can: m_can: add Bosch M_CAN controller support

The patch adds the basic CAN TX/RX function support for Bosch M_CAN controller.
For TX, only one dedicated tx buffer is used for sending data.
For RX, RXFIFO 0 is used for receiving data to avoid overflow.
Rx FIFO 1 and Rx Buffers are not used currently, as well as Tx Event FIFO.

Due to the message ram can be shared by multi m_can instances
and the fifo element is configurable which is SoC dependant,
the design is to parse the message ram related configuration data from device
tree rather than hardcode define it in driver which can make the message
ram sharing fully transparent to M_CAN controller driver,
then we can gain better driver maintainability and future features upgrade.

M_CAN also supports CANFD protocol features like data payload up to 64 bytes
and bitrate switch at runtime, however, this patch still does not add the
support for these features.

Cc: Wolfgang Grandegger <wg@grandegger.com>
Cc: Marc Kleine-Budde <mkl@pengutronix.de>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Oliver Hartkopp <socketcan@hartkopp.net>
Cc: Varka Bhadram <varkabhadram@gmail.com>
Signed-off-by: Dong Aisheng <b29396@freescale.com>
Reviewed-by: Varka Bhadram <varkabhadram@gmail.com>
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
[mkl: Squahed semicolon cleanup by Fengguang Wu]
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

5 files changed, 1214 insertions, 0 deletions

diff --git a/drivers/net/can/Kconfig b/drivers/net/can/Kconfig
index 41688229c570..e78d6b32431d 100644
--- a/drivers/net/can/Kconfig
+++ b/drivers/net/can/Kconfig
@@ -143,6 +143,8 @@ source "drivers/net/can/sja1000/Kconfig"
 
 source "drivers/net/can/c_can/Kconfig"
 
+source "drivers/net/can/m_can/Kconfig"
+
 source "drivers/net/can/cc770/Kconfig"
 
 source "drivers/net/can/spi/Kconfig"
diff --git a/drivers/net/can/Makefile b/drivers/net/can/Makefile
index 14b4c2af1e5d..fc9304143f44 100644
--- a/drivers/net/can/Makefile
+++ b/drivers/net/can/Makefile
@@ -17,6 +17,7 @@ obj-y				+= softing/
 obj-$(CONFIG_CAN_SJA1000)	+= sja1000/
 obj-$(CONFIG_CAN_MSCAN)		+= mscan/
 obj-$(CONFIG_CAN_C_CAN)		+= c_can/
+obj-$(CONFIG_CAN_M_CAN)		+= m_can/
 obj-$(CONFIG_CAN_CC770)		+= cc770/
 obj-$(CONFIG_CAN_AT91)		+= at91_can.o
 obj-$(CONFIG_CAN_TI_HECC)	+= ti_hecc.o
diff --git a/drivers/net/can/m_can/Kconfig b/drivers/net/can/m_can/Kconfig
new file mode 100644
index 000000000000..fca5482c09ac
--- /dev/null
+++ b/drivers/net/can/m_can/Kconfig
@@ -0,0 +1,4 @@
+config CAN_M_CAN
+	tristate "Bosch M_CAN devices"
+	---help---
+	  Say Y here if you want to support for Bosch M_CAN controller.
diff --git a/drivers/net/can/m_can/Makefile b/drivers/net/can/m_can/Makefile
new file mode 100644
index 000000000000..8bbd7f24f5be
--- /dev/null
+++ b/drivers/net/can/m_can/Makefile
@@ -0,0 +1,5 @@
+#
+#  Makefile for the Bosch M_CAN controller driver.
+#
+
+obj-$(CONFIG_CAN_M_CAN) += m_can.o
diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
new file mode 100644
index 000000000000..10d571eaed85
--- /dev/null
+++ b/drivers/net/can/m_can/m_can.c
@@ -0,0 +1,1202 @@
+/*
+ * CAN bus driver for Bosch M_CAN controller
+ *
+ * Copyright (C) 2014 Freescale Semiconductor, Inc.
+ *	Dong Aisheng <b29396@freescale.com>
+ *
+ * Bosch M_CAN user manual can be obtained from:
+ * http://www.bosch-semiconductors.de/media/pdf_1/ipmodules_1/m_can/
+ * mcan_users_manual_v302.pdf
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2. This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+
+#include <linux/clk.h>
+#include <linux/delay.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/netdevice.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+
+#include <linux/can/dev.h>
+
+/* napi related */
+#define M_CAN_NAPI_WEIGHT	64
+
+/* message ram configuration data length */
+#define MRAM_CFG_LEN	8
+
+/* registers definition */
+enum m_can_reg {
+	M_CAN_CREL	= 0x0,
+	M_CAN_ENDN	= 0x4,
+	M_CAN_CUST	= 0x8,
+	M_CAN_FBTP	= 0xc,
+	M_CAN_TEST	= 0x10,
+	M_CAN_RWD	= 0x14,
+	M_CAN_CCCR	= 0x18,
+	M_CAN_BTP	= 0x1c,
+	M_CAN_TSCC	= 0x20,
+	M_CAN_TSCV	= 0x24,
+	M_CAN_TOCC	= 0x28,
