/* Xilinx CAN device driver
 *
 * Copyright (C) 2012 - 2014 Xilinx, Inc.
 * Copyright (C) 2009 PetaLogix. All rights reserved.
 * Copyright (C) 2017 Sandvik Mining and Construction Oy
 *
 * Description:
 * This driver is developed for Axi CAN IP and for Zynq CANPS Controller.
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include <linux/clk.h>
#include <linux/errno.h>
#include <linux/init.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/skbuff.h>
#include <linux/spinlock.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/can/dev.h>
#include <linux/can/error.h>
#include <linux/can/led.h>
#include <linux/pm_runtime.h>

#define DRIVER_NAME     "xilinx_can"

/* CAN registers set */
enum xcan_reg {
        XCAN_SRR_OFFSET         = 0x00, /* Software reset */
        XCAN_MSR_OFFSET         = 0x04, /* Mode select */
        XCAN_BRPR_OFFSET        = 0x08, /* Baud rate prescaler */
        XCAN_BTR_OFFSET         = 0x0C, /* Bit timing */
        XCAN_ECR_OFFSET         = 0x10, /* Error counter */
        XCAN_ESR_OFFSET         = 0x14, /* Error status */
        XCAN_SR_OFFSET          = 0x18, /* Status */
        XCAN_ISR_OFFSET         = 0x1C, /* Interrupt status */
        XCAN_IER_OFFSET         = 0x20, /* Interrupt enable */
        XCAN_ICR_OFFSET         = 0x24, /* Interrupt clear */
        XCAN_TXFIFO_ID_OFFSET   = 0x30,/* TX FIFO ID */
        XCAN_TXFIFO_DLC_OFFSET  = 0x34, /* TX FIFO DLC */
        XCAN_TXFIFO_DW1_OFFSET  = 0x38, /* TX FIFO Data Word 1 */
        XCAN_TXFIFO_DW2_OFFSET  = 0x3C, /* TX FIFO Data Word 2 */
        XCAN_RXFIFO_ID_OFFSET   = 0x50, /* RX FIFO ID */
        XCAN_RXFIFO_DLC_OFFSET  = 0x54, /* RX FIFO DLC */
        XCAN_RXFIFO_DW1_OFFSET  = 0x58, /* RX FIFO Data Word 1 */
        XCAN_RXFIFO_DW2_OFFSET  = 0x5C, /* RX FIFO Data Word 2 */
};

/* CAN register bit masks - XCAN_<REG>_<BIT>_MASK */
#define XCAN_SRR_CEN_MASK               0x00000002 /* CAN enable */
#define XCAN_SRR_RESET_MASK             0x00000001 /* Soft Reset the CAN core */
#define XCAN_MSR_LBACK_MASK             0x00000002 /* Loop back mode select */
#define XCAN_MSR_SLEEP_MASK             0x00000001 /* Sleep mode select */
#define XCAN_BRPR_BRP_MASK              0x000000FF /* Baud rate prescaler */
#define XCAN_BTR_SJW_MASK               0x00000180 /* Synchronous jump width */
#define XCAN_BTR_TS2_MASK               0x00000070 /* Time segment 2 */
#define XCAN_BTR_TS1_MASK               0x0000000F /* Time segment 1 */
#define XCAN_ECR_REC_MASK               0x0000FF00 /* Receive error counter */
#define XCAN_ECR_TEC_MASK               0x000000FF /* Transmit error counter */
#define XCAN_ESR_ACKER_MASK             0x00000010 /* ACK error */
#define XCAN_ESR_BERR_MASK              0x00000008 /* Bit error */
#define XCAN_ESR_STER_MASK              0x00000004 /* Stuff error */
#define XCAN_ESR_FMER_MASK              0x00000002 /* Form error */
#define XCAN_ESR_CRCER_MASK             0x00000001 /* CRC error */
#define XCAN_SR_TXFLL_MASK              0x00000400 /* TX FIFO is full */
#define XCAN_SR_ESTAT_MASK              0x00000180 /* Error status */
#define XCAN_SR_ERRWRN_MASK             0x00000040 /* Error warning */
#define XCAN_SR_NORMAL_MASK             0x00000008 /* Normal mode */
#define XCAN_SR_LBACK_MASK              0x00000002 /* Loop back mode */
#define XCAN_SR_CONFIG_MASK             0x00000001 /* Configuration mode */
#define XCAN_IXR_TXFEMP_MASK            0x00004000 /* TX FIFO Empty */
#define XCAN_IXR_WKUP_MASK              0x00000800 /* Wake up interrupt */
#define XCAN_IXR_SLP_MASK               0x00000400 /* Sleep interrupt */
#define XCAN_IXR_BSOFF_MASK             0x00000200 /* Bus off interrupt */
#define XCAN_IXR_ERROR_MASK             0x00000100 /* Error interrupt */
#define XCAN_IXR_RXNEMP_MASK            0x00000080 /* RX FIFO NotEmpty intr */
#define XCAN_IXR_RXOFLW_MASK            0x00000040 /* RX FIFO Overflow intr */
#define XCAN_IXR_RXOK_MASK              0x00000010 /* Message received intr */
#define XCAN_IXR_TXFLL_MASK             0x00000004 /* Tx FIFO Full intr */
#define XCAN_IXR_TXOK_MASK              0x00000002 /* TX successful intr */
#define XCAN_IXR_ARBLST_MASK            0x00000001 /* Arbitration lost intr */
#define XCAN_IDR_ID1_MASK               0xFFE00000 /* Standard msg identifier */
#define XCAN_IDR_SRR_MASK               0x00100000 /* Substitute remote TXreq */
#define XCAN_IDR_IDE_MASK               0x00080000 /* Identifier extension */
#define XCAN_IDR_ID2_MASK               0x0007FFFE /* Extended message ident */
#define XCAN_IDR_RTR_MASK               0x00000001 /* Remote TX request */
#define XCAN_DLCR_DLC_MASK              0xF0000000 /* Data length code */

#define XCAN_INTR_ALL           (XCAN_IXR_TXOK_MASK | XCAN_IXR_BSOFF_MASK |\
                                 XCAN_IXR_WKUP_MASK | XCAN_IXR_SLP_MASK | \
                                 XCAN_IXR_RXNEMP_MASK | XCAN_IXR_ERROR_MASK | \
                                 XCAN_IXR_RXOFLW_MASK | XCAN_IXR_ARBLST_MASK)

