Merge tag 'for-linus-20190706' of git://git.kernel.dk/linux-block

[linux/fpc-iii.git] / drivers / net / can / at91_can.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * at91_can.c - CAN network driver for AT91 SoC CAN controller
 *
 * (C) 2007 by Hans J. Koch <hjk@hansjkoch.de>
 * (C) 2008, 2009, 2010, 2011 by Marc Kleine-Budde <kernel@pengutronix.de>
 */

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

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

#define AT91_MB_MASK(i)         ((1 << (i)) - 1)

/* 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_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)

enum at91_devtype {
        AT91_DEVTYPE_SAM9263,
        AT91_DEVTYPE_SAM9X5,
};

struct at91_devtype_data {
        unsigned int rx_first;
        unsigned int rx_split;
        unsigned int rx_last;
        unsigned int tx_shift;
        enum at91_devtype type;
};

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

        void __iomem *reg_base;

        u32 reg_sr;
        unsigned int tx_next;
        unsigned int tx_echo;
        unsigned int rx_next;
        struct at91_devtype_data devtype_data;

        struct clk *clk;
        struct at91_can_data *pdata;

        canid_t mb0_id;
};

static const struct at91_devtype_data at91_at91sam9263_data = {
        .rx_first = 1,
        .rx_split = 8,
        .rx_last = 11,
        .tx_shift = 2,
        .type = AT91_DEVTYPE_SAM9263,
};

static const struct at91_devtype_data at91_at91sam9x5_data = {
        .rx_first = 0,
        .rx_split = 4,
        .rx_last = 5,
        .tx_shift = 1,
        .type = AT91_DEVTYPE_SAM9X5,
};

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

#define AT91_IS(_model) \
static inline int at91_is_sam##_model(const struct at91_priv *priv) \
{ \
        return priv->devtype_data.type == AT91_DEVTYPE_SAM##_model; \
}

AT91_IS(9263);
AT91_IS(9X5);

static inline unsigned int get_mb_rx_first(const struct at91_priv *priv)
{
        return priv->devtype_data.rx_first;
}

static inline unsigned int get_mb_rx_last(const struct at91_priv *priv)
{
        return priv->devtype_data.rx_last;
}

static inline unsigned int get_mb_rx_split(const struct at91_priv *priv)
{
        return priv->devtype_data.rx_split;
}

static inline unsigned int get_mb_rx_num(const struct at91_priv *priv)
{
        return get_mb_rx_last(priv) - get_mb_rx_first(priv) + 1;
}

static inline unsigned int get_mb_rx_low_last(const struct at91_priv *priv)
{
        return get_mb_rx_split(priv) - 1;
}

static inline unsigned int get_mb_rx_low_mask(const struct at91_priv *priv)
{
        return AT91_MB_MASK(get_mb_rx_split(priv)) &
                ~AT91_MB_MASK(get_mb_rx_first(priv));
}

static inline unsigned int get_mb_tx_shift(const struct at91_priv *priv)
{
        return priv->devtype_data.tx_shift;
}

static inline unsigned int get_mb_tx_num(const struct at91_priv *priv)
{
        return 1 << get_mb_tx_shift(priv);
}

static inline unsigned int get_mb_tx_first(const struct at91_priv *priv)
{
        return get_mb_rx_last(priv) + 1;
}

static inline unsigned int get_mb_tx_last(const struct at91_priv *priv)
{
        return get_mb_tx_first(priv) + get_mb_tx_num(priv) - 1;
}

static inline unsigned int get_next_prio_shift(const struct at91_priv *priv)
{
        return get_mb_tx_shift(priv);
}

static inline unsigned int get_next_prio_mask(const struct at91_priv *priv)
{
        return 0xf << get_mb_tx_shift(priv);
}

static inline unsigned int get_next_mb_mask(const struct at91_priv *priv)
{
        return AT91_MB_MASK(get_mb_tx_shift(priv));
}

static inline unsigned int get_next_mask(const struct at91_priv *priv)
{
        return get_next_mb_mask(priv) | get_next_prio_mask(priv);
}

static inline unsigned int get_irq_mb_rx(const struct at91_priv *priv)
{
        return AT91_MB_MASK(get_mb_rx_last(priv) + 1) &
                ~AT91_MB_MASK(get_mb_rx_first(priv));
}

static inline unsigned int get_irq_mb_tx(const struct at91_priv *priv)
{
        return AT91_MB_MASK(get_mb_tx_last(priv) + 1) &
                ~AT91_MB_MASK(get_mb_tx_first(priv));
}

