/*
 * CAN bus driver for Bosch C_CAN controller
 *
 * Copyright (C) 2010 ST Microelectronics
 * Bhupesh Sharma <bhupesh.sharma@st.com>
 *
 * Borrowed heavily from the C_CAN driver originally written by:
 * Copyright (C) 2007
 * - Sascha Hauer, Marc Kleine-Budde, Pengutronix <s.hauer@pengutronix.de>
 * - Simon Kallweit, intefo AG <simon.kallweit@intefo.ch>
 *
 * TX and RX NAPI implementation has been borrowed from at91 CAN driver
 * written by:
 * Copyright
 * (C) 2007 by Hans J. Koch <hjk@hansjkoch.de>
 * (C) 2008, 2009 by Marc Kleine-Budde <kernel@pengutronix.de>
 *
 * Bosch C_CAN controller is compliant to CAN protocol version 2.0 part A and B.
 * Bosch C_CAN user manual can be obtained from:
 * http://www.semiconductors.bosch.de/media/en/pdf/ipmodules_1/c_can/
 * users_manual_c_can.pdf
 *
 * This file is licensed under the terms of the GNU General Public
 * License version 2. This program is licensed "as is" without any
 * warranty of any kind, whether express or implied.
 */

#include <linux/kernel.h>
#include <linux/version.h>
#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/delay.h>
#include <linux/netdevice.h>
#include <linux/if_arp.h>
#include <linux/if_ether.h>
#include <linux/list.h>
#include <linux/delay.h>
#include <linux/io.h>

#include <linux/can.h>
#include <linux/can/dev.h>
#include <linux/can/error.h>

#include "c_can.h"

/* control register */
#define CONTROL_TEST            BIT(7)
#define CONTROL_CCE             BIT(6)
#define CONTROL_DISABLE_AR      BIT(5)
#define CONTROL_ENABLE_AR       (0 << 5)
#define CONTROL_EIE             BIT(3)
#define CONTROL_SIE             BIT(2)
#define CONTROL_IE              BIT(1)
#define CONTROL_INIT            BIT(0)

/* test register */
#define TEST_RX                 BIT(7)
#define TEST_TX1                BIT(6)
#define TEST_TX2                BIT(5)
#define TEST_LBACK              BIT(4)
#define TEST_SILENT             BIT(3)
#define TEST_BASIC              BIT(2)

/* status register */
#define STATUS_BOFF             BIT(7)
#define STATUS_EWARN            BIT(6)
#define STATUS_EPASS            BIT(5)
#define STATUS_RXOK             BIT(4)
#define STATUS_TXOK             BIT(3)

/* error counter register */
#define ERR_CNT_TEC_MASK        0xff
#define ERR_CNT_TEC_SHIFT       0
#define ERR_CNT_REC_SHIFT       8
#define ERR_CNT_REC_MASK        (0x7f << ERR_CNT_REC_SHIFT)
#define ERR_CNT_RP_SHIFT        15
#define ERR_CNT_RP_MASK         (0x1 << ERR_CNT_RP_SHIFT)

/* bit-timing register */
#define BTR_BRP_MASK            0x3f
#define BTR_BRP_SHIFT           0
#define BTR_SJW_SHIFT           6
#define BTR_SJW_MASK            (0x3 << BTR_SJW_SHIFT)
#define BTR_TSEG1_SHIFT         8
#define BTR_TSEG1_MASK          (0xf << BTR_TSEG1_SHIFT)
#define BTR_TSEG2_SHIFT         12
#define BTR_TSEG2_MASK          (0x7 << BTR_TSEG2_SHIFT)

/* brp extension register */
#define BRP_EXT_BRPE_MASK       0x0f
#define BRP_EXT_BRPE_SHIFT      0

/* IFx command request */
#define IF_COMR_BUSY            BIT(15)

/* IFx command mask */
#define IF_COMM_WR              BIT(7)
#define IF_COMM_MASK            BIT(6)
#define IF_COMM_ARB             BIT(5)
#define IF_COMM_CONTROL         BIT(4)
#define IF_COMM_CLR_INT_PND     BIT(3)
#define IF_COMM_TXRQST          BIT(2)
#define IF_COMM_DATAA           BIT(1)
#define IF_COMM_DATAB           BIT(0)
#define IF_COMM_ALL             (IF_COMM_MASK | IF_COMM_ARB | \
                                IF_COMM_CONTROL | IF_COMM_TXRQST | \
                                IF_COMM_DATAA | IF_COMM_DATAB)

/* IFx arbitration */
#define IF_ARB_MSGVAL           BIT(15)
#define IF_ARB_MSGXTD           BIT(14)
#define IF_ARB_TRANSMIT         BIT(13)

/* IFx message control */
#define IF_MCONT_NEWDAT         BIT(15)
#define IF_MCONT_MSGLST         BIT(14)
#define IF_MCONT_CLR_MSGLST     (0 << 14)
#define IF_MCONT_INTPND         BIT(13)
#define IF_MCONT_UMASK          BIT(12)
#define IF_MCONT_TXIE           BIT(11)
#define IF_MCONT_RXIE           BIT(10)
#define IF_MCONT_RMTEN          BIT(9)
#define IF_MCONT_TXRQST         BIT(8)
#define IF_MCONT_EOB            BIT(7)
#define IF_MCONT_DLC_MASK       0xf

/*
 * IFx register masks:
 * allow easy operation on 16-bit registers when the
 * argument is 32-bit instead
 */
#define IFX_WRITE_LOW_16BIT(x)  ((x) & 0xFFFF)
#define IFX_WRITE_HIGH_16BIT(x) (((x) & 0xFFFF0000) >> 16)