/* CAN register bit shift - XCAN_<REG>_<BIT>_SHIFT */
#define XCAN_BTR_SJW_SHIFT              7  /* Synchronous jump width */
#define XCAN_BTR_TS2_SHIFT              4  /* Time segment 2 */
#define XCAN_IDR_ID1_SHIFT              21 /* Standard Messg Identifier */
#define XCAN_IDR_ID2_SHIFT              1  /* Extended Message Identifier */
#define XCAN_DLCR_DLC_SHIFT             28 /* Data length code */
#define XCAN_ESR_REC_SHIFT              8  /* Rx Error Count */

/* CAN frame length constants */
#define XCAN_FRAME_MAX_DATA_LEN         8
#define XCAN_TIMEOUT                    (1 * HZ)

/**
 * struct xcan_priv - This definition define CAN driver instance
 * @can:                        CAN private data structure.
 * @tx_lock:                    Lock for synchronizing TX interrupt handling
 * @tx_head:                    Tx CAN packets ready to send on the queue
 * @tx_tail:                    Tx CAN packets successfully sended on the queue
 * @tx_max:                     Maximum number packets the driver can send
 * @napi:                       NAPI structure
 * @read_reg:                   For reading data from CAN registers
 * @write_reg:                  For writing data to CAN registers
 * @dev:                        Network device data structure
 * @reg_base:                   Ioremapped address to registers
 * @irq_flags:                  For request_irq()
 * @bus_clk:                    Pointer to struct clk
 * @can_clk:                    Pointer to struct clk
 */
struct xcan_priv {
        struct can_priv can;
        spinlock_t tx_lock;
        unsigned int tx_head;
        unsigned int tx_tail;
        unsigned int tx_max;
        struct napi_struct napi;
        u32 (*read_reg)(const struct xcan_priv *priv, enum xcan_reg reg);
        void (*write_reg)(const struct xcan_priv *priv, enum xcan_reg reg,
                        u32 val);
        struct device *dev;
        void __iomem *reg_base;
        unsigned long irq_flags;
        struct clk *bus_clk;
        struct clk *can_clk;
};

/* CAN Bittiming constants as per Xilinx CAN specs */
static const struct can_bittiming_const xcan_bittiming_const = {
        .name = DRIVER_NAME,
        .tseg1_min = 1,
        .tseg1_max = 16,
        .tseg2_min = 1,
        .tseg2_max = 8,
        .sjw_max = 4,
        .brp_min = 1,
        .brp_max = 256,
        .brp_inc = 1,
};

#define XCAN_CAP_WATERMARK      0x0001
struct xcan_devtype_data {
        unsigned int caps;
};

/**
 * xcan_write_reg_le - Write a value to the device register little endian
 * @priv:       Driver private data structure
 * @reg:        Register offset
 * @val:        Value to write at the Register offset
 *
 * Write data to the paricular CAN register
 */
static void xcan_write_reg_le(const struct xcan_priv *priv, enum xcan_reg reg,
                        u32 val)
{
        iowrite32(val, priv->reg_base + reg);
}

/**
 * xcan_read_reg_le - Read a value from the device register little endian
 * @priv:       Driver private data structure
 * @reg:        Register offset
 *
 * Read data from the particular CAN register
 * Return: value read from the CAN register
 */
static u32 xcan_read_reg_le(const struct xcan_priv *priv, enum xcan_reg reg)
{
        return ioread32(priv->reg_base + reg);
}

/**
 * xcan_write_reg_be - Write a value to the device register big endian
 * @priv:       Driver private data structure
 * @reg:        Register offset
 * @val:        Value to write at the Register offset
 *
 * Write data to the paricular CAN register
 */
static void xcan_write_reg_be(const struct xcan_priv *priv, enum xcan_reg reg,
                        u32 val)
{
        iowrite32be(val, priv->reg_base + reg);
}

/**
 * xcan_read_reg_be - Read a value from the device register big endian
 * @priv:       Driver private data structure
 * @reg:        Register offset
 *
 * Read data from the particular CAN register
 * Return: value read from the CAN register
 */
static u32 xcan_read_reg_be(const struct xcan_priv *priv, enum xcan_reg reg)
{
        return ioread32be(priv->reg_base + reg);
}

/**
 * set_reset_mode - Resets the CAN device mode
 * @ndev:       Pointer to net_device structure
 *
 * This is the driver reset mode routine.The driver
 * enters into configuration mode.
 *
 * Return: 0 on success and failure value on error
 */
static int set_reset_mode(struct net_device *ndev)
{
        struct xcan_priv *priv = netdev_priv(ndev);
        unsigned long timeout;

        priv->write_reg(priv, XCAN_SRR_OFFSET, XCAN_SRR_RESET_MASK);

        timeout = jiffies + XCAN_TIMEOUT;
        while (!(priv->read_reg(priv, XCAN_SR_OFFSET) & XCAN_SR_CONFIG_MASK)) {
                if (time_after(jiffies, timeout)) {
                        netdev_warn(ndev, "timed out for config mode\n");
                        return -ETIMEDOUT;
                }
                usleep_range(500, 10000);
        }

        /* reset clears FIFOs */
        priv->tx_head = 0;
        priv->tx_tail = 0;

        return 0;
}

/**
 * xcan_set_bittiming - CAN set bit timing routine
 * @ndev:       Pointer to net_device structure
 *
 * This is the driver set bittiming  routine.
 * Return: 0 on success and failure value on error
 */
static int xcan_set_bittiming(struct net_device *ndev)
{
        struct xcan_priv *priv = netdev_priv(ndev);
        struct can_bittiming *bt = &priv->can.bittiming;
        u32 btr0, btr1;
        u32 is_config_mode;

        /* Check whether Xilinx CAN is in configuration mode.
         * It cannot set bit timing if Xilinx CAN is not in configuration mode.
         */
        is_config_mode = priv->read_reg(priv, XCAN_SR_OFFSET) &
                                XCAN_SR_CONFIG_MASK;
        if (!is_config_mode) {
                netdev_alert(ndev,
                     "BUG! Cannot set bittiming - CAN is not in config mode\n");
                return -EPERM;
        }

        /* Setting Baud Rate prescalar value in BRPR Register */
        btr0 = (bt->brp - 1);

        /* Setting Time Segment 1 in BTR Register */
        btr1 = (bt->prop_seg + bt->phase_seg1 - 1);

        /* Setting Time Segment 2 in BTR Register */
        btr1 |= (bt->phase_seg2 - 1) << XCAN_BTR_TS2_SHIFT;