+	M_CAN_TOCV	= 0x2c,
+	M_CAN_ECR	= 0x40,
+	M_CAN_PSR	= 0x44,
+	M_CAN_IR	= 0x50,
+	M_CAN_IE	= 0x54,
+	M_CAN_ILS	= 0x58,
+	M_CAN_ILE	= 0x5c,
+	M_CAN_GFC	= 0x80,
+	M_CAN_SIDFC	= 0x84,
+	M_CAN_XIDFC	= 0x88,
+	M_CAN_XIDAM	= 0x90,
+	M_CAN_HPMS	= 0x94,
+	M_CAN_NDAT1	= 0x98,
+	M_CAN_NDAT2	= 0x9c,
+	M_CAN_RXF0C	= 0xa0,
+	M_CAN_RXF0S	= 0xa4,
+	M_CAN_RXF0A	= 0xa8,
+	M_CAN_RXBC	= 0xac,
+	M_CAN_RXF1C	= 0xb0,
+	M_CAN_RXF1S	= 0xb4,
+	M_CAN_RXF1A	= 0xb8,
+	M_CAN_RXESC	= 0xbc,
+	M_CAN_TXBC	= 0xc0,
+	M_CAN_TXFQS	= 0xc4,
+	M_CAN_TXESC	= 0xc8,
+	M_CAN_TXBRP	= 0xcc,
+	M_CAN_TXBAR	= 0xd0,
+	M_CAN_TXBCR	= 0xd4,
+	M_CAN_TXBTO	= 0xd8,
+	M_CAN_TXBCF	= 0xdc,
+	M_CAN_TXBTIE	= 0xe0,
+	M_CAN_TXBCIE	= 0xe4,
+	M_CAN_TXEFC	= 0xf0,
+	M_CAN_TXEFS	= 0xf4,
+	M_CAN_TXEFA	= 0xf8,
+};
+
+/* m_can lec values */
+enum m_can_lec_type {
+	LEC_NO_ERROR = 0,
+	LEC_STUFF_ERROR,
+	LEC_FORM_ERROR,
+	LEC_ACK_ERROR,
+	LEC_BIT1_ERROR,
+	LEC_BIT0_ERROR,
+	LEC_CRC_ERROR,
+	LEC_UNUSED,
+};
+
+enum m_can_mram_cfg {
+	MRAM_SIDF = 0,
+	MRAM_XIDF,
+	MRAM_RXF0,
+	MRAM_RXF1,
+	MRAM_RXB,
+	MRAM_TXE,
+	MRAM_TXB,
+	MRAM_CFG_NUM,
+};
+
+/* Test Register (TEST) */
+#define TEST_LBCK	BIT(4)
+
+/* CC Control Register(CCCR) */
+#define CCCR_TEST	BIT(7)
+#define CCCR_MON	BIT(5)
+#define CCCR_CCE	BIT(1)
+#define CCCR_INIT	BIT(0)
+
+/* Bit Timing & Prescaler Register (BTP) */
+#define BTR_BRP_MASK		0x3ff
+#define BTR_BRP_SHIFT		16
+#define BTR_TSEG1_SHIFT		8
+#define BTR_TSEG1_MASK		(0x3f << BTR_TSEG1_SHIFT)
+#define BTR_TSEG2_SHIFT		4
+#define BTR_TSEG2_MASK		(0xf << BTR_TSEG2_SHIFT)
+#define BTR_SJW_SHIFT		0
+#define BTR_SJW_MASK		0xf
+
+/* Error Counter Register(ECR) */
+#define ECR_RP			BIT(15)
+#define ECR_REC_SHIFT		8
+#define ECR_REC_MASK		(0x7f << ECR_REC_SHIFT)
+#define ECR_TEC_SHIFT		0
+#define ECR_TEC_MASK		0xff
+
+/* Protocol Status Register(PSR) */
+#define PSR_BO		BIT(7)
+#define PSR_EW		BIT(6)
+#define PSR_EP		BIT(5)
+#define PSR_LEC_MASK	0x7
+
+/* Interrupt Register(IR) */
+#define IR_ALL_INT	0xffffffff
+#define IR_STE		BIT(31)
+#define IR_FOE		BIT(30)
+#define IR_ACKE		BIT(29)
+#define IR_BE		BIT(28)
+#define IR_CRCE		BIT(27)
+#define IR_WDI		BIT(26)
+#define IR_BO		BIT(25)
+#define IR_EW		BIT(24)
+#define IR_EP		BIT(23)
+#define IR_ELO		BIT(22)
+#define IR_BEU		BIT(21)
+#define IR_BEC		BIT(20)
+#define IR_DRX		BIT(19)
+#define IR_TOO		BIT(18)
+#define IR_MRAF		BIT(17)
+#define IR_TSW		BIT(16)
+#define IR_TEFL		BIT(15)
+#define IR_TEFF		BIT(14)
+#define IR_TEFW		BIT(13)
+#define IR_TEFN		BIT(12)
+#define IR_TFE		BIT(11)
+#define IR_TCF		BIT(10)
+#define IR_TC		BIT(9)
+#define IR_HPM		BIT(8)
+#define IR_RF1L		BIT(7)
+#define IR_RF1F		BIT(6)
+#define IR_RF1W		BIT(5)
+#define IR_RF1N		BIT(4)
+#define IR_RF0L		BIT(3)
+#define IR_RF0F		BIT(2)
+#define IR_RF0W		BIT(1)
+#define IR_RF0N		BIT(0)
+#define IR_ERR_STATE	(IR_BO | IR_EW | IR_EP)
+#define IR_ERR_LEC	(IR_STE	| IR_FOE | IR_ACKE | IR_BE | IR_CRCE)
+#define IR_ERR_BUS	(IR_ERR_LEC | IR_WDI | IR_ELO | IR_BEU | \
+			 IR_BEC | IR_TOO | IR_MRAF | IR_TSW | IR_TEFL | \
+			 IR_RF1L | IR_RF0L)
+#define IR_ERR_ALL	(IR_ERR_STATE | IR_ERR_BUS)
+
+/* Interrupt Line Select (ILS) */
+#define ILS_ALL_INT0	0x0
+#define ILS_ALL_INT1	0xFFFFFFFF
+
+/* Interrupt Line Enable (ILE) */
+#define ILE_EINT0	BIT(0)
+#define ILE_EINT1	BIT(1)
+
+/* Rx FIFO 0/1 Configuration (RXF0C/RXF1C) */
+#define RXFC_FWM_OFF	24
+#define RXFC_FWM_MASK	0x7f
+#define RXFC_FWM_1	(1 << RXFC_FWM_OFF)
+#define RXFC_FS_OFF	16
+#define RXFC_FS_MASK	0x7f
+
+/* Rx FIFO 0/1 Status (RXF0S/RXF1S) */
+#define RXFS_RFL	BIT(25)
+#define RXFS_FF		BIT(24)
+#define RXFS_FPI_OFF	16
+#define RXFS_FPI_MASK	0x3f0000
+#define RXFS_FGI_OFF	8
+#define RXFS_FGI_MASK	0x3f00
+#define RXFS_FFL_MASK	0x7f
+
+/* Rx Buffer / FIFO Element Size Configuration (RXESC) */
+#define M_CAN_RXESC_8BYTES	0x0
+
+/* Tx Buffer Configuration(TXBC) */
+#define TXBC_NDTB_OFF		16
+#define TXBC_NDTB_MASK		0x3f
+
+/* Tx Buffer Element Size Configuration(TXESC) */
+#define TXESC_TBDS_8BYTES	0x0
+
+/* Tx Event FIFO Con.guration (TXEFC) */
+#define TXEFC_EFS_OFF		16
+#define TXEFC_EFS_MASK		0x3f
+
+/* Message RAM Configuration (in bytes) */
+#define SIDF_ELEMENT_SIZE	4