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

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

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

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

static inline void at91_write(const struct at91_priv *priv, enum at91_reg reg,
                u32 value)
{
        writel_relaxed(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 inline u32 at91_can_id_to_reg_mid(canid_t can_id)
{
        u32 reg_mid;

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

        return reg_mid;
}

static void at91_setup_mailboxes(struct net_device *dev)
{
        struct at91_priv *priv = netdev_priv(dev);
        unsigned int i;
        u32 reg_mid;

        /*
         * Due to a chip bug (errata 50.2.6.3 & 50.3.5.3) the first
         * mailbox is disabled. The next 11 mailboxes are used as a
         * reception FIFO. The last mailbox is configured with
         * overwrite option. The overwrite flag indicates a FIFO
         * overflow.
         */
        reg_mid = at91_can_id_to_reg_mid(priv->mb0_id);
        for (i = 0; i < get_mb_rx_first(priv); i++) {
                set_mb_mode(priv, i, AT91_MB_MODE_DISABLED);
                at91_write(priv, AT91_MID(i), reg_mid);
                at91_write(priv, AT91_MCR(i), 0x0);     /* clear dlc */
        }

        for (i = get_mb_rx_first(priv); i < get_mb_rx_last(priv); i++)
                set_mb_mode(priv, i, AT91_MB_MODE_RX);
        set_mb_mode(priv, get_mb_rx_last(priv), AT91_MB_MODE_RX_OVRWR);

        /* reset acceptance mask and id register */
        for (i = get_mb_rx_first(priv); i <= get_mb_rx_last(priv); i++) {
                at91_write(priv, AT91_MAM(i), 0x0);
                at91_write(priv, AT91_MID(i), AT91_MID_MIDE);
        }

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

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

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) ? 1 << 24 : 0) |
                ((bt->brp - 1) << 16) | ((bt->sjw - 1) << 12) |
                ((bt->prop_seg - 1) << 8) | ((bt->phase_seg1 - 1) << 4) |
                ((bt->phase_seg2 - 1) << 0);

        netdev_info(dev, "writing AT91_BR: 0x%08x\n", reg_br);

        at91_write(priv, AT91_BR, reg_br);

        return 0;
}

static int at91_get_berr_counter(const struct net_device *dev,
                struct can_berr_counter *bec)
{
        const struct at91_priv *priv = netdev_priv(dev);
        u32 reg_ecr = at91_read(priv, AT91_ECR);

        bec->rxerr = reg_ecr & 0xff;
        bec->txerr = reg_ecr >> 16;

        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_set_bittiming(dev);
        at91_setup_mailboxes(dev);

        /* enable chip */
        if (priv->can.ctrlmode & CAN_CTRLMODE_LISTENONLY)
                reg_mr = AT91_MR_CANEN | AT91_MR_ABM;
        else
                reg_mr = AT91_MR_CANEN;
        at91_write(priv, AT91_MR, reg_mr);

        priv->can.state = CAN_STATE_ERROR_ACTIVE;

        /* Enable interrupts */
        reg_ier = get_irq_mb_rx(priv) | 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);

        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 << get_next_prio_shift(priv)) |
 *                 (mb - get_mb_tx_first(priv));
 *
 */
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;

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

        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);

                netdev_err(dev, "BUG! TX buffer full when queue awake!\n");
                return NETDEV_TX_BUSY;
        }
        reg_mid = at91_can_id_to_reg_mid(cf->can_id);
        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;

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

        /*
         * 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 & get_next_mask(priv)) == 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 = get_mb_rx_low_mask(priv);
        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;

        netdev_dbg(dev, "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;

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

/**
 * 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));
        cf->can_dlc = get_can_dlc((reg_msr >> 16) & 0xf);

        if (reg_msr & AT91_MSR_MRTR)
                cf->can_id |= CAN_RTR_FLAG;
        else {
                *(u32 *)(cf->data + 0) = at91_read(priv, AT91_MDL(mb));
                *(u32 *)(cf->data + 4) = at91_read(priv, AT91_MDH(mb));
        }

        /* allow RX of extended frames */
        at91_write(priv, AT91_MID(mb), AT91_MID_MIDE);

        if (unlikely(mb == get_mb_rx_last(priv) && 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);

