/*
 * sun4i_can.c - CAN bus controller driver for Allwinner SUN4I&SUN7I based SoCs
 *
 * Copyright (C) 2013 Peter Chen
 * Copyright (C) 2015 Gerhard Bertelsmann
 * All rights reserved.
 *
 * Parts of this software are based on (derived from) the SJA1000 code by:
 *   Copyright (C) 2014 Oliver Hartkopp <oliver.hartkopp@volkswagen.de>
 *   Copyright (C) 2007 Wolfgang Grandegger <wg@grandegger.com>
 *   Copyright (C) 2002-2007 Volkswagen Group Electronic Research
 *   Copyright (C) 2003 Matthias Brukner, Trajet Gmbh, Rebenring 33,
 *   38106 Braunschweig, GERMANY
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of Volkswagen nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * Alternatively, provided that this notice is retained in full, this
 * software may be distributed under the terms of the GNU General
 * Public License ("GPL") version 2, in which case the provisions of the
 * GPL apply INSTEAD OF those given above.
 *
 * The provided data structures and external interfaces from this code
 * are not restricted to be used by modules with a GPL compatible license.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
 * DAMAGE.
 *
 */

#include <linux/netdevice.h>
#include <linux/can.h>
#include <linux/can/dev.h>
#include <linux/can/error.h>
#include <linux/can/led.h>
#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/interrupt.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/platform_device.h>

#define DRV_NAME "sun4i_can"

/* Registers address (physical base address 0x01C2BC00) */
#define SUN4I_REG_MSEL_ADDR     0x0000  /* CAN Mode Select */
#define SUN4I_REG_CMD_ADDR      0x0004  /* CAN Command */
#define SUN4I_REG_STA_ADDR      0x0008  /* CAN Status */
#define SUN4I_REG_INT_ADDR      0x000c  /* CAN Interrupt Flag */
#define SUN4I_REG_INTEN_ADDR    0x0010  /* CAN Interrupt Enable */
#define SUN4I_REG_BTIME_ADDR    0x0014  /* CAN Bus Timing 0 */
#define SUN4I_REG_TEWL_ADDR     0x0018  /* CAN Tx Error Warning Limit */
#define SUN4I_REG_ERRC_ADDR     0x001c  /* CAN Error Counter */
#define SUN4I_REG_RMCNT_ADDR    0x0020  /* CAN Receive Message Counter */
#define SUN4I_REG_RBUFSA_ADDR   0x0024  /* CAN Receive Buffer Start Address */
#define SUN4I_REG_BUF0_ADDR     0x0040  /* CAN Tx/Rx Buffer 0 */
#define SUN4I_REG_BUF1_ADDR     0x0044  /* CAN Tx/Rx Buffer 1 */
#define SUN4I_REG_BUF2_ADDR     0x0048  /* CAN Tx/Rx Buffer 2 */
#define SUN4I_REG_BUF3_ADDR     0x004c  /* CAN Tx/Rx Buffer 3 */
#define SUN4I_REG_BUF4_ADDR     0x0050  /* CAN Tx/Rx Buffer 4 */
#define SUN4I_REG_BUF5_ADDR     0x0054  /* CAN Tx/Rx Buffer 5 */
#define SUN4I_REG_BUF6_ADDR     0x0058  /* CAN Tx/Rx Buffer 6 */
#define SUN4I_REG_BUF7_ADDR     0x005c  /* CAN Tx/Rx Buffer 7 */
#define SUN4I_REG_BUF8_ADDR     0x0060  /* CAN Tx/Rx Buffer 8 */
#define SUN4I_REG_BUF9_ADDR     0x0064  /* CAN Tx/Rx Buffer 9 */
#define SUN4I_REG_BUF10_ADDR    0x0068  /* CAN Tx/Rx Buffer 10 */
#define SUN4I_REG_BUF11_ADDR    0x006c  /* CAN Tx/Rx Buffer 11 */
#define SUN4I_REG_BUF12_ADDR    0x0070  /* CAN Tx/Rx Buffer 12 */
#define SUN4I_REG_ACPC_ADDR     0x0040  /* CAN Acceptance Code 0 */
#define SUN4I_REG_ACPM_ADDR     0x0044  /* CAN Acceptance Mask 0 */
#define SUN4I_REG_RBUF_RBACK_START_ADDR 0x0180  /* CAN transmit buffer start */
#define SUN4I_REG_RBUF_RBACK_END_ADDR   0x01b0  /* CAN transmit buffer end */

