at91_can: Forgotten git 'add' of at91_can.c

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 1186 insertions, 0 deletions

diff --git a/drivers/net/can/at91_can.c b/drivers/net/can/at91_can.c
new file mode 100644
index 000000000000..f67ae285a35a
--- /dev/null
+++ b/drivers/net/can/at91_can.c
@@ -0,0 +1,1186 @@
+/*
+ * 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");