/*
 * at91_can.c - CAN network driver for AT91 SoC CAN controller
 *
 * (C) 2007 by Hans J. Koch <hjk@linutronix.de>
 * (C) 2008, 2009 by Marc Kleine-Budde <kernel@pengutronix.de>
 *
 * This software may be distributed under the terms of the GNU General
 * Public License ("GPL") version 2 as distributed in the 'COPYING'
 * file from the main directory of the linux kernel source.
 *
 * Send feedback to <socketcan-users@lists.berlios.de>
 *
 *
 * Your platform definition file should specify something like:
 *
 * static struct at91_can_data ek_can_data = {
 *      transceiver_switch = sam9263ek_transceiver_switch,
 * };
 *
 * at91_add_device_can(&ek_can_data);
 *
 */

#include <linux/clk.h>
#include <linux/errno.h>
#include <linux/if_arp.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/netdevice.h>
#include <linux/platform_device.h>
#include <linux/skbuff.h>
#include <linux/spinlock.h>
#include <linux/string.h>
#include <linux/types.h>

#include <linux/can.h>
#include <linux/can/dev.h>
#include <linux/can/error.h>

#include <mach/board.h>

#define DRV_NAME                "at91_can"
#define AT91_NAPI_WEIGHT        12

/*
 * RX/TX Mailbox split
 * don't dare to touch
 */
#define AT91_MB_RX_NUM          12
#define AT91_MB_TX_SHIFT        2

#define AT91_MB_RX_FIRST        0
#define AT91_MB_RX_LAST         (AT91_MB_RX_FIRST + AT91_MB_RX_NUM - 1)

#define AT91_MB_RX_MASK(i)      ((1 << (i)) - 1)
#define AT91_MB_RX_SPLIT        8
#define AT91_MB_RX_LOW_LAST     (AT91_MB_RX_SPLIT - 1)
#define AT91_MB_RX_LOW_MASK     (AT91_MB_RX_MASK(AT91_MB_RX_SPLIT))

#define AT91_MB_TX_NUM          (1 << AT91_MB_TX_SHIFT)
#define AT91_MB_TX_FIRST        (AT91_MB_RX_LAST + 1)
#define AT91_MB_TX_LAST         (AT91_MB_TX_FIRST + AT91_MB_TX_NUM - 1)

#define AT91_NEXT_PRIO_SHIFT    (AT91_MB_TX_SHIFT)
#define AT91_NEXT_PRIO_MASK     (0xf << AT91_MB_TX_SHIFT)
#define AT91_NEXT_MB_MASK       (AT91_MB_TX_NUM - 1)
#define AT91_NEXT_MASK          ((AT91_MB_TX_NUM - 1) | AT91_NEXT_PRIO_MASK)

/* Common registers */
enum at91_reg {
        AT91_MR         = 0x000,
        AT91_IER        = 0x004,
        AT91_IDR        = 0x008,
        AT91_IMR        = 0x00C,
        AT91_SR         = 0x010,
        AT91_BR         = 0x014,
        AT91_TIM        = 0x018,
        AT91_TIMESTP    = 0x01C,
        AT91_ECR        = 0x020,
        AT91_TCR        = 0x024,
        AT91_ACR        = 0x028,
};

/* Mailbox registers (0 <= i <= 15) */
#define AT91_MMR(i)             (enum at91_reg)(0x200 + ((i) * 0x20))
#define AT91_MAM(i)             (enum at91_reg)(0x204 + ((i) * 0x20))
#define AT91_MID(i)             (enum at91_reg)(0x208 + ((i) * 0x20))
#define AT91_MFID(i)            (enum at91_reg)(0x20C + ((i) * 0x20))
#define AT91_MSR(i)             (enum at91_reg)(0x210 + ((i) * 0x20))
#define AT91_MDL(i)             (enum at91_reg)(0x214 + ((i) * 0x20))
#define AT91_MDH(i)             (enum at91_reg)(0x218 + ((i) * 0x20))
#define AT91_MCR(i)             (enum at91_reg)(0x21C + ((i) * 0x20))

/* Register bits */
#define AT91_MR_CANEN           BIT(0)
#define AT91_MR_LPM             BIT(1)
#define AT91_MR_ABM             BIT(2)
#define AT91_MR_OVL             BIT(3)
#define AT91_MR_TEOF            BIT(4)
#define AT91_MR_TTM             BIT(5)
#define AT91_MR_TIMFRZ          BIT(6)
#define AT91_MR_DRPT            BIT(7)

#define AT91_SR_RBSY            BIT(29)

#define AT91_MMR_PRIO_SHIFT     (16)

#define AT91_MID_MIDE           BIT(29)

#define AT91_MSR_MRTR           BIT(20)
#define AT91_MSR_MABT           BIT(22)
#define AT91_MSR_MRDY           BIT(23)
#define AT91_MSR_MMI            BIT(24)

#define AT91_MCR_MRTR           BIT(20)
#define AT91_MCR_MTCR           BIT(23)

/* Mailbox Modes */
enum at91_mb_mode {
        AT91_MB_MODE_DISABLED   = 0,
        AT91_MB_MODE_RX         = 1,
        AT91_MB_MODE_RX_OVRWR   = 2,
        AT91_MB_MODE_TX         = 3,
        AT91_MB_MODE_CONSUMER   = 4,
        AT91_MB_MODE_PRODUCER   = 5,
};