/* Controller Register Description */

/* mode select register (r/w)
 * offset:0x0000 default:0x0000_0001
 */
#define SUN4I_MSEL_SLEEP_MODE           (0x01 << 4) /* write in reset mode */
#define SUN4I_MSEL_WAKE_UP              (0x00 << 4)
#define SUN4I_MSEL_SINGLE_FILTER        (0x01 << 3) /* write in reset mode */
#define SUN4I_MSEL_DUAL_FILTERS         (0x00 << 3)
#define SUN4I_MSEL_LOOPBACK_MODE        BIT(2)
#define SUN4I_MSEL_LISTEN_ONLY_MODE     BIT(1)
#define SUN4I_MSEL_RESET_MODE           BIT(0)

/* command register (w)
 * offset:0x0004 default:0x0000_0000
 */
#define SUN4I_CMD_BUS_OFF_REQ   BIT(5)
#define SUN4I_CMD_SELF_RCV_REQ  BIT(4)
#define SUN4I_CMD_CLEAR_OR_FLAG BIT(3)
#define SUN4I_CMD_RELEASE_RBUF  BIT(2)
#define SUN4I_CMD_ABORT_REQ     BIT(1)
#define SUN4I_CMD_TRANS_REQ     BIT(0)

/* status register (r)
 * offset:0x0008 default:0x0000_003c
 */
#define SUN4I_STA_BIT_ERR       (0x00 << 22)
#define SUN4I_STA_FORM_ERR      (0x01 << 22)
#define SUN4I_STA_STUFF_ERR     (0x02 << 22)
#define SUN4I_STA_OTHER_ERR     (0x03 << 22)
#define SUN4I_STA_MASK_ERR      (0x03 << 22)
#define SUN4I_STA_ERR_DIR       BIT(21)
#define SUN4I_STA_ERR_SEG_CODE  (0x1f << 16)
#define SUN4I_STA_START         (0x03 << 16)
#define SUN4I_STA_ID28_21       (0x02 << 16)
#define SUN4I_STA_ID20_18       (0x06 << 16)
#define SUN4I_STA_SRTR          (0x04 << 16)
#define SUN4I_STA_IDE           (0x05 << 16)
#define SUN4I_STA_ID17_13       (0x07 << 16)
#define SUN4I_STA_ID12_5        (0x0f << 16)
#define SUN4I_STA_ID4_0         (0x0e << 16)
#define SUN4I_STA_RTR           (0x0c << 16)
#define SUN4I_STA_RB1           (0x0d << 16)
#define SUN4I_STA_RB0           (0x09 << 16)
#define SUN4I_STA_DLEN          (0x0b << 16)
#define SUN4I_STA_DATA_FIELD    (0x0a << 16)
#define SUN4I_STA_CRC_SEQUENCE  (0x08 << 16)
#define SUN4I_STA_CRC_DELIMITER (0x18 << 16)
#define SUN4I_STA_ACK           (0x19 << 16)
#define SUN4I_STA_ACK_DELIMITER (0x1b << 16)
#define SUN4I_STA_END           (0x1a << 16)
#define SUN4I_STA_INTERMISSION  (0x12 << 16)
#define SUN4I_STA_ACTIVE_ERROR  (0x11 << 16)
#define SUN4I_STA_PASSIVE_ERROR (0x16 << 16)
#define SUN4I_STA_TOLERATE_DOMINANT_BITS        (0x13 << 16)
#define SUN4I_STA_ERROR_DELIMITER       (0x17 << 16)
#define SUN4I_STA_OVERLOAD      (0x1c << 16)
#define SUN4I_STA_BUS_OFF       BIT(7)
#define SUN4I_STA_ERR_STA       BIT(6)
#define SUN4I_STA_TRANS_BUSY    BIT(5)
#define SUN4I_STA_RCV_BUSY      BIT(4)
#define SUN4I_STA_TRANS_OVER    BIT(3)
#define SUN4I_STA_TBUF_RDY      BIT(2)
#define SUN4I_STA_DATA_ORUN     BIT(1)
#define SUN4I_STA_RBUF_RDY      BIT(0)

