hecc_write(priv, HECC_CANRMP, mbx_mask);

        return skb;
}

static int ti_hecc_error(struct net_device *ndev, int int_status,
                         int err_status)
{
        struct ti_hecc_priv *priv = netdev_priv(ndev);
        struct can_frame *cf;
        struct sk_buff *skb;
        u32 timestamp;
        int err;

        if (err_status & HECC_BUS_ERROR) {
                /* propagate the error condition to the can stack */
                skb = alloc_can_err_skb(ndev, &cf);
                if (!skb) {
                        if (net_ratelimit())
                                netdev_err(priv->ndev,
                                           "%s: alloc_can_err_skb() failed\n",
                                           __func__);
                        return -ENOMEM;
                }

                ++priv->can.can_stats.bus_error;
                cf->can_id |= CAN_ERR_BUSERROR | CAN_ERR_PROT;
                if (err_status & HECC_CANES_FE)
                        cf->data[2] |= CAN_ERR_PROT_FORM;
                if (err_status & HECC_CANES_BE)
                        cf->data[2] |= CAN_ERR_PROT_BIT;
                if (err_status & HECC_CANES_SE)
                        cf->data[2] |= CAN_ERR_PROT_STUFF;
                if (err_status & HECC_CANES_CRCE)
                        cf->data[3] = CAN_ERR_PROT_LOC_CRC_SEQ;
                if (err_status & HECC_CANES_ACKE)
                        cf->data[3] = CAN_ERR_PROT_LOC_ACK;

                timestamp = hecc_read(priv, HECC_CANLNT);
                err = can_rx_offload_queue_sorted(&priv->offload, skb,
                                                  timestamp);
                if (err)
                        ndev->stats.rx_fifo_errors++;
        }

        hecc_write(priv, HECC_CANES, HECC_CANES_FLAGS);

        return 0;
}

static void ti_hecc_change_state(struct net_device *ndev,
                                 enum can_state rx_state,
                                 enum can_state tx_state)
{
        struct ti_hecc_priv *priv = netdev_priv(ndev);
        struct can_frame *cf;
        struct sk_buff *skb;
        u32 timestamp;
        int err;

        skb = alloc_can_err_skb(priv->ndev, &cf);
        if (unlikely(!skb)) {
                priv->can.state = max(tx_state, rx_state);
                return;
        }

        can_change_state(priv->ndev, cf, tx_state, rx_state);

        if (max(tx_state, rx_state) != CAN_STATE_BUS_OFF) {
                cf->data[6] = hecc_read(priv, HECC_CANTEC);
                cf->data[7] = hecc_read(priv, HECC_CANREC);
        }

        timestamp = hecc_read(priv, HECC_CANLNT);
        err = can_rx_offload_queue_sorted(&priv->offload, skb, timestamp);
        if (err)
                ndev->stats.rx_fifo_errors++;
}

static irqreturn_t ti_hecc_interrupt(int irq, void *dev_id)
{
        struct net_device *ndev = (struct net_device *)dev_id;
        struct ti_hecc_priv *priv = netdev_priv(ndev);
        struct net_device_stats *stats = &ndev->stats;
        u32 mbxno, mbx_mask, int_status, err_status, stamp;
        unsigned long flags, rx_pending;
        u32 handled = 0;

        int_status = hecc_read(priv,
                               priv->use_hecc1int ?
                               HECC_CANGIF1 : HECC_CANGIF0);

        if (!int_status)
                return IRQ_NONE;

        err_status = hecc_read(priv, HECC_CANES);
        if (unlikely(err_status & HECC_CANES_FLAGS))
                ti_hecc_error(ndev, int_status, err_status);

        if (unlikely(int_status & HECC_CANGIM_DEF_MASK)) {
                enum can_state rx_state, tx_state;
                u32 rec = hecc_read(priv, HECC_CANREC);
                u32 tec = hecc_read(priv, HECC_CANTEC);

                if (int_status & HECC_CANGIF_WLIF) {
                        handled |= HECC_CANGIF_WLIF;
                        rx_state = rec >= tec ? CAN_STATE_ERROR_WARNING : 0;
                        tx_state = rec <= tec ? CAN_STATE_ERROR_WARNING : 0;
                        netdev_dbg(priv->ndev, "Error Warning interrupt\n");
                        ti_hecc_change_state(ndev, rx_state, tx_state);
                }

