/*
 * QEMU model of the Xilinx ZynqMP CAN controller.
 * This implementation is based on the following datasheet:
 * https://www.xilinx.com/support/documentation/user_guides/ug1085-zynq-ultrascale-trm.pdf
 *
 * Copyright (c) 2020 Xilinx Inc.
 *
 * Written-by: Vikram Garhwal<fnu.vikram@xilinx.com>
 *
 * Based on QEMU CAN Device emulation implemented by Jin Yang, Deniz Eren and
 * Pavel Pisa
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

#include "qemu/osdep.h"
#include "hw/sysbus.h"
#include "hw/register.h"
#include "hw/irq.h"
#include "qapi/error.h"
#include "qemu/bitops.h"
#include "qemu/log.h"
#include "qemu/cutils.h"
#include "migration/vmstate.h"
#include "hw/qdev-properties.h"
#include "net/can_emu.h"
#include "net/can_host.h"
#include "qemu/event_notifier.h"
#include "qom/object_interfaces.h"
#include "hw/net/xlnx-zynqmp-can.h"
#include "trace.h"

#ifndef XLNX_ZYNQMP_CAN_ERR_DEBUG
#define XLNX_ZYNQMP_CAN_ERR_DEBUG 0
#endif

#define MAX_DLC            8
#undef ERROR

REG32(SOFTWARE_RESET_REGISTER, 0x0)
    FIELD(SOFTWARE_RESET_REGISTER, CEN, 1, 1)
    FIELD(SOFTWARE_RESET_REGISTER, SRST, 0, 1)
REG32(MODE_SELECT_REGISTER, 0x4)
    FIELD(MODE_SELECT_REGISTER, SNOOP, 2, 1)
    FIELD(MODE_SELECT_REGISTER, LBACK, 1, 1)
    FIELD(MODE_SELECT_REGISTER, SLEEP, 0, 1)
REG32(ARBITRATION_PHASE_BAUD_RATE_PRESCALER_REGISTER, 0x8)
    FIELD(ARBITRATION_PHASE_BAUD_RATE_PRESCALER_REGISTER, BRP, 0, 8)
REG32(ARBITRATION_PHASE_BIT_TIMING_REGISTER, 0xc)
    FIELD(ARBITRATION_PHASE_BIT_TIMING_REGISTER, SJW, 7, 2)
    FIELD(ARBITRATION_PHASE_BIT_TIMING_REGISTER, TS2, 4, 3)
    FIELD(ARBITRATION_PHASE_BIT_TIMING_REGISTER, TS1, 0, 4)
REG32(ERROR_COUNTER_REGISTER, 0x10)
    FIELD(ERROR_COUNTER_REGISTER, REC, 8, 8)
    FIELD(ERROR_COUNTER_REGISTER, TEC, 0, 8)
REG32(ERROR_STATUS_REGISTER, 0x14)
    FIELD(ERROR_STATUS_REGISTER, ACKER, 4, 1)
    FIELD(ERROR_STATUS_REGISTER, BERR, 3, 1)
    FIELD(ERROR_STATUS_REGISTER, STER, 2, 1)
    FIELD(ERROR_STATUS_REGISTER, FMER, 1, 1)
    FIELD(ERROR_STATUS_REGISTER, CRCER, 0, 1)
REG32(STATUS_REGISTER, 0x18)
    FIELD(STATUS_REGISTER, SNOOP, 12, 1)