/* message object split */
#define C_CAN_NO_OF_OBJECTS     32
#define C_CAN_MSG_OBJ_RX_NUM    16
#define C_CAN_MSG_OBJ_TX_NUM    16

#define C_CAN_MSG_OBJ_RX_FIRST  1
#define C_CAN_MSG_OBJ_RX_LAST   (C_CAN_MSG_OBJ_RX_FIRST + \
                                C_CAN_MSG_OBJ_RX_NUM - 1)

#define C_CAN_MSG_OBJ_TX_FIRST  (C_CAN_MSG_OBJ_RX_LAST + 1)
#define C_CAN_MSG_OBJ_TX_LAST   (C_CAN_MSG_OBJ_TX_FIRST + \
                                C_CAN_MSG_OBJ_TX_NUM - 1)

#define C_CAN_MSG_OBJ_RX_SPLIT  9
#define C_CAN_MSG_RX_LOW_LAST   (C_CAN_MSG_OBJ_RX_SPLIT - 1)

#define C_CAN_NEXT_MSG_OBJ_MASK (C_CAN_MSG_OBJ_TX_NUM - 1)
#define RECEIVE_OBJECT_BITS     0x0000ffff

/* status interrupt */
#define STATUS_INTERRUPT        0x8000

/* global interrupt masks */
#define ENABLE_ALL_INTERRUPTS   1
#define DISABLE_ALL_INTERRUPTS  0

/* minimum timeout for checking BUSY status */
#define MIN_TIMEOUT_VALUE       6

/* napi related */
#define C_CAN_NAPI_WEIGHT       C_CAN_MSG_OBJ_RX_NUM

/* c_can lec values */
enum c_can_lec_type {
        LEC_NO_ERROR = 0,
        LEC_STUFF_ERROR,
        LEC_FORM_ERROR,
        LEC_ACK_ERROR,
        LEC_BIT1_ERROR,
        LEC_BIT0_ERROR,
        LEC_CRC_ERROR,
        LEC_UNUSED,
};

/*
 * c_can error types:
 * Bus errors (BUS_OFF, ERROR_WARNING, ERROR_PASSIVE) are supported
 */
enum c_can_bus_error_types {
        C_CAN_NO_ERROR = 0,
        C_CAN_BUS_OFF,
        C_CAN_ERROR_WARNING,
        C_CAN_ERROR_PASSIVE,
};

static struct can_bittiming_const c_can_bittiming_const = {
        .name = KBUILD_MODNAME,
        .tseg1_min = 2,         /* Time segment 1 = prop_seg + phase_seg1 */
        .tseg1_max = 16,
        .tseg2_min = 1,         /* Time segment 2 = phase_seg2 */
        .tseg2_max = 8,
        .sjw_max = 4,
        .brp_min = 1,
        .brp_max = 1024,        /* 6-bit BRP field + 4-bit BRPE field*/
        .brp_inc = 1,
};

static inline int get_tx_next_msg_obj(const struct c_can_priv *priv)
{
        return (priv->tx_next & C_CAN_NEXT_MSG_OBJ_MASK) +
                        C_CAN_MSG_OBJ_TX_FIRST;
}

static inline int get_tx_echo_msg_obj(const struct c_can_priv *priv)
{
        return (priv->tx_echo & C_CAN_NEXT_MSG_OBJ_MASK) +
                        C_CAN_MSG_OBJ_TX_FIRST;
}

static u32 c_can_read_reg32(struct c_can_priv *priv, void *reg)
{
        u32 val = priv->read_reg(priv, reg);
        val |= ((u32) priv->read_reg(priv, reg + 2)) << 16;
        return val;
}

static void c_can_enable_all_interrupts(struct c_can_priv *priv,
                                                int enable)
{
        unsigned int cntrl_save = priv->read_reg(priv,
                                                &priv->regs->control);

        if (enable)
                cntrl_save |= (CONTROL_SIE | CONTROL_EIE | CONTROL_IE);
        else
                cntrl_save &= ~(CONTROL_EIE | CONTROL_IE | CONTROL_SIE);

        priv->write_reg(priv, &priv->regs->control, cntrl_save);
}

static inline int c_can_msg_obj_is_busy(struct c_can_priv *priv, int iface)
{
        int count = MIN_TIMEOUT_VALUE;

        while (count && priv->read_reg(priv,
                                &priv->regs->ifregs[iface].com_req) &
                                IF_COMR_BUSY) {
                count--;
                udelay(1);
        }

        if (!count)
                return 1;

        return 0;
}

static inline void c_can_object_get(struct net_device *dev,
                                        int iface, int objno, int mask)
{
        struct c_can_priv *priv = netdev_priv(dev);

        /*
         * As per specs, after writting the message object number in the
         * IF command request register the transfer b/w interface
         * register and message RAM must be complete in 6 CAN-CLK
         * period.
         */
        priv->write_reg(priv, &priv->regs->ifregs[iface].com_mask,
                        IFX_WRITE_LOW_16BIT(mask));
        priv->write_reg(priv, &priv->regs->ifregs[iface].com_req,
                        IFX_WRITE_LOW_16BIT(objno));

        if (c_can_msg_obj_is_busy(priv, iface))
                netdev_err(dev, "timed out in object get\n");
}

static inline void c_can_object_put(struct net_device *dev,
                                        int iface, int objno, int mask)
{
        struct c_can_priv *priv = netdev_priv(dev);

