linux/drivers/net/can/pch_can.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 1999 - 2010 Intel Corporation.
 * Copyright (C) 2010 LAPIS SEMICONDUCTOR CO., LTD.
 */

#include <linux/interrupt.h>
#include <linux/delay.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/pci.h>
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/can.h>
#include <linux/can/dev.h>
#include <linux/can/error.h>

#define PCH_CTRL_INIT		BIT(0) /* The INIT bit of CANCONT register. */
#define PCH_CTRL_IE		BIT(1) /* The IE bit of CAN control register */
#define PCH_CTRL_IE_SIE_EIE	(BIT(3) | BIT(2) | BIT(1))
#define PCH_CTRL_CCE		BIT(6)
#define PCH_CTRL_OPT		BIT(7) /* The OPT bit of CANCONT register. */
#define PCH_OPT_SILENT		BIT(3) /* The Silent bit of CANOPT reg. */
#define PCH_OPT_LBACK		BIT(4) /* The LoopBack bit of CANOPT reg. */

#define PCH_CMASK_RX_TX_SET	0x00f3
#define PCH_CMASK_RX_TX_GET	0x0073
#define PCH_CMASK_ALL		0xff
#define PCH_CMASK_NEWDAT	BIT(2)
#define PCH_CMASK_CLRINTPND	BIT(3)
#define PCH_CMASK_CTRL		BIT(4)
#define PCH_CMASK_ARB		BIT(5)
#define PCH_CMASK_MASK		BIT(6)
#define PCH_CMASK_RDWR		BIT(7)
#define PCH_IF_MCONT_NEWDAT	BIT(15)
#define PCH_IF_MCONT_MSGLOST	BIT(14)
#define PCH_IF_MCONT_INTPND	BIT(13)
#define PCH_IF_MCONT_UMASK	BIT(12)
#define PCH_IF_MCONT_TXIE	BIT(11)
#define PCH_IF_MCONT_RXIE	BIT(10)
#define PCH_IF_MCONT_RMTEN	BIT(9)
#define PCH_IF_MCONT_TXRQXT	BIT(8)
#define PCH_IF_MCONT_EOB	BIT(7)
#define PCH_IF_MCONT_DLC	(BIT(0) | BIT(1) | BIT(2) | BIT(3))
#define PCH_MASK2_MDIR_MXTD	(BIT(14) | BIT(15))
#define PCH_ID2_DIR		BIT(13)
#define PCH_ID2_XTD		BIT(14)
#define PCH_ID_MSGVAL		BIT(15)
#define PCH_IF_CREQ_BUSY	BIT(15)

#define PCH_STATUS_INT		0x8000
#define PCH_RP			0x00008000
#define PCH_REC			0x00007f00
#define PCH_TEC			0x000000ff

#define PCH_TX_OK		BIT(3)
#define PCH_RX_OK		BIT(4)
#define PCH_EPASSIV		BIT(5)
#define PCH_EWARN		BIT(6)
#define PCH_BUS_OFF		BIT(7)

/* bit position of certain controller bits. */
#define PCH_BIT_BRP_SHIFT	0
#define PCH_BIT_SJW_SHIFT	6
#define PCH_BIT_TSEG1_SHIFT	8
#define PCH_BIT_TSEG2_SHIFT	12
#define PCH_BIT_BRPE_BRPE_SHIFT	6

#define PCH_MSK_BITT_BRP	0x3f
#define PCH_MSK_BRPE_BRPE	0x3c0
#define PCH_MSK_CTRL_IE_SIE_EIE	0x07
#define PCH_COUNTER_LIMIT	10

#define PCH_CAN_CLK		50000000	/* 50MHz */

/*
 * Define the number of message object.
 * PCH CAN communications are done via Message RAM.
 * The Message RAM consists of 32 message objects.
 */
#define PCH_RX_OBJ_NUM		26
#define PCH_TX_OBJ_NUM		6
#define PCH_RX_OBJ_START	1
#define PCH_RX_OBJ_END		PCH_RX_OBJ_NUM
#define PCH_TX_OBJ_START	(PCH_RX_OBJ_END + 1)
#define PCH_TX_OBJ_END		(PCH_RX_OBJ_NUM + PCH_TX_OBJ_NUM)

#define PCH_FIFO_THRESH		16

/* TxRqst2 show status of MsgObjNo.17~32 */
#define PCH_TREQ2_TX_MASK	(((1 << PCH_TX_OBJ_NUM) - 1) <<\
							(PCH_RX_OBJ_END - 16))

enum pch_ifreg {
	PCH_RX_IFREG,
	PCH_TX_IFREG,
};

enum pch_can_err {
	PCH_STUF_ERR = 1,
	PCH_FORM_ERR,
	PCH_ACK_ERR,
	PCH_BIT1_ERR,
	PCH_BIT0_ERR,
	PCH_CRC_ERR,
	PCH_LEC_ALL,
};

enum pch_can_mode {
	PCH_CAN_ENABLE,
	PCH_CAN_DISABLE,
	PCH_CAN_ALL,
	PCH_CAN_NONE,
	PCH_CAN_STOP,
	PCH_CAN_RUN,
};

struct pch_can_if_regs {
	u32 creq;
	u32 cmask;
	u32 mask1;
	u32 mask2;
	u32 id1;
	u32 id2;
	u32 mcont;
	u32 data[4];
	u32 rsv[13];
};

struct pch_can_regs {
	u32 cont;
	u32 stat;
	u32 errc;
	u32 bitt;
	u32 intr;
	u32 opt;
	u32 brpe;
	u32 reserve;
	struct pch_can_if_regs ifregs[2]; /* [0]=if1  [1]=if2 */
	u32 reserve1[8];
	u32 treq1;
	u32 treq2;
	u32 reserve2[6];
	u32 data1;
	u32 data2;
	u32 reserve3[6];
	u32 canipend1;
	u32 canipend2;
	u32 reserve4[6];
	u32 canmval1;
	u32 canmval2;
	u32 reserve5[37];
	u32 srst;
};