/* Interrupt mask bits */
#define AT91_IRQ_MB_RX          ((1 << (AT91_MB_RX_LAST + 1)) \
                                 - (1 << AT91_MB_RX_FIRST))
#define AT91_IRQ_MB_TX          ((1 << (AT91_MB_TX_LAST + 1)) \
                                 - (1 << AT91_MB_TX_FIRST))
#define AT91_IRQ_MB_ALL         (AT91_IRQ_MB_RX | AT91_IRQ_MB_TX)

#define AT91_IRQ_ERRA           (1 << 16)
#define AT91_IRQ_WARN           (1 << 17)
#define AT91_IRQ_ERRP           (1 << 18)
#define AT91_IRQ_BOFF           (1 << 19)
#define AT91_IRQ_SLEEP          (1 << 20)
#define AT91_IRQ_WAKEUP         (1 << 21)
#define AT91_IRQ_TOVF           (1 << 22)
#define AT91_IRQ_TSTP           (1 << 23)
#define AT91_IRQ_CERR           (1 << 24)
#define AT91_IRQ_SERR           (1 << 25)
#define AT91_IRQ_AERR           (1 << 26)
#define AT91_IRQ_FERR           (1 << 27)
#define AT91_IRQ_BERR           (1 << 28)

#define AT91_IRQ_ERR_ALL        (0x1fff0000)
#define AT91_IRQ_ERR_FRAME      (AT91_IRQ_CERR | AT91_IRQ_SERR | \
                                 AT91_IRQ_AERR | AT91_IRQ_FERR | AT91_IRQ_BERR)
#define AT91_IRQ_ERR_LINE       (AT91_IRQ_ERRA | AT91_IRQ_WARN | \
                                 AT91_IRQ_ERRP | AT91_IRQ_BOFF)

#define AT91_IRQ_ALL            (0x1fffffff)

struct at91_priv {
        struct can_priv         can;       /* must be the first member! */
        struct net_device       *dev;
        struct napi_struct      napi;

        void __iomem            *reg_base;

        u32                     reg_sr;
        unsigned int            tx_next;
        unsigned int            tx_echo;
        unsigned int            rx_next;

        struct clk              *clk;
        struct at91_can_data    *pdata;
};

static struct can_bittiming_const at91_bittiming_const = {
        .tseg1_min      = 4,
        .tseg1_max      = 16,
        .tseg2_min      = 2,
        .tseg2_max      = 8,
        .sjw_max        = 4,
        .brp_min        = 2,
        .brp_max        = 128,
        .brp_inc        = 1,
};

static inline int get_tx_next_mb(const struct at91_priv *priv)
{
        return (priv->tx_next & AT91_NEXT_MB_MASK) + AT91_MB_TX_FIRST;
}

static inline int get_tx_next_prio(const struct at91_priv *priv)
{
        return (priv->tx_next >> AT91_NEXT_PRIO_SHIFT) & 0xf;
}

static inline int get_tx_echo_mb(const struct at91_priv *priv)
{
        return (priv->tx_echo & AT91_NEXT_MB_MASK) + AT91_MB_TX_FIRST;
}

static inline u32 at91_read(const struct at91_priv *priv, enum at91_reg reg)
{
        return readl(priv->reg_base + reg);
}

static inline void at91_write(const struct at91_priv *priv, enum at91_reg reg,
                u32 value)
{
        writel(value, priv->reg_base + reg);
}

static inline void set_mb_mode_prio(const struct at91_priv *priv,
                unsigned int mb, enum at91_mb_mode mode, int prio)
{
        at91_write(priv, AT91_MMR(mb), (mode << 24) | (prio << 16));
}

static inline void set_mb_mode(const struct at91_priv *priv, unsigned int mb,
                enum at91_mb_mode mode)
{
        set_mb_mode_prio(priv, mb, mode, 0);
}

static struct sk_buff *alloc_can_skb(struct net_device *dev,
                struct can_frame **cf)
{
        struct sk_buff *skb;

        skb = netdev_alloc_skb(dev, sizeof(struct can_frame));
        if (unlikely(!skb))
                return NULL;

        skb->protocol = htons(ETH_P_CAN);
        skb->ip_summed = CHECKSUM_UNNECESSARY;
        *cf = (struct can_frame *)skb_put(skb, sizeof(struct can_frame));

        return skb;
}

static struct sk_buff *alloc_can_err_skb(struct net_device *dev,
                struct can_frame **cf)
{
        struct sk_buff *skb;

        skb = alloc_can_skb(dev, cf);
        if (unlikely(!skb))
                return NULL;

        memset(*cf, 0, sizeof(struct can_frame));
        (*cf)->can_id = CAN_ERR_FLAG;
        (*cf)->can_dlc = CAN_ERR_DLC;

        return skb;
}

/*
 * Swtich transceiver on or off
 */
static void at91_transceiver_switch(const struct at91_priv *priv, int on)
{
        if (priv->pdata && priv->pdata->transceiver_switch)
                priv->pdata->transceiver_switch(on);
}

static void at91_setup_mailboxes(struct net_device *dev)
{
        struct at91_priv *priv = netdev_priv(dev);
        unsigned int i;