                if (int_status & HECC_CANGIF_EPIF) {
                        handled |= HECC_CANGIF_EPIF;
                        rx_state = rec >= tec ? CAN_STATE_ERROR_PASSIVE : 0;
                        tx_state = rec <= tec ? CAN_STATE_ERROR_PASSIVE : 0;
                        netdev_dbg(priv->ndev, "Error passive interrupt\n");
                        ti_hecc_change_state(ndev, rx_state, tx_state);
                }

                if (int_status & HECC_CANGIF_BOIF) {
                        handled |= HECC_CANGIF_BOIF;
                        rx_state = CAN_STATE_BUS_OFF;
                        tx_state = CAN_STATE_BUS_OFF;
                        netdev_dbg(priv->ndev, "Bus off interrupt\n");

                        /* Disable all interrupts */
                        hecc_write(priv, HECC_CANGIM, 0);
                        can_bus_off(ndev);
                        ti_hecc_change_state(ndev, rx_state, tx_state);
                }
        } else if (unlikely(priv->can.state != CAN_STATE_ERROR_ACTIVE)) {
                enum can_state new_state, tx_state, rx_state;
                u32 rec = hecc_read(priv, HECC_CANREC);
                u32 tec = hecc_read(priv, HECC_CANTEC);

                if (rec >= 128 || tec >= 128)
                        new_state = CAN_STATE_ERROR_PASSIVE;
                else if (rec >= 96 || tec >= 96)
                        new_state = CAN_STATE_ERROR_WARNING;
                else
                        new_state = CAN_STATE_ERROR_ACTIVE;

                if (new_state < priv->can.state) {
                        rx_state = rec >= tec ? new_state : 0;
                        tx_state = rec <= tec ? new_state : 0;
                        ti_hecc_change_state(ndev, rx_state, tx_state);
                }
        }

        if (int_status & HECC_CANGIF_GMIF) {
                while (priv->tx_tail - priv->tx_head > 0) {
                        mbxno = get_tx_tail_mb(priv);
                        mbx_mask = BIT(mbxno);
                        if (!(mbx_mask & hecc_read(priv, HECC_CANTA)))
                                break;
                        hecc_write(priv, HECC_CANTA, mbx_mask);
                        spin_lock_irqsave(&priv->mbx_lock, flags);
                        hecc_clear_bit(priv, HECC_CANME, mbx_mask);
                        spin_unlock_irqrestore(&priv->mbx_lock, flags);
                        stamp = hecc_read_stamp(priv, mbxno);
                        stats->tx_bytes +=
                                can_rx_offload_get_echo_skb(&priv->offload,
                                                            mbxno, stamp, NULL);
                        stats->tx_packets++;
                        can_led_event(ndev, CAN_LED_EVENT_TX);
                        --priv->tx_tail;
                }

                /* restart queue if wrap-up or if queue stalled on last pkt */
                if ((priv->tx_head == priv->tx_tail &&
                     ((priv->tx_head & HECC_TX_MASK) != HECC_TX_MASK)) ||
                    (((priv->tx_tail & HECC_TX_MASK) == HECC_TX_MASK) &&
                     ((priv->tx_head & HECC_TX_MASK) == HECC_TX_MASK)))
                        netif_wake_queue(ndev);

                /* offload RX mailboxes and let NAPI deliver them */
                while ((rx_pending = hecc_read(priv, HECC_CANRMP))) {
                        can_rx_offload_irq_offload_timestamp(&priv->offload,
                                                             rx_pending);
                }
        }

        /* clear all interrupt conditions - read back to avoid spurious ints */
        if (priv->use_hecc1int) {
                hecc_write(priv, HECC_CANGIF1, handled);
                int_status = hecc_read(priv, HECC_CANGIF1);
        } else {
                hecc_write(priv, HECC_CANGIF0, handled);
                int_status = hecc_read(priv, HECC_CANGIF0);
        }

        can_rx_offload_irq_finish(&priv->offload);

        return IRQ_HANDLED;
}

static int ti_hecc_open(struct net_device *ndev)
{
        struct ti_hecc_priv *priv = netdev_priv(ndev);
        int err;

        err = request_irq(ndev->irq, ti_hecc_interrupt, IRQF_SHARED,
                          ndev->name, ndev);
        if (err) {
                netdev_err(ndev, "error requesting interrupt\n");
                return err;
        }

        ti_hecc_transceiver_switch(priv, 1);