struct pch_can_priv {
	struct can_priv can;
	struct pci_dev *dev;
	u32 tx_enable[PCH_TX_OBJ_END];
	u32 rx_enable[PCH_TX_OBJ_END];
	u32 rx_link[PCH_TX_OBJ_END];
	u32 int_enables;
	struct net_device *ndev;
	struct pch_can_regs __iomem *regs;
	struct napi_struct napi;
	int tx_obj;	/* Point next Tx Obj index */
	int use_msi;
};

static const struct can_bittiming_const pch_can_bittiming_const = {
	.name = KBUILD_MODNAME,
	.tseg1_min = 2,
	.tseg1_max = 16,
	.tseg2_min = 1,
	.tseg2_max = 8,
	.sjw_max = 4,
	.brp_min = 1,
	.brp_max = 1024, /* 6bit + extended 4bit */
	.brp_inc = 1,
};

static const struct pci_device_id pch_pci_tbl[] = {
	{PCI_VENDOR_ID_INTEL, 0x8818, PCI_ANY_ID, PCI_ANY_ID,},
	{0,}
};
MODULE_DEVICE_TABLE(pci, pch_pci_tbl);

static inline void pch_can_bit_set(void __iomem *addr, u32 mask)
{
	iowrite32(ioread32(addr) | mask, addr);
}

static inline void pch_can_bit_clear(void __iomem *addr, u32 mask)
{
	iowrite32(ioread32(addr) & ~mask, addr);
}

static void pch_can_set_run_mode(struct pch_can_priv *priv,
				 enum pch_can_mode mode)
{
	switch (mode) {
	case PCH_CAN_RUN:
		pch_can_bit_clear(&priv->regs->cont, PCH_CTRL_INIT);
		break;

	case PCH_CAN_STOP:
		pch_can_bit_set(&priv->regs->cont, PCH_CTRL_INIT);
		break;

	default:
		netdev_err(priv->ndev, "%s -> Invalid Mode.\n", __func__);
		break;
	}
}

static void pch_can_set_optmode(struct pch_can_priv *priv)
{
	u32 reg_val = ioread32(&priv->regs->opt);

	if (priv->can.ctrlmode & CAN_CTRLMODE_LISTENONLY)
		reg_val |= PCH_OPT_SILENT;

	if (priv->can.ctrlmode & CAN_CTRLMODE_LOOPBACK)
		reg_val |= PCH_OPT_LBACK;

	pch_can_bit_set(&priv->regs->cont, PCH_CTRL_OPT);
	iowrite32(reg_val, &priv->regs->opt);
}

static void pch_can_rw_msg_obj(void __iomem *creq_addr, u32 num)
{
	int counter = PCH_COUNTER_LIMIT;
	u32 ifx_creq;

	iowrite32(num, creq_addr);
	while (counter) {
		ifx_creq = ioread32(creq_addr) & PCH_IF_CREQ_BUSY;
		if (!ifx_creq)
			break;
		counter--;
		udelay(1);
	}
	if (!counter)
		pr_err("%s:IF1 BUSY Flag is set forever.\n", __func__);
}

static void pch_can_set_int_enables(struct pch_can_priv *priv,
				    enum pch_can_mode interrupt_no)
{
	switch (interrupt_no) {
	case PCH_CAN_DISABLE:
		pch_can_bit_clear(&priv->regs->cont, PCH_CTRL_IE);
		break;

	case PCH_CAN_ALL:
		pch_can_bit_set(&priv->regs->cont, PCH_CTRL_IE_SIE_EIE);
		break;

	case PCH_CAN_NONE:
		pch_can_bit_clear(&priv->regs->cont, PCH_CTRL_IE_SIE_EIE);
		break;

	default:
		netdev_err(priv->ndev, "Invalid interrupt number.\n");
		break;
	}
}

static void pch_can_set_rxtx(struct pch_can_priv *priv, u32 buff_num,
			     int set, enum pch_ifreg dir)
{
	u32 ie;

	if (dir)
		ie = PCH_IF_MCONT_TXIE;
	else
		ie = PCH_IF_MCONT_RXIE;

	/* Reading the Msg buffer from Message RAM to IF1/2 registers. */
	iowrite32(PCH_CMASK_RX_TX_GET, &priv->regs->ifregs[dir].cmask);
	pch_can_rw_msg_obj(&priv->regs->ifregs[dir].creq, buff_num);

	/* Setting the IF1/2MASK1 register to access MsgVal and RxIE bits */
	iowrite32(PCH_CMASK_RDWR | PCH_CMASK_ARB | PCH_CMASK_CTRL,
		  &priv->regs->ifregs[dir].cmask);

	if (set) {
		/* Setting the MsgVal and RxIE/TxIE bits */
		pch_can_bit_set(&priv->regs->ifregs[dir].mcont, ie);
		pch_can_bit_set(&priv->regs->ifregs[dir].id2, PCH_ID_MSGVAL);
	} else {
		/* Clearing the MsgVal and RxIE/TxIE bits */
		pch_can_bit_clear(&priv->regs->ifregs[dir].mcont, ie);
		pch_can_bit_clear(&priv->regs->ifregs[dir].id2, PCH_ID_MSGVAL);
	}

	pch_can_rw_msg_obj(&priv->regs->ifregs[dir].creq, buff_num);
}

static void pch_can_set_rx_all(struct pch_can_priv *priv, int set)
{
	int i;

	/* Traversing to obtain the object configured as receivers. */
	for (i = PCH_RX_OBJ_START; i <= PCH_RX_OBJ_END; i++)
		pch_can_set_rxtx(priv, i, set, PCH_RX_IFREG);
}

static void pch_can_set_tx_all(struct pch_can_priv *priv, int set)
{
	int i;