    FIELD(STATUS_REGISTER, ACFBSY, 11, 1)
    FIELD(STATUS_REGISTER, TXFLL, 10, 1)
    FIELD(STATUS_REGISTER, TXBFLL, 9, 1)
    FIELD(STATUS_REGISTER, ESTAT, 7, 2)
    FIELD(STATUS_REGISTER, ERRWRN, 6, 1)
    FIELD(STATUS_REGISTER, BBSY, 5, 1)
    FIELD(STATUS_REGISTER, BIDLE, 4, 1)
    FIELD(STATUS_REGISTER, NORMAL, 3, 1)
    FIELD(STATUS_REGISTER, SLEEP, 2, 1)
    FIELD(STATUS_REGISTER, LBACK, 1, 1)
    FIELD(STATUS_REGISTER, CONFIG, 0, 1)
REG32(INTERRUPT_STATUS_REGISTER, 0x1c)
    FIELD(INTERRUPT_STATUS_REGISTER, TXFEMP, 14, 1)
    FIELD(INTERRUPT_STATUS_REGISTER, TXFWMEMP, 13, 1)
    FIELD(INTERRUPT_STATUS_REGISTER, RXFWMFLL, 12, 1)
    FIELD(INTERRUPT_STATUS_REGISTER, WKUP, 11, 1)
    FIELD(INTERRUPT_STATUS_REGISTER, SLP, 10, 1)
    FIELD(INTERRUPT_STATUS_REGISTER, BSOFF, 9, 1)
    FIELD(INTERRUPT_STATUS_REGISTER, ERROR, 8, 1)
    FIELD(INTERRUPT_STATUS_REGISTER, RXNEMP, 7, 1)
    FIELD(INTERRUPT_STATUS_REGISTER, RXOFLW, 6, 1)
    FIELD(INTERRUPT_STATUS_REGISTER, RXUFLW, 5, 1)
    FIELD(INTERRUPT_STATUS_REGISTER, RXOK, 4, 1)
    FIELD(INTERRUPT_STATUS_REGISTER, TXBFLL, 3, 1)
    FIELD(INTERRUPT_STATUS_REGISTER, TXFLL, 2, 1)
    FIELD(INTERRUPT_STATUS_REGISTER, TXOK, 1, 1)
    FIELD(INTERRUPT_STATUS_REGISTER, ARBLST, 0, 1)
REG32(INTERRUPT_ENABLE_REGISTER, 0x20)
    FIELD(INTERRUPT_ENABLE_REGISTER, ETXFEMP, 14, 1)
    FIELD(INTERRUPT_ENABLE_REGISTER, ETXFWMEMP, 13, 1)
    FIELD(INTERRUPT_ENABLE_REGISTER, ERXFWMFLL, 12, 1)
    FIELD(INTERRUPT_ENABLE_REGISTER, EWKUP, 11, 1)
    FIELD(INTERRUPT_ENABLE_REGISTER, ESLP, 10, 1)
    FIELD(INTERRUPT_ENABLE_REGISTER, EBSOFF, 9, 1)
    FIELD(INTERRUPT_ENABLE_REGISTER, EERROR, 8, 1)
    FIELD(INTERRUPT_ENABLE_REGISTER, ERXNEMP, 7, 1)
    FIELD(INTERRUPT_ENABLE_REGISTER, ERXOFLW, 6, 1)
    FIELD(INTERRUPT_ENABLE_REGISTER, ERXUFLW, 5, 1)
    FIELD(INTERRUPT_ENABLE_REGISTER, ERXOK, 4, 1)
    FIELD(INTERRUPT_ENABLE_REGISTER, ETXBFLL, 3, 1)
    FIELD(INTERRUPT_ENABLE_REGISTER, ETXFLL, 2, 1)
    FIELD(INTERRUPT_ENABLE_REGISTER, ETXOK, 1, 1)
    FIELD(INTERRUPT_ENABLE_REGISTER, EARBLST, 0, 1)
REG32(INTERRUPT_CLEAR_REGISTER, 0x24)