        /*
         * As per specs, after writting the message object number in the
         * IF command request register the transfer b/w interface
         * register and message RAM must be complete in 6 CAN-CLK
         * period.
         */
        priv->write_reg(priv, &priv->regs->ifregs[iface].com_mask,
                        (IF_COMM_WR | IFX_WRITE_LOW_16BIT(mask)));
        priv->write_reg(priv, &priv->regs->ifregs[iface].com_req,
                        IFX_WRITE_LOW_16BIT(objno));

        if (c_can_msg_obj_is_busy(priv, iface))
                netdev_err(dev, "timed out in object put\n");
}

static void c_can_write_msg_object(struct net_device *dev,
                        int iface, struct can_frame *frame, int objno)
{
        int i;
        u16 flags = 0;
        unsigned int id;
        struct c_can_priv *priv = netdev_priv(dev);

        if (!(frame->can_id & CAN_RTR_FLAG))
                flags |= IF_ARB_TRANSMIT;

        if (frame->can_id & CAN_EFF_FLAG) {
                id = frame->can_id & CAN_EFF_MASK;
                flags |= IF_ARB_MSGXTD;
        } else
                id = ((frame->can_id & CAN_SFF_MASK) << 18);

        flags |= IF_ARB_MSGVAL;

        priv->write_reg(priv, &priv->regs->ifregs[iface].arb1,
                                IFX_WRITE_LOW_16BIT(id));
        priv->write_reg(priv, &priv->regs->ifregs[iface].arb2, flags |
                                IFX_WRITE_HIGH_16BIT(id));

        for (i = 0; i < frame->can_dlc; i += 2) {
                priv->write_reg(priv, &priv->regs->ifregs[iface].data[i / 2],
                                frame->data[i] | (frame->data[i + 1] << 8));
        }

        /* enable interrupt for this message object */
        priv->write_reg(priv, &priv->regs->ifregs[iface].msg_cntrl,
                        IF_MCONT_TXIE | IF_MCONT_TXRQST | IF_MCONT_EOB |
                        frame->can_dlc);
        c_can_object_put(dev, iface, objno, IF_COMM_ALL);
}

static inline void c_can_mark_rx_msg_obj(struct net_device *dev,
                                                int iface, int ctrl_mask,
                                                int obj)
{
        struct c_can_priv *priv = netdev_priv(dev);

        priv->write_reg(priv, &priv->regs->ifregs[iface].msg_cntrl,
                        ctrl_mask & ~(IF_MCONT_MSGLST | IF_MCONT_INTPND));
        c_can_object_put(dev, iface, obj, IF_COMM_CONTROL);

}

static inline void c_can_activate_all_lower_rx_msg_obj(struct net_device *dev,
                                                int iface,
                                                int ctrl_mask)
{
        int i;
        struct c_can_priv *priv = netdev_priv(dev);

        for (i = C_CAN_MSG_OBJ_RX_FIRST; i <= C_CAN_MSG_RX_LOW_LAST; i++) {
                priv->write_reg(priv, &priv->regs->ifregs[iface].msg_cntrl,
                                ctrl_mask & ~(IF_MCONT_MSGLST |
                                        IF_MCONT_INTPND | IF_MCONT_NEWDAT));
                c_can_object_put(dev, iface, i, IF_COMM_CONTROL);
        }
}

static inline void c_can_activate_rx_msg_obj(struct net_device *dev,
                                                int iface, int ctrl_mask,
                                                int obj)
{
        struct c_can_priv *priv = netdev_priv(dev);

        priv->write_reg(priv, &priv->regs->ifregs[iface].msg_cntrl,
                        ctrl_mask & ~(IF_MCONT_MSGLST |
                                IF_MCONT_INTPND | IF_MCONT_NEWDAT));
        c_can_object_put(dev, iface, obj, IF_COMM_CONTROL);
}

static void c_can_handle_lost_msg_obj(struct net_device *dev,
                                        int iface, int objno)
{
        struct c_can_priv *priv = netdev_priv(dev);
        struct net_device_stats *stats = &dev->stats;
        struct sk_buff *skb;
        struct can_frame *frame;

        netdev_err(dev, "msg lost in buffer %d\n", objno);

        c_can_object_get(dev, iface, objno, IF_COMM_ALL & ~IF_COMM_TXRQST);

        priv->write_reg(priv, &priv->regs->ifregs[iface].msg_cntrl,
                        IF_MCONT_CLR_MSGLST);

        c_can_object_put(dev, 0, objno, IF_COMM_CONTROL);

        /* create an error msg */
        skb = alloc_can_err_skb(dev, &frame);
        if (unlikely(!skb))
                return;

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

        netif_receive_skb(skb);
}

static int c_can_read_msg_object(struct net_device *dev, int iface, int ctrl)
{
        u16 flags, data;
        int i;
        unsigned int val;
        struct c_can_priv *priv = netdev_priv(dev);
        struct net_device_stats *stats = &dev->stats;
        struct sk_buff *skb;
        struct can_frame *frame;

        skb = alloc_can_skb(dev, &frame);
        if (!skb) {
                stats->rx_dropped++;
                return -ENOMEM;
        }

        frame->can_dlc = get_can_dlc(ctrl & 0x0F);

        flags = priv->read_reg(priv, &priv->regs->ifregs[iface].arb2);
        val = priv->read_reg(priv, &priv->regs->ifregs[iface].arb1) |
                (flags << 16);

        if (flags & IF_ARB_MSGXTD)
                frame->can_id = (val & CAN_EFF_MASK) | CAN_EFF_FLAG;
        else
                frame->can_id = (val >> 18) & CAN_SFF_MASK;