+#define XIDF_ELEMENT_SIZE	8
+#define RXF0_ELEMENT_SIZE	16
+#define RXF1_ELEMENT_SIZE	16
+#define RXB_ELEMENT_SIZE	16
+#define TXE_ELEMENT_SIZE	8
+#define TXB_ELEMENT_SIZE	16
+
+/* Message RAM Elements */
+#define M_CAN_FIFO_ID		0x0
+#define M_CAN_FIFO_DLC		0x4
+#define M_CAN_FIFO_DATA(n)	(0x8 + ((n) << 2))
+
+/* Rx Buffer Element */
+#define RX_BUF_ESI		BIT(31)
+#define RX_BUF_XTD		BIT(30)
+#define RX_BUF_RTR		BIT(29)
+
+/* Tx Buffer Element */
+#define TX_BUF_XTD		BIT(30)
+#define TX_BUF_RTR		BIT(29)
+
+/* address offset and element number for each FIFO/Buffer in the Message RAM */
+struct mram_cfg {
+	u16 off;
+	u8  num;
+};
+
+/* m_can private data structure */
+struct m_can_priv {
+	struct can_priv can;	/* must be the first member */
+	struct napi_struct napi;
+	struct net_device *dev;
+	struct device *device;
+	struct clk *hclk;
+	struct clk *cclk;
+	void __iomem *base;
+	u32 irqstatus;
+
+	/* message ram configuration */
+	void __iomem *mram_base;
+	struct mram_cfg mcfg[MRAM_CFG_NUM];
+};
+
+static inline u32 m_can_read(const struct m_can_priv *priv, enum m_can_reg reg)
+{
+	return readl(priv->base + reg);
+}
+
+static inline void m_can_write(const struct m_can_priv *priv,
+			       enum m_can_reg reg, u32 val)
+{
+	writel(val, priv->base + reg);
+}
+
+static inline u32 m_can_fifo_read(const struct m_can_priv *priv,
+				  u32 fgi, unsigned int offset)
+{
+	return readl(priv->mram_base + priv->mcfg[MRAM_RXF0].off +
+		     fgi * RXF0_ELEMENT_SIZE + offset);
+}
+
+static inline void m_can_fifo_write(const struct m_can_priv *priv,
+				    u32 fpi, unsigned int offset, u32 val)
+{
+	return writel(val, priv->mram_base + priv->mcfg[MRAM_TXB].off +
+		      fpi * TXB_ELEMENT_SIZE + offset);
+}
+
+static inline void m_can_config_endisable(const struct m_can_priv *priv,
+					  bool enable)
+{
+	u32 cccr = m_can_read(priv, M_CAN_CCCR);
+	u32 timeout = 10;
+	u32 val = 0;
+
+	if (enable) {
+		/* enable m_can configuration */
+		m_can_write(priv, M_CAN_CCCR, cccr | CCCR_INIT);
+		/* CCCR.CCE can only be set/reset while CCCR.INIT = '1' */
+		m_can_write(priv, M_CAN_CCCR, cccr | CCCR_INIT | CCCR_CCE);
+	} else {
+		m_can_write(priv, M_CAN_CCCR, cccr & ~(CCCR_INIT | CCCR_CCE));
+	}
+
+	/* there's a delay for module initialization */
+	if (enable)
+		val = CCCR_INIT | CCCR_CCE;
+
+	while ((m_can_read(priv, M_CAN_CCCR) & (CCCR_INIT | CCCR_CCE)) != val) {
+		if (timeout == 0) {
+			netdev_warn(priv->dev, "Failed to init module\n");
+			return;
+		}
+		timeout--;
+		udelay(1);
+	}
+}
+
+static inline void m_can_enable_all_interrupts(const struct m_can_priv *priv)
+{
+	m_can_write(priv, M_CAN_ILE, ILE_EINT0 | ILE_EINT1);
+}
+
+static inline void m_can_disable_all_interrupts(const struct m_can_priv *priv)
+{
+	m_can_write(priv, M_CAN_ILE, 0x0);
+}
+
+static void m_can_read_fifo(const struct net_device *dev, struct can_frame *cf,
+			    u32 rxfs)
+{
+	struct m_can_priv *priv = netdev_priv(dev);
+	u32 id, fgi;
+
+	/* calculate the fifo get index for where to read data */
+	fgi = (rxfs & RXFS_FGI_MASK) >> RXFS_FGI_OFF;
+	id = m_can_fifo_read(priv, fgi, M_CAN_FIFO_ID);
+	if (id & RX_BUF_XTD)
+		cf->can_id = (id & CAN_EFF_MASK) | CAN_EFF_FLAG;
+	else
+		cf->can_id = (id >> 18) & CAN_SFF_MASK;
+
+	if (id & RX_BUF_RTR) {
+		cf->can_id |= CAN_RTR_FLAG;
+	} else {
+		id = m_can_fifo_read(priv, fgi, M_CAN_FIFO_DLC);
+		cf->can_dlc = get_can_dlc((id >> 16) & 0x0F);
+		*(u32 *)(cf->data + 0) = m_can_fifo_read(priv, fgi,
+							 M_CAN_FIFO_DATA(0));
+		*(u32 *)(cf->data + 4) = m_can_fifo_read(priv, fgi,
+							 M_CAN_FIFO_DATA(1));
+	}
+
+	/* acknowledge rx fifo 0 */
+	m_can_write(priv, M_CAN_RXF0A, fgi);
+}
+
+static int m_can_do_rx_poll(struct net_device *dev, int quota)
+{
+	struct m_can_priv *priv = netdev_priv(dev);
+	struct net_device_stats *stats = &dev->stats;
+	struct sk_buff *skb;
+	struct can_frame *frame;
+	u32 pkts = 0;
+	u32 rxfs;
+
+	rxfs = m_can_read(priv, M_CAN_RXF0S);
+	if (!(rxfs & RXFS_FFL_MASK)) {
+		netdev_dbg(dev, "no messages in fifo0\n");
+		return 0;
+	}
+
+	while ((rxfs & RXFS_FFL_MASK) && (quota > 0)) {
+		if (rxfs & RXFS_RFL)