    FIELD(INTERRUPT_CLEAR_REGISTER, CTXFEMP, 14, 1)
    FIELD(INTERRUPT_CLEAR_REGISTER, CTXFWMEMP, 13, 1)
    FIELD(INTERRUPT_CLEAR_REGISTER, CRXFWMFLL, 12, 1)
    FIELD(INTERRUPT_CLEAR_REGISTER, CWKUP, 11, 1)
    FIELD(INTERRUPT_CLEAR_REGISTER, CSLP, 10, 1)
    FIELD(INTERRUPT_CLEAR_REGISTER, CBSOFF, 9, 1)
    FIELD(INTERRUPT_CLEAR_REGISTER, CERROR, 8, 1)
    FIELD(INTERRUPT_CLEAR_REGISTER, CRXNEMP, 7, 1)
    FIELD(INTERRUPT_CLEAR_REGISTER, CRXOFLW, 6, 1)
    FIELD(INTERRUPT_CLEAR_REGISTER, CRXUFLW, 5, 1)
    FIELD(INTERRUPT_CLEAR_REGISTER, CRXOK, 4, 1)
    FIELD(INTERRUPT_CLEAR_REGISTER, CTXBFLL, 3, 1)
    FIELD(INTERRUPT_CLEAR_REGISTER, CTXFLL, 2, 1)
    FIELD(INTERRUPT_CLEAR_REGISTER, CTXOK, 1, 1)
    FIELD(INTERRUPT_CLEAR_REGISTER, CARBLST, 0, 1)
REG32(TIMESTAMP_REGISTER, 0x28)
    FIELD(TIMESTAMP_REGISTER, CTS, 0, 1)
REG32(WIR, 0x2c)
    FIELD(WIR, EW, 8, 8)
    FIELD(WIR, FW, 0, 8)
REG32(TXFIFO_ID, 0x30)
    FIELD(TXFIFO_ID, IDH, 21, 11)
    FIELD(TXFIFO_ID, SRRRTR, 20, 1)
    FIELD(TXFIFO_ID, IDE, 19, 1)
    FIELD(TXFIFO_ID, IDL, 1, 18)
    FIELD(TXFIFO_ID, RTR, 0, 1)
REG32(TXFIFO_DLC, 0x34)
    FIELD(TXFIFO_DLC, DLC, 28, 4)
REG32(TXFIFO_DATA1, 0x38)
    FIELD(TXFIFO_DATA1, DB0, 24, 8)
    FIELD(TXFIFO_DATA1, DB1, 16, 8)
    FIELD(TXFIFO_DATA1, DB2, 8, 8)
    FIELD(TXFIFO_DATA1, DB3, 0, 8)
REG32(TXFIFO_DATA2, 0x3c)
    FIELD(TXFIFO_DATA2, DB4, 24, 8)
    FIELD(TXFIFO_DATA2, DB5, 16, 8)
    FIELD(TXFIFO_DATA2, DB6, 8, 8)
    FIELD(TXFIFO_DATA2, DB7, 0, 8)
REG32(TXHPB_ID, 0x40)
    FIELD(TXHPB_ID, IDH, 21, 11)
    FIELD(TXHPB_ID, SRRRTR, 20, 1)
    FIELD(TXHPB_ID, IDE, 19, 1)
    FIELD(TXHPB_ID, IDL, 1, 18)
    FIELD(TXHPB_ID, RTR, 0, 1)
REG32(TXHPB_DLC, 0x44)
    FIELD(TXHPB_DLC, DLC, 28, 4)
REG32(TXHPB_DATA1, 0x48)
    FIELD(TXHPB_DATA1, DB0, 24, 8)
    FIELD(TXHPB_DATA1, DB1, 16, 8)
    FIELD(TXHPB_DATA1, DB2, 8, 8)
    FIELD(TXHPB_DATA1, DB3, 0, 8)
REG32(TXHPB_DATA2, 0x4c)
    FIELD(TXHPB_DATA2, DB4, 24, 8)
    FIELD(TXHPB_DATA2, DB5, 16, 8)
    FIELD(TXHPB_DATA2, DB6, 8, 8)
    FIELD(TXHPB_DATA2, DB7, 0, 8)
REG32(RXFIFO_ID, 0x50)