	/* Traversing to obtain the object configured as transmit object. */
	for (i = PCH_TX_OBJ_START; i <= PCH_TX_OBJ_END; i++)
		pch_can_set_rxtx(priv, i, set, PCH_TX_IFREG);
}

static u32 pch_can_int_pending(struct pch_can_priv *priv)
{
	return ioread32(&priv->regs->intr) & 0xffff;
}

static void pch_can_clear_if_buffers(struct pch_can_priv *priv)
{
	int i; /* Msg Obj ID (1~32) */

	for (i = PCH_RX_OBJ_START; i <= PCH_TX_OBJ_END; i++) {
		iowrite32(PCH_CMASK_RX_TX_SET, &priv->regs->ifregs[0].cmask);
		iowrite32(0xffff, &priv->regs->ifregs[0].mask1);
		iowrite32(0xffff, &priv->regs->ifregs[0].mask2);
		iowrite32(0x0, &priv->regs->ifregs[0].id1);
		iowrite32(0x0, &priv->regs->ifregs[0].id2);
		iowrite32(0x0, &priv->regs->ifregs[0].mcont);
		iowrite32(0x0, &priv->regs->ifregs[0].data[0]);
		iowrite32(0x0, &priv->regs->ifregs[0].data[1]);
		iowrite32(0x0, &priv->regs->ifregs[0].data[2]);
		iowrite32(0x0, &priv->regs->ifregs[0].data[3]);
		iowrite32(PCH_CMASK_RDWR | PCH_CMASK_MASK |
			  PCH_CMASK_ARB | PCH_CMASK_CTRL,
			  &priv->regs->ifregs[0].cmask);
		pch_can_rw_msg_obj(&priv->regs->ifregs[0].creq, i);
	}
}

static void pch_can_config_rx_tx_buffers(struct pch_can_priv *priv)
{
	int i;

	for (i = PCH_RX_OBJ_START; i <= PCH_RX_OBJ_END; i++) {
		iowrite32(PCH_CMASK_RX_TX_GET, &priv->regs->ifregs[0].cmask);
		pch_can_rw_msg_obj(&priv->regs->ifregs[0].creq, i);

		iowrite32(0x0, &priv->regs->ifregs[0].id1);
		iowrite32(0x0, &priv->regs->ifregs[0].id2);

		pch_can_bit_set(&priv->regs->ifregs[0].mcont,
				PCH_IF_MCONT_UMASK);

		/* In case FIFO mode, Last EoB of Rx Obj must be 1 */
		if (i == PCH_RX_OBJ_END)
			pch_can_bit_set(&priv->regs->ifregs[0].mcont,
					PCH_IF_MCONT_EOB);
		else
			pch_can_bit_clear(&priv->regs->ifregs[0].mcont,
					  PCH_IF_MCONT_EOB);

		iowrite32(0, &priv->regs->ifregs[0].mask1);
		pch_can_bit_clear(&priv->regs->ifregs[0].mask2,
				  0x1fff | PCH_MASK2_MDIR_MXTD);

		/* Setting CMASK for writing */
		iowrite32(PCH_CMASK_RDWR | PCH_CMASK_MASK | PCH_CMASK_ARB |
			  PCH_CMASK_CTRL, &priv->regs->ifregs[0].cmask);

		pch_can_rw_msg_obj(&priv->regs->ifregs[0].creq, i);
	}

	for (i = PCH_TX_OBJ_START; i <= PCH_TX_OBJ_END; i++) {
		iowrite32(PCH_CMASK_RX_TX_GET, &priv->regs->ifregs[1].cmask);
		pch_can_rw_msg_obj(&priv->regs->ifregs[1].creq, i);

		/* Resetting DIR bit for reception */
		iowrite32(0x0, &priv->regs->ifregs[1].id1);
		iowrite32(PCH_ID2_DIR, &priv->regs->ifregs[1].id2);

		/* Setting EOB bit for transmitter */
		iowrite32(PCH_IF_MCONT_EOB | PCH_IF_MCONT_UMASK,
			  &priv->regs->ifregs[1].mcont);

		iowrite32(0, &priv->regs->ifregs[1].mask1);
		pch_can_bit_clear(&priv->regs->ifregs[1].mask2, 0x1fff);

		/* Setting CMASK for writing */
		iowrite32(PCH_CMASK_RDWR | PCH_CMASK_MASK | PCH_CMASK_ARB |
			  PCH_CMASK_CTRL, &priv->regs->ifregs[1].cmask);

		pch_can_rw_msg_obj(&priv->regs->ifregs[1].creq, i);
	}
}

static void pch_can_init(struct pch_can_priv *priv)
{
	/* Stopping the Can device. */
	pch_can_set_run_mode(priv, PCH_CAN_STOP);

	/* Clearing all the message object buffers. */
	pch_can_clear_if_buffers(priv);

	/* Configuring the respective message object as either rx/tx object. */
	pch_can_config_rx_tx_buffers(priv);

	/* Enabling the interrupts. */
	pch_can_set_int_enables(priv, PCH_CAN_ALL);
}

static void pch_can_release(struct pch_can_priv *priv)
{
	/* Stooping the CAN device. */
	pch_can_set_run_mode(priv, PCH_CAN_STOP);

	/* Disabling the interrupts. */
	pch_can_set_int_enables(priv, PCH_CAN_NONE);

	/* Disabling all the receive object. */
	pch_can_set_rx_all(priv, 0);

	/* Disabling all the transmit object. */
	pch_can_set_tx_all(priv, 0);
}

/* This function clears interrupt(s) from the CAN device. */
static void pch_can_int_clr(struct pch_can_priv *priv, u32 mask)
{
	/* Clear interrupt for transmit object */
	if ((mask >= PCH_RX_OBJ_START) && (mask <= PCH_RX_OBJ_END)) {
		/* Setting CMASK for clearing the reception interrupts. */
		iowrite32(PCH_CMASK_RDWR | PCH_CMASK_CTRL | PCH_CMASK_ARB,
			  &priv->regs->ifregs[0].cmask);

		/* Clearing the Dir bit. */
		pch_can_bit_clear(&priv->regs->ifregs[0].id2, PCH_ID2_DIR);

