/* Renesas R-Car CAN device driver
 *
 * Copyright (C) 2013 Cogent Embedded, Inc. <source@cogentembedded.com>
 * Copyright (C) 2013 Renesas Solutions Corp.
 *
 * 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;  either version 2 of the  License, or (at your
 * option) any later version.
 */

#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/platform_device.h>
#include <linux/can/led.h>
#include <linux/can/dev.h>
#include <linux/clk.h>
#include <linux/can/platform/rcar_can.h>

#define RCAR_CAN_DRV_NAME       "rcar_can"

/* Mailbox configuration:
 * mailbox 60 - 63 - Rx FIFO mailboxes
 * mailbox 56 - 59 - Tx FIFO mailboxes
 * non-FIFO mailboxes are not used
 */
#define RCAR_CAN_N_MBX          64 /* Number of mailboxes in non-FIFO mode */
#define RCAR_CAN_RX_FIFO_MBX    60 /* Mailbox - window to Rx FIFO */
#define RCAR_CAN_TX_FIFO_MBX    56 /* Mailbox - window to Tx FIFO */
#define RCAR_CAN_FIFO_DEPTH     4

/* Mailbox registers structure */
struct rcar_can_mbox_regs {
        u32 id;         /* IDE and RTR bits, SID and EID */
        u8 stub;        /* Not used */
        u8 dlc;         /* Data Length Code - bits [0..3] */
        u8 data[8];     /* Data Bytes */
        u8 tsh;         /* Time Stamp Higher Byte */
        u8 tsl;         /* Time Stamp Lower Byte */
};

struct rcar_can_regs {
        struct rcar_can_mbox_regs mb[RCAR_CAN_N_MBX]; /* Mailbox registers */
        u32 mkr_2_9[8]; /* Mask Registers 2-9 */
        u32 fidcr[2];   /* FIFO Received ID Compare Register */
        u32 mkivlr1;    /* Mask Invalid Register 1 */
        u32 mier1;      /* Mailbox Interrupt Enable Register 1 */
        u32 mkr_0_1[2]; /* Mask Registers 0-1 */
        u32 mkivlr0;    /* Mask Invalid Register 0*/
        u32 mier0;      /* Mailbox Interrupt Enable Register 0 */
        u8 pad_440[0x3c0];
        u8 mctl[64];    /* Message Control Registers */
        u16 ctlr;       /* Control Register */
        u16 str;        /* Status register */
        u8 bcr[3];      /* Bit Configuration Register */
        u8 clkr;        /* Clock Select Register */
        u8 rfcr;        /* Receive FIFO Control Register */
        u8 rfpcr;       /* Receive FIFO Pointer Control Register */
        u8 tfcr;        /* Transmit FIFO Control Register */
        u8 tfpcr;       /* Transmit FIFO Pointer Control Register */
        u8 eier;        /* Error Interrupt Enable Register */
        u8 eifr;        /* Error Interrupt Factor Judge Register */
        u8 recr;        /* Receive Error Count Register */
        u8 tecr;        /* Transmit Error Count Register */
        u8 ecsr;        /* Error Code Store Register */
        u8 cssr;        /* Channel Search Support Register */
        u8 mssr;        /* Mailbox Search Status Register */
        u8 msmr;        /* Mailbox Search Mode Register */
        u16 tsr;        /* Time Stamp Register */
        u8 afsr;        /* Acceptance Filter Support Register */
        u8 pad_857;
        u8 tcr;         /* Test Control Register */
        u8 pad_859[7];
        u8 ier;         /* Interrupt Enable Register */
        u8 isr;         /* Interrupt Status Register */
        u8 pad_862;
        u8 mbsmr;       /* Mailbox Search Mask Register */
};

struct rcar_can_priv {
        struct can_priv can;    /* Must be the first member! */
        struct net_device *ndev;
        struct napi_struct napi;
        struct rcar_can_regs __iomem *regs;
        struct clk *clk;
        u8 tx_dlc[RCAR_CAN_FIFO_DEPTH];
        u32 tx_head;
        u32 tx_tail;
        u8 clock_select;
        u8 ier;
};

static const struct can_bittiming_const rcar_can_bittiming_const = {
        .name = RCAR_CAN_DRV_NAME,
        .tseg1_min = 4,
        .tseg1_max = 16,
        .tseg2_min = 2,
        .tseg2_max = 8,
        .sjw_max = 4,
        .brp_min = 1,
        .brp_max = 1024,
        .brp_inc = 1,
};