    FIELD(RXFIFO_ID, IDH, 21, 11)
    FIELD(RXFIFO_ID, SRRRTR, 20, 1)
    FIELD(RXFIFO_ID, IDE, 19, 1)
    FIELD(RXFIFO_ID, IDL, 1, 18)
    FIELD(RXFIFO_ID, RTR, 0, 1)
REG32(RXFIFO_DLC, 0x54)
    FIELD(RXFIFO_DLC, DLC, 28, 4)
    FIELD(RXFIFO_DLC, RXT, 0, 16)
REG32(RXFIFO_DATA1, 0x58)
    FIELD(RXFIFO_DATA1, DB0, 24, 8)
    FIELD(RXFIFO_DATA1, DB1, 16, 8)
    FIELD(RXFIFO_DATA1, DB2, 8, 8)
    FIELD(RXFIFO_DATA1, DB3, 0, 8)
REG32(RXFIFO_DATA2, 0x5c)
    FIELD(RXFIFO_DATA2, DB4, 24, 8)
    FIELD(RXFIFO_DATA2, DB5, 16, 8)
    FIELD(RXFIFO_DATA2, DB6, 8, 8)
    FIELD(RXFIFO_DATA2, DB7, 0, 8)
REG32(AFR, 0x60)
    FIELD(AFR, UAF4, 3, 1)
    FIELD(AFR, UAF3, 2, 1)
    FIELD(AFR, UAF2, 1, 1)
    FIELD(AFR, UAF1, 0, 1)
REG32(AFMR1, 0x64)
    FIELD(AFMR1, AMIDH, 21, 11)
    FIELD(AFMR1, AMSRR, 20, 1)
    FIELD(AFMR1, AMIDE, 19, 1)
    FIELD(AFMR1, AMIDL, 1, 18)
    FIELD(AFMR1, AMRTR, 0, 1)
REG32(AFIR1, 0x68)
    FIELD(AFIR1, AIIDH, 21, 11)
    FIELD(AFIR1, AISRR, 20, 1)
    FIELD(AFIR1, AIIDE, 19, 1)
    FIELD(AFIR1, AIIDL, 1, 18)
    FIELD(AFIR1, AIRTR, 0, 1)
REG32(AFMR2, 0x6c)
    FIELD(AFMR2, AMIDH, 21, 11)
    FIELD(AFMR2, AMSRR, 20, 1)
    FIELD(AFMR2, AMIDE, 19, 1)
    FIELD(AFMR2, AMIDL, 1, 18)
    FIELD(AFMR2, AMRTR, 0, 1)
REG32(AFIR2, 0x70)
    FIELD(AFIR2, AIIDH, 21, 11)
    FIELD(AFIR2, AISRR, 20, 1)
    FIELD(AFIR2, AIIDE, 19, 1)
    FIELD(AFIR2, AIIDL, 1, 18)
    FIELD(AFIR2, AIRTR, 0, 1)
REG32(AFMR3, 0x74)
    FIELD(AFMR3, AMIDH, 21, 11)
    FIELD(AFMR3, AMSRR, 20, 1)
    FIELD(AFMR3, AMIDE, 19, 1)
    FIELD(AFMR3, AMIDL, 1, 18)
    FIELD(AFMR3, AMRTR, 0, 1)
REG32(AFIR3, 0x78)
    FIELD(AFIR3, AIIDH, 21, 11)
    FIELD(AFIR3, AISRR, 20, 1)
    FIELD(AFIR3, AIIDE, 19, 1)
    FIELD(AFIR3, AIIDL, 1, 18)
    FIELD(AFIR3, AIRTR, 0, 1)
REG32(AFMR4, 0x7c)
    FIELD(AFMR4, AMIDH, 21, 11)
    FIELD(AFMR4, AMSRR, 20, 1)
    FIELD(AFMR4, AMIDE, 19, 1)
    FIELD(AFMR4, AMIDL, 1, 18)
    FIELD(AFMR4, AMRTR, 0, 1)
REG32(AFIR4, 0x80)
    FIELD(AFIR4, AIIDH, 21, 11)
    FIELD(AFIR4, AISRR, 20, 1)
    FIELD(AFIR4, AIIDE, 19, 1)
    FIELD(AFIR4, AIIDL, 1, 18)
    FIELD(AFIR4, AIRTR, 0, 1)