        /* Setting Synchronous jump width in BTR Register */
        btr1 |= (bt->sjw - 1) << XCAN_BTR_SJW_SHIFT;

        priv->write_reg(priv, XCAN_BRPR_OFFSET, btr0);
        priv->write_reg(priv, XCAN_BTR_OFFSET, btr1);

        netdev_dbg(ndev, "BRPR=0x%08x, BTR=0x%08x\n",
                        priv->read_reg(priv, XCAN_BRPR_OFFSET),
                        priv->read_reg(priv, XCAN_BTR_OFFSET));

        return 0;
}

/**
 * xcan_chip_start - This the drivers start routine
 * @ndev:       Pointer to net_device structure
 *
 * This is the drivers start routine.
 * Based on the State of the CAN device it puts
 * the CAN device into a proper mode.
 *
 * Return: 0 on success and failure value on error
 */
static int xcan_chip_start(struct net_device *ndev)
{
        struct xcan_priv *priv = netdev_priv(ndev);
        u32 reg_msr, reg_sr_mask;
        int err;
        unsigned long timeout;

        /* Check if it is in reset mode */
        err = set_reset_mode(ndev);
        if (err < 0)
                return err;

        err = xcan_set_bittiming(ndev);
        if (err < 0)
                return err;

        /* Enable interrupts */
        priv->write_reg(priv, XCAN_IER_OFFSET, XCAN_INTR_ALL);

        /* Check whether it is loopback mode or normal mode  */
        if (priv->can.ctrlmode & CAN_CTRLMODE_LOOPBACK) {
                reg_msr = XCAN_MSR_LBACK_MASK;
                reg_sr_mask = XCAN_SR_LBACK_MASK;
        } else {
                reg_msr = 0x0;
                reg_sr_mask = XCAN_SR_NORMAL_MASK;
        }

        priv->write_reg(priv, XCAN_MSR_OFFSET, reg_msr);
        priv->write_reg(priv, XCAN_SRR_OFFSET, XCAN_SRR_CEN_MASK);

        timeout = jiffies + XCAN_TIMEOUT;
        while (!(priv->read_reg(priv, XCAN_SR_OFFSET) & reg_sr_mask)) {
                if (time_after(jiffies, timeout)) {
                        netdev_warn(ndev,
                                "timed out for correct mode\n");
                        return -ETIMEDOUT;
                }
        }
        netdev_dbg(ndev, "status:#x%08x\n",
                        priv->read_reg(priv, XCAN_SR_OFFSET));

        priv->can.state = CAN_STATE_ERROR_ACTIVE;
        return 0;
}

/**
 * xcan_do_set_mode - This sets the mode of the driver
 * @ndev:       Pointer to net_device structure
 * @mode:       Tells the mode of the driver
 *
 * This check the drivers state and calls the
 * the corresponding modes to set.
 *
 * Return: 0 on success and failure value on error
 */
static int xcan_do_set_mode(struct net_device *ndev, enum can_mode mode)
{
        int ret;

        switch (mode) {
        case CAN_MODE_START:
                ret = xcan_chip_start(ndev);
                if (ret < 0) {
                        netdev_err(ndev, "xcan_chip_start failed!\n");
                        return ret;
                }
                netif_wake_queue(ndev);
                break;
        default:
                ret = -EOPNOTSUPP;
                break;
        }

        return ret;
}

/**
 * xcan_start_xmit - Starts the transmission
 * @skb:        sk_buff pointer that contains data to be Txed
 * @ndev:       Pointer to net_device structure
 *
 * This function is invoked from upper layers to initiate transmission. This
 * function uses the next available free txbuff and populates their fields to
 * start the transmission.
 *
 * Return: 0 on success and failure value on error
 */
static int xcan_start_xmit(struct sk_buff *skb, struct net_device *ndev)
{
        struct xcan_priv *priv = netdev_priv(ndev);
        struct net_device_stats *stats = &ndev->stats;
        struct can_frame *cf = (struct can_frame *)skb->data;
        u32 id, dlc, data[2] = {0, 0};
        unsigned long flags;

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

        /* Check if the TX buffer is full */
        if (unlikely(priv->read_reg(priv, XCAN_SR_OFFSET) &
                        XCAN_SR_TXFLL_MASK)) {
                netif_stop_queue(ndev);
                netdev_err(ndev, "BUG!, TX FIFO full when queue awake!\n");
                return NETDEV_TX_BUSY;
        }

        /* Watch carefully on the bit sequence */
        if (cf->can_id & CAN_EFF_FLAG) {
                /* Extended CAN ID format */
                id = ((cf->can_id & CAN_EFF_MASK) << XCAN_IDR_ID2_SHIFT) &
                        XCAN_IDR_ID2_MASK;
                id |= (((cf->can_id & CAN_EFF_MASK) >>
                        (CAN_EFF_ID_BITS-CAN_SFF_ID_BITS)) <<
                        XCAN_IDR_ID1_SHIFT) & XCAN_IDR_ID1_MASK;

                /* The substibute remote TX request bit should be "1"
                 * for extended frames as in the Xilinx CAN datasheet
                 */
                id |= XCAN_IDR_IDE_MASK | XCAN_IDR_SRR_MASK;

                if (cf->can_id & CAN_RTR_FLAG)
                        /* Extended frames remote TX request */
                        id |= XCAN_IDR_RTR_MASK;
        } else {
                /* Standard CAN ID format */
                id = ((cf->can_id & CAN_SFF_MASK) << XCAN_IDR_ID1_SHIFT) &
                        XCAN_IDR_ID1_MASK;

                if (cf->can_id & CAN_RTR_FLAG)
                        /* Standard frames remote TX request */
                        id |= XCAN_IDR_SRR_MASK;
        }

        dlc = cf->can_dlc << XCAN_DLCR_DLC_SHIFT;

        if (cf->can_dlc > 0)
                data[0] = be32_to_cpup((__be32 *)(cf->data + 0));
        if (cf->can_dlc > 4)
                data[1] = be32_to_cpup((__be32 *)(cf->data + 4));

        can_put_echo_skb(skb, ndev, priv->tx_head % priv->tx_max);

        spin_lock_irqsave(&priv->tx_lock, flags);

        priv->tx_head++;

        /* Write the Frame to Xilinx CAN TX FIFO */
        priv->write_reg(priv, XCAN_TXFIFO_ID_OFFSET, id);
        /* If the CAN frame is RTR frame this write triggers tranmission */
        priv->write_reg(priv, XCAN_TXFIFO_DLC_OFFSET, dlc);
        if (!(cf->can_id & CAN_RTR_FLAG)) {
                priv->write_reg(priv, XCAN_TXFIFO_DW1_OFFSET, data[0]);
                /* If the CAN frame is Standard/Extended frame this
                 * write triggers tranmission
                 */
                priv->write_reg(priv, XCAN_TXFIFO_DW2_OFFSET, data[1]);
                stats->tx_bytes += cf->can_dlc;
        }