        /*
         * The first 12 mailboxes are used as a reception FIFO. The
         * last mailbox is configured with overwrite option. The
         * overwrite flag indicates a FIFO overflow.
         */
        for (i = AT91_MB_RX_FIRST; i < AT91_MB_RX_LAST; i++)
                set_mb_mode(priv, i, AT91_MB_MODE_RX);
        set_mb_mode(priv, AT91_MB_RX_LAST, AT91_MB_MODE_RX_OVRWR);

        /* The last 4 mailboxes are used for transmitting. */
        for (i = AT91_MB_TX_FIRST; i <= AT91_MB_TX_LAST; i++)
                set_mb_mode_prio(priv, i, AT91_MB_MODE_TX, 0);

        /* Reset tx and rx helper pointers */
        priv->tx_next = priv->tx_echo = priv->rx_next = 0;
}

static int at91_set_bittiming(struct net_device *dev)
{
        const struct at91_priv *priv = netdev_priv(dev);
        const struct can_bittiming *bt = &priv->can.bittiming;
        u32 reg_br;

        reg_br = ((priv->can.ctrlmode & CAN_CTRLMODE_3_SAMPLES) << 24) |
                ((bt->brp - 1) << 16) | ((bt->sjw - 1) << 12) |
                ((bt->prop_seg - 1) << 8) | ((bt->phase_seg1 - 1) << 4) |
                ((bt->phase_seg2 - 1) << 0);

        dev_info(dev->dev.parent, "writing AT91_BR: 0x%08x\n", reg_br);

        at91_write(priv, AT91_BR, reg_br);

        return 0;
}

static void at91_chip_start(struct net_device *dev)
{
        struct at91_priv *priv = netdev_priv(dev);
        u32 reg_mr, reg_ier;

        /* disable interrupts */
        at91_write(priv, AT91_IDR, AT91_IRQ_ALL);

        /* disable chip */
        reg_mr = at91_read(priv, AT91_MR);
        at91_write(priv, AT91_MR, reg_mr & ~AT91_MR_CANEN);

        at91_setup_mailboxes(dev);
        at91_transceiver_switch(priv, 1);

        /* enable chip */
        at91_write(priv, AT91_MR, AT91_MR_CANEN);

        priv->can.state = CAN_STATE_ERROR_ACTIVE;

        /* Enable interrupts */
        reg_ier = AT91_IRQ_MB_RX | AT91_IRQ_ERRP | AT91_IRQ_ERR_FRAME;
        at91_write(priv, AT91_IDR, AT91_IRQ_ALL);
        at91_write(priv, AT91_IER, reg_ier);
}

static void at91_chip_stop(struct net_device *dev, enum can_state state)
{
        struct at91_priv *priv = netdev_priv(dev);
        u32 reg_mr;

        /* disable interrupts */
        at91_write(priv, AT91_IDR, AT91_IRQ_ALL);

        reg_mr = at91_read(priv, AT91_MR);
        at91_write(priv, AT91_MR, reg_mr & ~AT91_MR_CANEN);

        at91_transceiver_switch(priv, 0);
        priv->can.state = state;
}

/*
 * theory of operation:
 *
 * According to the datasheet priority 0 is the highest priority, 15
 * is the lowest. If two mailboxes have the same priority level the
 * message of the mailbox with the lowest number is sent first.
 *
 * We use the first TX mailbox (AT91_MB_TX_FIRST) with prio 0, then
 * the next mailbox with prio 0, and so on, until all mailboxes are
 * used. Then we start from the beginning with mailbox
 * AT91_MB_TX_FIRST, but with prio 1, mailbox AT91_MB_TX_FIRST + 1
 * prio 1. When we reach the last mailbox with prio 15, we have to
 * stop sending, waiting for all messages to be delivered, then start
 * again with mailbox AT91_MB_TX_FIRST prio 0.
 *
 * We use the priv->tx_next as counter for the next transmission
 * mailbox, but without the offset AT91_MB_TX_FIRST. The lower bits
 * encode the mailbox number, the upper 4 bits the mailbox priority:
 *
 * priv->tx_next = (prio << AT91_NEXT_PRIO_SHIFT) ||
 *                 (mb - AT91_MB_TX_FIRST);
 *
 */
static netdev_tx_t at91_start_xmit(struct sk_buff *skb, struct net_device *dev)
{
        struct at91_priv *priv = netdev_priv(dev);
        struct net_device_stats *stats = &dev->stats;
        struct can_frame *cf = (struct can_frame *)skb->data;
        unsigned int mb, prio;
        u32 reg_mid, reg_mcr;

        mb = get_tx_next_mb(priv);
        prio = get_tx_next_prio(priv);

        if (unlikely(!(at91_read(priv, AT91_MSR(mb)) & AT91_MSR_MRDY))) {
                netif_stop_queue(dev);

                dev_err(dev->dev.parent,
                        "BUG! TX buffer full when queue awake!\n");
                return NETDEV_TX_BUSY;
        }

        if (cf->can_id & CAN_EFF_FLAG)
                reg_mid = (cf->can_id & CAN_EFF_MASK) | AT91_MID_MIDE;
        else
                reg_mid = (cf->can_id & CAN_SFF_MASK) << 18;

        reg_mcr = ((cf->can_id & CAN_RTR_FLAG) ? AT91_MCR_MRTR : 0) |
                (cf->can_dlc << 16) | AT91_MCR_MTCR;