+			netdev_warn(dev, "Rx FIFO 0 Message Lost\n");
+
+		skb = alloc_can_skb(dev, &frame);
+		if (!skb) {
+			stats->rx_dropped++;
+			return pkts;
+		}
+
+		m_can_read_fifo(dev, frame, rxfs);
+
+		stats->rx_packets++;
+		stats->rx_bytes += frame->can_dlc;
+
+		netif_receive_skb(skb);
+
+		quota--;
+		pkts++;
+		rxfs = m_can_read(priv, M_CAN_RXF0S);
+	}
+
+	if (pkts)
+		can_led_event(dev, CAN_LED_EVENT_RX);
+
+	return pkts;
+}
+
+static int m_can_handle_lost_msg(struct net_device *dev)
+{
+	struct net_device_stats *stats = &dev->stats;
+	struct sk_buff *skb;
+	struct can_frame *frame;
+
+	netdev_err(dev, "msg lost in rxf0\n");
+
+	stats->rx_errors++;
+	stats->rx_over_errors++;
+
+	skb = alloc_can_err_skb(dev, &frame);
+	if (unlikely(!skb))
+		return 0;
+
+	frame->can_id |= CAN_ERR_CRTL;
+	frame->data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
+
+	netif_receive_skb(skb);
+
+	return 1;
+}
+
+static int m_can_handle_lec_err(struct net_device *dev,
+				enum m_can_lec_type lec_type)
+{
+	struct m_can_priv *priv = netdev_priv(dev);
+	struct net_device_stats *stats = &dev->stats;
+	struct can_frame *cf;
+	struct sk_buff *skb;
+
+	priv->can.can_stats.bus_error++;
+	stats->rx_errors++;
+
+	/* propagate the error condition to the CAN stack */
+	skb = alloc_can_err_skb(dev, &cf);
+	if (unlikely(!skb))
+		return 0;
+
+	/* check for 'last error code' which tells us the
+	 * type of the last error to occur on the CAN bus
+	 */
+	cf->can_id |= CAN_ERR_PROT | CAN_ERR_BUSERROR;
+	cf->data[2] |= CAN_ERR_PROT_UNSPEC;
+
+	switch (lec_type) {
+	case LEC_STUFF_ERROR:
+		netdev_dbg(dev, "stuff error\n");
+		cf->data[2] |= CAN_ERR_PROT_STUFF;
+		break;
+	case LEC_FORM_ERROR:
+		netdev_dbg(dev, "form error\n");
+		cf->data[2] |= CAN_ERR_PROT_FORM;
+		break;
+	case LEC_ACK_ERROR:
+		netdev_dbg(dev, "ack error\n");
+		cf->data[3] |= (CAN_ERR_PROT_LOC_ACK |
+				CAN_ERR_PROT_LOC_ACK_DEL);
+		break;
+	case LEC_BIT1_ERROR:
+		netdev_dbg(dev, "bit1 error\n");
+		cf->data[2] |= CAN_ERR_PROT_BIT1;
+		break;
+	case LEC_BIT0_ERROR:
+		netdev_dbg(dev, "bit0 error\n");
+		cf->data[2] |= CAN_ERR_PROT_BIT0;
+		break;
+	case LEC_CRC_ERROR:
+		netdev_dbg(dev, "CRC error\n");
+		cf->data[3] |= (CAN_ERR_PROT_LOC_CRC_SEQ |
+				CAN_ERR_PROT_LOC_CRC_DEL);
+		break;
+	default:
+		break;
+	}
+
+	stats->rx_packets++;
+	stats->rx_bytes += cf->can_dlc;
+	netif_receive_skb(skb);
+
+	return 1;
+}
+
+static int m_can_get_berr_counter(const struct net_device *dev,
+				  struct can_berr_counter *bec)
+{
+	struct m_can_priv *priv = netdev_priv(dev);
+	unsigned int ecr;
+	int err;
+
+	err = clk_prepare_enable(priv->hclk);
+	if (err)
+		return err;
+
+	err = clk_prepare_enable(priv->cclk);
+	if (err) {
+		clk_disable_unprepare(priv->hclk);
+		return err;
+	}
+
+	ecr = m_can_read(priv, M_CAN_ECR);
+	bec->rxerr = (ecr & ECR_REC_MASK) >> ECR_REC_SHIFT;
+	bec->txerr = ecr & ECR_TEC_MASK;
+
+	clk_disable_unprepare(priv->cclk);
+	clk_disable_unprepare(priv->hclk);
+
+	return 0;
+}
+
+static int m_can_handle_state_change(struct net_device *dev,
+				     enum can_state new_state)
+{
+	struct m_can_priv *priv = netdev_priv(dev);
+	struct net_device_stats *stats = &dev->stats;
+	struct can_frame *cf;
+	struct sk_buff *skb;
+	struct can_berr_counter bec;
+	unsigned int ecr;
+
+	switch (new_state) {
+	case CAN_STATE_ERROR_ACTIVE:
+		/* error warning state */
+		priv->can.can_stats.error_warning++;
+		priv->can.state = CAN_STATE_ERROR_WARNING;
+		break;
+	case CAN_STATE_ERROR_PASSIVE:
+		/* error passive state */
+		priv->can.can_stats.error_passive++;
+		priv->can.state = CAN_STATE_ERROR_PASSIVE;
+		break;
+	case CAN_STATE_BUS_OFF:
+		/* bus-off state */
+		priv->can.state = CAN_STATE_BUS_OFF;
+		m_can_disable_all_interrupts(priv);
+		can_bus_off(dev);
+		break;
+	default:
+		break;
+	}
+
+	/* propagate the error condition to the CAN stack */
+	skb = alloc_can_err_skb(dev, &cf);
+	if (unlikely(!skb))
+		return 0;
+
+	m_can_get_berr_counter(dev, &bec);
+
+	switch (new_state) {
+	case CAN_STATE_ERROR_ACTIVE:
+		/* error warning state */
+		cf->can_id |= CAN_ERR_CRTL;
+		cf->data[1] = (bec.txerr > bec.rxerr) ?