        /* Clear TX-FIFO-empty interrupt for xcan_tx_interrupt() */
        if (priv->tx_max > 1)
                priv->write_reg(priv, XCAN_ICR_OFFSET, XCAN_IXR_TXFEMP_MASK);

        /* Check if the TX buffer is full */
        if ((priv->tx_head - priv->tx_tail) == priv->tx_max)
                netif_stop_queue(ndev);

        spin_unlock_irqrestore(&priv->tx_lock, flags);

        return NETDEV_TX_OK;
}

/**
 * xcan_rx -  Is called from CAN isr to complete the received
 *              frame  processing
 * @ndev:       Pointer to net_device structure
 *
 * This function is invoked from the CAN isr(poll) to process the Rx frames. It
 * does minimal processing and invokes "netif_receive_skb" to complete further
 * processing.
 * Return: 1 on success and 0 on failure.
 */
static int xcan_rx(struct net_device *ndev)
{
        struct xcan_priv *priv = netdev_priv(ndev);
        struct net_device_stats *stats = &ndev->stats;
        struct can_frame *cf;
        struct sk_buff *skb;
        u32 id_xcan, dlc, data[2] = {0, 0};

        skb = alloc_can_skb(ndev, &cf);
        if (unlikely(!skb)) {
                stats->rx_dropped++;
                return 0;
        }

        /* Read a frame from Xilinx zynq CANPS */
        id_xcan = priv->read_reg(priv, XCAN_RXFIFO_ID_OFFSET);
        dlc = priv->read_reg(priv, XCAN_RXFIFO_DLC_OFFSET) >>
                                XCAN_DLCR_DLC_SHIFT;

        /* Change Xilinx CAN data length format to socketCAN data format */
        cf->can_dlc = get_can_dlc(dlc);

        /* Change Xilinx CAN ID format to socketCAN ID format */
        if (id_xcan & XCAN_IDR_IDE_MASK) {
                /* The received frame is an Extended format frame */
                cf->can_id = (id_xcan & XCAN_IDR_ID1_MASK) >> 3;
                cf->can_id |= (id_xcan & XCAN_IDR_ID2_MASK) >>
                                XCAN_IDR_ID2_SHIFT;
                cf->can_id |= CAN_EFF_FLAG;
                if (id_xcan & XCAN_IDR_RTR_MASK)
                        cf->can_id |= CAN_RTR_FLAG;
        } else {
                /* The received frame is a standard format frame */
                cf->can_id = (id_xcan & XCAN_IDR_ID1_MASK) >>
                                XCAN_IDR_ID1_SHIFT;
                if (id_xcan & XCAN_IDR_SRR_MASK)
                        cf->can_id |= CAN_RTR_FLAG;
        }

        /* DW1/DW2 must always be read to remove message from RXFIFO */
        data[0] = priv->read_reg(priv, XCAN_RXFIFO_DW1_OFFSET);
        data[1] = priv->read_reg(priv, XCAN_RXFIFO_DW2_OFFSET);

        if (!(cf->can_id & CAN_RTR_FLAG)) {
                /* Change Xilinx CAN data format to socketCAN data format */
                if (cf->can_dlc > 0)
                        *(__be32 *)(cf->data) = cpu_to_be32(data[0]);
                if (cf->can_dlc > 4)
                        *(__be32 *)(cf->data + 4) = cpu_to_be32(data[1]);
        }

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

        return 1;
}

/**
 * xcan_current_error_state - Get current error state from HW
 * @ndev:       Pointer to net_device structure
 *
 * Checks the current CAN error state from the HW. Note that this
 * only checks for ERROR_PASSIVE and ERROR_WARNING.
 *
 * Return:
 * ERROR_PASSIVE or ERROR_WARNING if either is active, ERROR_ACTIVE
 * otherwise.
 */
static enum can_state xcan_current_error_state(struct net_device *ndev)
{
        struct xcan_priv *priv = netdev_priv(ndev);
        u32 status = priv->read_reg(priv, XCAN_SR_OFFSET);

        if ((status & XCAN_SR_ESTAT_MASK) == XCAN_SR_ESTAT_MASK)
                return CAN_STATE_ERROR_PASSIVE;
        else if (status & XCAN_SR_ERRWRN_MASK)
                return CAN_STATE_ERROR_WARNING;
        else
                return CAN_STATE_ERROR_ACTIVE;
}

/**
 * xcan_set_error_state - Set new CAN error state
 * @ndev:       Pointer to net_device structure
 * @new_state:  The new CAN state to be set
 * @cf:         Error frame to be populated or NULL
 *
 * Set new CAN error state for the device, updating statistics and
 * populating the error frame if given.
 */
static void xcan_set_error_state(struct net_device *ndev,
                                 enum can_state new_state,
                                 struct can_frame *cf)
{
        struct xcan_priv *priv = netdev_priv(ndev);
        u32 ecr = priv->read_reg(priv, XCAN_ECR_OFFSET);
        u32 txerr = ecr & XCAN_ECR_TEC_MASK;
        u32 rxerr = (ecr & XCAN_ECR_REC_MASK) >> XCAN_ESR_REC_SHIFT;

        priv->can.state = new_state;

        if (cf) {
                cf->can_id |= CAN_ERR_CRTL;
                cf->data[6] = txerr;
                cf->data[7] = rxerr;
        }

        switch (new_state) {
        case CAN_STATE_ERROR_PASSIVE:
                priv->can.can_stats.error_passive++;
                if (cf)
                        cf->data[1] = (rxerr > 127) ?
                                        CAN_ERR_CRTL_RX_PASSIVE :
                                        CAN_ERR_CRTL_TX_PASSIVE;
                break;
        case CAN_STATE_ERROR_WARNING:
                priv->can.can_stats.error_warning++;
                if (cf)
                        cf->data[1] |= (txerr > rxerr) ?
                                        CAN_ERR_CRTL_TX_WARNING :
                                        CAN_ERR_CRTL_RX_WARNING;
                break;
        case CAN_STATE_ERROR_ACTIVE:
                if (cf)
                        cf->data[1] |= CAN_ERR_CRTL_ACTIVE;
                break;
        default:
                /* non-ERROR states are handled elsewhere */
                WARN_ON(1);
                break;
        }
}

/**
 * xcan_update_error_state_after_rxtx - Update CAN error state after RX/TX
 * @ndev:       Pointer to net_device structure
 *
 * If the device is in a ERROR-WARNING or ERROR-PASSIVE state, check if
 * the performed RX/TX has caused it to drop to a lesser state and set
 * the interface state accordingly.
 */
static void xcan_update_error_state_after_rxtx(struct net_device *ndev)
{
        struct xcan_priv *priv = netdev_priv(ndev);
        enum can_state old_state = priv->can.state;
        enum can_state new_state;