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

        can_led_event(dev, CAN_LED_EVENT_RX);
}

/**
 * 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:
 *
 * About 3/4 of the mailboxes (get_mb_rx_first()...get_mb_rx_last())
 * on the chip are reserved for RX. We split them into 2 groups. The
 * lower group ranges from get_mb_rx_first() to get_mb_rx_low_last().
 *
 * 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. 1 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|| | | | |
 * +-+-+-+-+-+-+-+-++-+-+-+-+
 *  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
 *  ^
 *  |
 *   \
 *     unused, due to chip bug
 *
 * 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 > get_mb_rx_low_last(priv) &&
            reg_sr & get_mb_rx_low_mask(priv))
                netdev_info(dev,
                        "order of incoming frames cannot be guaranteed\n");

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

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

                received++;
                quota--;
        }

        /* upper group completed, look again in lower */
        if (priv->rx_next > get_mb_rx_low_last(priv) &&
            mb > get_mb_rx_last(priv)) {
                priv->rx_next = get_mb_rx_first(priv);
                if (quota > 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) {
                netdev_dbg(dev, "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) {
                netdev_dbg(dev, "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) {
                netdev_dbg(dev, "AERR irq\n");
                dev->stats.tx_errors++;
                cf->can_id |= CAN_ERR_ACK;
        }

        /* Form error */
        if (reg_sr & AT91_IRQ_FERR) {
                netdev_dbg(dev, "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) {
                netdev_dbg(dev, "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);

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

        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 & get_irq_mb_rx(priv))
                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 |= get_irq_mb_rx(priv) & ~AT91_MB_MASK(priv->rx_next);

                napi_complete_done(napi, work_done);
                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_: subtract AT91_MB_TX_FIRST offset from mb! */
                        can_get_echo_skb(dev, mb - get_mb_tx_first(priv));
                        dev->stats.tx_packets++;
                        can_led_event(dev, CAN_LED_EVENT_TX);
                }
        }

        /*
         * 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 & get_next_mask(priv)) != 0 ||
            (priv->tx_echo & get_next_mask(priv)) == 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 = 0, reg_ier = 0;
        struct can_berr_counter bec;

        at91_get_berr_counter(dev, &bec);

        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) {
                        netdev_dbg(dev, "Error Warning IRQ\n");
                        priv->can.can_stats.error_warning++;

                        cf->can_id |= CAN_ERR_CRTL;
                        cf->data[1] = (bec.txerr > bec.rxerr) ?
                                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) {
                        netdev_dbg(dev, "Error Passive IRQ\n");
                        priv->can.can_stats.error_passive++;

                        cf->can_id |= CAN_ERR_CRTL;
                        cf->data[1] = (bec.txerr > bec.rxerr) ?
                                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;

                        netdev_dbg(dev, "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"
                 */
                netdev_dbg(dev, "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;

                netdev_dbg(dev, "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 int at91_get_state_by_bec(const struct net_device *dev,
                enum can_state *state)
{
        struct can_berr_counter bec;
        int err;

        err = at91_get_berr_counter(dev, &bec);
        if (err)
                return err;

        if (bec.txerr < 96 && bec.rxerr < 96)
                *state = CAN_STATE_ERROR_ACTIVE;
        else if (bec.txerr < 128 && bec.rxerr < 128)
                *state = CAN_STATE_ERROR_WARNING;
        else if (bec.txerr < 256 && bec.rxerr < 256)
                *state = CAN_STATE_ERROR_PASSIVE;
        else
                *state = CAN_STATE_BUS_OFF;

        return 0;
}


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;
        int err;

        if (at91_is_sam9263(priv)) {
                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 {
                        netdev_err(dev, "BUG! hardware in undefined state\n");
                        return;
                }
        } else {
                err = at91_get_state_by_bec(dev, &new_state);
                if (err)
                        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);

        dev->stats.rx_packets++;
        dev->stats.rx_bytes += cf->can_dlc;
        netif_rx(skb);

        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 & (get_irq_mb_rx(priv) | 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,
                           get_irq_mb_rx(priv) | AT91_IRQ_ERR_FRAME);
                napi_schedule(&priv->napi);
        }

        /* Transmission complete interrupt */
        if (reg_sr & get_irq_mb_tx(priv))
                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;

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

        /* 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;
        }

        can_led_event(dev, CAN_LED_EVENT_OPEN);

        /* 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_unprepare(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_unprepare(priv->clk);

        close_candev(dev);

        can_led_event(dev, CAN_LED_EVENT_STOP);