/* Control Register bits */
#define RCAR_CAN_CTLR_BOM       (3 << 11) /* Bus-Off Recovery Mode Bits */
#define RCAR_CAN_CTLR_BOM_ENT   (1 << 11) /* Entry to halt mode */
                                        /* at bus-off entry */
#define RCAR_CAN_CTLR_SLPM      (1 << 10)
#define RCAR_CAN_CTLR_CANM      (3 << 8) /* Operating Mode Select Bit */
#define RCAR_CAN_CTLR_CANM_HALT (1 << 9)
#define RCAR_CAN_CTLR_CANM_RESET (1 << 8)
#define RCAR_CAN_CTLR_CANM_FORCE_RESET (3 << 8)
#define RCAR_CAN_CTLR_MLM       (1 << 3) /* Message Lost Mode Select */
#define RCAR_CAN_CTLR_IDFM      (3 << 1) /* ID Format Mode Select Bits */
#define RCAR_CAN_CTLR_IDFM_MIXED (1 << 2) /* Mixed ID mode */
#define RCAR_CAN_CTLR_MBM       (1 << 0) /* Mailbox Mode select */

/* Status Register bits */
#define RCAR_CAN_STR_RSTST      (1 << 8) /* Reset Status Bit */

/* FIFO Received ID Compare Registers 0 and 1 bits */
#define RCAR_CAN_FIDCR_IDE      (1 << 31) /* ID Extension Bit */
#define RCAR_CAN_FIDCR_RTR      (1 << 30) /* Remote Transmission Request Bit */

/* Receive FIFO Control Register bits */
#define RCAR_CAN_RFCR_RFEST     (1 << 7) /* Receive FIFO Empty Status Flag */
#define RCAR_CAN_RFCR_RFE       (1 << 0) /* Receive FIFO Enable */

/* Transmit FIFO Control Register bits */
#define RCAR_CAN_TFCR_TFUST     (7 << 1) /* Transmit FIFO Unsent Message */
                                        /* Number Status Bits */
#define RCAR_CAN_TFCR_TFUST_SHIFT 1     /* Offset of Transmit FIFO Unsent */
                                        /* Message Number Status Bits */
#define RCAR_CAN_TFCR_TFE       (1 << 0) /* Transmit FIFO Enable */

#define RCAR_CAN_N_RX_MKREGS1   2       /* Number of mask registers */
                                        /* for Rx mailboxes 0-31 */
#define RCAR_CAN_N_RX_MKREGS2   8

/* Bit Configuration Register settings */
#define RCAR_CAN_BCR_TSEG1(x)   (((x) & 0x0f) << 20)
#define RCAR_CAN_BCR_BPR(x)     (((x) & 0x3ff) << 8)
#define RCAR_CAN_BCR_SJW(x)     (((x) & 0x3) << 4)
#define RCAR_CAN_BCR_TSEG2(x)   ((x) & 0x07)

/* Mailbox and Mask Registers bits */
#define RCAR_CAN_IDE            (1 << 31)
#define RCAR_CAN_RTR            (1 << 30)
#define RCAR_CAN_SID_SHIFT      18

/* Mailbox Interrupt Enable Register 1 bits */
#define RCAR_CAN_MIER1_RXFIE    (1 << 28) /* Receive  FIFO Interrupt Enable */
#define RCAR_CAN_MIER1_TXFIE    (1 << 24) /* Transmit FIFO Interrupt Enable */

/* Interrupt Enable Register bits */
#define RCAR_CAN_IER_ERSIE      (1 << 5) /* Error (ERS) Interrupt Enable Bit */
#define RCAR_CAN_IER_RXFIE      (1 << 4) /* Reception FIFO Interrupt */
                                        /* Enable Bit */
#define RCAR_CAN_IER_TXFIE      (1 << 3) /* Transmission FIFO Interrupt */
                                        /* Enable Bit */
/* Interrupt Status Register bits */
#define RCAR_CAN_ISR_ERSF       (1 << 5) /* Error (ERS) Interrupt Status Bit */
#define RCAR_CAN_ISR_RXFF       (1 << 4) /* Reception FIFO Interrupt */
                                        /* Status Bit */
#define RCAR_CAN_ISR_TXFF       (1 << 3) /* Transmission FIFO Interrupt */
                                        /* Status Bit */

/* Error Interrupt Enable Register bits */
#define RCAR_CAN_EIER_BLIE      (1 << 7) /* Bus Lock Interrupt Enable */
#define RCAR_CAN_EIER_OLIE      (1 << 6) /* Overload Frame Transmit */
                                        /* Interrupt Enable */
#define RCAR_CAN_EIER_ORIE      (1 << 5) /* Receive Overrun  Interrupt Enable */
#define RCAR_CAN_EIER_BORIE     (1 << 4) /* Bus-Off Recovery Interrupt Enable */
#define RCAR_CAN_EIER_BOEIE     (1 << 3) /* Bus-Off Entry Interrupt Enable */
#define RCAR_CAN_EIER_EPIE      (1 << 2) /* Error Passive Interrupt Enable */
#define RCAR_CAN_EIER_EWIE      (1 << 1) /* Error Warning Interrupt Enable */
#define RCAR_CAN_EIER_BEIE      (1 << 0) /* Bus Error Interrupt Enable */

