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");