        /* changing error state due to successful frame RX/TX can only
         * occur from these states
         */
        if (old_state != CAN_STATE_ERROR_WARNING &&
            old_state != CAN_STATE_ERROR_PASSIVE)
                return;

        new_state = xcan_current_error_state(ndev);

        if (new_state != old_state) {
                struct sk_buff *skb;
                struct can_frame *cf;

                skb = alloc_can_err_skb(ndev, &cf);

                xcan_set_error_state(ndev, new_state, skb ? cf : NULL);

                if (skb) {
                        struct net_device_stats *stats = &ndev->stats;

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

/**
 * xcan_err_interrupt - error frame Isr
 * @ndev:       net_device pointer
 * @isr:        interrupt status register value
 *
 * This is the CAN error interrupt and it will
 * check the the type of error and forward the error
 * frame to upper layers.
 */
static void xcan_err_interrupt(struct net_device *ndev, u32 isr)
{
        struct xcan_priv *priv = netdev_priv(ndev);
        struct net_device_stats *stats = &ndev->stats;
        struct can_frame *cf;
        struct sk_buff *skb;
        u32 err_status;

        skb = alloc_can_err_skb(ndev, &cf);

        err_status = priv->read_reg(priv, XCAN_ESR_OFFSET);
        priv->write_reg(priv, XCAN_ESR_OFFSET, err_status);

        if (isr & XCAN_IXR_BSOFF_MASK) {
                priv->can.state = CAN_STATE_BUS_OFF;
                priv->can.can_stats.bus_off++;
                /* Leave device in Config Mode in bus-off state */
                priv->write_reg(priv, XCAN_SRR_OFFSET, XCAN_SRR_RESET_MASK);
                can_bus_off(ndev);
                if (skb)
                        cf->can_id |= CAN_ERR_BUSOFF;
        } else {
                enum can_state new_state = xcan_current_error_state(ndev);

                xcan_set_error_state(ndev, new_state, skb ? cf : NULL);
        }

        /* Check for Arbitration lost interrupt */
        if (isr & XCAN_IXR_ARBLST_MASK) {
                priv->can.can_stats.arbitration_lost++;
                if (skb) {
                        cf->can_id |= CAN_ERR_LOSTARB;
                        cf->data[0] = CAN_ERR_LOSTARB_UNSPEC;
                }
        }

        /* Check for RX FIFO Overflow interrupt */
        if (isr & XCAN_IXR_RXOFLW_MASK) {
                stats->rx_over_errors++;
                stats->rx_errors++;
                if (skb) {
                        cf->can_id |= CAN_ERR_CRTL;
                        cf->data[1] |= CAN_ERR_CRTL_RX_OVERFLOW;
                }
        }

        /* Check for error interrupt */
        if (isr & XCAN_IXR_ERROR_MASK) {
                if (skb)
                        cf->can_id |= CAN_ERR_PROT | CAN_ERR_BUSERROR;

                /* Check for Ack error interrupt */
                if (err_status & XCAN_ESR_ACKER_MASK) {
                        stats->tx_errors++;
                        if (skb) {
                                cf->can_id |= CAN_ERR_ACK;
                                cf->data[3] = CAN_ERR_PROT_LOC_ACK;
                        }
                }

                /* Check for Bit error interrupt */
                if (err_status & XCAN_ESR_BERR_MASK) {
                        stats->tx_errors++;
                        if (skb) {
                                cf->can_id |= CAN_ERR_PROT;
                                cf->data[2] = CAN_ERR_PROT_BIT;
                        }
                }

                /* Check for Stuff error interrupt */
                if (err_status & XCAN_ESR_STER_MASK) {
                        stats->rx_errors++;
                        if (skb) {
                                cf->can_id |= CAN_ERR_PROT;
                                cf->data[2] = CAN_ERR_PROT_STUFF;
                        }
                }

                /* Check for Form error interrupt */
                if (err_status & XCAN_ESR_FMER_MASK) {
                        stats->rx_errors++;
                        if (skb) {
                                cf->can_id |= CAN_ERR_PROT;
                                cf->data[2] = CAN_ERR_PROT_FORM;
                        }
                }

                /* Check for CRC error interrupt */
                if (err_status & XCAN_ESR_CRCER_MASK) {
                        stats->rx_errors++;
                        if (skb) {
                                cf->can_id |= CAN_ERR_PROT;
                                cf->data[3] = CAN_ERR_PROT_LOC_CRC_SEQ;
                        }
                }
                        priv->can.can_stats.bus_error++;
        }

        if (skb) {
                stats->rx_packets++;
                stats->rx_bytes += cf->can_dlc;
                netif_rx(skb);
        }

        netdev_dbg(ndev, "%s: error status register:0x%x\n",
                        __func__, priv->read_reg(priv, XCAN_ESR_OFFSET));
}

/**
 * xcan_state_interrupt - It will check the state of the CAN device
 * @ndev:       net_device pointer
 * @isr:        interrupt status register value
 *
 * This will checks the state of the CAN device
 * and puts the device into appropriate state.
 */
static void xcan_state_interrupt(struct net_device *ndev, u32 isr)
{
        struct xcan_priv *priv = netdev_priv(ndev);

        /* Check for Sleep interrupt if set put CAN device in sleep state */
        if (isr & XCAN_IXR_SLP_MASK)
                priv->can.state = CAN_STATE_SLEEPING;

        /* Check for Wake up interrupt if set put CAN device in Active state */
        if (isr & XCAN_IXR_WKUP_MASK)
                priv->can.state = CAN_STATE_ERROR_ACTIVE;
}

/**
 * xcan_rx_poll - Poll routine for rx packets (NAPI)
 * @napi:       napi structure pointer
 * @quota:      Max number of rx packets to be processed.
 *
 * This is the poll routine for rx part.
 * It will process the packets maximux quota value.
 *
 * Return: number of packets received
 */
static int xcan_rx_poll(struct napi_struct *napi, int quota)
{
        struct net_device *ndev = napi->dev;
        struct xcan_priv *priv = netdev_priv(ndev);
        u32 isr, ier;
        int work_done = 0;

        isr = priv->read_reg(priv, XCAN_ISR_OFFSET);
        while ((isr & XCAN_IXR_RXNEMP_MASK) && (work_done < quota)) {
                work_done += xcan_rx(ndev);
                priv->write_reg(priv, XCAN_ICR_OFFSET, XCAN_IXR_RXNEMP_MASK);
                isr = priv->read_reg(priv, XCAN_ISR_OFFSET);
        }

        if (work_done) {
                can_led_event(ndev, CAN_LED_EVENT_RX);
                xcan_update_error_state_after_rxtx(ndev);
        }

        if (work_done < quota) {
                napi_complete_done(napi, work_done);
                ier = priv->read_reg(priv, XCAN_IER_OFFSET);
                ier |= XCAN_IXR_RXNEMP_MASK;
                priv->write_reg(priv, XCAN_IER_OFFSET, ier);
        }
        return work_done;
}