/* interrupt register (r)
 * offset:0x000c default:0x0000_0000
 */
#define SUN4I_INT_BUS_ERR       BIT(7)
#define SUN4I_INT_ARB_LOST      BIT(6)
#define SUN4I_INT_ERR_PASSIVE   BIT(5)
#define SUN4I_INT_WAKEUP        BIT(4)
#define SUN4I_INT_DATA_OR       BIT(3)
#define SUN4I_INT_ERR_WRN       BIT(2)
#define SUN4I_INT_TBUF_VLD      BIT(1)
#define SUN4I_INT_RBUF_VLD      BIT(0)

/* interrupt enable register (r/w)
 * offset:0x0010 default:0x0000_0000
 */
#define SUN4I_INTEN_BERR        BIT(7)
#define SUN4I_INTEN_ARB_LOST    BIT(6)
#define SUN4I_INTEN_ERR_PASSIVE BIT(5)
#define SUN4I_INTEN_WAKEUP      BIT(4)
#define SUN4I_INTEN_OR          BIT(3)
#define SUN4I_INTEN_ERR_WRN     BIT(2)
#define SUN4I_INTEN_TX          BIT(1)
#define SUN4I_INTEN_RX          BIT(0)

/* error code */
#define SUN4I_ERR_INRCV         (0x1 << 5)
#define SUN4I_ERR_INTRANS       (0x0 << 5)

/* filter mode */
#define SUN4I_FILTER_CLOSE      0
#define SUN4I_SINGLE_FLTER_MODE 1
#define SUN4I_DUAL_FILTER_MODE  2

/* message buffer flags */
#define SUN4I_MSG_EFF_FLAG      BIT(7)
#define SUN4I_MSG_RTR_FLAG      BIT(6)

/* max. number of interrupts handled in ISR */
#define SUN4I_CAN_MAX_IRQ       20
#define SUN4I_MODE_MAX_RETRIES  100

struct sun4ican_priv {
        struct can_priv can;
        void __iomem *base;
        struct clk *clk;
        spinlock_t cmdreg_lock; /* lock for concurrent cmd register writes */
};

static const struct can_bittiming_const sun4ican_bittiming_const = {
        .name = DRV_NAME,
        .tseg1_min = 1,
        .tseg1_max = 16,
        .tseg2_min = 1,
        .tseg2_max = 8,
        .sjw_max = 4,
        .brp_min = 1,
        .brp_max = 64,
        .brp_inc = 1,
};

static void sun4i_can_write_cmdreg(struct sun4ican_priv *priv, u8 val)
{
        unsigned long flags;

        spin_lock_irqsave(&priv->cmdreg_lock, flags);
        writel(val, priv->base + SUN4I_REG_CMD_ADDR);
        spin_unlock_irqrestore(&priv->cmdreg_lock, flags);
}

static int set_normal_mode(struct net_device *dev)
{
        struct sun4ican_priv *priv = netdev_priv(dev);
        int retry = SUN4I_MODE_MAX_RETRIES;
        u32 mod_reg_val = 0;

        do {
                mod_reg_val = readl(priv->base + SUN4I_REG_MSEL_ADDR);
                mod_reg_val &= ~SUN4I_MSEL_RESET_MODE;
                writel(mod_reg_val, priv->base + SUN4I_REG_MSEL_ADDR);
        } while (retry-- && (mod_reg_val & SUN4I_MSEL_RESET_MODE));

        if (readl(priv->base + SUN4I_REG_MSEL_ADDR) & SUN4I_MSEL_RESET_MODE) {
                netdev_err(dev,
                           "setting controller into normal mode failed!\n");
                return -ETIMEDOUT;
        }

        return 0;
}

static int set_reset_mode(struct net_device *dev)
{
        struct sun4ican_priv *priv = netdev_priv(dev);
        int retry = SUN4I_MODE_MAX_RETRIES;
        u32 mod_reg_val = 0;