		/* Clearing NewDat & IntPnd */
		pch_can_bit_clear(&priv->regs->ifregs[0].mcont,
				  PCH_IF_MCONT_NEWDAT | PCH_IF_MCONT_INTPND);

		pch_can_rw_msg_obj(&priv->regs->ifregs[0].creq, mask);
	} else if ((mask >= PCH_TX_OBJ_START) && (mask <= PCH_TX_OBJ_END)) {
		/*
		 * Setting CMASK for clearing interrupts for frame transmission.
		 */
		iowrite32(PCH_CMASK_RDWR | PCH_CMASK_CTRL | PCH_CMASK_ARB,
			  &priv->regs->ifregs[1].cmask);

		/* Resetting the ID registers. */
		pch_can_bit_set(&priv->regs->ifregs[1].id2,
			       PCH_ID2_DIR | (0x7ff << 2));
		iowrite32(0x0, &priv->regs->ifregs[1].id1);

		/* Claring NewDat, TxRqst & IntPnd */
		pch_can_bit_clear(&priv->regs->ifregs[1].mcont,
				  PCH_IF_MCONT_NEWDAT | PCH_IF_MCONT_INTPND |
				  PCH_IF_MCONT_TXRQXT);
		pch_can_rw_msg_obj(&priv->regs->ifregs[1].creq, mask);
	}
}

static void pch_can_reset(struct pch_can_priv *priv)
{
	/* write to sw reset register */
	iowrite32(1, &priv->regs->srst);
	iowrite32(0, &priv->regs->srst);
}

static void pch_can_error(struct net_device *ndev, u32 status)
{
	struct sk_buff *skb;
	struct pch_can_priv *priv = netdev_priv(ndev);
	struct can_frame *cf;
	u32 errc, lec;
	struct net_device_stats *stats = &(priv->ndev->stats);
	enum can_state state = priv->can.state;

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

	if (status & PCH_BUS_OFF) {
		pch_can_set_tx_all(priv, 0);
		pch_can_set_rx_all(priv, 0);
		state = CAN_STATE_BUS_OFF;
		cf->can_id |= CAN_ERR_BUSOFF;
		priv->can.can_stats.bus_off++;
		can_bus_off(ndev);
	}

	errc = ioread32(&priv->regs->errc);
	/* Warning interrupt. */
	if (status & PCH_EWARN) {
		state = CAN_STATE_ERROR_WARNING;
		priv->can.can_stats.error_warning++;
		cf->can_id |= CAN_ERR_CRTL;
		if (((errc & PCH_REC) >> 8) > 96)
			cf->data[1] |= CAN_ERR_CRTL_RX_WARNING;
		if ((errc & PCH_TEC) > 96)
			cf->data[1] |= CAN_ERR_CRTL_TX_WARNING;
		netdev_dbg(ndev,
			"%s -> Error Counter is more than 96.\n", __func__);
	}
	/* Error passive interrupt. */
	if (status & PCH_EPASSIV) {
		priv->can.can_stats.error_passive++;
		state = CAN_STATE_ERROR_PASSIVE;
		cf->can_id |= CAN_ERR_CRTL;
		if (errc & PCH_RP)
			cf->data[1] |= CAN_ERR_CRTL_RX_PASSIVE;
		if ((errc & PCH_TEC) > 127)
			cf->data[1] |= CAN_ERR_CRTL_TX_PASSIVE;
		netdev_dbg(ndev,
			"%s -> CAN controller is ERROR PASSIVE .\n", __func__);
	}

	lec = status & PCH_LEC_ALL;
	switch (lec) {
	case PCH_STUF_ERR:
		cf->data[2] |= CAN_ERR_PROT_STUFF;
		priv->can.can_stats.bus_error++;
		stats->rx_errors++;
		break;
	case PCH_FORM_ERR:
		cf->data[2] |= CAN_ERR_PROT_FORM;
		priv->can.can_stats.bus_error++;
		stats->rx_errors++;
		break;
	case PCH_ACK_ERR:
		cf->can_id |= CAN_ERR_ACK;
		priv->can.can_stats.bus_error++;
		stats->rx_errors++;
		break;
	case PCH_BIT1_ERR:
	case PCH_BIT0_ERR:
		cf->data[2] |= CAN_ERR_PROT_BIT;
		priv->can.can_stats.bus_error++;
		stats->rx_errors++;
		break;
	case PCH_CRC_ERR:
		cf->data[3] = CAN_ERR_PROT_LOC_CRC_SEQ;
		priv->can.can_stats.bus_error++;
		stats->rx_errors++;
		break;
	case PCH_LEC_ALL: /* Written by CPU. No error status */
		break;
	}

	cf->data[6] = errc & PCH_TEC;
	cf->data[7] = (errc & PCH_REC) >> 8;

	priv->can.state = state;
	netif_receive_skb(skb);

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

static irqreturn_t pch_can_interrupt(int irq, void *dev_id)
{
	struct net_device *ndev = (struct net_device *)dev_id;
	struct pch_can_priv *priv = netdev_priv(ndev);

	if (!pch_can_int_pending(priv))
		return IRQ_NONE;

	pch_can_set_int_enables(priv, PCH_CAN_NONE);
	napi_schedule(&priv->napi);
	return IRQ_HANDLED;
}

static void pch_fifo_thresh(struct pch_can_priv *priv, int obj_id)
{
	if (obj_id < PCH_FIFO_THRESH) {
		iowrite32(PCH_CMASK_RDWR | PCH_CMASK_CTRL |
			  PCH_CMASK_ARB, &priv->regs->ifregs[0].cmask);

		/* Clearing the Dir bit. */
		pch_can_bit_clear(&priv->regs->ifregs[0].id2, PCH_ID2_DIR);