+			CAN_ERR_CRTL_TX_WARNING :
+			CAN_ERR_CRTL_RX_WARNING;
+		cf->data[6] = bec.txerr;
+		cf->data[7] = bec.rxerr;
+		break;
+	case CAN_STATE_ERROR_PASSIVE:
+		/* error passive state */
+		cf->can_id |= CAN_ERR_CRTL;
+		ecr = m_can_read(priv, M_CAN_ECR);
+		if (ecr & ECR_RP)
+			cf->data[1] |= CAN_ERR_CRTL_RX_PASSIVE;
+		if (bec.txerr > 127)
+			cf->data[1] |= CAN_ERR_CRTL_TX_PASSIVE;
+		cf->data[6] = bec.txerr;
+		cf->data[7] = bec.rxerr;
+		break;
+	case CAN_STATE_BUS_OFF:
+		/* bus-off state */
+		cf->can_id |= CAN_ERR_BUSOFF;
+		break;
+	default:
+		break;
+	}
+
+	stats->rx_packets++;
+	stats->rx_bytes += cf->can_dlc;
+	netif_receive_skb(skb);
+
+	return 1;
+}
+
+static int m_can_handle_state_errors(struct net_device *dev, u32 psr)
+{
+	struct m_can_priv *priv = netdev_priv(dev);
+	int work_done = 0;
+
+	if ((psr & PSR_EW) &&
+	    (priv->can.state != CAN_STATE_ERROR_WARNING)) {
+		netdev_dbg(dev, "entered error warning state\n");
+		work_done += m_can_handle_state_change(dev,
+						       CAN_STATE_ERROR_WARNING);
+	}
+
+	if ((psr & PSR_EP) &&
+	    (priv->can.state != CAN_STATE_ERROR_PASSIVE)) {
+		netdev_dbg(dev, "entered error warning state\n");
+		work_done += m_can_handle_state_change(dev,
+						       CAN_STATE_ERROR_PASSIVE);
+	}
+
+	if ((psr & PSR_BO) &&
+	    (priv->can.state != CAN_STATE_BUS_OFF)) {
+		netdev_dbg(dev, "entered error warning state\n");
+		work_done += m_can_handle_state_change(dev,
+						       CAN_STATE_BUS_OFF);
+	}
+
+	return work_done;
+}
+
+static void m_can_handle_other_err(struct net_device *dev, u32 irqstatus)
+{
+	if (irqstatus & IR_WDI)
+		netdev_err(dev, "Message RAM Watchdog event due to missing READY\n");
+	if (irqstatus & IR_BEU)
+		netdev_err(dev, "Error Logging Overflow\n");
+	if (irqstatus & IR_BEU)
+		netdev_err(dev, "Bit Error Uncorrected\n");
+	if (irqstatus & IR_BEC)
+		netdev_err(dev, "Bit Error Corrected\n");
+	if (irqstatus & IR_TOO)
+		netdev_err(dev, "Timeout reached\n");
+	if (irqstatus & IR_MRAF)
+		netdev_err(dev, "Message RAM access failure occurred\n");
+}
+
+static inline bool is_lec_err(u32 psr)
+{
+	psr &= LEC_UNUSED;
+
+	return psr && (psr != LEC_UNUSED);
+}
+
+static int m_can_handle_bus_errors(struct net_device *dev, u32 irqstatus,
+				   u32 psr)
+{
+	struct m_can_priv *priv = netdev_priv(dev);
+	int work_done = 0;
+
+	if (irqstatus & IR_RF0L)
+		work_done += m_can_handle_lost_msg(dev);
+
+	/* handle lec errors on the bus */
+	if ((priv->can.ctrlmode & CAN_CTRLMODE_BERR_REPORTING) &&
+	    is_lec_err(psr))
+		work_done += m_can_handle_lec_err(dev, psr & LEC_UNUSED);
+
+	/* other unproccessed error interrupts */
+	m_can_handle_other_err(dev, irqstatus);
+
+	return work_done;
+}
+
+static int m_can_poll(struct napi_struct *napi, int quota)
+{
+	struct net_device *dev = napi->dev;
+	struct m_can_priv *priv = netdev_priv(dev);
+	int work_done = 0;
+	u32 irqstatus, psr;
+
+	irqstatus = priv->irqstatus | m_can_read(priv, M_CAN_IR);
+	if (!irqstatus)
+		goto end;
+
+	psr = m_can_read(priv, M_CAN_PSR);
+	if (irqstatus & IR_ERR_STATE)
+		work_done += m_can_handle_state_errors(dev, psr);
+
+	if (irqstatus & IR_ERR_BUS)
+		work_done += m_can_handle_bus_errors(dev, irqstatus, psr);
+
+	if (irqstatus & IR_RF0N)
+		work_done += m_can_do_rx_poll(dev, (quota - work_done));
+
+	if (work_done < quota) {
+		napi_complete(napi);
+		m_can_enable_all_interrupts(priv);
+	}
+
+end:
+	return work_done;
+}
+
+static irqreturn_t m_can_isr(int irq, void *dev_id)
+{
+	struct net_device *dev = (struct net_device *)dev_id;
+	struct m_can_priv *priv = netdev_priv(dev);
+	struct net_device_stats *stats = &dev->stats;
+	u32 ir;
+
+	ir = m_can_read(priv, M_CAN_IR);
+	if (!ir)
+		return IRQ_NONE;
+
+	/* ACK all irqs */
+	if (ir & IR_ALL_INT)
+		m_can_write(priv, M_CAN_IR, ir);
+
+	/* schedule NAPI in case of
+	 * - rx IRQ
+	 * - state change IRQ
+	 * - bus error IRQ and bus error reporting
+	 */
+	if ((ir & IR_RF0N) || (ir & IR_ERR_ALL)) {
+		priv->irqstatus = ir;
+		m_can_disable_all_interrupts(priv);
+		napi_schedule(&priv->napi);
+	}
+
+	/* transmission complete interrupt */
+	if (ir & IR_TC) {
+		stats->tx_bytes += can_get_echo_skb(dev, 0);
+		stats->tx_packets++;