        /* disable MB while writing ID (see datasheet) */
        set_mb_mode(priv, mb, AT91_MB_MODE_DISABLED);
        at91_write(priv, AT91_MID(mb), reg_mid);
        set_mb_mode_prio(priv, mb, AT91_MB_MODE_TX, prio);

        at91_write(priv, AT91_MDL(mb), *(u32 *)(cf->data + 0));
        at91_write(priv, AT91_MDH(mb), *(u32 *)(cf->data + 4));

        /* This triggers transmission */
        at91_write(priv, AT91_MCR(mb), reg_mcr);

        stats->tx_bytes += cf->can_dlc;
        dev->trans_start = jiffies;

        /* _NOTE_: substract AT91_MB_TX_FIRST offset from mb! */
        can_put_echo_skb(skb, dev, mb - AT91_MB_TX_FIRST);

        /*
         * we have to stop the queue and deliver all messages in case
         * of a prio+mb counter wrap around. This is the case if
         * tx_next buffer prio and mailbox equals 0.
         *
         * also stop the queue if next buffer is still in use
         * (== not ready)
         */
        priv->tx_next++;
        if (!(at91_read(priv, AT91_MSR(get_tx_next_mb(priv))) &
              AT91_MSR_MRDY) ||
            (priv->tx_next & AT91_NEXT_MASK) == 0)
                netif_stop_queue(dev);

        /* Enable interrupt for this mailbox */
        at91_write(priv, AT91_IER, 1 << mb);

        return NETDEV_TX_OK;
}

/**
 * at91_activate_rx_low - activate lower rx mailboxes
 * @priv: a91 context
 *
 * Reenables the lower mailboxes for reception of new CAN messages
 */
static inline void at91_activate_rx_low(const struct at91_priv *priv)
{
        u32 mask = AT91_MB_RX_LOW_MASK;
        at91_write(priv, AT91_TCR, mask);
}

/**
 * at91_activate_rx_mb - reactive single rx mailbox
 * @priv: a91 context
 * @mb: mailbox to reactivate
 *
 * Reenables given mailbox for reception of new CAN messages
 */
static inline void at91_activate_rx_mb(const struct at91_priv *priv,
                unsigned int mb)
{
        u32 mask = 1 << mb;
        at91_write(priv, AT91_TCR, mask);
}

/**
 * at91_rx_overflow_err - send error frame due to rx overflow
 * @dev: net device
 */
static void at91_rx_overflow_err(struct net_device *dev)
{
        struct net_device_stats *stats = &dev->stats;
        struct sk_buff *skb;
        struct can_frame *cf;

        dev_dbg(dev->dev.parent, "RX buffer overflow\n");
        stats->rx_over_errors++;
        stats->rx_errors++;

        skb = alloc_can_err_skb(dev, &cf);
        if (unlikely(!skb))
                return;

        cf->can_id |= CAN_ERR_CRTL;
        cf->data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
        netif_receive_skb(skb);

        stats->rx_packets++;
        stats->rx_bytes += cf->can_dlc;
}

/**
 * at91_read_mb - read CAN msg from mailbox (lowlevel impl)
 * @dev: net device
 * @mb: mailbox number to read from
 * @cf: can frame where to store message
 *
 * Reads a CAN message from the given mailbox and stores data into
 * given can frame. "mb" and "cf" must be valid.
 */
static void at91_read_mb(struct net_device *dev, unsigned int mb,
                struct can_frame *cf)
{
        const struct at91_priv *priv = netdev_priv(dev);
        u32 reg_msr, reg_mid;

        reg_mid = at91_read(priv, AT91_MID(mb));
        if (reg_mid & AT91_MID_MIDE)
                cf->can_id = ((reg_mid >> 0) & CAN_EFF_MASK) | CAN_EFF_FLAG;
        else
                cf->can_id = (reg_mid >> 18) & CAN_SFF_MASK;

        reg_msr = at91_read(priv, AT91_MSR(mb));
        if (reg_msr & AT91_MSR_MRTR)
                cf->can_id |= CAN_RTR_FLAG;
        cf->can_dlc = min_t(__u8, (reg_msr >> 16) & 0xf, 8);

        *(u32 *)(cf->data + 0) = at91_read(priv, AT91_MDL(mb));
        *(u32 *)(cf->data + 4) = at91_read(priv, AT91_MDH(mb));

        if (unlikely(mb == AT91_MB_RX_LAST && reg_msr & AT91_MSR_MMI))
                at91_rx_overflow_err(dev);
}

/**
 * at91_read_msg - read CAN message from mailbox
 * @dev: net device
 * @mb: mail box to read from
 *
 * Reads a CAN message from given mailbox, and put into linux network
 * RX queue, does all housekeeping chores (stats, ...)
 */
static void at91_read_msg(struct net_device *dev, unsigned int mb)
{
        struct net_device_stats *stats = &dev->stats;
        struct can_frame *cf;
        struct sk_buff *skb;