        do {
                mod_reg_val = readl(priv->base + SUN4I_REG_MSEL_ADDR);
                mod_reg_val |= SUN4I_MSEL_RESET_MODE;
                writel(mod_reg_val, priv->base + SUN4I_REG_MSEL_ADDR);
        } while (retry-- && !(mod_reg_val & SUN4I_MSEL_RESET_MODE));

        if (!(readl(priv->base + SUN4I_REG_MSEL_ADDR) &
              SUN4I_MSEL_RESET_MODE)) {
                netdev_err(dev, "setting controller into reset mode failed!\n");
                return -ETIMEDOUT;
        }

        return 0;
}

/* bittiming is called in reset_mode only */
static int sun4ican_set_bittiming(struct net_device *dev)
{
        struct sun4ican_priv *priv = netdev_priv(dev);
        struct can_bittiming *bt = &priv->can.bittiming;
        u32 cfg;

        cfg = ((bt->brp - 1) & 0x3FF) |
             (((bt->sjw - 1) & 0x3) << 14) |
             (((bt->prop_seg + bt->phase_seg1 - 1) & 0xf) << 16) |
             (((bt->phase_seg2 - 1) & 0x7) << 20);
        if (priv->can.ctrlmode & CAN_CTRLMODE_3_SAMPLES)
                cfg |= 0x800000;

        netdev_dbg(dev, "setting BITTIMING=0x%08x\n", cfg);
        writel(cfg, priv->base + SUN4I_REG_BTIME_ADDR);

        return 0;
}

static int sun4ican_get_berr_counter(const struct net_device *dev,
                                     struct can_berr_counter *bec)
{
        struct sun4ican_priv *priv = netdev_priv(dev);
        u32 errors;
        int err;

        err = clk_prepare_enable(priv->clk);
        if (err) {
                netdev_err(dev, "could not enable clock\n");
                return err;
        }

        errors = readl(priv->base + SUN4I_REG_ERRC_ADDR);

        bec->txerr = errors & 0xFF;
        bec->rxerr = (errors >> 16) & 0xFF;

        clk_disable_unprepare(priv->clk);

        return 0;
}

static int sun4i_can_start(struct net_device *dev)
{
        struct sun4ican_priv *priv = netdev_priv(dev);
        int err;
        u32 mod_reg_val;

        /* we need to enter the reset mode */
        err = set_reset_mode(dev);
        if (err) {
                netdev_err(dev, "could not enter reset mode\n");
                return err;
        }

        /* set filters - we accept all */
        writel(0x00000000, priv->base + SUN4I_REG_ACPC_ADDR);
        writel(0xFFFFFFFF, priv->base + SUN4I_REG_ACPM_ADDR);

        /* clear error counters and error code capture */
        writel(0, priv->base + SUN4I_REG_ERRC_ADDR);

        /* enable interrupts */
        if (priv->can.ctrlmode & CAN_CTRLMODE_BERR_REPORTING)
                writel(0xFF, priv->base + SUN4I_REG_INTEN_ADDR);
        else
                writel(0xFF & ~SUN4I_INTEN_BERR,
                       priv->base + SUN4I_REG_INTEN_ADDR);

        /* enter the selected mode */
        mod_reg_val = readl(priv->base + SUN4I_REG_MSEL_ADDR);
        if (priv->can.ctrlmode & CAN_CTRLMODE_PRESUME_ACK)
                mod_reg_val |= SUN4I_MSEL_LOOPBACK_MODE;
        else if (priv->can.ctrlmode & CAN_CTRLMODE_LISTENONLY)
                mod_reg_val |= SUN4I_MSEL_LISTEN_ONLY_MODE;
        writel(mod_reg_val, priv->base + SUN4I_REG_MSEL_ADDR);

        err = sun4ican_set_bittiming(dev);
        if (err)
                return err;

        /* we are ready to enter the normal mode */
        err = set_normal_mode(dev);
        if (err) {
                netdev_err(dev, "could not enter normal mode\n");
                return err;
        }

        priv->can.state = CAN_STATE_ERROR_ACTIVE;

        return 0;
}

static int sun4i_can_stop(struct net_device *dev)
{
        struct sun4ican_priv *priv = netdev_priv(dev);
        int err;

        priv->can.state = CAN_STATE_STOPPED;
        /* we need to enter reset mode */
        err = set_reset_mode(dev);
        if (err) {
                netdev_err(dev, "could not enter reset mode\n");
                return err;
        }