/**
 * xcan_tx_interrupt - Tx Done Isr
 * @ndev:       net_device pointer
 * @isr:        Interrupt status register value
 */
static void xcan_tx_interrupt(struct net_device *ndev, u32 isr)
{
        struct xcan_priv *priv = netdev_priv(ndev);
        struct net_device_stats *stats = &ndev->stats;
        unsigned int frames_in_fifo;
        int frames_sent = 1; /* TXOK => at least 1 frame was sent */
        unsigned long flags;
        int retries = 0;

        /* Synchronize with xmit as we need to know the exact number
         * of frames in the FIFO to stay in sync due to the TXFEMP
         * handling.
         * This also prevents a race between netif_wake_queue() and
         * netif_stop_queue().
         */
        spin_lock_irqsave(&priv->tx_lock, flags);

        frames_in_fifo = priv->tx_head - priv->tx_tail;

        if (WARN_ON_ONCE(frames_in_fifo == 0)) {
                /* clear TXOK anyway to avoid getting back here */
                priv->write_reg(priv, XCAN_ICR_OFFSET, XCAN_IXR_TXOK_MASK);
                spin_unlock_irqrestore(&priv->tx_lock, flags);
                return;
        }

        /* Check if 2 frames were sent (TXOK only means that at least 1
         * frame was sent).
         */
        if (frames_in_fifo > 1) {
                WARN_ON(frames_in_fifo > priv->tx_max);

                /* Synchronize TXOK and isr so that after the loop:
                 * (1) isr variable is up-to-date at least up to TXOK clear
                 *     time. This avoids us clearing a TXOK of a second frame
                 *     but not noticing that the FIFO is now empty and thus
                 *     marking only a single frame as sent.
                 * (2) No TXOK is left. Having one could mean leaving a
                 *     stray TXOK as we might process the associated frame
                 *     via TXFEMP handling as we read TXFEMP *after* TXOK
                 *     clear to satisfy (1).
                 */
                while ((isr & XCAN_IXR_TXOK_MASK) && !WARN_ON(++retries == 100)) {
                        priv->write_reg(priv, XCAN_ICR_OFFSET, XCAN_IXR_TXOK_MASK);
                        isr = priv->read_reg(priv, XCAN_ISR_OFFSET);
                }

                if (isr & XCAN_IXR_TXFEMP_MASK) {
                        /* nothing in FIFO anymore */
                        frames_sent = frames_in_fifo;
                }
        } else {
                /* single frame in fifo, just clear TXOK */
                priv->write_reg(priv, XCAN_ICR_OFFSET, XCAN_IXR_TXOK_MASK);
        }

        while (frames_sent--) {
                can_get_echo_skb(ndev, priv->tx_tail %
                                        priv->tx_max);
                priv->tx_tail++;
                stats->tx_packets++;
        }

        netif_wake_queue(ndev);

        spin_unlock_irqrestore(&priv->tx_lock, flags);

        can_led_event(ndev, CAN_LED_EVENT_TX);
        xcan_update_error_state_after_rxtx(ndev);
}

/**
 * xcan_interrupt - CAN Isr
 * @irq:        irq number
 * @dev_id:     device id poniter
 *
 * This is the xilinx CAN Isr. It checks for the type of interrupt
 * and invokes the corresponding ISR.
 *
 * Return:
 * IRQ_NONE - If CAN device is in sleep mode, IRQ_HANDLED otherwise
 */
static irqreturn_t xcan_interrupt(int irq, void *dev_id)
{
        struct net_device *ndev = (struct net_device *)dev_id;
        struct xcan_priv *priv = netdev_priv(ndev);
        u32 isr, ier;
        u32 isr_errors;

        /* Get the interrupt status from Xilinx CAN */
        isr = priv->read_reg(priv, XCAN_ISR_OFFSET);
        if (!isr)
                return IRQ_NONE;

        /* Check for the type of interrupt and Processing it */
        if (isr & (XCAN_IXR_SLP_MASK | XCAN_IXR_WKUP_MASK)) {
                priv->write_reg(priv, XCAN_ICR_OFFSET, (XCAN_IXR_SLP_MASK |
                                XCAN_IXR_WKUP_MASK));
                xcan_state_interrupt(ndev, isr);
        }

        /* Check for Tx interrupt and Processing it */
        if (isr & XCAN_IXR_TXOK_MASK)
                xcan_tx_interrupt(ndev, isr);

        /* Check for the type of error interrupt and Processing it */
        isr_errors = isr & (XCAN_IXR_ERROR_MASK | XCAN_IXR_RXOFLW_MASK |
                            XCAN_IXR_BSOFF_MASK | XCAN_IXR_ARBLST_MASK);
        if (isr_errors) {
                priv->write_reg(priv, XCAN_ICR_OFFSET, isr_errors);
                xcan_err_interrupt(ndev, isr);
        }

        /* Check for the type of receive interrupt and Processing it */
        if (isr & XCAN_IXR_RXNEMP_MASK) {
                ier = priv->read_reg(priv, XCAN_IER_OFFSET);
                ier &= ~XCAN_IXR_RXNEMP_MASK;
                priv->write_reg(priv, XCAN_IER_OFFSET, ier);
                napi_schedule(&priv->napi);
        }
        return IRQ_HANDLED;
}

/**
 * xcan_chip_stop - Driver stop routine
 * @ndev:       Pointer to net_device structure
 *
 * This is the drivers stop routine. It will disable the
 * interrupts and put the device into configuration mode.
 */
static void xcan_chip_stop(struct net_device *ndev)
{
        struct xcan_priv *priv = netdev_priv(ndev);

        /* Disable interrupts and leave the can in configuration mode */
        set_reset_mode(ndev);
        priv->can.state = CAN_STATE_STOPPED;
}

/**
 * xcan_open - Driver open routine
 * @ndev:       Pointer to net_device structure
 *
 * This is the driver open routine.
 * Return: 0 on success and failure value on error
 */
static int xcan_open(struct net_device *ndev)