        if (flags & IF_ARB_TRANSMIT)
                frame->can_id |= CAN_RTR_FLAG;
        else {
                for (i = 0; i < frame->can_dlc; i += 2) {
                        data = priv->read_reg(priv,
                                &priv->regs->ifregs[iface].data[i / 2]);
                        frame->data[i] = data;
                        frame->data[i + 1] = data >> 8;
                }
        }

        netif_receive_skb(skb);

        stats->rx_packets++;
        stats->rx_bytes += frame->can_dlc;

        return 0;
}

static void c_can_setup_receive_object(struct net_device *dev, int iface,
                                        int objno, unsigned int mask,
                                        unsigned int id, unsigned int mcont)
{
        struct c_can_priv *priv = netdev_priv(dev);

        priv->write_reg(priv, &priv->regs->ifregs[iface].mask1,
                        IFX_WRITE_LOW_16BIT(mask));
        priv->write_reg(priv, &priv->regs->ifregs[iface].mask2,
                        IFX_WRITE_HIGH_16BIT(mask));

        priv->write_reg(priv, &priv->regs->ifregs[iface].arb1,
                        IFX_WRITE_LOW_16BIT(id));
        priv->write_reg(priv, &priv->regs->ifregs[iface].arb2,
                        (IF_ARB_MSGVAL | IFX_WRITE_HIGH_16BIT(id)));

        priv->write_reg(priv, &priv->regs->ifregs[iface].msg_cntrl, mcont);
        c_can_object_put(dev, iface, objno, IF_COMM_ALL & ~IF_COMM_TXRQST);

        netdev_dbg(dev, "obj no:%d, msgval:0x%08x\n", objno,
                        c_can_read_reg32(priv, &priv->regs->msgval1));
}

static void c_can_inval_msg_object(struct net_device *dev, int iface, int objno)
{
        struct c_can_priv *priv = netdev_priv(dev);

        priv->write_reg(priv, &priv->regs->ifregs[iface].arb1, 0);
        priv->write_reg(priv, &priv->regs->ifregs[iface].arb2, 0);
        priv->write_reg(priv, &priv->regs->ifregs[iface].msg_cntrl, 0);

        c_can_object_put(dev, iface, objno, IF_COMM_ARB | IF_COMM_CONTROL);

        netdev_dbg(dev, "obj no:%d, msgval:0x%08x\n", objno,
                        c_can_read_reg32(priv, &priv->regs->msgval1));
}

static inline int c_can_is_next_tx_obj_busy(struct c_can_priv *priv, int objno)
{
        int val = c_can_read_reg32(priv, &priv->regs->txrqst1);

        /*
         * as transmission request register's bit n-1 corresponds to
         * message object n, we need to handle the same properly.
         */
        if (val & (1 << (objno - 1)))
                return 1;

        return 0;
}

static netdev_tx_t c_can_start_xmit(struct sk_buff *skb,
                                        struct net_device *dev)
{
        u32 msg_obj_no;
        struct c_can_priv *priv = netdev_priv(dev);
        struct can_frame *frame = (struct can_frame *)skb->data;

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

        msg_obj_no = get_tx_next_msg_obj(priv);

        /* prepare message object for transmission */
        c_can_write_msg_object(dev, 0, frame, msg_obj_no);
        can_put_echo_skb(skb, dev, msg_obj_no - C_CAN_MSG_OBJ_TX_FIRST);

        /*
         * we have to stop the queue in case of a wrap around or
         * if the next TX message object is still in use
         */
        priv->tx_next++;
        if (c_can_is_next_tx_obj_busy(priv, get_tx_next_msg_obj(priv)) ||
                        (priv->tx_next & C_CAN_NEXT_MSG_OBJ_MASK) == 0)
                netif_stop_queue(dev);

        return NETDEV_TX_OK;
}

static int c_can_set_bittiming(struct net_device *dev)
{
        unsigned int reg_btr, reg_brpe, ctrl_save;
        u8 brp, brpe, sjw, tseg1, tseg2;
        u32 ten_bit_brp;
        struct c_can_priv *priv = netdev_priv(dev);
        const struct can_bittiming *bt = &priv->can.bittiming;

        /* c_can provides a 6-bit brp and 4-bit brpe fields */
        ten_bit_brp = bt->brp - 1;
        brp = ten_bit_brp & BTR_BRP_MASK;
        brpe = ten_bit_brp >> 6;

        sjw = bt->sjw - 1;
        tseg1 = bt->prop_seg + bt->phase_seg1 - 1;
        tseg2 = bt->phase_seg2 - 1;
        reg_btr = brp | (sjw << BTR_SJW_SHIFT) | (tseg1 << BTR_TSEG1_SHIFT) |
                        (tseg2 << BTR_TSEG2_SHIFT);
        reg_brpe = brpe & BRP_EXT_BRPE_MASK;

        netdev_info(dev,
                "setting BTR=%04x BRPE=%04x\n", reg_btr, reg_brpe);

        ctrl_save = priv->read_reg(priv, &priv->regs->control);
        priv->write_reg(priv, &priv->regs->control,
                        ctrl_save | CONTROL_CCE | CONTROL_INIT);
        priv->write_reg(priv, &priv->regs->btr, reg_btr);
        priv->write_reg(priv, &priv->regs->brp_ext, reg_brpe);
        priv->write_reg(priv, &priv->regs->control, ctrl_save);

        return 0;
}

/*
 * Configure C_CAN message objects for Tx and Rx purposes:
 * C_CAN provides a total of 32 message objects that can be configured
 * either for Tx or Rx purposes. Here the first 16 message objects are used as
 * a reception FIFO. The end of reception FIFO is signified by the EoB bit
 * being SET. The remaining 16 message objects are kept aside for Tx purposes.
 * See user guide document for further details on configuring message
 * objects.
 */
static void c_can_configure_msg_objects(struct net_device *dev)
{
        int i;