+		can_led_event(dev, CAN_LED_EVENT_TX);
+		netif_wake_queue(dev);
+	}
+
+	return IRQ_HANDLED;
+}
+
+static const struct can_bittiming_const m_can_bittiming_const = {
+	.name = KBUILD_MODNAME,
+	.tseg1_min = 2,		/* Time segment 1 = prop_seg + phase_seg1 */
+	.tseg1_max = 64,
+	.tseg2_min = 1,		/* Time segment 2 = phase_seg2 */
+	.tseg2_max = 16,
+	.sjw_max = 16,
+	.brp_min = 1,
+	.brp_max = 1024,
+	.brp_inc = 1,
+};
+
+static int m_can_set_bittiming(struct net_device *dev)
+{
+	struct m_can_priv *priv = netdev_priv(dev);
+	const struct can_bittiming *bt = &priv->can.bittiming;
+	u16 brp, sjw, tseg1, tseg2;
+	u32 reg_btp;
+
+	brp = bt->brp - 1;
+	sjw = bt->sjw - 1;
+	tseg1 = bt->prop_seg + bt->phase_seg1 - 1;
+	tseg2 = bt->phase_seg2 - 1;
+	reg_btp = (brp << BTR_BRP_SHIFT) | (sjw << BTR_SJW_SHIFT) |
+			(tseg1 << BTR_TSEG1_SHIFT) | (tseg2 << BTR_TSEG2_SHIFT);
+	m_can_write(priv, M_CAN_BTP, reg_btp);
+	netdev_dbg(dev, "setting BTP 0x%x\n", reg_btp);
+
+	return 0;
+}
+
+/* Configure M_CAN chip:
+ * - set rx buffer/fifo element size
+ * - configure rx fifo
+ * - accept non-matching frame into fifo 0
+ * - configure tx buffer
+ * - configure mode
+ * - setup bittiming
+ */
+static void m_can_chip_config(struct net_device *dev)
+{
+	struct m_can_priv *priv = netdev_priv(dev);
+	u32 cccr, test;
+
+	m_can_config_endisable(priv, true);
+
+	/* RX Buffer/FIFO Element Size 8 bytes data field */
+	m_can_write(priv, M_CAN_RXESC, M_CAN_RXESC_8BYTES);
+
+	/* Accept Non-matching Frames Into FIFO 0 */
+	m_can_write(priv, M_CAN_GFC, 0x0);
+
+	/* only support one Tx Buffer currently */
+	m_can_write(priv, M_CAN_TXBC, (1 << TXBC_NDTB_OFF) |
+		    priv->mcfg[MRAM_TXB].off);
+
+	/* only support 8 bytes firstly */
+	m_can_write(priv, M_CAN_TXESC, TXESC_TBDS_8BYTES);
+
+	m_can_write(priv, M_CAN_TXEFC, (1 << TXEFC_EFS_OFF) |
+		    priv->mcfg[MRAM_TXE].off);
+
+	/* rx fifo configuration, blocking mode, fifo size 1 */
+	m_can_write(priv, M_CAN_RXF0C,
+		    (priv->mcfg[MRAM_RXF0].num << RXFC_FS_OFF) |
+		    RXFC_FWM_1 | priv->mcfg[MRAM_RXF0].off);
+
+	m_can_write(priv, M_CAN_RXF1C,
+		    (priv->mcfg[MRAM_RXF1].num << RXFC_FS_OFF) |
+		    RXFC_FWM_1 | priv->mcfg[MRAM_RXF1].off);
+
+	cccr = m_can_read(priv, M_CAN_CCCR);
+	cccr &= ~(CCCR_TEST | CCCR_MON);
+	test = m_can_read(priv, M_CAN_TEST);
+	test &= ~TEST_LBCK;
+
+	if (priv->can.ctrlmode & CAN_CTRLMODE_LISTENONLY)
+		cccr |= CCCR_MON;
+
+	if (priv->can.ctrlmode & CAN_CTRLMODE_LOOPBACK) {
+		cccr |= CCCR_TEST;
+		test |= TEST_LBCK;
+	}
+
+	m_can_write(priv, M_CAN_CCCR, cccr);
+	m_can_write(priv, M_CAN_TEST, test);
+
+	/* enable interrupts */
+	m_can_write(priv, M_CAN_IR, IR_ALL_INT);
+	if (!(priv->can.ctrlmode & CAN_CTRLMODE_BERR_REPORTING))
+		m_can_write(priv, M_CAN_IE, IR_ALL_INT & ~IR_ERR_LEC);
+	else
+		m_can_write(priv, M_CAN_IE, IR_ALL_INT);
+
+	/* route all interrupts to INT0 */
+	m_can_write(priv, M_CAN_ILS, ILS_ALL_INT0);
+
+	/* set bittiming params */
+	m_can_set_bittiming(dev);
+
+	m_can_config_endisable(priv, false);
+}
+
+static void m_can_start(struct net_device *dev)
+{
+	struct m_can_priv *priv = netdev_priv(dev);
+
+	/* basic m_can configuration */
+	m_can_chip_config(dev);
+
+	priv->can.state = CAN_STATE_ERROR_ACTIVE;
+
+	m_can_enable_all_interrupts(priv);
+}
+
+static int m_can_set_mode(struct net_device *dev, enum can_mode mode)
+{
+	switch (mode) {
+	case CAN_MODE_START:
+		m_can_start(dev);
+		netif_wake_queue(dev);
+		break;
+	default:
+		return -EOPNOTSUPP;
+	}
+
+	return 0;
+}
+
+static void free_m_can_dev(struct net_device *dev)
+{
+	free_candev(dev);
+}
+
+static struct net_device *alloc_m_can_dev(void)
+{
+	struct net_device *dev;
+	struct m_can_priv *priv;
+
+	dev = alloc_candev(sizeof(*priv), 1);
+	if (!dev)
+		return NULL;
+
+	priv = netdev_priv(dev);
+	netif_napi_add(dev, &priv->napi, m_can_poll, M_CAN_NAPI_WEIGHT);
+
+	priv->dev = dev;
+	priv->can.bittiming_const = &m_can_bittiming_const;
+	priv->can.do_set_mode = m_can_set_mode;
+	priv->can.do_get_berr_counter = m_can_get_berr_counter;
+	priv->can.ctrlmode_supported = CAN_CTRLMODE_LOOPBACK |
+					CAN_CTRLMODE_LISTENONLY |
+					CAN_CTRLMODE_BERR_REPORTING;
+
+	return dev;
+}
+