static void can_update_irq(XlnxZynqMPCANState *s)
{
    uint32_t irq;

    /* Watermark register interrupts. */
    if ((fifo32_num_free(&s->tx_fifo) / CAN_FRAME_SIZE) >
            ARRAY_FIELD_EX32(s->regs, WIR, EW)) {
        ARRAY_FIELD_DP32(s->regs, INTERRUPT_STATUS_REGISTER, TXFWMEMP, 1);
    }

    if ((fifo32_num_used(&s->rx_fifo) / CAN_FRAME_SIZE) >
            ARRAY_FIELD_EX32(s->regs, WIR, FW)) {
        ARRAY_FIELD_DP32(s->regs, INTERRUPT_STATUS_REGISTER, RXFWMFLL, 1);
    }

    /* RX Interrupts. */
    if (fifo32_num_used(&s->rx_fifo) >= CAN_FRAME_SIZE) {
        ARRAY_FIELD_DP32(s->regs, INTERRUPT_STATUS_REGISTER, RXNEMP, 1);
    }

    /* TX interrupts. */
    if (fifo32_is_empty(&s->tx_fifo)) {
        ARRAY_FIELD_DP32(s->regs, INTERRUPT_STATUS_REGISTER, TXFEMP, 1);
    }

    if (fifo32_is_full(&s->tx_fifo)) {
        ARRAY_FIELD_DP32(s->regs, INTERRUPT_STATUS_REGISTER, TXFLL, 1);
    }

    if (fifo32_is_full(&s->txhpb_fifo)) {
        ARRAY_FIELD_DP32(s->regs, INTERRUPT_STATUS_REGISTER, TXBFLL, 1);
    }

    irq = s->regs[R_INTERRUPT_STATUS_REGISTER];
    irq &= s->regs[R_INTERRUPT_ENABLE_REGISTER];

    trace_xlnx_can_update_irq(s->regs[R_INTERRUPT_STATUS_REGISTER],
                              s->regs[R_INTERRUPT_ENABLE_REGISTER], irq);
    qemu_set_irq(s->irq, irq);
}

static void can_ier_post_write(RegisterInfo *reg, uint64_t val)
{
    XlnxZynqMPCANState *s = XLNX_ZYNQMP_CAN(reg->opaque);

    can_update_irq(s);
}

static uint64_t can_icr_pre_write(RegisterInfo *reg, uint64_t val)
{
    XlnxZynqMPCANState *s = XLNX_ZYNQMP_CAN(reg->opaque);

    s->regs[R_INTERRUPT_STATUS_REGISTER] &= ~val;
    can_update_irq(s);

    return 0;
}

static void can_config_reset(XlnxZynqMPCANState *s)
{
    /* Reset all the configuration registers. */
    register_reset(&s->reg_info[R_SOFTWARE_RESET_REGISTER]);
    register_reset(&s->reg_info[R_MODE_SELECT_REGISTER]);
    register_reset(
              &s->reg_info[R_ARBITRATION_PHASE_BAUD_RATE_PRESCALER_REGISTER]);
    register_reset(&s->reg_info[R_ARBITRATION_PHASE_BIT_TIMING_REGISTER]);
    register_reset(&s->reg_info[R_STATUS_REGISTER]);
    register_reset(&s->reg_info[R_INTERRUPT_STATUS_REGISTER]);
    register_reset(&s->reg_info[R_INTERRUPT_ENABLE_REGISTER]);
    register_reset(&s->reg_info[R_INTERRUPT_CLEAR_REGISTER]);
    register_reset(&s->reg_info[R_WIR]);
}

static void can_config_mode(XlnxZynqMPCANState *s)
{
    register_reset(&s->reg_info[R_ERROR_COUNTER_REGISTER]);
    register_reset(&s->reg_info[R_ERROR_STATUS_REGISTER]);