		/* Clearing NewDat & IntPnd */
		pch_can_bit_clear(&priv->regs->ifregs[0].mcont,
				  PCH_IF_MCONT_INTPND);
		pch_can_rw_msg_obj(&priv->regs->ifregs[0].creq, obj_id);
	} else if (obj_id > PCH_FIFO_THRESH) {
		pch_can_int_clr(priv, obj_id);
	} else if (obj_id == PCH_FIFO_THRESH) {
		int cnt;
		for (cnt = 0; cnt < PCH_FIFO_THRESH; cnt++)
			pch_can_int_clr(priv, cnt + 1);
	}
}

static void pch_can_rx_msg_lost(struct net_device *ndev, int obj_id)
{
	struct pch_can_priv *priv = netdev_priv(ndev);
	struct net_device_stats *stats = &(priv->ndev->stats);
	struct sk_buff *skb;
	struct can_frame *cf;

	netdev_dbg(priv->ndev, "Msg Obj is overwritten.\n");
	pch_can_bit_clear(&priv->regs->ifregs[0].mcont,
			  PCH_IF_MCONT_MSGLOST);
	iowrite32(PCH_CMASK_RDWR | PCH_CMASK_CTRL,
		  &priv->regs->ifregs[0].cmask);
	pch_can_rw_msg_obj(&priv->regs->ifregs[0].creq, obj_id);

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

	cf->can_id |= CAN_ERR_CRTL;
	cf->data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
	stats->rx_over_errors++;
	stats->rx_errors++;

	netif_receive_skb(skb);
}

static int pch_can_rx_normal(struct net_device *ndev, u32 obj_num, int quota)
{
	u32 reg;
	canid_t id;
	int rcv_pkts = 0;
	struct sk_buff *skb;
	struct can_frame *cf;
	struct pch_can_priv *priv = netdev_priv(ndev);
	struct net_device_stats *stats = &(priv->ndev->stats);
	int i;
	u32 id2;
	u16 data_reg;

	do {
		/* Reading the message object from the Message RAM */
		iowrite32(PCH_CMASK_RX_TX_GET, &priv->regs->ifregs[0].cmask);
		pch_can_rw_msg_obj(&priv->regs->ifregs[0].creq, obj_num);

		/* Reading the MCONT register. */
		reg = ioread32(&priv->regs->ifregs[0].mcont);

		if (reg & PCH_IF_MCONT_EOB)
			break;

		/* If MsgLost bit set. */
		if (reg & PCH_IF_MCONT_MSGLOST) {
			pch_can_rx_msg_lost(ndev, obj_num);
			rcv_pkts++;
			quota--;
			obj_num++;
			continue;
		} else if (!(reg & PCH_IF_MCONT_NEWDAT)) {
			obj_num++;
			continue;
		}

		skb = alloc_can_skb(priv->ndev, &cf);
		if (!skb) {
			netdev_err(ndev, "alloc_can_skb Failed\n");
			return rcv_pkts;
		}

		/* Get Received data */
		id2 = ioread32(&priv->regs->ifregs[0].id2);
		if (id2 & PCH_ID2_XTD) {
			id = (ioread32(&priv->regs->ifregs[0].id1) & 0xffff);
			id |= (((id2) & 0x1fff) << 16);
			cf->can_id = id | CAN_EFF_FLAG;
		} else {
			id = (id2 >> 2) & CAN_SFF_MASK;
			cf->can_id = id;
		}

		if (id2 & PCH_ID2_DIR)
			cf->can_id |= CAN_RTR_FLAG;

		cf->can_dlc = get_can_dlc((ioread32(&priv->regs->
						    ifregs[0].mcont)) & 0xF);

		for (i = 0; i < cf->can_dlc; i += 2) {
			data_reg = ioread16(&priv->regs->ifregs[0].data[i / 2]);
			cf->data[i] = data_reg;
			cf->data[i + 1] = data_reg >> 8;
		}

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

		pch_fifo_thresh(priv, obj_num);
		obj_num++;
	} while (quota > 0);

	return rcv_pkts;
}

static void pch_can_tx_complete(struct net_device *ndev, u32 int_stat)
{
	struct pch_can_priv *priv = netdev_priv(ndev);
	struct net_device_stats *stats = &(priv->ndev->stats);
	u32 dlc;

	can_get_echo_skb(ndev, int_stat - PCH_RX_OBJ_END - 1);
	iowrite32(PCH_CMASK_RX_TX_GET | PCH_CMASK_CLRINTPND,
		  &priv->regs->ifregs[1].cmask);
	pch_can_rw_msg_obj(&priv->regs->ifregs[1].creq, int_stat);
	dlc = get_can_dlc(ioread32(&priv->regs->ifregs[1].mcont) &
			  PCH_IF_MCONT_DLC);
	stats->tx_bytes += dlc;
	stats->tx_packets++;
	if (int_stat == PCH_TX_OBJ_END)
		netif_wake_queue(ndev);
}

static int pch_can_poll(struct napi_struct *napi, int quota)
{
	struct net_device *ndev = napi->dev;
	struct pch_can_priv *priv = netdev_priv(ndev);
	u32 int_stat;
	u32 reg_stat;
	int quota_save = quota;

	int_stat = pch_can_int_pending(priv);
	if (!int_stat)
		goto end;

	if (int_stat == PCH_STATUS_INT) {
		reg_stat = ioread32(&priv->regs->stat);

		if ((reg_stat & (PCH_BUS_OFF | PCH_LEC_ALL)) &&
		   ((reg_stat & PCH_LEC_ALL) != PCH_LEC_ALL)) {
			pch_can_error(ndev, reg_stat);
			quota--;
		}

		if (reg_stat & (PCH_TX_OK | PCH_RX_OK))
			pch_can_bit_clear(&priv->regs->stat,
					  reg_stat & (PCH_TX_OK | PCH_RX_OK));

		int_stat = pch_can_int_pending(priv);
	}

	if (quota == 0)
		goto end;

	if ((int_stat >= PCH_RX_OBJ_START) && (int_stat <= PCH_RX_OBJ_END)) {
		quota -= pch_can_rx_normal(ndev, int_stat, quota);
	} else if ((int_stat >= PCH_TX_OBJ_START) &&
		   (int_stat <= PCH_TX_OBJ_END)) {
		/* Handle transmission interrupt */
		pch_can_tx_complete(ndev, int_stat);
	}

end:
	napi_complete(napi);
	pch_can_set_int_enables(priv, PCH_CAN_ALL);

	return quota_save - quota;
}

static int pch_set_bittiming(struct net_device *ndev)
{
	struct pch_can_priv *priv = netdev_priv(ndev);
	const struct can_bittiming *bt = &priv->can.bittiming;
	u32 canbit;
	u32 bepe;