        /* disable all interrupts */
        writel(0, priv->base + SUN4I_REG_INTEN_ADDR);

        return 0;
}

static int sun4ican_set_mode(struct net_device *dev, enum can_mode mode)
{
        int err;

        switch (mode) {
        case CAN_MODE_START:
                err = sun4i_can_start(dev);
                if (err) {
                        netdev_err(dev, "starting CAN controller failed!\n");
                        return err;
                }
                if (netif_queue_stopped(dev))
                        netif_wake_queue(dev);
                break;

        default:
                return -EOPNOTSUPP;
        }
        return 0;
}

/* transmit a CAN message
 * message layout in the sk_buff should be like this:
 * xx xx xx xx         ff         ll 00 11 22 33 44 55 66 77
 * [ can_id ] [flags] [len] [can data (up to 8 bytes]
 */
static int sun4ican_start_xmit(struct sk_buff *skb, struct net_device *dev)
{
        struct sun4ican_priv *priv = netdev_priv(dev);
        struct can_frame *cf = (struct can_frame *)skb->data;
        u8 dlc;
        u32 dreg, msg_flag_n;
        canid_t id;
        int i;

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

        netif_stop_queue(dev);

        id = cf->can_id;
        dlc = cf->can_dlc;
        msg_flag_n = dlc;

        if (id & CAN_RTR_FLAG)
                msg_flag_n |= SUN4I_MSG_RTR_FLAG;

        if (id & CAN_EFF_FLAG) {
                msg_flag_n |= SUN4I_MSG_EFF_FLAG;
                dreg = SUN4I_REG_BUF5_ADDR;
                writel((id >> 21) & 0xFF, priv->base + SUN4I_REG_BUF1_ADDR);
                writel((id >> 13) & 0xFF, priv->base + SUN4I_REG_BUF2_ADDR);
                writel((id >> 5)  & 0xFF, priv->base + SUN4I_REG_BUF3_ADDR);
                writel((id << 3)  & 0xF8, priv->base + SUN4I_REG_BUF4_ADDR);
        } else {
                dreg = SUN4I_REG_BUF3_ADDR;
                writel((id >> 3) & 0xFF, priv->base + SUN4I_REG_BUF1_ADDR);
                writel((id << 5) & 0xE0, priv->base + SUN4I_REG_BUF2_ADDR);
        }

        for (i = 0; i < dlc; i++)
                writel(cf->data[i], priv->base + (dreg + i * 4));

        writel(msg_flag_n, priv->base + SUN4I_REG_BUF0_ADDR);

        can_put_echo_skb(skb, dev, 0);

        if (priv->can.ctrlmode & CAN_CTRLMODE_LOOPBACK)
                sun4i_can_write_cmdreg(priv, SUN4I_CMD_SELF_RCV_REQ);
        else
                sun4i_can_write_cmdreg(priv, SUN4I_CMD_TRANS_REQ);

        return NETDEV_TX_OK;
}

static void sun4i_can_rx(struct net_device *dev)
{
        struct sun4ican_priv *priv = netdev_priv(dev);
        struct net_device_stats *stats = &dev->stats;
        struct can_frame *cf;
        struct sk_buff *skb;
        u8 fi;
        u32 dreg;
        canid_t id;
        int i;

        /* create zero'ed CAN frame buffer */
        skb = alloc_can_skb(dev, &cf);
        if (!skb)
                return;

        fi = readl(priv->base + SUN4I_REG_BUF0_ADDR);
        cf->can_dlc = get_can_dlc(fi & 0x0F);
        if (fi & SUN4I_MSG_EFF_FLAG) {
                dreg = SUN4I_REG_BUF5_ADDR;
                id = (readl(priv->base + SUN4I_REG_BUF1_ADDR) << 21) |
                     (readl(priv->base + SUN4I_REG_BUF2_ADDR) << 13) |
                     (readl(priv->base + SUN4I_REG_BUF3_ADDR) << 5)  |
                    ((readl(priv->base + SUN4I_REG_BUF4_ADDR) >> 3)  & 0x1f);
                id |= CAN_EFF_FLAG;
        } else {
                dreg = SUN4I_REG_BUF3_ADDR;
                id = (readl(priv->base + SUN4I_REG_BUF1_ADDR) << 3) |
                    ((readl(priv->base + SUN4I_REG_BUF2_ADDR) >> 5) & 0x7);
        }