/* Error Interrupt Factor Judge Register bits */
#define RCAR_CAN_EIFR_BLIF      (1 << 7) /* Bus Lock Detect Flag */
#define RCAR_CAN_EIFR_OLIF      (1 << 6) /* Overload Frame Transmission */
                                         /* Detect Flag */
#define RCAR_CAN_EIFR_ORIF      (1 << 5) /* Receive Overrun Detect Flag */
#define RCAR_CAN_EIFR_BORIF     (1 << 4) /* Bus-Off Recovery Detect Flag */
#define RCAR_CAN_EIFR_BOEIF     (1 << 3) /* Bus-Off Entry Detect Flag */
#define RCAR_CAN_EIFR_EPIF      (1 << 2) /* Error Passive Detect Flag */
#define RCAR_CAN_EIFR_EWIF      (1 << 1) /* Error Warning Detect Flag */
#define RCAR_CAN_EIFR_BEIF      (1 << 0) /* Bus Error Detect Flag */

/* Error Code Store Register bits */
#define RCAR_CAN_ECSR_EDPM      (1 << 7) /* Error Display Mode Select Bit */
#define RCAR_CAN_ECSR_ADEF      (1 << 6) /* ACK Delimiter Error Flag */
#define RCAR_CAN_ECSR_BE0F      (1 << 5) /* Bit Error (dominant) Flag */
#define RCAR_CAN_ECSR_BE1F      (1 << 4) /* Bit Error (recessive) Flag */
#define RCAR_CAN_ECSR_CEF       (1 << 3) /* CRC Error Flag */
#define RCAR_CAN_ECSR_AEF       (1 << 2) /* ACK Error Flag */
#define RCAR_CAN_ECSR_FEF       (1 << 1) /* Form Error Flag */
#define RCAR_CAN_ECSR_SEF       (1 << 0) /* Stuff Error Flag */

#define RCAR_CAN_NAPI_WEIGHT    4
#define MAX_STR_READS           0x100

static void tx_failure_cleanup(struct net_device *ndev)
{
        int i;

        for (i = 0; i < RCAR_CAN_FIFO_DEPTH; i++)
                can_free_echo_skb(ndev, i);
}

static void rcar_can_error(struct net_device *ndev)
{
        struct rcar_can_priv *priv = netdev_priv(ndev);
        struct net_device_stats *stats = &ndev->stats;
        struct can_frame *cf;
        struct sk_buff *skb;
        u8 eifr, txerr = 0, rxerr = 0;

        /* Propagate the error condition to the CAN stack */
        skb = alloc_can_err_skb(ndev, &cf);

        eifr = readb(&priv->regs->eifr);
        if (eifr & (RCAR_CAN_EIFR_EWIF | RCAR_CAN_EIFR_EPIF)) {
                txerr = readb(&priv->regs->tecr);
                rxerr = readb(&priv->regs->recr);
                if (skb) {
                        cf->can_id |= CAN_ERR_CRTL;
                        cf->data[6] = txerr;
                        cf->data[7] = rxerr;
                }
        }
        if (eifr & RCAR_CAN_EIFR_BEIF) {
                int rx_errors = 0, tx_errors = 0;
                u8 ecsr;

                netdev_dbg(priv->ndev, "Bus error interrupt:\n");
                if (skb) {
                        cf->can_id |= CAN_ERR_BUSERROR | CAN_ERR_PROT;
                        cf->data[2] = CAN_ERR_PROT_UNSPEC;
                }
                ecsr = readb(&priv->regs->ecsr);
                if (ecsr & RCAR_CAN_ECSR_ADEF) {
                        netdev_dbg(priv->ndev, "ACK Delimiter Error\n");
                        tx_errors++;
                        writeb(~RCAR_CAN_ECSR_ADEF, &priv->regs->ecsr);
                        if (skb)
                                cf->data[3] |= CAN_ERR_PROT_LOC_ACK_DEL;
                }
                if (ecsr & RCAR_CAN_ECSR_BE0F) {
                        netdev_dbg(priv->ndev, "Bit Error (dominant)\n");
                        tx_errors++;
                        writeb(~RCAR_CAN_ECSR_BE0F, &priv->regs->ecsr);
                        if (skb)
                                cf->data[2] |= CAN_ERR_PROT_BIT0;
                }
                if (ecsr & RCAR_CAN_ECSR_BE1F) {
                        netdev_dbg(priv->ndev, "Bit Error (recessive)\n");
                        tx_errors++;
                        writeb(~RCAR_CAN_ECSR_BE1F, &priv->regs->ecsr);
                        if (skb)
                                cf->data[2] |= CAN_ERR_PROT_BIT1;
                }
                if (ecsr & RCAR_CAN_ECSR_CEF) {
                        netdev_dbg(priv->ndev, "CRC Error\n");
                        rx_errors++;
                        writeb(~RCAR_CAN_ECSR_CEF, &priv->regs->ecsr);
                        if (skb)
                                cf->data[3] |= CAN_ERR_PROT_LOC_CRC_SEQ;
                }
                if (ecsr & RCAR_CAN_ECSR_AEF) {
                        netdev_dbg(priv->ndev, "ACK Error\n");
                        tx_errors++;
                        writeb(~RCAR_CAN_ECSR_AEF, &priv->regs->ecsr);
                        if (skb) {
                                cf->can_id |= CAN_ERR_ACK;
                                cf->data[3] |= CAN_ERR_PROT_LOC_ACK;
                        }
                }
                if (ecsr & RCAR_CAN_ECSR_FEF) {
                        netdev_dbg(priv->ndev, "Form Error\n");
                        rx_errors++;
                        writeb(~RCAR_CAN_ECSR_FEF, &priv->regs->ecsr);
                        if (skb)
                                cf->data[2] |= CAN_ERR_PROT_FORM;
                }
                if (ecsr & RCAR_CAN_ECSR_SEF) {
                        netdev_dbg(priv->ndev, "Stuff Error\n");
                        rx_errors++;
                        writeb(~RCAR_CAN_ECSR_SEF, &priv->regs->ecsr);
                        if (skb)
                                cf->data[2] |= CAN_ERR_PROT_STUFF;
                }