        /* first invalidate all message objects */
        for (i = C_CAN_MSG_OBJ_RX_FIRST; i <= C_CAN_NO_OF_OBJECTS; i++)
                c_can_inval_msg_object(dev, 0, i);

        /* setup receive message objects */
        for (i = C_CAN_MSG_OBJ_RX_FIRST; i < C_CAN_MSG_OBJ_RX_LAST; i++)
                c_can_setup_receive_object(dev, 0, i, 0, 0,
                        (IF_MCONT_RXIE | IF_MCONT_UMASK) & ~IF_MCONT_EOB);

        c_can_setup_receive_object(dev, 0, C_CAN_MSG_OBJ_RX_LAST, 0, 0,
                        IF_MCONT_EOB | IF_MCONT_RXIE | IF_MCONT_UMASK);
}

/*
 * Configure C_CAN chip:
 * - enable/disable auto-retransmission
 * - set operating mode
 * - configure message objects
 */
static void c_can_chip_config(struct net_device *dev)
{
        struct c_can_priv *priv = netdev_priv(dev);

        /* enable automatic retransmission */
        priv->write_reg(priv, &priv->regs->control,
                        CONTROL_ENABLE_AR);

        if (priv->can.ctrlmode & (CAN_CTRLMODE_LISTENONLY &
                                        CAN_CTRLMODE_LOOPBACK)) {
                /* loopback + silent mode : useful for hot self-test */
                priv->write_reg(priv, &priv->regs->control, CONTROL_EIE |
                                CONTROL_SIE | CONTROL_IE | CONTROL_TEST);
                priv->write_reg(priv, &priv->regs->test,
                                TEST_LBACK | TEST_SILENT);
        } else if (priv->can.ctrlmode & CAN_CTRLMODE_LOOPBACK) {
                /* loopback mode : useful for self-test function */
                priv->write_reg(priv, &priv->regs->control, CONTROL_EIE |
                                CONTROL_SIE | CONTROL_IE | CONTROL_TEST);
                priv->write_reg(priv, &priv->regs->test, TEST_LBACK);
        } else if (priv->can.ctrlmode & CAN_CTRLMODE_LISTENONLY) {
                /* silent mode : bus-monitoring mode */
                priv->write_reg(priv, &priv->regs->control, CONTROL_EIE |
                                CONTROL_SIE | CONTROL_IE | CONTROL_TEST);
                priv->write_reg(priv, &priv->regs->test, TEST_SILENT);
        } else
                /* normal mode*/
                priv->write_reg(priv, &priv->regs->control,
                                CONTROL_EIE | CONTROL_SIE | CONTROL_IE);

        /* configure message objects */
        c_can_configure_msg_objects(dev);

        /* set a `lec` value so that we can check for updates later */
        priv->write_reg(priv, &priv->regs->status, LEC_UNUSED);

        /* set bittiming params */
        c_can_set_bittiming(dev);
}

static void c_can_start(struct net_device *dev)
{
        struct c_can_priv *priv = netdev_priv(dev);

        /* basic c_can configuration */
        c_can_chip_config(dev);

        priv->can.state = CAN_STATE_ERROR_ACTIVE;

        /* reset tx helper pointers */
        priv->tx_next = priv->tx_echo = 0;

        /* enable status change, error and module interrupts */
        c_can_enable_all_interrupts(priv, ENABLE_ALL_INTERRUPTS);
}

static void c_can_stop(struct net_device *dev)
{
        struct c_can_priv *priv = netdev_priv(dev);

        /* disable all interrupts */
        c_can_enable_all_interrupts(priv, DISABLE_ALL_INTERRUPTS);

        /* set the state as STOPPED */
        priv->can.state = CAN_STATE_STOPPED;
}

static int c_can_set_mode(struct net_device *dev, enum can_mode mode)
{
        switch (mode) {
        case CAN_MODE_START:
                c_can_start(dev);
                netif_wake_queue(dev);
                break;
        default:
                return -EOPNOTSUPP;
        }

        return 0;
}

static int c_can_get_berr_counter(const struct net_device *dev,
                                        struct can_berr_counter *bec)
{
        unsigned int reg_err_counter;
        struct c_can_priv *priv = netdev_priv(dev);

        reg_err_counter = priv->read_reg(priv, &priv->regs->err_cnt);
        bec->rxerr = (reg_err_counter & ERR_CNT_REC_MASK) >>
                                ERR_CNT_REC_SHIFT;
        bec->txerr = reg_err_counter & ERR_CNT_TEC_MASK;

        return 0;
}

/*
 * theory of operation:
 *
 * priv->tx_echo holds the number of the oldest can_frame put for
 * transmission into the hardware, but not yet ACKed by the CAN tx
 * complete IRQ.
 *
 * We iterate from priv->tx_echo to priv->tx_next and check if the
 * packet has been transmitted, echo it back to the CAN framework.
 * If we discover a not yet transmitted package, stop looking for more.
 */
static void c_can_do_tx(struct net_device *dev)
{
        u32 val;
        u32 msg_obj_no;
        struct c_can_priv *priv = netdev_priv(dev);
        struct net_device_stats *stats = &dev->stats;

        for (/* nix */; (priv->tx_next - priv->tx_echo) > 0; priv->tx_echo++) {
                msg_obj_no = get_tx_echo_msg_obj(priv);
                val = c_can_read_reg32(priv, &priv->regs->txrqst1);
                if (!(val & (1 << msg_obj_no))) {
                        can_get_echo_skb(dev,
                                        msg_obj_no - C_CAN_MSG_OBJ_TX_FIRST);
                        stats->tx_bytes += priv->read_reg(priv,
                                        &priv->regs->ifregs[0].msg_cntrl)
                                        & IF_MCONT_DLC_MASK;
                        stats->tx_packets++;
                        c_can_inval_msg_object(dev, 0, msg_obj_no);
                }
        }