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

        at91_read_mb(dev, mb, cf);
        netif_receive_skb(skb);

        stats->rx_packets++;
        stats->rx_bytes += cf->can_dlc;
}

/**
 * at91_poll_rx - read multiple CAN messages from mailboxes
 * @dev: net device
 * @quota: max number of pkgs we're allowed to receive
 *
 * Theory of Operation:
 *
 * 12 of the 16 mailboxes on the chip are reserved for RX. we split
 * them into 2 groups. The lower group holds 8 and upper 4 mailboxes.
 *
 * Like it or not, but the chip always saves a received CAN message
 * into the first free mailbox it finds (starting with the
 * lowest). This makes it very difficult to read the messages in the
 * right order from the chip. This is how we work around that problem:
 *
 * The first message goes into mb nr. 0 and issues an interrupt. All
 * rx ints are disabled in the interrupt handler and a napi poll is
 * scheduled. We read the mailbox, but do _not_ reenable the mb (to
 * receive another message).
 *
 *    lower mbxs      upper
 *   ______^______    __^__
 *  /             \  /     \
 * +-+-+-+-+-+-+-+-++-+-+-+-+
 * |x|x|x|x|x|x|x|x|| | | | |
 * +-+-+-+-+-+-+-+-++-+-+-+-+
 *  0 0 0 0 0 0  0 0 0 0 1 1  \ mail
 *  0 1 2 3 4 5  6 7 8 9 0 1  / box
 *
 * The variable priv->rx_next points to the next mailbox to read a
 * message from. As long we're in the lower mailboxes we just read the
 * mailbox but not reenable it.
 *
 * With completion of the last of the lower mailboxes, we reenable the
 * whole first group, but continue to look for filled mailboxes in the
 * upper mailboxes. Imagine the second group like overflow mailboxes,
 * which takes CAN messages if the lower goup is full. While in the
 * upper group we reenable the mailbox right after reading it. Giving
 * the chip more room to store messages.
 *
 * After finishing we look again in the lower group if we've still
 * quota.
 *
 */
static int at91_poll_rx(struct net_device *dev, int quota)
{
        struct at91_priv *priv = netdev_priv(dev);
        u32 reg_sr = at91_read(priv, AT91_SR);
        const unsigned long *addr = (unsigned long *)&reg_sr;
        unsigned int mb;
        int received = 0;

        if (priv->rx_next > AT91_MB_RX_LOW_LAST &&
            reg_sr & AT91_MB_RX_LOW_MASK)
                dev_info(dev->dev.parent,
                         "order of incoming frames cannot be guaranteed\n");

 again:
        for (mb = find_next_bit(addr, AT91_MB_RX_NUM, priv->rx_next);
             mb < AT91_MB_RX_NUM && quota > 0;
             reg_sr = at91_read(priv, AT91_SR),
             mb = find_next_bit(addr, AT91_MB_RX_NUM, ++priv->rx_next)) {
                at91_read_msg(dev, mb);

                /* reactivate mailboxes */
                if (mb == AT91_MB_RX_LOW_LAST)
                        /* all lower mailboxed, if just finished it */
                        at91_activate_rx_low(priv);
                else if (mb > AT91_MB_RX_LOW_LAST)
                        /* only the mailbox we read */
                        at91_activate_rx_mb(priv, mb);

                received++;
                quota--;
        }

        /* upper group completed, look again in lower */
        if (priv->rx_next > AT91_MB_RX_LOW_LAST &&
            quota > 0 && mb >= AT91_MB_RX_NUM) {
                priv->rx_next = 0;
                goto again;
        }

        return received;
}

static void at91_poll_err_frame(struct net_device *dev,
                struct can_frame *cf, u32 reg_sr)
{
        struct at91_priv *priv = netdev_priv(dev);

        /* CRC error */
        if (reg_sr & AT91_IRQ_CERR) {
                dev_dbg(dev->dev.parent, "CERR irq\n");
                dev->stats.rx_errors++;
                priv->can.can_stats.bus_error++;
                cf->can_id |= CAN_ERR_PROT | CAN_ERR_BUSERROR;
        }

        /* Stuffing Error */
        if (reg_sr & AT91_IRQ_SERR) {
                dev_dbg(dev->dev.parent, "SERR irq\n");
                dev->stats.rx_errors++;
                priv->can.can_stats.bus_error++;
                cf->can_id |= CAN_ERR_PROT | CAN_ERR_BUSERROR;
                cf->data[2] |= CAN_ERR_PROT_STUFF;
        }

        /* Acknowledgement Error */
        if (reg_sr & AT91_IRQ_AERR) {
                dev_dbg(dev->dev.parent, "AERR irq\n");
                dev->stats.tx_errors++;
                cf->can_id |= CAN_ERR_ACK;
        }

        /* Form error */
        if (reg_sr & AT91_IRQ_FERR) {
                dev_dbg(dev->dev.parent, "FERR irq\n");
                dev->stats.rx_errors++;
                priv->can.can_stats.bus_error++;
                cf->can_id |= CAN_ERR_PROT | CAN_ERR_BUSERROR;
                cf->data[2] |= CAN_ERR_PROT_FORM;
        }