                priv->can.can_stats.bus_error++;
                ndev->stats.rx_errors += rx_errors;
                ndev->stats.tx_errors += tx_errors;
                writeb(~RCAR_CAN_EIFR_BEIF, &priv->regs->eifr);
        }
        if (eifr & RCAR_CAN_EIFR_EWIF) {
                netdev_dbg(priv->ndev, "Error warning interrupt\n");
                priv->can.state = CAN_STATE_ERROR_WARNING;
                priv->can.can_stats.error_warning++;
                /* Clear interrupt condition */
                writeb(~RCAR_CAN_EIFR_EWIF, &priv->regs->eifr);
                if (skb)
                        cf->data[1] = txerr > rxerr ? CAN_ERR_CRTL_TX_WARNING :
                                              CAN_ERR_CRTL_RX_WARNING;
        }
        if (eifr & RCAR_CAN_EIFR_EPIF) {
                netdev_dbg(priv->ndev, "Error passive interrupt\n");
                priv->can.state = CAN_STATE_ERROR_PASSIVE;
                priv->can.can_stats.error_passive++;
                /* Clear interrupt condition */
                writeb(~RCAR_CAN_EIFR_EPIF, &priv->regs->eifr);
                if (skb)
                        cf->data[1] = txerr > rxerr ? CAN_ERR_CRTL_TX_PASSIVE :
                                              CAN_ERR_CRTL_RX_PASSIVE;
        }
        if (eifr & RCAR_CAN_EIFR_BOEIF) {
                netdev_dbg(priv->ndev, "Bus-off entry interrupt\n");
                tx_failure_cleanup(ndev);
                priv->ier = RCAR_CAN_IER_ERSIE;
                writeb(priv->ier, &priv->regs->ier);
                priv->can.state = CAN_STATE_BUS_OFF;
                /* Clear interrupt condition */
                writeb(~RCAR_CAN_EIFR_BOEIF, &priv->regs->eifr);
                can_bus_off(ndev);
                if (skb)
                        cf->can_id |= CAN_ERR_BUSOFF;
        }
        if (eifr & RCAR_CAN_EIFR_ORIF) {
                netdev_dbg(priv->ndev, "Receive overrun error interrupt\n");
                ndev->stats.rx_over_errors++;
                ndev->stats.rx_errors++;
                writeb(~RCAR_CAN_EIFR_ORIF, &priv->regs->eifr);
                if (skb) {
                        cf->can_id |= CAN_ERR_CRTL;
                        cf->data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
                }
        }
        if (eifr & RCAR_CAN_EIFR_OLIF) {
                netdev_dbg(priv->ndev,
                           "Overload Frame Transmission error interrupt\n");
                ndev->stats.rx_over_errors++;
                ndev->stats.rx_errors++;
                writeb(~RCAR_CAN_EIFR_OLIF, &priv->regs->eifr);
                if (skb) {
                        cf->can_id |= CAN_ERR_PROT;
                        cf->data[2] |= CAN_ERR_PROT_OVERLOAD;
                }
        }

        if (skb) {
                stats->rx_packets++;
                stats->rx_bytes += cf->can_dlc;
                netif_rx(skb);
        }
}

static void rcar_can_tx_done(struct net_device *ndev)
{
        struct rcar_can_priv *priv = netdev_priv(ndev);
        struct net_device_stats *stats = &ndev->stats;
        u8 isr;

        while (1) {
                u8 unsent = readb(&priv->regs->tfcr);