        /* restart queue if wrap-up or if queue stalled on last pkt */
        if (((priv->tx_next & C_CAN_NEXT_MSG_OBJ_MASK) != 0) ||
                        ((priv->tx_echo & C_CAN_NEXT_MSG_OBJ_MASK) == 0))
                netif_wake_queue(dev);
}

/*
 * theory of operation:
 *
 * c_can core saves a received CAN message into the first free message
 * object it finds free (starting with the lowest). Bits NEWDAT and
 * INTPND are set for this message object indicating that a new message
 * has arrived. To work-around this issue, we keep two groups of message
 * objects whose partitioning is defined by C_CAN_MSG_OBJ_RX_SPLIT.
 *
 * To ensure in-order frame reception we use the following
 * approach while re-activating a message object to receive further
 * frames:
 * - if the current message object number is lower than
 *   C_CAN_MSG_RX_LOW_LAST, do not clear the NEWDAT bit while clearing
 *   the INTPND bit.
 * - if the current message object number is equal to
 *   C_CAN_MSG_RX_LOW_LAST then clear the NEWDAT bit of all lower
 *   receive message objects.
 * - if the current message object number is greater than
 *   C_CAN_MSG_RX_LOW_LAST then clear the NEWDAT bit of
 *   only this message object.
 */
static int c_can_do_rx_poll(struct net_device *dev, int quota)
{
        u32 num_rx_pkts = 0;
        unsigned int msg_obj, msg_ctrl_save;
        struct c_can_priv *priv = netdev_priv(dev);
        u32 val = c_can_read_reg32(priv, &priv->regs->intpnd1);

        for (msg_obj = C_CAN_MSG_OBJ_RX_FIRST;
                        msg_obj <= C_CAN_MSG_OBJ_RX_LAST && quota > 0;
                        val = c_can_read_reg32(priv, &priv->regs->intpnd1),
                        msg_obj++) {
                /*
                 * as interrupt pending register's bit n-1 corresponds to
                 * message object n, we need to handle the same properly.
                 */
                if (val & (1 << (msg_obj - 1))) {
                        c_can_object_get(dev, 0, msg_obj, IF_COMM_ALL &
                                        ~IF_COMM_TXRQST);
                        msg_ctrl_save = priv->read_reg(priv,
                                        &priv->regs->ifregs[0].msg_cntrl);

                        if (msg_ctrl_save & IF_MCONT_EOB)
                                return num_rx_pkts;

                        if (msg_ctrl_save & IF_MCONT_MSGLST) {
                                c_can_handle_lost_msg_obj(dev, 0, msg_obj);
                                num_rx_pkts++;
                                quota--;
                                continue;
                        }

                        if (!(msg_ctrl_save & IF_MCONT_NEWDAT))
                                continue;

                        /* read the data from the message object */
                        c_can_read_msg_object(dev, 0, msg_ctrl_save);

                        if (msg_obj < C_CAN_MSG_RX_LOW_LAST)
                                c_can_mark_rx_msg_obj(dev, 0,
                                                msg_ctrl_save, msg_obj);
                        else if (msg_obj > C_CAN_MSG_RX_LOW_LAST)
                                /* activate this msg obj */
                                c_can_activate_rx_msg_obj(dev, 0,
                                                msg_ctrl_save, msg_obj);
                        else if (msg_obj == C_CAN_MSG_RX_LOW_LAST)
                                /* activate all lower message objects */
                                c_can_activate_all_lower_rx_msg_obj(dev,
                                                0, msg_ctrl_save);

                        num_rx_pkts++;
                        quota--;
                }
        }

        return num_rx_pkts;
}

static inline int c_can_has_and_handle_berr(struct c_can_priv *priv)
{
        return (priv->can.ctrlmode & CAN_CTRLMODE_BERR_REPORTING) &&
                (priv->current_status & LEC_UNUSED);
}

static int c_can_handle_state_change(struct net_device *dev,
                                enum c_can_bus_error_types error_type)
{
        unsigned int reg_err_counter;
        unsigned int rx_err_passive;
        struct c_can_priv *priv = netdev_priv(dev);
        struct net_device_stats *stats = &dev->stats;
        struct can_frame *cf;
        struct sk_buff *skb;
        struct can_berr_counter bec;