        /* remote frame ? */
        if (fi & SUN4I_MSG_RTR_FLAG)
                id |= CAN_RTR_FLAG;
        else
                for (i = 0; i < cf->can_dlc; i++)
                        cf->data[i] = readl(priv->base + dreg + i * 4);

        cf->can_id = id;

        sun4i_can_write_cmdreg(priv, SUN4I_CMD_RELEASE_RBUF);

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

        can_led_event(dev, CAN_LED_EVENT_RX);
}

static int sun4i_can_err(struct net_device *dev, u8 isrc, u8 status)
{
        struct sun4ican_priv *priv = netdev_priv(dev);
        struct net_device_stats *stats = &dev->stats;
        struct can_frame *cf;
        struct sk_buff *skb;
        enum can_state state = priv->can.state;
        enum can_state rx_state, tx_state;
        unsigned int rxerr, txerr, errc;
        u32 ecc, alc;

        /* we don't skip if alloc fails because we want the stats anyhow */
        skb = alloc_can_err_skb(dev, &cf);

        errc = readl(priv->base + SUN4I_REG_ERRC_ADDR);
        rxerr = (errc >> 16) & 0xFF;
        txerr = errc & 0xFF;

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

        if (isrc & SUN4I_INT_DATA_OR) {
                /* data overrun interrupt */
                netdev_dbg(dev, "data overrun interrupt\n");
                if (likely(skb)) {
                        cf->can_id |= CAN_ERR_CRTL;
                        cf->data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
                }
                stats->rx_over_errors++;
                stats->rx_errors++;
                /* clear bit */
                sun4i_can_write_cmdreg(priv, SUN4I_CMD_CLEAR_OR_FLAG);
        }
        if (isrc & SUN4I_INT_ERR_WRN) {
                /* error warning interrupt */
                netdev_dbg(dev, "error warning interrupt\n");

                if (status & SUN4I_STA_BUS_OFF)
                        state = CAN_STATE_BUS_OFF;
                else if (status & SUN4I_STA_ERR_STA)
                        state = CAN_STATE_ERROR_WARNING;
                else
                        state = CAN_STATE_ERROR_ACTIVE;
        }
        if (isrc & SUN4I_INT_BUS_ERR) {
                /* bus error interrupt */
                netdev_dbg(dev, "bus error interrupt\n");
                priv->can.can_stats.bus_error++;
                stats->rx_errors++;

                if (likely(skb)) {
                        ecc = readl(priv->base + SUN4I_REG_STA_ADDR);

                        cf->can_id |= CAN_ERR_PROT | CAN_ERR_BUSERROR;

                        switch (ecc & SUN4I_STA_MASK_ERR) {
                        case SUN4I_STA_BIT_ERR:
                                cf->data[2] |= CAN_ERR_PROT_BIT;
                                break;
                        case SUN4I_STA_FORM_ERR:
                                cf->data[2] |= CAN_ERR_PROT_FORM;
                                break;
                        case SUN4I_STA_STUFF_ERR:
                                cf->data[2] |= CAN_ERR_PROT_STUFF;
                                break;
                        default:
                                cf->data[3] = (ecc & SUN4I_STA_ERR_SEG_CODE)
                                               >> 16;
                                break;
                        }
                        /* error occurred during transmission? */
                        if ((ecc & SUN4I_STA_ERR_DIR) == 0)
                                cf->data[2] |= CAN_ERR_PROT_TX;
                }
        }
        if (isrc & SUN4I_INT_ERR_PASSIVE) {
                /* error passive interrupt */
                netdev_dbg(dev, "error passive interrupt\n");
                if (state == CAN_STATE_ERROR_PASSIVE)
                        state = CAN_STATE_ERROR_WARNING;
                else
                        state = CAN_STATE_ERROR_PASSIVE;
        }
        if (isrc & SUN4I_INT_ARB_LOST) {
                /* arbitration lost interrupt */
                netdev_dbg(dev, "arbitration lost interrupt\n");
                alc = readl(priv->base + SUN4I_REG_STA_ADDR);
                priv->can.can_stats.arbitration_lost++;
                stats->tx_errors++;
                if (likely(skb)) {
                        cf->can_id |= CAN_ERR_LOSTARB;
                        cf->data[0] = (alc >> 8) & 0x1f;
                }
        }