    /* Put XlnxZynqMPCAN in configuration mode. */
    ARRAY_FIELD_DP32(s->regs, STATUS_REGISTER, CONFIG, 1);
    ARRAY_FIELD_DP32(s->regs, INTERRUPT_STATUS_REGISTER, WKUP, 0);
    ARRAY_FIELD_DP32(s->regs, INTERRUPT_STATUS_REGISTER, SLP, 0);
    ARRAY_FIELD_DP32(s->regs, INTERRUPT_STATUS_REGISTER, BSOFF, 0);
    ARRAY_FIELD_DP32(s->regs, INTERRUPT_STATUS_REGISTER, ERROR, 0);
    ARRAY_FIELD_DP32(s->regs, INTERRUPT_STATUS_REGISTER, RXOFLW, 0);
    ARRAY_FIELD_DP32(s->regs, INTERRUPT_STATUS_REGISTER, RXOK, 0);
    ARRAY_FIELD_DP32(s->regs, INTERRUPT_STATUS_REGISTER, TXOK, 0);
    ARRAY_FIELD_DP32(s->regs, INTERRUPT_STATUS_REGISTER, ARBLST, 0);

    can_update_irq(s);
}

static void update_status_register_mode_bits(XlnxZynqMPCANState *s)
{
    bool sleep_status = ARRAY_FIELD_EX32(s->regs, STATUS_REGISTER, SLEEP);
    bool sleep_mode = ARRAY_FIELD_EX32(s->regs, MODE_SELECT_REGISTER, SLEEP);
    /* Wake up interrupt bit. */
    bool wakeup_irq_val = sleep_status && (sleep_mode == 0);
    /* Sleep interrupt bit. */
    bool sleep_irq_val = sleep_mode && (sleep_status == 0);

    /* Clear previous core mode status bits. */
    ARRAY_FIELD_DP32(s->regs, STATUS_REGISTER, LBACK, 0);
    ARRAY_FIELD_DP32(s->regs, STATUS_REGISTER, SLEEP, 0);
    ARRAY_FIELD_DP32(s->regs, STATUS_REGISTER, SNOOP, 0);
    ARRAY_FIELD_DP32(s->regs, STATUS_REGISTER, NORMAL, 0);

    /* set current mode bit and generate irqs accordingly. */
    if (ARRAY_FIELD_EX32(s->regs, MODE_SELECT_REGISTER, LBACK)) {
        ARRAY_FIELD_DP32(s->regs, STATUS_REGISTER, LBACK, 1);
    } else if (ARRAY_FIELD_EX32(s->regs, MODE_SELECT_REGISTER, SLEEP)) {
        ARRAY_FIELD_DP32(s->regs, STATUS_REGISTER, SLEEP, 1);
        ARRAY_FIELD_DP32(s->regs, INTERRUPT_STATUS_REGISTER, SLP,
                         sleep_irq_val);
    } else if (ARRAY_FIELD_EX32(s->regs, MODE_SELECT_REGISTER, SNOOP)) {
        ARRAY_FIELD_DP32(s->regs, STATUS_REGISTER, SNOOP, 1);
    } else {
        /*
         * If all bits are zero then XlnxZynqMPCAN is set in normal mode.
         */
        ARRAY_FIELD_DP32(s->regs, STATUS_REGISTER, NORMAL, 1);
        /* Set wakeup interrupt bit. */
        ARRAY_FIELD_DP32(s->regs, INTERRUPT_STATUS_REGISTER, WKUP,
                         wakeup_irq_val);
    }

    can_update_irq(s);
}

static void can_exit_sleep_mode(XlnxZynqMPCANState *s)
{
    ARRAY_FIELD_DP32(s->regs, MODE_SELECT_REGISTER, SLEEP, 0);
    update_status_register_mode_bits(s);
}

static void generate_frame(qemu_can_frame *frame, uint32_t *data)
{
    frame->can_id = data[0];
    frame->can_dlc = FIELD_EX32(data[1], TXFIFO_DLC, DLC);

    frame->data[0] = FIELD_EX32(data[2], TXFIFO_DATA1, DB3);
    frame->data[1] = FIELD_EX32(data[2], TXFIFO_DATA1, DB2);
    frame->data[2] = FIELD_EX32(data[2], TXFIFO_DATA1, DB1);
    frame->data[3] = FIELD_EX32(data[2], TXFIFO_DATA1, DB0);

    frame->data[4] = FIELD_EX32(data[3], TXFIFO_DATA2, DB7);
    frame->data[5] = FIELD_EX32(data[3], TXFIFO_DATA2, DB6);
    frame->data[6] = FIELD_EX32(data[3], TXFIFO_DATA2, DB5);
    frame->data[7] = FIELD_EX32(data[3], TXFIFO_DATA2, DB4);
}