                unsent = (unsent & RCAR_CAN_TFCR_TFUST) >>
                          RCAR_CAN_TFCR_TFUST_SHIFT;
                if (priv->tx_head - priv->tx_tail <= unsent)
                        break;
                stats->tx_packets++;
                stats->tx_bytes += priv->tx_dlc[priv->tx_tail %
                                                RCAR_CAN_FIFO_DEPTH];
                priv->tx_dlc[priv->tx_tail % RCAR_CAN_FIFO_DEPTH] = 0;
                can_get_echo_skb(ndev, priv->tx_tail % RCAR_CAN_FIFO_DEPTH);
                priv->tx_tail++;
                netif_wake_queue(ndev);
        }
        /* Clear interrupt */
        isr = readb(&priv->regs->isr);
        writeb(isr & ~RCAR_CAN_ISR_TXFF, &priv->regs->isr);
        can_led_event(ndev, CAN_LED_EVENT_TX);
}

static irqreturn_t rcar_can_interrupt(int irq, void *dev_id)
{
        struct net_device *ndev = dev_id;
        struct rcar_can_priv *priv = netdev_priv(ndev);
        u8 isr;

        isr = readb(&priv->regs->isr);
        if (!(isr & priv->ier))
                return IRQ_NONE;

        if (isr & RCAR_CAN_ISR_ERSF)
                rcar_can_error(ndev);

        if (isr & RCAR_CAN_ISR_TXFF)
                rcar_can_tx_done(ndev);

        if (isr & RCAR_CAN_ISR_RXFF) {
                if (napi_schedule_prep(&priv->napi)) {
                        /* Disable Rx FIFO interrupts */
                        priv->ier &= ~RCAR_CAN_IER_RXFIE;
                        writeb(priv->ier, &priv->regs->ier);
                        __napi_schedule(&priv->napi);
                }
        }

        return IRQ_HANDLED;
}

static void rcar_can_set_bittiming(struct net_device *dev)
{
        struct rcar_can_priv *priv = netdev_priv(dev);
        struct can_bittiming *bt = &priv->can.bittiming;
        u32 bcr;

        bcr = RCAR_CAN_BCR_TSEG1(bt->phase_seg1 + bt->prop_seg - 1) |
              RCAR_CAN_BCR_BPR(bt->brp - 1) | RCAR_CAN_BCR_SJW(bt->sjw - 1) |
              RCAR_CAN_BCR_TSEG2(bt->phase_seg2 - 1);
        /* Don't overwrite CLKR with 32-bit BCR access; CLKR has 8-bit access.
         * All the registers are big-endian but they get byte-swapped on 32-bit
         * read/write (but not on 8-bit, contrary to the manuals)...
         */
        writel((bcr << 8) | priv->clock_select, &priv->regs->bcr);
}

static void rcar_can_start(struct net_device *ndev)
{
        struct rcar_can_priv *priv = netdev_priv(ndev);
        u16 ctlr;
        int i;

        /* Set controller to known mode:
         * - FIFO mailbox mode
         * - accept all messages
         * - overrun mode
         * CAN is in sleep mode after MCU hardware or software reset.
         */
        ctlr = readw(&priv->regs->ctlr);
        ctlr &= ~RCAR_CAN_CTLR_SLPM;
        writew(ctlr, &priv->regs->ctlr);
        /* Go to reset mode */
        ctlr |= RCAR_CAN_CTLR_CANM_FORCE_RESET;
        writew(ctlr, &priv->regs->ctlr);
        for (i = 0; i < MAX_STR_READS; i++) {
                if (readw(&priv->regs->str) & RCAR_CAN_STR_RSTST)
                        break;
        }
        rcar_can_set_bittiming(ndev);
        ctlr |= RCAR_CAN_CTLR_IDFM_MIXED; /* Select mixed ID mode */
        ctlr |= RCAR_CAN_CTLR_BOM_ENT;  /* Entry to halt mode automatically */
                                        /* at bus-off */
        ctlr |= RCAR_CAN_CTLR_MBM;      /* Select FIFO mailbox mode */
        ctlr |= RCAR_CAN_CTLR_MLM;      /* Overrun mode */
        writew(ctlr, &priv->regs->ctlr);

        /* Accept all SID and EID */
        writel(0, &priv->regs->mkr_2_9[6]);
        writel(0, &priv->regs->mkr_2_9[7]);
        /* In FIFO mailbox mode, write "0" to bits 24 to 31 */
        writel(0, &priv->regs->mkivlr1);
        /* Accept all frames */
        writel(0, &priv->regs->fidcr[0]);
        writel(RCAR_CAN_FIDCR_IDE | RCAR_CAN_FIDCR_RTR, &priv->regs->fidcr[1]);
        /* Enable and configure FIFO mailbox interrupts */
        writel(RCAR_CAN_MIER1_RXFIE | RCAR_CAN_MIER1_TXFIE, &priv->regs->mier1);

        priv->ier = RCAR_CAN_IER_ERSIE | RCAR_CAN_IER_RXFIE |
                    RCAR_CAN_IER_TXFIE;
        writeb(priv->ier, &priv->regs->ier);