        if (state != priv->can.state) {
                tx_state = txerr >= rxerr ? state : 0;
                rx_state = txerr <= rxerr ? state : 0;

                if (likely(skb))
                        can_change_state(dev, cf, tx_state, rx_state);
                else
                        priv->can.state = state;
                if (state == CAN_STATE_BUS_OFF)
                        can_bus_off(dev);
        }

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

        return 0;
}

static irqreturn_t sun4i_can_interrupt(int irq, void *dev_id)
{
        struct net_device *dev = (struct net_device *)dev_id;
        struct sun4ican_priv *priv = netdev_priv(dev);
        struct net_device_stats *stats = &dev->stats;
        u8 isrc, status;
        int n = 0;

        while ((isrc = readl(priv->base + SUN4I_REG_INT_ADDR)) &&
               (n < SUN4I_CAN_MAX_IRQ)) {
                n++;
                status = readl(priv->base + SUN4I_REG_STA_ADDR);

                if (isrc & SUN4I_INT_WAKEUP)
                        netdev_warn(dev, "wakeup interrupt\n");

                if (isrc & SUN4I_INT_TBUF_VLD) {
                        /* transmission complete interrupt */
                        stats->tx_bytes +=
                            readl(priv->base +
                                  SUN4I_REG_RBUF_RBACK_START_ADDR) & 0xf;
                        stats->tx_packets++;
                        can_get_echo_skb(dev, 0);
                        netif_wake_queue(dev);
                        can_led_event(dev, CAN_LED_EVENT_TX);
                }
                if (isrc & SUN4I_INT_RBUF_VLD) {
                        /* receive interrupt */
                        while (status & SUN4I_STA_RBUF_RDY) {
                                /* RX buffer is not empty */
                                sun4i_can_rx(dev);
                                status = readl(priv->base + SUN4I_REG_STA_ADDR);
                        }
                }
                if (isrc &
                    (SUN4I_INT_DATA_OR | SUN4I_INT_ERR_WRN | SUN4I_INT_BUS_ERR |
                     SUN4I_INT_ERR_PASSIVE | SUN4I_INT_ARB_LOST)) {
                        /* error interrupt */
                        if (sun4i_can_err(dev, isrc, status))
                                netdev_err(dev, "can't allocate buffer - clearing pending interrupts\n");
                }
                /* clear interrupts */
                writel(isrc, priv->base + SUN4I_REG_INT_ADDR);
                readl(priv->base + SUN4I_REG_INT_ADDR);
        }
        if (n >= SUN4I_CAN_MAX_IRQ)
                netdev_dbg(dev, "%d messages handled in ISR", n);

        return (n) ? IRQ_HANDLED : IRQ_NONE;
}

static int sun4ican_open(struct net_device *dev)
{
        struct sun4ican_priv *priv = netdev_priv(dev);
        int err;

        /* common open */
        err = open_candev(dev);
        if (err)
                return err;

        /* register interrupt handler */
        err = request_irq(dev->irq, sun4i_can_interrupt, 0, dev->name, dev);
        if (err) {
                netdev_err(dev, "request_irq err: %d\n", err);
                goto exit_irq;
        }

        /* turn on clocking for CAN peripheral block */
        err = clk_prepare_enable(priv->clk);
        if (err) {
                netdev_err(dev, "could not enable CAN peripheral clock\n");
                goto exit_clock;
        }

        err = sun4i_can_start(dev);
        if (err) {
                netdev_err(dev, "could not start CAN peripheral\n");
                goto exit_can_start;
        }

        can_led_event(dev, CAN_LED_EVENT_OPEN);
        netif_start_queue(dev);

        return 0;

exit_can_start:
        clk_disable_unprepare(priv->clk);
exit_clock:
        free_irq(dev->irq, dev);
exit_irq:
        close_candev(dev);
        return err;
}