+static int m_can_open(struct net_device *dev)
+{
+	struct m_can_priv *priv = netdev_priv(dev);
+	int err;
+
+	err = clk_prepare_enable(priv->hclk);
+	if (err)
+		return err;
+
+	err = clk_prepare_enable(priv->cclk);
+	if (err)
+		goto exit_disable_hclk;
+
+	/* open the can device */
+	err = open_candev(dev);
+	if (err) {
+		netdev_err(dev, "failed to open can device\n");
+		goto exit_disable_cclk;
+	}
+
+	/* register interrupt handler */
+	err = request_irq(dev->irq, m_can_isr, IRQF_SHARED, dev->name,
+			  dev);
+	if (err < 0) {
+		netdev_err(dev, "failed to request interrupt\n");
+		goto exit_irq_fail;
+	}
+
+	/* start the m_can controller */
+	m_can_start(dev);
+
+	can_led_event(dev, CAN_LED_EVENT_OPEN);
+	napi_enable(&priv->napi);
+	netif_start_queue(dev);
+
+	return 0;
+
+exit_irq_fail:
+	close_candev(dev);
+exit_disable_cclk:
+	clk_disable_unprepare(priv->cclk);
+exit_disable_hclk:
+	clk_disable_unprepare(priv->hclk);
+	return err;
+}
+
+static void m_can_stop(struct net_device *dev)
+{
+	struct m_can_priv *priv = netdev_priv(dev);
+
+	/* disable all interrupts */
+	m_can_disable_all_interrupts(priv);
+
+	clk_disable_unprepare(priv->hclk);
+	clk_disable_unprepare(priv->cclk);
+
+	/* set the state as STOPPED */
+	priv->can.state = CAN_STATE_STOPPED;
+}
+
+static int m_can_close(struct net_device *dev)
+{
+	struct m_can_priv *priv = netdev_priv(dev);
+
+	netif_stop_queue(dev);
+	napi_disable(&priv->napi);
+	m_can_stop(dev);
+	free_irq(dev->irq, dev);
+	close_candev(dev);
+	can_led_event(dev, CAN_LED_EVENT_STOP);
+
+	return 0;
+}
+
+static netdev_tx_t m_can_start_xmit(struct sk_buff *skb,
+				    struct net_device *dev)
+{
+	struct m_can_priv *priv = netdev_priv(dev);
+	struct can_frame *cf = (struct can_frame *)skb->data;
+	u32 id;
+
+	if (can_dropped_invalid_skb(dev, skb))
+		return NETDEV_TX_OK;
+
+	netif_stop_queue(dev);
+
+	if (cf->can_id & CAN_EFF_FLAG) {
+		id = cf->can_id & CAN_EFF_MASK;
+		id |= TX_BUF_XTD;
+	} else {
+		id = ((cf->can_id & CAN_SFF_MASK) << 18);
+	}
+
+	if (cf->can_id & CAN_RTR_FLAG)
+		id |= TX_BUF_RTR;
+
+	/* message ram configuration */
+	m_can_fifo_write(priv, 0, M_CAN_FIFO_ID, id);
+	m_can_fifo_write(priv, 0, M_CAN_FIFO_DLC, cf->can_dlc << 16);
+	m_can_fifo_write(priv, 0, M_CAN_FIFO_DATA(0), *(u32 *)(cf->data + 0));
+	m_can_fifo_write(priv, 0, M_CAN_FIFO_DATA(1), *(u32 *)(cf->data + 4));
+	can_put_echo_skb(skb, dev, 0);
+
+	/* enable first TX buffer to start transfer  */
+	m_can_write(priv, M_CAN_TXBTIE, 0x1);
+	m_can_write(priv, M_CAN_TXBAR, 0x1);
+
+	return NETDEV_TX_OK;
+}
+
+static const struct net_device_ops m_can_netdev_ops = {
+	.ndo_open = m_can_open,
+	.ndo_stop = m_can_close,
+	.ndo_start_xmit = m_can_start_xmit,
+};
+
+static int register_m_can_dev(struct net_device *dev)
+{
+	dev->flags |= IFF_ECHO;	/* we support local echo */
+	dev->netdev_ops = &m_can_netdev_ops;
+
+	return register_candev(dev);
+}
+
+static int m_can_of_parse_mram(struct platform_device *pdev,
+			       struct m_can_priv *priv)
+{
+	struct device_node *np = pdev->dev.of_node;
+	struct resource *res;
+	void __iomem *addr;
+	u32 out_val[MRAM_CFG_LEN];
+	int ret;
+
+	/* message ram could be shared */
+	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "message_ram");
+	if (!res)
+		return -ENODEV;
+
+	addr = devm_ioremap(&pdev->dev, res->start, resource_size(res));
+	if (!addr)
+		return -ENOMEM;
+
+	/* get message ram configuration */
+	ret = of_property_read_u32_array(np, "bosch,mram-cfg",
+					 out_val, sizeof(out_val) / 4);
+	if (ret) {
+		dev_err(&pdev->dev, "can not get message ram configuration\n");
+		return -ENODEV;
+	}
+
+	priv->mram_base = addr;
+	priv->mcfg[MRAM_SIDF].off = out_val[0];
+	priv->mcfg[MRAM_SIDF].num = out_val[1];
+	priv->mcfg[MRAM_XIDF].off = priv->mcfg[MRAM_SIDF].off +
+			priv->mcfg[MRAM_SIDF].num * SIDF_ELEMENT_SIZE;
+	priv->mcfg[MRAM_XIDF].num = out_val[2];
+	priv->mcfg[MRAM_RXF0].off = priv->mcfg[MRAM_XIDF].off +
+			priv->mcfg[MRAM_XIDF].num * XIDF_ELEMENT_SIZE;
+	priv->mcfg[MRAM_RXF0].num = out_val[3] & RXFC_FS_MASK;
+	priv->mcfg[MRAM_RXF1].off = priv->mcfg[MRAM_RXF0].off +
+			priv->mcfg[MRAM_RXF0].num * RXF0_ELEMENT_SIZE;
+	priv->mcfg[MRAM_RXF1].num = out_val[4] & RXFC_FS_MASK;