        /* Accumulate error codes */
        writeb(RCAR_CAN_ECSR_EDPM, &priv->regs->ecsr);
        /* Enable error interrupts */
        writeb(RCAR_CAN_EIER_EWIE | RCAR_CAN_EIER_EPIE | RCAR_CAN_EIER_BOEIE |
               (priv->can.ctrlmode & CAN_CTRLMODE_BERR_REPORTING ?
               RCAR_CAN_EIER_BEIE : 0) | RCAR_CAN_EIER_ORIE |
               RCAR_CAN_EIER_OLIE, &priv->regs->eier);
        priv->can.state = CAN_STATE_ERROR_ACTIVE;

        /* Go to operation mode */
        writew(ctlr & ~RCAR_CAN_CTLR_CANM, &priv->regs->ctlr);
        for (i = 0; i < MAX_STR_READS; i++) {
                if (!(readw(&priv->regs->str) & RCAR_CAN_STR_RSTST))
                        break;
        }
        /* Enable Rx and Tx FIFO */
        writeb(RCAR_CAN_RFCR_RFE, &priv->regs->rfcr);
        writeb(RCAR_CAN_TFCR_TFE, &priv->regs->tfcr);
}

static int rcar_can_open(struct net_device *ndev)
{
        struct rcar_can_priv *priv = netdev_priv(ndev);
        int err;

        err = clk_prepare_enable(priv->clk);
        if (err) {
                netdev_err(ndev, "clk_prepare_enable() failed, error %d\n",
                           err);
                goto out;
        }
        err = open_candev(ndev);
        if (err) {
                netdev_err(ndev, "open_candev() failed, error %d\n", err);
                goto out_clock;
        }
        napi_enable(&priv->napi);
        err = request_irq(ndev->irq, rcar_can_interrupt, 0, ndev->name, ndev);
        if (err) {
                netdev_err(ndev, "error requesting interrupt %x\n", ndev->irq);
                goto out_close;
        }
        can_led_event(ndev, CAN_LED_EVENT_OPEN);
        rcar_can_start(ndev);
        netif_start_queue(ndev);
        return 0;
out_close:
        napi_disable(&priv->napi);
        close_candev(ndev);
out_clock:
        clk_disable_unprepare(priv->clk);
out:
        return err;
}

static void rcar_can_stop(struct net_device *ndev)
{
        struct rcar_can_priv *priv = netdev_priv(ndev);
        u16 ctlr;
        int i;

        /* Go to (force) reset mode */
        ctlr = readw(&priv->regs->ctlr);
        ctlr |= RCAR_CAN_CTLR_CANM_FORCE_RESET;
        writew(ctlr, &priv->regs->ctlr);
        for (i = 0; i < MAX_STR_READS; i++) {
                if (readw(&priv->regs->str) & RCAR_CAN_STR_RSTST)
                        break;
        }
        writel(0, &priv->regs->mier0);
        writel(0, &priv->regs->mier1);
        writeb(0, &priv->regs->ier);
        writeb(0, &priv->regs->eier);
        /* Go to sleep mode */
        ctlr |= RCAR_CAN_CTLR_SLPM;
        writew(ctlr, &priv->regs->ctlr);
        priv->can.state = CAN_STATE_STOPPED;
}

static int rcar_can_close(struct net_device *ndev)
{
        struct rcar_can_priv *priv = netdev_priv(ndev);

        netif_stop_queue(ndev);
        rcar_can_stop(ndev);
        free_irq(ndev->irq, ndev);
        napi_disable(&priv->napi);
        clk_disable_unprepare(priv->clk);
        close_candev(ndev);
        can_led_event(ndev, CAN_LED_EVENT_STOP);
        return 0;
}

static netdev_tx_t rcar_can_start_xmit(struct sk_buff *skb,
                                       struct net_device *ndev)
{
        struct rcar_can_priv *priv = netdev_priv(ndev);
        struct can_frame *cf = (struct can_frame *)skb->data;
        u32 data, i;