static int sun4ican_close(struct net_device *dev)
{
        struct sun4ican_priv *priv = netdev_priv(dev);

        netif_stop_queue(dev);
        sun4i_can_stop(dev);
        clk_disable_unprepare(priv->clk);

        free_irq(dev->irq, dev);
        close_candev(dev);
        can_led_event(dev, CAN_LED_EVENT_STOP);

        return 0;
}

static const struct net_device_ops sun4ican_netdev_ops = {
        .ndo_open = sun4ican_open,
        .ndo_stop = sun4ican_close,
        .ndo_start_xmit = sun4ican_start_xmit,
};

static const struct of_device_id sun4ican_of_match[] = {
        {.compatible = "allwinner,sun4i-a10-can"},
        {},
};

MODULE_DEVICE_TABLE(of, sun4ican_of_match);

static int sun4ican_remove(struct platform_device *pdev)
{
        struct net_device *dev = platform_get_drvdata(pdev);

        unregister_netdev(dev);
        free_candev(dev);

        return 0;
}

static int sun4ican_probe(struct platform_device *pdev)
{
        struct device_node *np = pdev->dev.of_node;
        struct resource *mem;
        struct clk *clk;
        void __iomem *addr;
        int err, irq;
        struct net_device *dev;
        struct sun4ican_priv *priv;

        clk = of_clk_get(np, 0);
        if (IS_ERR(clk)) {
                dev_err(&pdev->dev, "unable to request clock\n");
                err = -ENODEV;
                goto exit;
        }

        irq = platform_get_irq(pdev, 0);
        if (irq < 0) {
                dev_err(&pdev->dev, "could not get a valid irq\n");
                err = -ENODEV;
                goto exit;
        }

        mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        addr = devm_ioremap_resource(&pdev->dev, mem);
        if (IS_ERR(addr)) {
                err = -EBUSY;
                goto exit;
        }

        dev = alloc_candev(sizeof(struct sun4ican_priv), 1);
        if (!dev) {
                dev_err(&pdev->dev,
                        "could not allocate memory for CAN device\n");
                err = -ENOMEM;
                goto exit;
        }

        dev->netdev_ops = &sun4ican_netdev_ops;
        dev->irq = irq;
        dev->flags |= IFF_ECHO;

        priv = netdev_priv(dev);
        priv->can.clock.freq = clk_get_rate(clk);
        priv->can.bittiming_const = &sun4ican_bittiming_const;
        priv->can.do_set_mode = sun4ican_set_mode;
        priv->can.do_get_berr_counter = sun4ican_get_berr_counter;
        priv->can.ctrlmode_supported = CAN_CTRLMODE_BERR_REPORTING |
                                       CAN_CTRLMODE_LISTENONLY |
                                       CAN_CTRLMODE_LOOPBACK |
                                       CAN_CTRLMODE_PRESUME_ACK |
                                       CAN_CTRLMODE_3_SAMPLES;
        priv->base = addr;
        priv->clk = clk;
        spin_lock_init(&priv->cmdreg_lock);

        platform_set_drvdata(pdev, dev);
        SET_NETDEV_DEV(dev, &pdev->dev);

        err = register_candev(dev);
        if (err) {
                dev_err(&pdev->dev, "registering %s failed (err=%d)\n",
                        DRV_NAME, err);
                goto exit_free;
        }
        devm_can_led_init(dev);

        dev_info(&pdev->dev, "device registered (base=%p, irq=%d)\n",
                 priv->base, dev->irq);

        return 0;

exit_free:
        free_candev(dev);
exit:
        return err;
}

static struct platform_driver sun4i_can_driver = {
        .driver = {
                .name = DRV_NAME,
                .of_match_table = sun4ican_of_match,
        },
        .probe = sun4ican_probe,
        .remove = sun4ican_remove,
};

module_platform_driver(sun4i_can_driver);

MODULE_AUTHOR("Peter Chen <xingkongcp@gmail.com>");
MODULE_AUTHOR("Gerhard Bertelsmann <info@gerhard-bertelsmann.de>");
MODULE_LICENSE("Dual BSD/GPL");
MODULE_DESCRIPTION("CAN driver for Allwinner SoCs (A10/A20)");