+	priv->mcfg[MRAM_RXB].off = priv->mcfg[MRAM_RXF1].off +
+			priv->mcfg[MRAM_RXF1].num * RXF1_ELEMENT_SIZE;
+	priv->mcfg[MRAM_RXB].num = out_val[5];
+	priv->mcfg[MRAM_TXE].off = priv->mcfg[MRAM_RXB].off +
+			priv->mcfg[MRAM_RXB].num * RXB_ELEMENT_SIZE;
+	priv->mcfg[MRAM_TXE].num = out_val[6];
+	priv->mcfg[MRAM_TXB].off = priv->mcfg[MRAM_TXE].off +
+			priv->mcfg[MRAM_TXE].num * TXE_ELEMENT_SIZE;
+	priv->mcfg[MRAM_TXB].num = out_val[7] & TXBC_NDTB_MASK;
+
+	dev_dbg(&pdev->dev, "mram_base %p sidf 0x%x %d xidf 0x%x %d rxf0 0x%x %d rxf1 0x%x %d rxb 0x%x %d txe 0x%x %d txb 0x%x %d\n",
+		priv->mram_base,
+		priv->mcfg[MRAM_SIDF].off, priv->mcfg[MRAM_SIDF].num,
+		priv->mcfg[MRAM_XIDF].off, priv->mcfg[MRAM_XIDF].num,
+		priv->mcfg[MRAM_RXF0].off, priv->mcfg[MRAM_RXF0].num,
+		priv->mcfg[MRAM_RXF1].off, priv->mcfg[MRAM_RXF1].num,
+		priv->mcfg[MRAM_RXB].off, priv->mcfg[MRAM_RXB].num,
+		priv->mcfg[MRAM_TXE].off, priv->mcfg[MRAM_TXE].num,
+		priv->mcfg[MRAM_TXB].off, priv->mcfg[MRAM_TXB].num);
+
+	return 0;
+}
+
+static int m_can_plat_probe(struct platform_device *pdev)
+{
+	struct net_device *dev;
+	struct m_can_priv *priv;
+	struct resource *res;
+	void __iomem *addr;
+	struct clk *hclk, *cclk;
+	int irq, ret;
+
+	hclk = devm_clk_get(&pdev->dev, "hclk");
+	cclk = devm_clk_get(&pdev->dev, "cclk");
+	if (IS_ERR(hclk) || IS_ERR(cclk)) {
+		dev_err(&pdev->dev, "no clock find\n");
+		return -ENODEV;
+	}
+
+	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "m_can");
+	addr = devm_ioremap_resource(&pdev->dev, res);
+	irq = platform_get_irq_byname(pdev, "int0");
+	if (IS_ERR(addr) || irq < 0)
+		return -EINVAL;
+
+	/* allocate the m_can device */
+	dev = alloc_m_can_dev();
+	if (!dev)
+		return -ENOMEM;
+
+	priv = netdev_priv(dev);
+	dev->irq = irq;
+	priv->base = addr;
+	priv->device = &pdev->dev;
+	priv->hclk = hclk;
+	priv->cclk = cclk;
+	priv->can.clock.freq = clk_get_rate(cclk);
+
+	ret = m_can_of_parse_mram(pdev, priv);
+	if (ret)
+		goto failed_free_dev;
+
+	platform_set_drvdata(pdev, dev);
+	SET_NETDEV_DEV(dev, &pdev->dev);
+
+	ret = register_m_can_dev(dev);
+	if (ret) {
+		dev_err(&pdev->dev, "registering %s failed (err=%d)\n",
+			KBUILD_MODNAME, ret);
+		goto failed_free_dev;
+	}
+
+	devm_can_led_init(dev);
+
+	dev_info(&pdev->dev, "%s device registered (regs=%p, irq=%d)\n",
+		 KBUILD_MODNAME, priv->base, dev->irq);
+
+	return 0;
+
+failed_free_dev:
+	free_m_can_dev(dev);
+	return ret;
+}
+
+static __maybe_unused int m_can_suspend(struct device *dev)
+{
+	struct net_device *ndev = dev_get_drvdata(dev);
+	struct m_can_priv *priv = netdev_priv(ndev);
+
+	if (netif_running(ndev)) {
+		netif_stop_queue(ndev);
+		netif_device_detach(ndev);
+	}
+
+	/* TODO: enter low power */
+
+	priv->can.state = CAN_STATE_SLEEPING;
+
+	return 0;
+}
+
+static __maybe_unused int m_can_resume(struct device *dev)
+{
+	struct net_device *ndev = dev_get_drvdata(dev);
+	struct m_can_priv *priv = netdev_priv(ndev);
+
+	/* TODO: exit low power */
+
+	priv->can.state = CAN_STATE_ERROR_ACTIVE;
+
+	if (netif_running(ndev)) {
+		netif_device_attach(ndev);
+		netif_start_queue(ndev);
+	}
+
+	return 0;
+}
+
+static void unregister_m_can_dev(struct net_device *dev)
+{
+	unregister_candev(dev);
+}
+
+static int m_can_plat_remove(struct platform_device *pdev)
+{
+	struct net_device *dev = platform_get_drvdata(pdev);
+
+	unregister_m_can_dev(dev);
+	platform_set_drvdata(pdev, NULL);
+
+	free_m_can_dev(dev);
+
+	return 0;
+}
+
+static const struct dev_pm_ops m_can_pmops = {
+	SET_SYSTEM_SLEEP_PM_OPS(m_can_suspend, m_can_resume)
+};
+
+static const struct of_device_id m_can_of_table[] = {
+	{ .compatible = "bosch,m_can", .data = NULL },
+	{ /* sentinel */ },
+};
+MODULE_DEVICE_TABLE(of, m_can_of_table);
+
+static struct platform_driver m_can_plat_driver = {
+	.driver = {
+		.name = KBUILD_MODNAME,
+		.of_match_table = m_can_of_table,
+		.pm     = &m_can_pmops,
+	},
+	.probe = m_can_plat_probe,
+	.remove = m_can_plat_remove,
+};
+
+module_platform_driver(m_can_plat_driver);
+
+MODULE_AUTHOR("Dong Aisheng <b29396@freescale.com>");
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("CAN bus driver for Bosch M_CAN controller");