{
        struct xcan_priv *priv = netdev_priv(ndev);
        int ret;

        ret = pm_runtime_get_sync(priv->dev);
        if (ret < 0) {
                netdev_err(ndev, "%s: pm_runtime_get failed(%d)\n",
                                __func__, ret);
                return ret;
        }

        ret = request_irq(ndev->irq, xcan_interrupt, priv->irq_flags,
                        ndev->name, ndev);
        if (ret < 0) {
                netdev_err(ndev, "irq allocation for CAN failed\n");
                goto err;
        }

        /* Set chip into reset mode */
        ret = set_reset_mode(ndev);
        if (ret < 0) {
                netdev_err(ndev, "mode resetting failed!\n");
                goto err_irq;
        }

        /* Common open */
        ret = open_candev(ndev);
        if (ret)
                goto err_irq;

        ret = xcan_chip_start(ndev);
        if (ret < 0) {
                netdev_err(ndev, "xcan_chip_start failed!\n");
                goto err_candev;
        }

        can_led_event(ndev, CAN_LED_EVENT_OPEN);
        napi_enable(&priv->napi);
        netif_start_queue(ndev);

        return 0;

err_candev:
        close_candev(ndev);
err_irq:
        free_irq(ndev->irq, ndev);
err:
        pm_runtime_put(priv->dev);

        return ret;
}

/**
 * xcan_close - Driver close routine
 * @ndev:       Pointer to net_device structure
 *
 * Return: 0 always
 */
static int xcan_close(struct net_device *ndev)
{
        struct xcan_priv *priv = netdev_priv(ndev);

        netif_stop_queue(ndev);
        napi_disable(&priv->napi);
        xcan_chip_stop(ndev);
        free_irq(ndev->irq, ndev);
        close_candev(ndev);

        can_led_event(ndev, CAN_LED_EVENT_STOP);
        pm_runtime_put(priv->dev);

        return 0;
}

/**
 * xcan_get_berr_counter - error counter routine
 * @ndev:       Pointer to net_device structure
 * @bec:        Pointer to can_berr_counter structure
 *
 * This is the driver error counter routine.
 * Return: 0 on success and failure value on error
 */
static int xcan_get_berr_counter(const struct net_device *ndev,
                                        struct can_berr_counter *bec)
{
        struct xcan_priv *priv = netdev_priv(ndev);
        int ret;

        ret = pm_runtime_get_sync(priv->dev);
        if (ret < 0) {
                netdev_err(ndev, "%s: pm_runtime_get failed(%d)\n",
                                __func__, ret);
                return ret;
        }

        bec->txerr = priv->read_reg(priv, XCAN_ECR_OFFSET) & XCAN_ECR_TEC_MASK;
        bec->rxerr = ((priv->read_reg(priv, XCAN_ECR_OFFSET) &
                        XCAN_ECR_REC_MASK) >> XCAN_ESR_REC_SHIFT);

        pm_runtime_put(priv->dev);

        return 0;
}


static const struct net_device_ops xcan_netdev_ops = {
        .ndo_open       = xcan_open,
        .ndo_stop       = xcan_close,
        .ndo_start_xmit = xcan_start_xmit,
        .ndo_change_mtu = can_change_mtu,
};

/**
 * xcan_suspend - Suspend method for the driver
 * @dev:        Address of the device structure
 *
 * Put the driver into low power mode.
 * Return: 0 on success and failure value on error
 */
static int __maybe_unused xcan_suspend(struct device *dev)
{
        struct net_device *ndev = dev_get_drvdata(dev);

        if (netif_running(ndev)) {
                netif_stop_queue(ndev);
                netif_device_detach(ndev);
                xcan_chip_stop(ndev);
        }

        return pm_runtime_force_suspend(dev);
}

/**
 * xcan_resume - Resume from suspend
 * @dev:        Address of the device structure
 *
 * Resume operation after suspend.
 * Return: 0 on success and failure value on error
 */
static int __maybe_unused xcan_resume(struct device *dev)
{
        struct net_device *ndev = dev_get_drvdata(dev);
        int ret;

        ret = pm_runtime_force_resume(dev);
        if (ret) {
                dev_err(dev, "pm_runtime_force_resume failed on resume\n");
                return ret;
        }

        if (netif_running(ndev)) {
                ret = xcan_chip_start(ndev);
                if (ret) {
                        dev_err(dev, "xcan_chip_start failed on resume\n");
                        return ret;
                }

                netif_device_attach(ndev);
                netif_start_queue(ndev);
        }

        return 0;
}

/**
 * xcan_runtime_suspend - Runtime suspend method for the driver
 * @dev:        Address of the device structure
 *
 * Put the driver into low power mode.
 * Return: 0 always
 */
static int __maybe_unused xcan_runtime_suspend(struct device *dev)
{
        struct net_device *ndev = dev_get_drvdata(dev);
        struct xcan_priv *priv = netdev_priv(ndev);

        clk_disable_unprepare(priv->bus_clk);
        clk_disable_unprepare(priv->can_clk);

        return 0;
}

/**
 * xcan_runtime_resume - Runtime resume from suspend
 * @dev:        Address of the device structure
 *
 * Resume operation after suspend.
 * Return: 0 on success and failure value on error
 */
static int __maybe_unused xcan_runtime_resume(struct device *dev)
{
        struct net_device *ndev = dev_get_drvdata(dev);
        struct xcan_priv *priv = netdev_priv(ndev);
        int ret;

        ret = clk_prepare_enable(priv->bus_clk);
        if (ret) {
                dev_err(dev, "Cannot enable clock.\n");
                return ret;
        }
        ret = clk_prepare_enable(priv->can_clk);
        if (ret) {
                dev_err(dev, "Cannot enable clock.\n");
                clk_disable_unprepare(priv->bus_clk);
                return ret;
        }

        return 0;
}

static const struct dev_pm_ops xcan_dev_pm_ops = {
        SET_SYSTEM_SLEEP_PM_OPS(xcan_suspend, xcan_resume)
        SET_RUNTIME_PM_OPS(xcan_runtime_suspend, xcan_runtime_resume, NULL)
};

static const struct xcan_devtype_data xcan_zynq_data = {
        .caps = XCAN_CAP_WATERMARK,
};

/* Match table for OF platform binding */
static const struct of_device_id xcan_of_match[] = {
        { .compatible = "xlnx,zynq-can-1.0", .data = &xcan_zynq_data },
        { .compatible = "xlnx,axi-can-1.00.a", },
        { /* end of list */ },
};
MODULE_DEVICE_TABLE(of, xcan_of_match);