	/* Setting the CCE bit for accessing the Can Timing register. */
	pch_can_bit_set(&priv->regs->cont, PCH_CTRL_CCE);

	canbit = (bt->brp - 1) & PCH_MSK_BITT_BRP;
	canbit |= (bt->sjw - 1) << PCH_BIT_SJW_SHIFT;
	canbit |= (bt->phase_seg1 + bt->prop_seg - 1) << PCH_BIT_TSEG1_SHIFT;
	canbit |= (bt->phase_seg2 - 1) << PCH_BIT_TSEG2_SHIFT;
	bepe = ((bt->brp - 1) & PCH_MSK_BRPE_BRPE) >> PCH_BIT_BRPE_BRPE_SHIFT;
	iowrite32(canbit, &priv->regs->bitt);
	iowrite32(bepe, &priv->regs->brpe);
	pch_can_bit_clear(&priv->regs->cont, PCH_CTRL_CCE);

	return 0;
}

static void pch_can_start(struct net_device *ndev)
{
	struct pch_can_priv *priv = netdev_priv(ndev);

	if (priv->can.state != CAN_STATE_STOPPED)
		pch_can_reset(priv);

	pch_set_bittiming(ndev);
	pch_can_set_optmode(priv);

	pch_can_set_tx_all(priv, 1);
	pch_can_set_rx_all(priv, 1);

	/* Setting the CAN to run mode. */
	pch_can_set_run_mode(priv, PCH_CAN_RUN);

	priv->can.state = CAN_STATE_ERROR_ACTIVE;

	return;
}

static int pch_can_do_set_mode(struct net_device *ndev, enum can_mode mode)
{
	int ret = 0;

	switch (mode) {
	case CAN_MODE_START:
		pch_can_start(ndev);
		netif_wake_queue(ndev);
		break;
	default:
		ret = -EOPNOTSUPP;
		break;
	}

	return ret;
}

static int pch_can_open(struct net_device *ndev)
{
	struct pch_can_priv *priv = netdev_priv(ndev);
	int retval;

	/* Regstering the interrupt. */
	retval = request_irq(priv->dev->irq, pch_can_interrupt, IRQF_SHARED,
			     ndev->name, ndev);
	if (retval) {
		netdev_err(ndev, "request_irq failed.\n");
		goto req_irq_err;
	}

	/* Open common can device */
	retval = open_candev(ndev);
	if (retval) {
		netdev_err(ndev, "open_candev() failed %d\n", retval);
		goto err_open_candev;
	}

	pch_can_init(priv);
	pch_can_start(ndev);
	napi_enable(&priv->napi);
	netif_start_queue(ndev);

	return 0;

err_open_candev:
	free_irq(priv->dev->irq, ndev);
req_irq_err:
	pch_can_release(priv);

	return retval;
}

static int pch_close(struct net_device *ndev)
{
	struct pch_can_priv *priv = netdev_priv(ndev);

	netif_stop_queue(ndev);
	napi_disable(&priv->napi);
	pch_can_release(priv);
	free_irq(priv->dev->irq, ndev);
	close_candev(ndev);
	priv->can.state = CAN_STATE_STOPPED;
	return 0;
}

static netdev_tx_t pch_xmit(struct sk_buff *skb, struct net_device *ndev)
{
	struct pch_can_priv *priv = netdev_priv(ndev);
	struct can_frame *cf = (struct can_frame *)skb->data;
	int tx_obj_no;
	int i;
	u32 id2;

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

	tx_obj_no = priv->tx_obj;
	if (priv->tx_obj == PCH_TX_OBJ_END) {
		if (ioread32(&priv->regs->treq2) & PCH_TREQ2_TX_MASK)
			netif_stop_queue(ndev);

		priv->tx_obj = PCH_TX_OBJ_START;
	} else {
		priv->tx_obj++;
	}

	/* Setting the CMASK register. */
	pch_can_bit_set(&priv->regs->ifregs[1].cmask, PCH_CMASK_ALL);

	/* If ID extended is set. */
	if (cf->can_id & CAN_EFF_FLAG) {
		iowrite32(cf->can_id & 0xffff, &priv->regs->ifregs[1].id1);
		id2 = ((cf->can_id >> 16) & 0x1fff) | PCH_ID2_XTD;
	} else {
		iowrite32(0, &priv->regs->ifregs[1].id1);
		id2 = (cf->can_id & CAN_SFF_MASK) << 2;
	}

	id2 |= PCH_ID_MSGVAL;

	/* If remote frame has to be transmitted.. */
	if (!(cf->can_id & CAN_RTR_FLAG))
		id2 |= PCH_ID2_DIR;

	iowrite32(id2, &priv->regs->ifregs[1].id2);

	/* Copy data to register */
	for (i = 0; i < cf->can_dlc; i += 2) {
		iowrite16(cf->data[i] | (cf->data[i + 1] << 8),
			  &priv->regs->ifregs[1].data[i / 2]);
	}

	can_put_echo_skb(skb, ndev, tx_obj_no - PCH_RX_OBJ_END - 1);