        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,
        .ndo_change_mtu = can_change_mtu,
};

static ssize_t at91_sysfs_show_mb0_id(struct device *dev,
                struct device_attribute *attr, char *buf)
{
        struct at91_priv *priv = netdev_priv(to_net_dev(dev));

        if (priv->mb0_id & CAN_EFF_FLAG)
                return snprintf(buf, PAGE_SIZE, "0x%08x\n", priv->mb0_id);
        else
                return snprintf(buf, PAGE_SIZE, "0x%03x\n", priv->mb0_id);
}

static ssize_t at91_sysfs_set_mb0_id(struct device *dev,
                struct device_attribute *attr, const char *buf, size_t count)
{
        struct net_device *ndev = to_net_dev(dev);
        struct at91_priv *priv = netdev_priv(ndev);
        unsigned long can_id;
        ssize_t ret;
        int err;

        rtnl_lock();

        if (ndev->flags & IFF_UP) {
                ret = -EBUSY;
                goto out;
        }

        err = kstrtoul(buf, 0, &can_id);
        if (err) {
                ret = err;
                goto out;
        }

        if (can_id & CAN_EFF_FLAG)
                can_id &= CAN_EFF_MASK | CAN_EFF_FLAG;
        else
                can_id &= CAN_SFF_MASK;

        priv->mb0_id = can_id;
        ret = count;

 out:
        rtnl_unlock();
        return ret;
}

static DEVICE_ATTR(mb0_id, 0644, at91_sysfs_show_mb0_id, at91_sysfs_set_mb0_id);

static struct attribute *at91_sysfs_attrs[] = {
        &dev_attr_mb0_id.attr,
        NULL,
};

static const struct attribute_group at91_sysfs_attr_group = {
        .attrs = at91_sysfs_attrs,
};

#if defined(CONFIG_OF)
static const struct of_device_id at91_can_dt_ids[] = {
        {
                .compatible = "atmel,at91sam9x5-can",
                .data = &at91_at91sam9x5_data,
        }, {
                .compatible = "atmel,at91sam9263-can",
                .data = &at91_at91sam9263_data,
        }, {
                /* sentinel */
        }
};
MODULE_DEVICE_TABLE(of, at91_can_dt_ids);
#endif

static const struct at91_devtype_data *at91_can_get_driver_data(struct platform_device *pdev)
{
        if (pdev->dev.of_node) {
                const struct of_device_id *match;

                match = of_match_node(at91_can_dt_ids, pdev->dev.of_node);
                if (!match) {
                        dev_err(&pdev->dev, "no matching node found in dtb\n");
                        return NULL;
                }
                return (const struct at91_devtype_data *)match->data;
        }
        return (const struct at91_devtype_data *)
                platform_get_device_id(pdev)->driver_data;
}

static int at91_can_probe(struct platform_device *pdev)
{
        const struct at91_devtype_data *devtype_data;
        struct net_device *dev;
        struct at91_priv *priv;
        struct resource *res;
        struct clk *clk;
        void __iomem *addr;
        int err, irq;

        devtype_data = at91_can_get_driver_data(pdev);
        if (!devtype_data) {
                dev_err(&pdev->dev, "no driver data\n");
                err = -ENODEV;
                goto exit;
        }

        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 <= 0) {
                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),
                           1 << devtype_data->tx_shift);
        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_mode = at91_set_mode;
        priv->can.do_get_berr_counter = at91_get_berr_counter;
        priv->can.ctrlmode_supported = CAN_CTRLMODE_3_SAMPLES |
                CAN_CTRLMODE_LISTENONLY;
        priv->reg_base = addr;
        priv->devtype_data = *devtype_data;
        priv->clk = clk;
        priv->pdata = dev_get_platdata(&pdev->dev);
        priv->mb0_id = 0x7ff;

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

        if (at91_is_sam9263(priv))
                dev->sysfs_groups[0] = &at91_sysfs_attr_group;

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

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

        devm_can_led_init(dev);

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

        return 0;

 exit_free:
        free_candev(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 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);

        iounmap(priv->reg_base);

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

        clk_put(priv->clk);

        free_candev(dev);

        return 0;
}

static const struct platform_device_id at91_can_id_table[] = {
        {
                .name = "at91sam9x5_can",
                .driver_data = (kernel_ulong_t)&at91_at91sam9x5_data,
        }, {
                .name = "at91_can",
                .driver_data = (kernel_ulong_t)&at91_at91sam9263_data,
        }, {
                /* sentinel */
        }
};
MODULE_DEVICE_TABLE(platform, at91_can_id_table);

static struct platform_driver at91_can_driver = {
        .probe = at91_can_probe,
        .remove = at91_can_remove,
        .driver = {
                .name = KBUILD_MODNAME,
                .of_match_table = of_match_ptr(at91_can_dt_ids),
        },
        .id_table = at91_can_id_table,
};

module_platform_driver(at91_can_driver);

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