        /* Open common can device */
        err = open_candev(ndev);
        if (err) {
                netdev_err(ndev, "open_candev() failed %d\n", err);
                ti_hecc_transceiver_switch(priv, 0);
                free_irq(ndev->irq, ndev);
                return err;
        }

        can_led_event(ndev, CAN_LED_EVENT_OPEN);

        ti_hecc_start(ndev);
        can_rx_offload_enable(&priv->offload);
        netif_start_queue(ndev);

        return 0;
}

static int ti_hecc_close(struct net_device *ndev)
{
        struct ti_hecc_priv *priv = netdev_priv(ndev);

        netif_stop_queue(ndev);
        can_rx_offload_disable(&priv->offload);
        ti_hecc_stop(ndev);
        free_irq(ndev->irq, ndev);
        close_candev(ndev);
        ti_hecc_transceiver_switch(priv, 0);

        can_led_event(ndev, CAN_LED_EVENT_STOP);

        return 0;
}

static const struct net_device_ops ti_hecc_netdev_ops = {
        .ndo_open               = ti_hecc_open,
        .ndo_stop               = ti_hecc_close,
        .ndo_start_xmit         = ti_hecc_xmit,
        .ndo_change_mtu         = can_change_mtu,
};

static const struct of_device_id ti_hecc_dt_ids[] = {
        {
                .compatible = "ti,am3517-hecc",
        },
        { }
};
MODULE_DEVICE_TABLE(of, ti_hecc_dt_ids);

static int ti_hecc_probe(struct platform_device *pdev)
{
        struct net_device *ndev = (struct net_device *)0;
        struct ti_hecc_priv *priv;
        struct device_node *np = pdev->dev.of_node;
        struct resource *irq;
        struct regulator *reg_xceiver;
        int err = -ENODEV;

        if (!IS_ENABLED(CONFIG_OF) || !np)
                return -EINVAL;

        reg_xceiver = devm_regulator_get(&pdev->dev, "xceiver");
        if (PTR_ERR(reg_xceiver) == -EPROBE_DEFER)
                return -EPROBE_DEFER;
        else if (IS_ERR(reg_xceiver))
                reg_xceiver = NULL;

        ndev = alloc_candev(sizeof(struct ti_hecc_priv), HECC_MAX_TX_MBOX);
        if (!ndev) {
                dev_err(&pdev->dev, "alloc_candev failed\n");
                return -ENOMEM;
        }
        priv = netdev_priv(ndev);

        /* handle hecc memory */
        priv->base = devm_platform_ioremap_resource_byname(pdev, "hecc");
        if (IS_ERR(priv->base)) {
                dev_err(&pdev->dev, "hecc ioremap failed\n");
                err = PTR_ERR(priv->base);
                goto probe_exit_candev;
        }

        /* handle hecc-ram memory */
        priv->hecc_ram = devm_platform_ioremap_resource_byname(pdev,
                                                               "hecc-ram");
        if (IS_ERR(priv->hecc_ram)) {
                dev_err(&pdev->dev, "hecc-ram ioremap failed\n");
                err = PTR_ERR(priv->hecc_ram);
                goto probe_exit_candev;
        }

        /* handle mbx memory */
        priv->mbx = devm_platform_ioremap_resource_byname(pdev, "mbx");
        if (IS_ERR(priv->mbx)) {
                dev_err(&pdev->dev, "mbx ioremap failed\n");
                err = PTR_ERR(priv->mbx);
                goto probe_exit_candev;
        }

        irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
        if (!irq) {
                dev_err(&pdev->dev, "No irq resource\n");
                goto probe_exit_candev;
        }

        priv->ndev = ndev;
        priv->reg_xceiver = reg_xceiver;
        priv->use_hecc1int = of_property_read_bool(np, "ti,use-hecc1int");

        priv->can.bittiming_const = &ti_hecc_bittiming_const;
        priv->can.do_set_mode = ti_hecc_do_set_mode;
        priv->can.do_get_berr_counter = ti_hecc_get_berr_counter;
        priv->can.ctrlmode_supported = CAN_CTRLMODE_3_SAMPLES;