static bool tx_ready_check(XlnxZynqMPCANState *s)
{
    if (ARRAY_FIELD_EX32(s->regs, SOFTWARE_RESET_REGISTER, SRST)) {
        g_autofree char *path = object_get_canonical_path(OBJECT(s));

        qemu_log_mask(LOG_GUEST_ERROR, "%s: Attempting to transfer data while"
                      " data while controller is in reset mode.\n",
                      path);
        return false;
    }

    if (ARRAY_FIELD_EX32(s->regs, SOFTWARE_RESET_REGISTER, CEN) == 0) {
        g_autofree char *path = object_get_canonical_path(OBJECT(s));

        qemu_log_mask(LOG_GUEST_ERROR, "%s: Attempting to transfer"
                      " data while controller is in configuration mode. Reset"
                      " the core so operations can start fresh.\n",
                      path);
        return false;
    }

    if (ARRAY_FIELD_EX32(s->regs, STATUS_REGISTER, SNOOP)) {
        g_autofree char *path = object_get_canonical_path(OBJECT(s));

        qemu_log_mask(LOG_GUEST_ERROR, "%s: Attempting to transfer"
                      " data while controller is in SNOOP MODE.\n",
                      path);
        return false;
    }

    return true;
}

static void transfer_fifo(XlnxZynqMPCANState *s, Fifo32 *fifo)
{
    qemu_can_frame frame;
    uint32_t data[CAN_FRAME_SIZE];
    int i;
    bool can_tx = tx_ready_check(s);

    if (!can_tx) {
        g_autofree char *path = object_get_canonical_path(OBJECT(s));

        qemu_log_mask(LOG_GUEST_ERROR, "%s: Controller is not enabled for data"
                      " transfer.\n", path);
        can_update_irq(s);
        return;
    }

    while (!fifo32_is_empty(fifo)) {
        for (i = 0; i < CAN_FRAME_SIZE; i++) {
            data[i] = fifo32_pop(fifo);
        }

        if (ARRAY_FIELD_EX32(s->regs, STATUS_REGISTER, LBACK)) {
            /*
             * Controller is in loopback. In Loopback mode, the CAN core
             * transmits a recessive bitstream on to the XlnxZynqMPCAN Bus.
             * Any message transmitted is looped back to the RX line and
             * acknowledged. The XlnxZynqMPCAN core receives any message
             * that it transmits.
             */
            if (fifo32_is_full(&s->rx_fifo)) {
                ARRAY_FIELD_DP32(s->regs, INTERRUPT_STATUS_REGISTER, RXOFLW, 1);
            } else {
                for (i = 0; i < CAN_FRAME_SIZE; i++) {
                    fifo32_push(&s->rx_fifo, data[i]);
                }

                ARRAY_FIELD_DP32(s->regs, INTERRUPT_STATUS_REGISTER, RXOK, 1);
            }
        } else {
            /* Normal mode Tx. */
            generate_frame(&frame, data);

            trace_xlnx_can_tx_data(frame.can_id, frame.can_dlc,
                                   frame.data[0], frame.data[1],
                                   frame.data[2], frame.data[3],
                                   frame.data[4], frame.data[5],
                                   frame.data[6], frame.data[7]);
            can_bus_client_send(&s->bus_client, &frame, 1);
        }
    }

    ARRAY_FIELD_DP32(s->regs, INTERRUPT_STATUS_REGISTER, TXOK, 1);
    ARRAY_FIELD_DP32(s->regs, STATUS_REGISTER, TXBFLL, 0);

    if (ARRAY_FIELD_EX32(s->regs, STATUS_REGISTER, SLEEP)) {
        can_exit_sleep_mode(s);
    }

    can_update_irq(s);
}

static uint64_t can_srr_pre_write(RegisterInfo *reg, uint64_t val)
{
    XlnxZynqMPCANState *s = XLNX_ZYNQMP_CAN(reg->opaque);