        /* Bit Error */
        if (reg_sr & AT91_IRQ_BERR) {
                dev_dbg(dev->dev.parent, "BERR irq\n");
                dev->stats.tx_errors++;
                priv->can.can_stats.bus_error++;
                cf->can_id |= CAN_ERR_PROT | CAN_ERR_BUSERROR;
                cf->data[2] |= CAN_ERR_PROT_BIT;
        }
}

static int at91_poll_err(struct net_device *dev, int quota, u32 reg_sr)
{
        struct sk_buff *skb;
        struct can_frame *cf;

        if (quota == 0)
                return 0;

        skb = alloc_can_err_skb(dev, &cf);
        if (unlikely(!skb))
                return 0;

        at91_poll_err_frame(dev, cf, reg_sr);
        netif_receive_skb(skb);

        dev->last_rx = jiffies;
        dev->stats.rx_packets++;
        dev->stats.rx_bytes += cf->can_dlc;

        return 1;
}

static int at91_poll(struct napi_struct *napi, int quota)
{
        struct net_device *dev = napi->dev;
        const struct at91_priv *priv = netdev_priv(dev);
        u32 reg_sr = at91_read(priv, AT91_SR);
        int work_done = 0;

        if (reg_sr & AT91_IRQ_MB_RX)
                work_done += at91_poll_rx(dev, quota - work_done);

        /*
         * The error bits are clear on read,
         * so use saved value from irq handler.
         */
        reg_sr |= priv->reg_sr;
        if (reg_sr & AT91_IRQ_ERR_FRAME)
                work_done += at91_poll_err(dev, quota - work_done, reg_sr);

        if (work_done < quota) {
                /* enable IRQs for frame errors and all mailboxes >= rx_next */
                u32 reg_ier = AT91_IRQ_ERR_FRAME;
                reg_ier |= AT91_IRQ_MB_RX & ~AT91_MB_RX_MASK(priv->rx_next);

                napi_complete(napi);
                at91_write(priv, AT91_IER, reg_ier);
        }

        return work_done;
}

/*
 * theory of operation:
 *
 * priv->tx_echo holds the number of the oldest can_frame put for
 * transmission into the hardware, but not yet ACKed by the CAN tx
 * complete IRQ.
 *
 * We iterate from priv->tx_echo to priv->tx_next and check if the
 * packet has been transmitted, echo it back to the CAN framework. If
 * we discover a not yet transmitted package, stop looking for more.
 *
 */
static void at91_irq_tx(struct net_device *dev, u32 reg_sr)
{
        struct at91_priv *priv = netdev_priv(dev);
        u32 reg_msr;
        unsigned int mb;

        /* masking of reg_sr not needed, already done by at91_irq */

        for (/* nix */; (priv->tx_next - priv->tx_echo) > 0; priv->tx_echo++) {
                mb = get_tx_echo_mb(priv);

                /* no event in mailbox? */
                if (!(reg_sr & (1 << mb)))
                        break;

                /* Disable irq for this TX mailbox */
                at91_write(priv, AT91_IDR, 1 << mb);

                /*
                 * only echo if mailbox signals us a transfer
                 * complete (MSR_MRDY). Otherwise it's a tansfer
                 * abort. "can_bus_off()" takes care about the skbs
                 * parked in the echo queue.
                 */
                reg_msr = at91_read(priv, AT91_MSR(mb));
                if (likely(reg_msr & AT91_MSR_MRDY &&
                           ~reg_msr & AT91_MSR_MABT)) {
                        /* _NOTE_: substract AT91_MB_TX_FIRST offset from mb! */
                        can_get_echo_skb(dev, mb - AT91_MB_TX_FIRST);
                        dev->stats.tx_packets++;
                }
        }

        /*
         * restart queue if we don't have a wrap around but restart if
         * we get a TX int for the last can frame directly before a
         * wrap around.
         */
        if ((priv->tx_next & AT91_NEXT_MASK) != 0 ||
            (priv->tx_echo & AT91_NEXT_MASK) == 0)
                netif_wake_queue(dev);
}

static void at91_irq_err_state(struct net_device *dev,
                struct can_frame *cf, enum can_state new_state)
{
        struct at91_priv *priv = netdev_priv(dev);
        u32 reg_idr, reg_ier, reg_ecr;
        u8 tec, rec;

        reg_ecr = at91_read(priv, AT91_ECR);
        rec = reg_ecr & 0xff;
        tec = reg_ecr >> 16;

        switch (priv->can.state) {
        case CAN_STATE_ERROR_ACTIVE:
                /*
                 * from: ERROR_ACTIVE
                 * to  : ERROR_WARNING, ERROR_PASSIVE, BUS_OFF
                 * =>  : there was a warning int
                 */
                if (new_state >= CAN_STATE_ERROR_WARNING &&
                    new_state <= CAN_STATE_BUS_OFF) {
                        dev_dbg(dev->dev.parent, "Error Warning IRQ\n");
                        priv->can.can_stats.error_warning++;

                        cf->can_id |= CAN_ERR_CRTL;
                        cf->data[1] = (tec > rec) ?
                                CAN_ERR_CRTL_TX_WARNING :
                                CAN_ERR_CRTL_RX_WARNING;
                }
        case CAN_STATE_ERROR_WARNING:   /* fallthrough */
                /*
                 * from: ERROR_ACTIVE, ERROR_WARNING
                 * to  : ERROR_PASSIVE, BUS_OFF
                 * =>  : error passive int
                 */
                if (new_state >= CAN_STATE_ERROR_PASSIVE &&
                    new_state <= CAN_STATE_BUS_OFF) {
                        dev_dbg(dev->dev.parent, "Error Passive IRQ\n");
                        priv->can.can_stats.error_passive++;