	/* Set the size of the data. Update if2_mcont */
	iowrite32(cf->can_dlc | PCH_IF_MCONT_NEWDAT | PCH_IF_MCONT_TXRQXT |
		  PCH_IF_MCONT_TXIE, &priv->regs->ifregs[1].mcont);

	pch_can_rw_msg_obj(&priv->regs->ifregs[1].creq, tx_obj_no);

	return NETDEV_TX_OK;
}

static const struct net_device_ops pch_can_netdev_ops = {
	.ndo_open		= pch_can_open,
	.ndo_stop		= pch_close,
	.ndo_start_xmit		= pch_xmit,
	.ndo_change_mtu		= can_change_mtu,
};

static void pch_can_remove(struct pci_dev *pdev)
{
	struct net_device *ndev = pci_get_drvdata(pdev);
	struct pch_can_priv *priv = netdev_priv(ndev);

	unregister_candev(priv->ndev);
	if (priv->use_msi)
		pci_disable_msi(priv->dev);
	pci_release_regions(pdev);
	pci_disable_device(pdev);
	pch_can_reset(priv);
	pci_iounmap(pdev, priv->regs);
	free_candev(priv->ndev);
}

#ifdef CONFIG_PM
static void pch_can_set_int_custom(struct pch_can_priv *priv)
{
	/* Clearing the IE, SIE and EIE bits of Can control register. */
	pch_can_bit_clear(&priv->regs->cont, PCH_CTRL_IE_SIE_EIE);

	/* Appropriately setting them. */
	pch_can_bit_set(&priv->regs->cont,
			((priv->int_enables & PCH_MSK_CTRL_IE_SIE_EIE) << 1));
}

/* This function retrieves interrupt enabled for the CAN device. */
static u32 pch_can_get_int_enables(struct pch_can_priv *priv)
{
	/* Obtaining the status of IE, SIE and EIE interrupt bits. */
	return (ioread32(&priv->regs->cont) & PCH_CTRL_IE_SIE_EIE) >> 1;
}

static u32 pch_can_get_rxtx_ir(struct pch_can_priv *priv, u32 buff_num,
			       enum pch_ifreg dir)
{
	u32 ie, enable;

	if (dir)
		ie = PCH_IF_MCONT_RXIE;
	else
		ie = PCH_IF_MCONT_TXIE;

	iowrite32(PCH_CMASK_RX_TX_GET, &priv->regs->ifregs[dir].cmask);
	pch_can_rw_msg_obj(&priv->regs->ifregs[dir].creq, buff_num);

	if (((ioread32(&priv->regs->ifregs[dir].id2)) & PCH_ID_MSGVAL) &&
			((ioread32(&priv->regs->ifregs[dir].mcont)) & ie))
		enable = 1;
	else
		enable = 0;

	return enable;
}

static void pch_can_set_rx_buffer_link(struct pch_can_priv *priv,
				       u32 buffer_num, int set)
{
	iowrite32(PCH_CMASK_RX_TX_GET, &priv->regs->ifregs[0].cmask);
	pch_can_rw_msg_obj(&priv->regs->ifregs[0].creq, buffer_num);
	iowrite32(PCH_CMASK_RDWR | PCH_CMASK_CTRL,
		  &priv->regs->ifregs[0].cmask);
	if (set)
		pch_can_bit_clear(&priv->regs->ifregs[0].mcont,
				  PCH_IF_MCONT_EOB);
	else
		pch_can_bit_set(&priv->regs->ifregs[0].mcont, PCH_IF_MCONT_EOB);

	pch_can_rw_msg_obj(&priv->regs->ifregs[0].creq, buffer_num);
}

static u32 pch_can_get_rx_buffer_link(struct pch_can_priv *priv, u32 buffer_num)
{
	u32 link;

	iowrite32(PCH_CMASK_RX_TX_GET, &priv->regs->ifregs[0].cmask);
	pch_can_rw_msg_obj(&priv->regs->ifregs[0].creq, buffer_num);

	if (ioread32(&priv->regs->ifregs[0].mcont) & PCH_IF_MCONT_EOB)
		link = 0;
	else
		link = 1;
	return link;
}

static int pch_can_get_buffer_status(struct pch_can_priv *priv)
{
	return (ioread32(&priv->regs->treq1) & 0xffff) |
	       (ioread32(&priv->regs->treq2) << 16);
}

static int pch_can_suspend(struct pci_dev *pdev, pm_message_t state)
{
	int i;
	int retval;
	u32 buf_stat;	/* Variable for reading the transmit buffer status. */
	int counter = PCH_COUNTER_LIMIT;

	struct net_device *dev = pci_get_drvdata(pdev);
	struct pch_can_priv *priv = netdev_priv(dev);

	/* Stop the CAN controller */
	pch_can_set_run_mode(priv, PCH_CAN_STOP);

	/* Indicate that we are aboutto/in suspend */
	priv->can.state = CAN_STATE_STOPPED;

	/* Waiting for all transmission to complete. */
	while (counter) {
		buf_stat = pch_can_get_buffer_status(priv);
		if (!buf_stat)
			break;
		counter--;
		udelay(1);
	}
	if (!counter)
		dev_err(&pdev->dev, "%s -> Transmission time out.\n", __func__);

	/* Save interrupt configuration and then disable them */
	priv->int_enables = pch_can_get_int_enables(priv);
	pch_can_set_int_enables(priv, PCH_CAN_DISABLE);

	/* Save Tx buffer enable state */
	for (i = PCH_TX_OBJ_START; i <= PCH_TX_OBJ_END; i++)
		priv->tx_enable[i - 1] = pch_can_get_rxtx_ir(priv, i,
							     PCH_TX_IFREG);

	/* Disable all Transmit buffers */
	pch_can_set_tx_all(priv, 0);

	/* Save Rx buffer enable state */
	for (i = PCH_RX_OBJ_START; i <= PCH_RX_OBJ_END; i++) {
		priv->rx_enable[i - 1] = pch_can_get_rxtx_ir(priv, i,
							     PCH_RX_IFREG);
		priv->rx_link[i - 1] = pch_can_get_rx_buffer_link(priv, i);
	}