        /* propagate the error condition to the CAN stack */
        skb = alloc_can_err_skb(dev, &cf);
        if (unlikely(!skb))
                return 0;

        c_can_get_berr_counter(dev, &bec);
        reg_err_counter = priv->read_reg(priv, &priv->regs->err_cnt);
        rx_err_passive = (reg_err_counter & ERR_CNT_RP_MASK) >>
                                ERR_CNT_RP_SHIFT;

        switch (error_type) {
        case C_CAN_ERROR_WARNING:
                /* error warning state */
                priv->can.can_stats.error_warning++;
                priv->can.state = CAN_STATE_ERROR_WARNING;
                cf->can_id |= CAN_ERR_CRTL;
                cf->data[1] = (bec.txerr > bec.rxerr) ?
                        CAN_ERR_CRTL_TX_WARNING :
                        CAN_ERR_CRTL_RX_WARNING;
                cf->data[6] = bec.txerr;
                cf->data[7] = bec.rxerr;

                break;
        case C_CAN_ERROR_PASSIVE:
                /* error passive state */
                priv->can.can_stats.error_passive++;
                priv->can.state = CAN_STATE_ERROR_PASSIVE;
                cf->can_id |= CAN_ERR_CRTL;
                if (rx_err_passive)
                        cf->data[1] |= CAN_ERR_CRTL_RX_PASSIVE;
                if (bec.txerr > 127)
                        cf->data[1] |= CAN_ERR_CRTL_TX_PASSIVE;

                cf->data[6] = bec.txerr;
                cf->data[7] = bec.rxerr;
                break;
        case C_CAN_BUS_OFF:
                /* bus-off state */
                priv->can.state = CAN_STATE_BUS_OFF;
                cf->can_id |= CAN_ERR_BUSOFF;
                /*
                 * disable all interrupts in bus-off mode to ensure that
                 * the CPU is not hogged down
                 */
                c_can_enable_all_interrupts(priv, DISABLE_ALL_INTERRUPTS);
                can_bus_off(dev);
                break;
        default:
                break;
        }

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

        return 1;
}

static int c_can_handle_bus_err(struct net_device *dev,
                                enum c_can_lec_type lec_type)
{
        struct c_can_priv *priv = netdev_priv(dev);
        struct net_device_stats *stats = &dev->stats;
        struct can_frame *cf;
        struct sk_buff *skb;

        /*
         * early exit if no lec update or no error.
         * no lec update means that no CAN bus event has been detected
         * since CPU wrote 0x7 value to status reg.
         */
        if (lec_type == LEC_UNUSED || lec_type == LEC_NO_ERROR)
                return 0;

        /* propagate the error condition to the CAN stack */
        skb = alloc_can_err_skb(dev, &cf);
        if (unlikely(!skb))
                return 0;

        /*
         * check for 'last error code' which tells us the
         * type of the last error to occur on the CAN bus
         */

        /* common for all type of bus errors */
        priv->can.can_stats.bus_error++;
        stats->rx_errors++;
        cf->can_id |= CAN_ERR_PROT | CAN_ERR_BUSERROR;
        cf->data[2] |= CAN_ERR_PROT_UNSPEC;

        switch (lec_type) {
        case LEC_STUFF_ERROR:
                netdev_dbg(dev, "stuff error\n");
                cf->data[2] |= CAN_ERR_PROT_STUFF;
                break;
        case LEC_FORM_ERROR:
                netdev_dbg(dev, "form error\n");
                cf->data[2] |= CAN_ERR_PROT_FORM;
                break;
        case LEC_ACK_ERROR:
                netdev_dbg(dev, "ack error\n");
                cf->data[2] |= (CAN_ERR_PROT_LOC_ACK |
                                CAN_ERR_PROT_LOC_ACK_DEL);
                break;
        case LEC_BIT1_ERROR:
                netdev_dbg(dev, "bit1 error\n");
                cf->data[2] |= CAN_ERR_PROT_BIT1;
                break;
        case LEC_BIT0_ERROR:
                netdev_dbg(dev, "bit0 error\n");
                cf->data[2] |= CAN_ERR_PROT_BIT0;
                break;
        case LEC_CRC_ERROR:
                netdev_dbg(dev, "CRC error\n");
                cf->data[2] |= (CAN_ERR_PROT_LOC_CRC_SEQ |
                                CAN_ERR_PROT_LOC_CRC_DEL);
                break;
        default:
                break;
        }

        /* set a `lec` value so that we can check for updates later */
        priv->write_reg(priv, &priv->regs->status, LEC_UNUSED);

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

        return 1;
}

static int c_can_poll(struct napi_struct *napi, int quota)
{
        u16 irqstatus;
        int lec_type = 0;
        int work_done = 0;
        struct net_device *dev = napi->dev;
        struct c_can_priv *priv = netdev_priv(dev);

        irqstatus = priv->read_reg(priv, &priv->regs->interrupt);
        if (!irqstatus)
                goto end;

        /* status events have the highest priority */
        if (irqstatus == STATUS_INTERRUPT) {
                priv->current_status = priv->read_reg(priv,
                                        &priv->regs->status);

                /* handle Tx/Rx events */
                if (priv->current_status & STATUS_TXOK)
                        priv->write_reg(priv, &priv->regs->status,
                                        priv->current_status & ~STATUS_TXOK);

                if (priv->current_status & STATUS_RXOK)
                        priv->write_reg(priv, &priv->regs->status,
                                        priv->current_status & ~STATUS_RXOK);

                /* handle state changes */
                if ((priv->current_status & STATUS_EWARN) &&
                                (!(priv->last_status & STATUS_EWARN))) {
                        netdev_dbg(dev, "entered error warning state\n");
                        work_done += c_can_handle_state_change(dev,
                                                C_CAN_ERROR_WARNING);
                }
                if ((priv->current_status & STATUS_EPASS) &&
                                (!(priv->last_status & STATUS_EPASS))) {
                        netdev_dbg(dev, "entered error passive state\n");
                        work_done += c_can_handle_state_change(dev,
                                                C_CAN_ERROR_PASSIVE);
                }
                if ((priv->current_status & STATUS_BOFF) &&
                                (!(priv->last_status & STATUS_BOFF))) {
                        netdev_dbg(dev, "entered bus off state\n");
                        work_done += c_can_handle_state_change(dev,
                                                C_CAN_BUS_OFF);
                }