                        cf->can_id |= CAN_ERR_CRTL;
                        cf->data[1] = (tec > rec) ?
                                CAN_ERR_CRTL_TX_PASSIVE :
                                CAN_ERR_CRTL_RX_PASSIVE;
                }
                break;
        case CAN_STATE_BUS_OFF:
                /*
                 * from: BUS_OFF
                 * to  : ERROR_ACTIVE, ERROR_WARNING, ERROR_PASSIVE
                 */
                if (new_state <= CAN_STATE_ERROR_PASSIVE) {
                        cf->can_id |= CAN_ERR_RESTARTED;

                        dev_dbg(dev->dev.parent, "restarted\n");
                        priv->can.can_stats.restarts++;

                        netif_carrier_on(dev);
                        netif_wake_queue(dev);
                }
                break;
        default:
                break;
        }


        /* process state changes depending on the new state */
        switch (new_state) {
        case CAN_STATE_ERROR_ACTIVE:
                /*
                 * actually we want to enable AT91_IRQ_WARN here, but
                 * it screws up the system under certain
                 * circumstances. so just enable AT91_IRQ_ERRP, thus
                 * the "fallthrough"
                 */
                dev_dbg(dev->dev.parent, "Error Active\n");
                cf->can_id |= CAN_ERR_PROT;
                cf->data[2] = CAN_ERR_PROT_ACTIVE;
        case CAN_STATE_ERROR_WARNING:   /* fallthrough */
                reg_idr = AT91_IRQ_ERRA | AT91_IRQ_WARN | AT91_IRQ_BOFF;
                reg_ier = AT91_IRQ_ERRP;
                break;
        case CAN_STATE_ERROR_PASSIVE:
                reg_idr = AT91_IRQ_ERRA | AT91_IRQ_WARN | AT91_IRQ_ERRP;
                reg_ier = AT91_IRQ_BOFF;
                break;
        case CAN_STATE_BUS_OFF:
                reg_idr = AT91_IRQ_ERRA | AT91_IRQ_ERRP |
                        AT91_IRQ_WARN | AT91_IRQ_BOFF;
                reg_ier = 0;

                cf->can_id |= CAN_ERR_BUSOFF;

                dev_dbg(dev->dev.parent, "bus-off\n");
                netif_carrier_off(dev);
                priv->can.can_stats.bus_off++;

                /* turn off chip, if restart is disabled */
                if (!priv->can.restart_ms) {
                        at91_chip_stop(dev, CAN_STATE_BUS_OFF);
                        return;
                }
                break;
        default:
                break;
        }

        at91_write(priv, AT91_IDR, reg_idr);
        at91_write(priv, AT91_IER, reg_ier);
}

static void at91_irq_err(struct net_device *dev)
{
        struct at91_priv *priv = netdev_priv(dev);
        struct sk_buff *skb;
        struct can_frame *cf;
        enum can_state new_state;
        u32 reg_sr;

        reg_sr = at91_read(priv, AT91_SR);

        /* we need to look at the unmasked reg_sr */
        if (unlikely(reg_sr & AT91_IRQ_BOFF))
                new_state = CAN_STATE_BUS_OFF;
        else if (unlikely(reg_sr & AT91_IRQ_ERRP))
                new_state = CAN_STATE_ERROR_PASSIVE;
        else if (unlikely(reg_sr & AT91_IRQ_WARN))
                new_state = CAN_STATE_ERROR_WARNING;
        else if (likely(reg_sr & AT91_IRQ_ERRA))
                new_state = CAN_STATE_ERROR_ACTIVE;
        else {
                dev_err(dev->dev.parent, "BUG! hardware in undefined state\n");
                return;
        }

        /* state hasn't changed */
        if (likely(new_state == priv->can.state))
                return;

        skb = alloc_can_err_skb(dev, &cf);
        if (unlikely(!skb))
                return;

        at91_irq_err_state(dev, cf, new_state);
        netif_rx(skb);

        dev->last_rx = jiffies;
        dev->stats.rx_packets++;
        dev->stats.rx_bytes += cf->can_dlc;

        priv->can.state = new_state;
}

/*
 * interrupt handler
 */
static irqreturn_t at91_irq(int irq, void *dev_id)
{
        struct net_device *dev = dev_id;
        struct at91_priv *priv = netdev_priv(dev);
        irqreturn_t handled = IRQ_NONE;
        u32 reg_sr, reg_imr;

        reg_sr = at91_read(priv, AT91_SR);
        reg_imr = at91_read(priv, AT91_IMR);

        /* Ignore masked interrupts */
        reg_sr &= reg_imr;
        if (!reg_sr)
                goto exit;

        handled = IRQ_HANDLED;

        /* Receive or error interrupt? -> napi */
        if (reg_sr & (AT91_IRQ_MB_RX | AT91_IRQ_ERR_FRAME)) {
                /*
                 * The error bits are clear on read,
                 * save for later use.
                 */
                priv->reg_sr = reg_sr;
                at91_write(priv, AT91_IDR,
                           AT91_IRQ_MB_RX | AT91_IRQ_ERR_FRAME);
                napi_schedule(&priv->napi);
        }