        spin_lock_init(&priv->mbx_lock);
        ndev->irq = irq->start;
        ndev->flags |= IFF_ECHO;
        platform_set_drvdata(pdev, ndev);
        SET_NETDEV_DEV(ndev, &pdev->dev);
        ndev->netdev_ops = &ti_hecc_netdev_ops;

        priv->clk = clk_get(&pdev->dev, "hecc_ck");
        if (IS_ERR(priv->clk)) {
                dev_err(&pdev->dev, "No clock available\n");
                err = PTR_ERR(priv->clk);
                priv->clk = NULL;
                goto probe_exit_candev;
        }
        priv->can.clock.freq = clk_get_rate(priv->clk);

        err = clk_prepare_enable(priv->clk);
        if (err) {
                dev_err(&pdev->dev, "clk_prepare_enable() failed\n");
                goto probe_exit_release_clk;
        }

        priv->offload.mailbox_read = ti_hecc_mailbox_read;
        priv->offload.mb_first = HECC_RX_FIRST_MBOX;
        priv->offload.mb_last = HECC_RX_LAST_MBOX;
        err = can_rx_offload_add_timestamp(ndev, &priv->offload);
        if (err) {
                dev_err(&pdev->dev, "can_rx_offload_add_timestamp() failed\n");
                goto probe_exit_disable_clk;
        }

        err = register_candev(ndev);
        if (err) {
                dev_err(&pdev->dev, "register_candev() failed\n");
                goto probe_exit_offload;
        }

        devm_can_led_init(ndev);

        dev_info(&pdev->dev, "device registered (reg_base=%p, irq=%u)\n",
                 priv->base, (u32)ndev->irq);

        return 0;

probe_exit_offload:
        can_rx_offload_del(&priv->offload);
probe_exit_disable_clk:
        clk_disable_unprepare(priv->clk);
probe_exit_release_clk:
        clk_put(priv->clk);
probe_exit_candev:
        free_candev(ndev);

        return err;
}

static int ti_hecc_remove(struct platform_device *pdev)
{
        struct net_device *ndev = platform_get_drvdata(pdev);
        struct ti_hecc_priv *priv = netdev_priv(ndev);

        unregister_candev(ndev);
        clk_disable_unprepare(priv->clk);
        clk_put(priv->clk);
        can_rx_offload_del(&priv->offload);
        free_candev(ndev);

        return 0;
}

#ifdef CONFIG_PM
static int ti_hecc_suspend(struct platform_device *pdev, pm_message_t state)
{
        struct net_device *dev = platform_get_drvdata(pdev);
        struct ti_hecc_priv *priv = netdev_priv(dev);

        if (netif_running(dev)) {
                netif_stop_queue(dev);
                netif_device_detach(dev);

        }

        hecc_set_bit(priv, HECC_CANMC, HECC_CANMC_PDR);
        priv->can.state = CAN_STATE_SLEEPING;

        clk_disable_unprepare(priv->clk);

        return 0;
}

static int ti_hecc_resume(struct platform_device *pdev)
{
        struct net_device *dev = platform_get_drvdata(pdev);
        struct ti_hecc_priv *priv = netdev_priv(dev);
        int err;

        err = clk_prepare_enable(priv->clk);
        if (err)
                return err;

        hecc_clear_bit(priv, HECC_CANMC, HECC_CANMC_PDR);
        priv->can.state = CAN_STATE_ERROR_ACTIVE;

        if (netif_running(dev)) {
                netif_device_attach(dev);
                netif_start_queue(dev);
        }

        return 0;
}
#else
#define ti_hecc_suspend NULL
#define ti_hecc_resume NULL
#endif

/* TI HECC netdevice driver: platform driver structure */
static struct platform_driver ti_hecc_driver = {
        .driver = {
                .name    = DRV_NAME,
                .of_match_table = ti_hecc_dt_ids,
        },
        .probe = ti_hecc_probe,
        .remove = ti_hecc_remove,
        .suspend = ti_hecc_suspend,
        .resume = ti_hecc_resume,
};

module_platform_driver(ti_hecc_driver);

MODULE_AUTHOR("Anant Gole <anantgole@ti.com>");
MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION(DRV_DESC);
MODULE_ALIAS("platform:" DRV_NAME);