                /* handle bus recovery events */
                if ((!(priv->current_status & STATUS_BOFF)) &&
                                (priv->last_status & STATUS_BOFF)) {
                        netdev_dbg(dev, "left bus off state\n");
                        priv->can.state = CAN_STATE_ERROR_ACTIVE;
                }
                if ((!(priv->current_status & STATUS_EPASS)) &&
                                (priv->last_status & STATUS_EPASS)) {

                        netdev_dbg(dev, "left error passive state\n");
                        priv->can.state = CAN_STATE_ERROR_ACTIVE;
                }

                priv->last_status = priv->current_status;

                /* handle lec errors on the bus */
                lec_type = c_can_has_and_handle_berr(priv);
                if (lec_type)
                        work_done += c_can_handle_bus_err(dev, lec_type);
        } else if ((irqstatus >= C_CAN_MSG_OBJ_RX_FIRST) &&
                        (irqstatus <= C_CAN_MSG_OBJ_RX_LAST)) {
                /* handle events corresponding to receive message objects */
                work_done += c_can_do_rx_poll(dev, (quota - work_done));
        } else if ((irqstatus >= C_CAN_MSG_OBJ_TX_FIRST) &&
                        (irqstatus <= C_CAN_MSG_OBJ_TX_LAST)) {
                /* handle events corresponding to transmit message objects */
                c_can_do_tx(dev);
        }

end:
        if (work_done < quota) {
                napi_complete(napi);
                /* enable all IRQs */
                c_can_enable_all_interrupts(priv, ENABLE_ALL_INTERRUPTS);
        }

        return work_done;
}

static irqreturn_t c_can_isr(int irq, void *dev_id)
{
        u16 irqstatus;
        struct net_device *dev = (struct net_device *)dev_id;
        struct c_can_priv *priv = netdev_priv(dev);

        irqstatus = priv->read_reg(priv, &priv->regs->interrupt);
        if (!irqstatus)
                return IRQ_NONE;

        /* disable all interrupts and schedule the NAPI */
        c_can_enable_all_interrupts(priv, DISABLE_ALL_INTERRUPTS);
        napi_schedule(&priv->napi);

        return IRQ_HANDLED;
}

static int c_can_open(struct net_device *dev)
{
        int err;
        struct c_can_priv *priv = netdev_priv(dev);

        /* open the can device */
        err = open_candev(dev);
        if (err) {
                netdev_err(dev, "failed to open can device\n");
                return err;
        }

        /* register interrupt handler */
        err = request_irq(dev->irq, &c_can_isr, IRQF_SHARED, dev->name,
                                dev);
        if (err < 0) {
                netdev_err(dev, "failed to request interrupt\n");
                goto exit_irq_fail;
        }

        /* start the c_can controller */
        c_can_start(dev);

        napi_enable(&priv->napi);
        netif_start_queue(dev);

        return 0;

exit_irq_fail:
        close_candev(dev);
        return err;
}

static int c_can_close(struct net_device *dev)
{
        struct c_can_priv *priv = netdev_priv(dev);

        netif_stop_queue(dev);
        napi_disable(&priv->napi);
        c_can_stop(dev);
        free_irq(dev->irq, dev);
        close_candev(dev);

        return 0;
}

struct net_device *alloc_c_can_dev(void)
{
        struct net_device *dev;
        struct c_can_priv *priv;

        dev = alloc_candev(sizeof(struct c_can_priv), C_CAN_MSG_OBJ_TX_NUM);
        if (!dev)
                return NULL;

        priv = netdev_priv(dev);
        netif_napi_add(dev, &priv->napi, c_can_poll, C_CAN_NAPI_WEIGHT);

        priv->dev = dev;
        priv->can.bittiming_const = &c_can_bittiming_const;
        priv->can.do_set_mode = c_can_set_mode;
        priv->can.do_get_berr_counter = c_can_get_berr_counter;
        priv->can.ctrlmode_supported = CAN_CTRLMODE_LOOPBACK |
                                        CAN_CTRLMODE_LISTENONLY |
                                        CAN_CTRLMODE_BERR_REPORTING;

        return dev;
}
EXPORT_SYMBOL_GPL(alloc_c_can_dev);

void free_c_can_dev(struct net_device *dev)
{
        free_candev(dev);
}
EXPORT_SYMBOL_GPL(free_c_can_dev);

static const struct net_device_ops c_can_netdev_ops = {
        .ndo_open = c_can_open,
        .ndo_stop = c_can_close,
        .ndo_start_xmit = c_can_start_xmit,
};

int register_c_can_dev(struct net_device *dev)
{
        dev->flags |= IFF_ECHO; /* we support local echo */
        dev->netdev_ops = &c_can_netdev_ops;

        return register_candev(dev);
}
EXPORT_SYMBOL_GPL(register_c_can_dev);

void unregister_c_can_dev(struct net_device *dev)
{
        struct c_can_priv *priv = netdev_priv(dev);

        /* disable all interrupts */
        c_can_enable_all_interrupts(priv, DISABLE_ALL_INTERRUPTS);

        unregister_candev(dev);
}
EXPORT_SYMBOL_GPL(unregister_c_can_dev);

MODULE_AUTHOR("Bhupesh Sharma <bhupesh.sharma@st.com>");
MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("CAN bus driver for Bosch C_CAN controller");