	/* Disable all Receive buffers */
	pch_can_set_rx_all(priv, 0);
	retval = pci_save_state(pdev);
	if (retval) {
		dev_err(&pdev->dev, "pci_save_state failed.\n");
	} else {
		pci_enable_wake(pdev, PCI_D3hot, 0);
		pci_disable_device(pdev);
		pci_set_power_state(pdev, pci_choose_state(pdev, state));
	}

	return retval;
}

static int pch_can_resume(struct pci_dev *pdev)
{
	int i;
	int retval;
	struct net_device *dev = pci_get_drvdata(pdev);
	struct pch_can_priv *priv = netdev_priv(dev);

	pci_set_power_state(pdev, PCI_D0);
	pci_restore_state(pdev);
	retval = pci_enable_device(pdev);
	if (retval) {
		dev_err(&pdev->dev, "pci_enable_device failed.\n");
		return retval;
	}

	pci_enable_wake(pdev, PCI_D3hot, 0);

	priv->can.state = CAN_STATE_ERROR_ACTIVE;

	/* Disabling all interrupts. */
	pch_can_set_int_enables(priv, PCH_CAN_DISABLE);

	/* Setting the CAN device in Stop Mode. */
	pch_can_set_run_mode(priv, PCH_CAN_STOP);

	/* Configuring the transmit and receive buffers. */
	pch_can_config_rx_tx_buffers(priv);

	/* Restore the CAN state */
	pch_set_bittiming(dev);

	/* Listen/Active */
	pch_can_set_optmode(priv);

	/* Enabling the transmit buffer. */
	for (i = PCH_TX_OBJ_START; i <= PCH_TX_OBJ_END; i++)
		pch_can_set_rxtx(priv, i, priv->tx_enable[i - 1], PCH_TX_IFREG);

	/* Configuring the receive buffer and enabling them. */
	for (i = PCH_RX_OBJ_START; i <= PCH_RX_OBJ_END; i++) {
		/* Restore buffer link */
		pch_can_set_rx_buffer_link(priv, i, priv->rx_link[i - 1]);

		/* Restore buffer enables */
		pch_can_set_rxtx(priv, i, priv->rx_enable[i - 1], PCH_RX_IFREG);
	}

	/* Enable CAN Interrupts */
	pch_can_set_int_custom(priv);

	/* Restore Run Mode */
	pch_can_set_run_mode(priv, PCH_CAN_RUN);

	return retval;
}
#else
#define pch_can_suspend NULL
#define pch_can_resume NULL
#endif

static int pch_can_get_berr_counter(const struct net_device *dev,
				    struct can_berr_counter *bec)
{
	struct pch_can_priv *priv = netdev_priv(dev);
	u32 errc = ioread32(&priv->regs->errc);

	bec->txerr = errc & PCH_TEC;
	bec->rxerr = (errc & PCH_REC) >> 8;

	return 0;
}

static int pch_can_probe(struct pci_dev *pdev,
				   const struct pci_device_id *id)
{
	struct net_device *ndev;
	struct pch_can_priv *priv;
	int rc;
	void __iomem *addr;

	rc = pci_enable_device(pdev);
	if (rc) {
		dev_err(&pdev->dev, "Failed pci_enable_device %d\n", rc);
		goto probe_exit_endev;
	}

	rc = pci_request_regions(pdev, KBUILD_MODNAME);
	if (rc) {
		dev_err(&pdev->dev, "Failed pci_request_regions %d\n", rc);
		goto probe_exit_pcireq;
	}

	addr = pci_iomap(pdev, 1, 0);
	if (!addr) {
		rc = -EIO;
		dev_err(&pdev->dev, "Failed pci_iomap\n");
		goto probe_exit_ipmap;
	}

	ndev = alloc_candev(sizeof(struct pch_can_priv), PCH_TX_OBJ_END);
	if (!ndev) {
		rc = -ENOMEM;
		dev_err(&pdev->dev, "Failed alloc_candev\n");
		goto probe_exit_alloc_candev;
	}

	priv = netdev_priv(ndev);
	priv->ndev = ndev;
	priv->regs = addr;
	priv->dev = pdev;
	priv->can.bittiming_const = &pch_can_bittiming_const;
	priv->can.do_set_mode = pch_can_do_set_mode;
	priv->can.do_get_berr_counter = pch_can_get_berr_counter;
	priv->can.ctrlmode_supported = CAN_CTRLMODE_LISTENONLY |
				       CAN_CTRLMODE_LOOPBACK;
	priv->tx_obj = PCH_TX_OBJ_START; /* Point head of Tx Obj */

	ndev->irq = pdev->irq;
	ndev->flags |= IFF_ECHO;

	pci_set_drvdata(pdev, ndev);
	SET_NETDEV_DEV(ndev, &pdev->dev);
	ndev->netdev_ops = &pch_can_netdev_ops;
	priv->can.clock.freq = PCH_CAN_CLK; /* Hz */

	netif_napi_add(ndev, &priv->napi, pch_can_poll, PCH_RX_OBJ_END);

	rc = pci_enable_msi(priv->dev);
	if (rc) {
		netdev_err(ndev, "PCH CAN opened without MSI\n");
		priv->use_msi = 0;
	} else {
		netdev_err(ndev, "PCH CAN opened with MSI\n");
		pci_set_master(pdev);
		priv->use_msi = 1;
	}

	rc = register_candev(ndev);
	if (rc) {
		dev_err(&pdev->dev, "Failed register_candev %d\n", rc);
		goto probe_exit_reg_candev;
	}

	return 0;

probe_exit_reg_candev:
	if (priv->use_msi)
		pci_disable_msi(priv->dev);
	free_candev(ndev);
probe_exit_alloc_candev:
	pci_iounmap(pdev, addr);
probe_exit_ipmap:
	pci_release_regions(pdev);
probe_exit_pcireq:
	pci_disable_device(pdev);
probe_exit_endev:
	return rc;
}

static struct pci_driver pch_can_pci_driver = {
	.name = "pch_can",
	.id_table = pch_pci_tbl,
	.probe = pch_can_probe,
	.remove = pch_can_remove,
	.suspend = pch_can_suspend,
	.resume = pch_can_resume,
};

module_pci_driver(pch_can_pci_driver);

MODULE_DESCRIPTION("Intel EG20T PCH CAN(Controller Area Network) Driver");
MODULE_LICENSE("GPL v2");
MODULE_VERSION("0.94");