        /* Transmission complete interrupt */
        if (reg_sr & AT91_IRQ_MB_TX)
                at91_irq_tx(dev, reg_sr);

        at91_irq_err(dev);

 exit:
        return handled;
}

static int at91_open(struct net_device *dev)
{
        struct at91_priv *priv = netdev_priv(dev);
        int err;

        clk_enable(priv->clk);

        /* check or determine and set bittime */
        err = open_candev(dev);
        if (err)
                goto out;

        /* register interrupt handler */
        if (request_irq(dev->irq, at91_irq, IRQF_SHARED,
                        dev->name, dev)) {
                err = -EAGAIN;
                goto out_close;
        }

        /* start chip and queuing */
        at91_chip_start(dev);

        napi_enable(&priv->napi);
        netif_start_queue(dev);

        return 0;

 out_close:
        close_candev(dev);
 out:
        clk_disable(priv->clk);

        return err;
}

/*
 * stop CAN bus activity
 */
static int at91_close(struct net_device *dev)
{
        struct at91_priv *priv = netdev_priv(dev);

        netif_stop_queue(dev);
        napi_disable(&priv->napi);
        at91_chip_stop(dev, CAN_STATE_STOPPED);

        free_irq(dev->irq, dev);
        clk_disable(priv->clk);

        close_candev(dev);

        return 0;
}

static int at91_set_mode(struct net_device *dev, enum can_mode mode)
{
        switch (mode) {
        case CAN_MODE_START:
                at91_chip_start(dev);
                netif_wake_queue(dev);
                break;

        default:
                return -EOPNOTSUPP;
        }

        return 0;
}

static const struct net_device_ops at91_netdev_ops = {
        .ndo_open       = at91_open,
        .ndo_stop       = at91_close,
        .ndo_start_xmit = at91_start_xmit,
};

static int __init at91_can_probe(struct platform_device *pdev)
{
        struct net_device *dev;
        struct at91_priv *priv;
        struct resource *res;
        struct clk *clk;
        void __iomem *addr;
        int err, irq;

        clk = clk_get(&pdev->dev, "can_clk");
        if (IS_ERR(clk)) {
                dev_err(&pdev->dev, "no clock defined\n");
                err = -ENODEV;
                goto exit;
        }

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        irq = platform_get_irq(pdev, 0);
        if (!res || !irq) {
                err = -ENODEV;
                goto exit_put;
        }

        if (!request_mem_region(res->start,
                                resource_size(res),
                                pdev->name)) {
                err = -EBUSY;
                goto exit_put;
        }

        addr = ioremap_nocache(res->start, resource_size(res));
        if (!addr) {
                err = -ENOMEM;
                goto exit_release;
        }

        dev = alloc_candev(sizeof(struct at91_priv));
        if (!dev) {
                err = -ENOMEM;
                goto exit_iounmap;
        }

        dev->netdev_ops = &at91_netdev_ops;
        dev->irq = irq;
        dev->flags |= IFF_ECHO;

        priv = netdev_priv(dev);
        priv->can.clock.freq = clk_get_rate(clk);
        priv->can.bittiming_const = &at91_bittiming_const;
        priv->can.do_set_bittiming = at91_set_bittiming;
        priv->can.do_set_mode = at91_set_mode;
        priv->reg_base = addr;
        priv->dev = dev;
        priv->clk = clk;
        priv->pdata = pdev->dev.platform_data;

        netif_napi_add(dev, &priv->napi, at91_poll, AT91_NAPI_WEIGHT);

        dev_set_drvdata(&pdev->dev, dev);
        SET_NETDEV_DEV(dev, &pdev->dev);

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

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

        return 0;

 exit_free:
        free_netdev(dev);
 exit_iounmap:
        iounmap(addr);
 exit_release:
        release_mem_region(res->start, resource_size(res));
 exit_put:
        clk_put(clk);
 exit:
        return err;
}

static int __devexit at91_can_remove(struct platform_device *pdev)
{
        struct net_device *dev = platform_get_drvdata(pdev);
        struct at91_priv *priv = netdev_priv(dev);
        struct resource *res;

        unregister_netdev(dev);

        platform_set_drvdata(pdev, NULL);

        free_netdev(dev);

        iounmap(priv->reg_base);

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        release_mem_region(res->start, resource_size(res));

        clk_put(priv->clk);

        return 0;
}

static struct platform_driver at91_can_driver = {
        .probe          = at91_can_probe,
        .remove         = __devexit_p(at91_can_remove),
        .driver         = {
                .name   = DRV_NAME,
                .owner  = THIS_MODULE,
        },
};

static int __init at91_can_module_init(void)
{
        printk(KERN_INFO "%s netdevice driver\n", DRV_NAME);
        return platform_driver_register(&at91_can_driver);
}

static void __exit at91_can_module_exit(void)
{
        platform_driver_unregister(&at91_can_driver);
        printk(KERN_INFO "%s: driver removed\n", DRV_NAME);
}

module_init(at91_can_module_init);
module_exit(at91_can_module_exit);

MODULE_AUTHOR("Marc Kleine-Budde <mkl@pengutronix.de>");
MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION(DRV_NAME " CAN netdevice driver");