/**
 * xcan_probe - Platform registration call
 * @pdev:       Handle to the platform device structure
 *
 * This function does all the memory allocation and registration for the CAN
 * device.
 *
 * Return: 0 on success and failure value on error
 */
static int xcan_probe(struct platform_device *pdev)
{
        struct resource *res; /* IO mem resources */
        struct net_device *ndev;
        struct xcan_priv *priv;
        const struct of_device_id *of_id;
        int caps = 0;
        void __iomem *addr;
        int ret, rx_max, tx_max, tx_fifo_depth;

        /* Get the virtual base address for the device */
        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        addr = devm_ioremap_resource(&pdev->dev, res);
        if (IS_ERR(addr)) {
                ret = PTR_ERR(addr);
                goto err;
        }

        ret = of_property_read_u32(pdev->dev.of_node, "tx-fifo-depth",
                                   &tx_fifo_depth);
        if (ret < 0)
                goto err;

        ret = of_property_read_u32(pdev->dev.of_node, "rx-fifo-depth", &rx_max);
        if (ret < 0)
                goto err;

        of_id = of_match_device(xcan_of_match, &pdev->dev);
        if (of_id) {
                const struct xcan_devtype_data *devtype_data = of_id->data;

                if (devtype_data)
                        caps = devtype_data->caps;
        }

        /* There is no way to directly figure out how many frames have been
         * sent when the TXOK interrupt is processed. If watermark programming
         * is supported, we can have 2 frames in the FIFO and use TXFEMP
         * to determine if 1 or 2 frames have been sent.
         * Theoretically we should be able to use TXFWMEMP to determine up
         * to 3 frames, but it seems that after putting a second frame in the
         * FIFO, with watermark at 2 frames, it can happen that TXFWMEMP (less
         * than 2 frames in FIFO) is set anyway with no TXOK (a frame was
         * sent), which is not a sensible state - possibly TXFWMEMP is not
         * completely synchronized with the rest of the bits?
         */
        if (caps & XCAN_CAP_WATERMARK)
                tx_max = min(tx_fifo_depth, 2);
        else
                tx_max = 1;

        /* Create a CAN device instance */
        ndev = alloc_candev(sizeof(struct xcan_priv), tx_max);
        if (!ndev)
                return -ENOMEM;

        priv = netdev_priv(ndev);
        priv->dev = &pdev->dev;
        priv->can.bittiming_const = &xcan_bittiming_const;
        priv->can.do_set_mode = xcan_do_set_mode;
        priv->can.do_get_berr_counter = xcan_get_berr_counter;
        priv->can.ctrlmode_supported = CAN_CTRLMODE_LOOPBACK |
                                        CAN_CTRLMODE_BERR_REPORTING;
        priv->reg_base = addr;
        priv->tx_max = tx_max;
        spin_lock_init(&priv->tx_lock);

        /* Get IRQ for the device */
        ndev->irq = platform_get_irq(pdev, 0);
        ndev->flags |= IFF_ECHO;        /* We support local echo */

        platform_set_drvdata(pdev, ndev);
        SET_NETDEV_DEV(ndev, &pdev->dev);
        ndev->netdev_ops = &xcan_netdev_ops;

        /* Getting the CAN can_clk info */
        priv->can_clk = devm_clk_get(&pdev->dev, "can_clk");
        if (IS_ERR(priv->can_clk)) {
                dev_err(&pdev->dev, "Device clock not found.\n");
                ret = PTR_ERR(priv->can_clk);
                goto err_free;
        }
        /* Check for type of CAN device */
        if (of_device_is_compatible(pdev->dev.of_node,
                                    "xlnx,zynq-can-1.0")) {
                priv->bus_clk = devm_clk_get(&pdev->dev, "pclk");
                if (IS_ERR(priv->bus_clk)) {
                        dev_err(&pdev->dev, "bus clock not found\n");
                        ret = PTR_ERR(priv->bus_clk);
                        goto err_free;
                }
        } else {
                priv->bus_clk = devm_clk_get(&pdev->dev, "s_axi_aclk");
                if (IS_ERR(priv->bus_clk)) {
                        dev_err(&pdev->dev, "bus clock not found\n");
                        ret = PTR_ERR(priv->bus_clk);
                        goto err_free;
                }
        }

        priv->write_reg = xcan_write_reg_le;
        priv->read_reg = xcan_read_reg_le;

        pm_runtime_enable(&pdev->dev);
        ret = pm_runtime_get_sync(&pdev->dev);
        if (ret < 0) {
                netdev_err(ndev, "%s: pm_runtime_get failed(%d)\n",
                        __func__, ret);
                goto err_pmdisable;
        }

        if (priv->read_reg(priv, XCAN_SR_OFFSET) != XCAN_SR_CONFIG_MASK) {
                priv->write_reg = xcan_write_reg_be;
                priv->read_reg = xcan_read_reg_be;
        }

        priv->can.clock.freq = clk_get_rate(priv->can_clk);

        netif_napi_add(ndev, &priv->napi, xcan_rx_poll, rx_max);

        ret = register_candev(ndev);
        if (ret) {
                dev_err(&pdev->dev, "fail to register failed (err=%d)\n", ret);
                goto err_disableclks;
        }

        devm_can_led_init(ndev);

        pm_runtime_put(&pdev->dev);

        netdev_dbg(ndev, "reg_base=0x%p irq=%d clock=%d, tx fifo depth: actual %d, using %d\n",
                        priv->reg_base, ndev->irq, priv->can.clock.freq,
                        tx_fifo_depth, priv->tx_max);

        return 0;

err_disableclks:
        pm_runtime_put(priv->dev);
err_pmdisable:
        pm_runtime_disable(&pdev->dev);
err_free:
        free_candev(ndev);
err:
        return ret;
}

/**
 * xcan_remove - Unregister the device after releasing the resources
 * @pdev:       Handle to the platform device structure
 *
 * This function frees all the resources allocated to the device.
 * Return: 0 always
 */
static int xcan_remove(struct platform_device *pdev)
{
        struct net_device *ndev = platform_get_drvdata(pdev);
        struct xcan_priv *priv = netdev_priv(ndev);

        unregister_candev(ndev);
        pm_runtime_disable(&pdev->dev);
        netif_napi_del(&priv->napi);
        free_candev(ndev);

        return 0;
}

static struct platform_driver xcan_driver = {
        .probe = xcan_probe,
        .remove = xcan_remove,
        .driver = {
                .name = DRIVER_NAME,
                .pm = &xcan_dev_pm_ops,
                .of_match_table = xcan_of_match,
        },
};

module_platform_driver(xcan_driver);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Xilinx Inc");
MODULE_DESCRIPTION("Xilinx CAN interface");