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

        if (cf->can_id & CAN_EFF_FLAG)  /* Extended frame format */
                data = (cf->can_id & CAN_EFF_MASK) | RCAR_CAN_IDE;
        else                            /* Standard frame format */
                data = (cf->can_id & CAN_SFF_MASK) << RCAR_CAN_SID_SHIFT;

        if (cf->can_id & CAN_RTR_FLAG) { /* Remote transmission request */
                data |= RCAR_CAN_RTR;
        } else {
                for (i = 0; i < cf->can_dlc; i++)
                        writeb(cf->data[i],
                               &priv->regs->mb[RCAR_CAN_TX_FIFO_MBX].data[i]);
        }

        writel(data, &priv->regs->mb[RCAR_CAN_TX_FIFO_MBX].id);

        writeb(cf->can_dlc, &priv->regs->mb[RCAR_CAN_TX_FIFO_MBX].dlc);

        priv->tx_dlc[priv->tx_head % RCAR_CAN_FIFO_DEPTH] = cf->can_dlc;
        can_put_echo_skb(skb, ndev, priv->tx_head % RCAR_CAN_FIFO_DEPTH);
        priv->tx_head++;
        /* Start Tx: write 0xff to the TFPCR register to increment
         * the CPU-side pointer for the transmit FIFO to the next
         * mailbox location
         */
        writeb(0xff, &priv->regs->tfpcr);
        /* Stop the queue if we've filled all FIFO entries */
        if (priv->tx_head - priv->tx_tail >= RCAR_CAN_FIFO_DEPTH)
                netif_stop_queue(ndev);

        return NETDEV_TX_OK;
}

static const struct net_device_ops rcar_can_netdev_ops = {
        .ndo_open = rcar_can_open,
        .ndo_stop = rcar_can_close,
        .ndo_start_xmit = rcar_can_start_xmit,
};

static void rcar_can_rx_pkt(struct rcar_can_priv *priv)
{
        struct net_device_stats *stats = &priv->ndev->stats;
        struct can_frame *cf;
        struct sk_buff *skb;
        u32 data;
        u8 dlc;

        skb = alloc_can_skb(priv->ndev, &cf);
        if (!skb) {
                stats->rx_dropped++;
                return;
        }

        data = readl(&priv->regs->mb[RCAR_CAN_RX_FIFO_MBX].id);
        if (data & RCAR_CAN_IDE)
                cf->can_id = (data & CAN_EFF_MASK) | CAN_EFF_FLAG;
        else
                cf->can_id = (data >> RCAR_CAN_SID_SHIFT) & CAN_SFF_MASK;

        dlc = readb(&priv->regs->mb[RCAR_CAN_RX_FIFO_MBX].dlc);
        cf->can_dlc = get_can_dlc(dlc);
        if (data & RCAR_CAN_RTR) {
                cf->can_id |= CAN_RTR_FLAG;
        } else {
                for (dlc = 0; dlc < cf->can_dlc; dlc++)
                        cf->data[dlc] =
                        readb(&priv->regs->mb[RCAR_CAN_RX_FIFO_MBX].data[dlc]);
        }

        can_led_event(priv->ndev, CAN_LED_EVENT_RX);

        stats->rx_bytes += cf->can_dlc;
        stats->rx_packets++;
        netif_receive_skb(skb);
}

static int rcar_can_rx_poll(struct napi_struct *napi, int quota)
{
        struct rcar_can_priv *priv = container_of(napi,
                                                  struct rcar_can_priv, napi);
        int num_pkts;

        for (num_pkts = 0; num_pkts < quota; num_pkts++) {
                u8 rfcr, isr;

                isr = readb(&priv->regs->isr);
                /* Clear interrupt bit */
                if (isr & RCAR_CAN_ISR_RXFF)
                        writeb(isr & ~RCAR_CAN_ISR_RXFF, &priv->regs->isr);
                rfcr = readb(&priv->regs->rfcr);
                if (rfcr & RCAR_CAN_RFCR_RFEST)
                        break;
                rcar_can_rx_pkt(priv);
                /* Write 0xff to the RFPCR register to increment
                 * the CPU-side pointer for the receive FIFO
                 * to the next mailbox location
                 */
                writeb(0xff, &priv->regs->rfpcr);
        }
        /* All packets processed */
        if (num_pkts < quota) {
                napi_complete(napi);
                priv->ier |= RCAR_CAN_IER_RXFIE;
                writeb(priv->ier, &priv->regs->ier);
        }
        return num_pkts;
}

static int rcar_can_do_set_mode(struct net_device *ndev, enum can_mode mode)
{
        switch (mode) {
        case CAN_MODE_START:
                rcar_can_start(ndev);
                netif_wake_queue(ndev);
                return 0;
        default:
                return -EOPNOTSUPP;
        }
}

static int rcar_can_get_berr_counter(const struct net_device *dev,
                                     struct can_berr_counter *bec)
{
        struct rcar_can_priv *priv = netdev_priv(dev);
        int err;

        err = clk_prepare_enable(priv->clk);
        if (err)
                return err;
        bec->txerr = readb(&priv->regs->tecr);
        bec->rxerr = readb(&priv->regs->recr);
        clk_disable_unprepare(priv->clk);
        return 0;
}

static int rcar_can_probe(struct platform_device *pdev)
{
        struct rcar_can_platform_data *pdata;
        struct rcar_can_priv *priv;
        struct net_device *ndev;
        struct resource *mem;
        void __iomem *addr;
        int err = -ENODEV;
        int irq;

        pdata = dev_get_platdata(&pdev->dev);
        if (!pdata) {
                dev_err(&pdev->dev, "No platform data provided!\n");
                goto fail;
        }

        irq = platform_get_irq(pdev, 0);
        if (!irq) {
                dev_err(&pdev->dev, "No IRQ resource\n");
                goto fail;
        }

        mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        addr = devm_ioremap_resource(&pdev->dev, mem);
        if (IS_ERR(addr)) {
                err = PTR_ERR(addr);
                goto fail;
        }

        ndev = alloc_candev(sizeof(struct rcar_can_priv), RCAR_CAN_FIFO_DEPTH);
        if (!ndev) {
                dev_err(&pdev->dev, "alloc_candev() failed\n");
                err = -ENOMEM;
                goto fail;
        }

        priv = netdev_priv(ndev);

        priv->clk = devm_clk_get(&pdev->dev, NULL);
        if (IS_ERR(priv->clk)) {
                err = PTR_ERR(priv->clk);
                dev_err(&pdev->dev, "cannot get clock: %d\n", err);
                goto fail_clk;
        }

        ndev->netdev_ops = &rcar_can_netdev_ops;
        ndev->irq = irq;
        ndev->flags |= IFF_ECHO;
        priv->ndev = ndev;
        priv->regs = addr;
        priv->clock_select = pdata->clock_select;
        priv->can.clock.freq = clk_get_rate(priv->clk);
        priv->can.bittiming_const = &rcar_can_bittiming_const;
        priv->can.do_set_mode = rcar_can_do_set_mode;
        priv->can.do_get_berr_counter = rcar_can_get_berr_counter;
        priv->can.ctrlmode_supported = CAN_CTRLMODE_BERR_REPORTING;
        platform_set_drvdata(pdev, ndev);
        SET_NETDEV_DEV(ndev, &pdev->dev);

        netif_napi_add(ndev, &priv->napi, rcar_can_rx_poll,
                       RCAR_CAN_NAPI_WEIGHT);
        err = register_candev(ndev);
        if (err) {
                dev_err(&pdev->dev, "register_candev() failed, error %d\n",
                        err);
                goto fail_candev;
        }

        devm_can_led_init(ndev);

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

        return 0;
fail_candev:
        netif_napi_del(&priv->napi);
fail_clk:
        free_candev(ndev);
fail:
        return err;
}

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

        unregister_candev(ndev);
        netif_napi_del(&priv->napi);
        free_candev(ndev);
        return 0;
}

static int __maybe_unused rcar_can_suspend(struct device *dev)
{
        struct net_device *ndev = dev_get_drvdata(dev);
        struct rcar_can_priv *priv = netdev_priv(ndev);
        u16 ctlr;

        if (netif_running(ndev)) {
                netif_stop_queue(ndev);
                netif_device_detach(ndev);
        }
        ctlr = readw(&priv->regs->ctlr);
        ctlr |= RCAR_CAN_CTLR_CANM_HALT;
        writew(ctlr, &priv->regs->ctlr);
        ctlr |= RCAR_CAN_CTLR_SLPM;
        writew(ctlr, &priv->regs->ctlr);
        priv->can.state = CAN_STATE_SLEEPING;

        clk_disable(priv->clk);
        return 0;
}

static int __maybe_unused rcar_can_resume(struct device *dev)
{
        struct net_device *ndev = dev_get_drvdata(dev);
        struct rcar_can_priv *priv = netdev_priv(ndev);
        u16 ctlr;
        int err;

        err = clk_enable(priv->clk);
        if (err) {
                netdev_err(ndev, "clk_enable() failed, error %d\n", err);
                return err;
        }

        ctlr = readw(&priv->regs->ctlr);
        ctlr &= ~RCAR_CAN_CTLR_SLPM;
        writew(ctlr, &priv->regs->ctlr);
        ctlr &= ~RCAR_CAN_CTLR_CANM;
        writew(ctlr, &priv->regs->ctlr);
        priv->can.state = CAN_STATE_ERROR_ACTIVE;

        if (netif_running(ndev)) {
                netif_device_attach(ndev);
                netif_start_queue(ndev);
        }
        return 0;
}

static SIMPLE_DEV_PM_OPS(rcar_can_pm_ops, rcar_can_suspend, rcar_can_resume);

static struct platform_driver rcar_can_driver = {
        .driver = {
                .name = RCAR_CAN_DRV_NAME,
                .owner = THIS_MODULE,
                .pm = &rcar_can_pm_ops,
        },
        .probe = rcar_can_probe,
        .remove = rcar_can_remove,
};

module_platform_driver(rcar_can_driver);

MODULE_AUTHOR("Cogent Embedded, Inc.");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("CAN driver for Renesas R-Car SoC");
MODULE_ALIAS("platform:" RCAR_CAN_DRV_NAME);