    ARRAY_FIELD_DP32(s->regs, SOFTWARE_RESET_REGISTER, CEN,
                     FIELD_EX32(val, SOFTWARE_RESET_REGISTER, CEN));

    if (FIELD_EX32(val, SOFTWARE_RESET_REGISTER, SRST)) {
        trace_xlnx_can_reset(val);

        /* First, core will do software reset then will enter in config mode. */
        can_config_reset(s);
    }

    if (ARRAY_FIELD_EX32(s->regs, SOFTWARE_RESET_REGISTER, CEN) == 0) {
        can_config_mode(s);
    } else {
        /*
         * Leave config mode. Now XlnxZynqMPCAN core will enter normal,
         * sleep, snoop or loopback mode depending upon LBACK, SLEEP, SNOOP
         * register states.
         */
        ARRAY_FIELD_DP32(s->regs, STATUS_REGISTER, CONFIG, 0);

        ptimer_transaction_begin(s->can_timer);
        ptimer_set_count(s->can_timer, 0);
        ptimer_transaction_commit(s->can_timer);

        /* XlnxZynqMPCAN is out of config mode. It will send pending data. */
        transfer_fifo(s, &s->txhpb_fifo);
        transfer_fifo(s, &s->tx_fifo);
    }

    update_status_register_mode_bits(s);

    return s->regs[R_SOFTWARE_RESET_REGISTER];
}

static uint64_t can_msr_pre_write(RegisterInfo *reg, uint64_t val)
{
    XlnxZynqMPCANState *s = XLNX_ZYNQMP_CAN(reg->opaque);
    uint8_t multi_mode;

    /*
     * Multiple mode set check. This is done to make sure user doesn't set
     * multiple modes.
     */
    multi_mode = FIELD_EX32(val, MODE_SELECT_REGISTER, LBACK) +
                 FIELD_EX32(val, MODE_SELECT_REGISTER, SLEEP) +
                 FIELD_EX32(val, MODE_SELECT_REGISTER, SNOOP);

    if (multi_mode > 1) {
        g_autofree char *path = object_get_canonical_path(OBJECT(s));

        qemu_log_mask(LOG_GUEST_ERROR, "%s: Attempting to config"
                      " several modes simultaneously. One mode will be selected"
                      " according to their priority: LBACK > SLEEP > SNOOP.\n",
                      path);
    }

    if (ARRAY_FIELD_EX32(s->regs, SOFTWARE_RESET_REGISTER, CEN) == 0) {
        /* We are in configuration mode, any mode can be selected. */
        s->regs[R_MODE_SELECT_REGISTER] = val;
    } else {
        bool sleep_mode_bit = FIELD_EX32(val, MODE_SELECT_REGISTER, SLEEP);

        ARRAY_FIELD_DP32(s->regs, MODE_SELECT_REGISTER, SLEEP, sleep_mode_bit);

        if (FIELD_EX32(val, MODE_SELECT_REGISTER, LBACK)) {
            g_autofree char *path = object_get_canonical_path(OBJECT(s));

            qemu_log_mask(LOG_GUEST_ERROR, "%s: Attempting to set"
                          " LBACK mode without setting CEN bit as 0.\n",
                          path);
        } else if (FIELD_EX32(val, MODE_SELECT_REGISTER, SNOOP)) {
            g_autofree char *path = object_get_canonical_path(OBJECT(s));

            qemu_log_mask(LOG_GUEST_ERROR, "%s: Attempting to set"
                          " SNOOP mode without setting CEN bit as 0.\n",
                          path);
        }

        update_status_register_mode_bits(s);
    }

    return s->regs[R_MODE_SELECT_REGISTER];
}

static uint64_t can_brpr_pre_write(RegisterInfo  *reg, uint64_t val)
{
    XlnxZynqMPCANState *s = XLNX_ZYNQMP_CAN(reg->opaque);

    /* Only allow writes when in config mode. */
    if (ARRAY_FIELD_EX32(s->regs, SOFTWARE_RESET_REGISTER, CEN)) {
        return s->regs[R_ARBITRATION_PHASE_BAUD_RATE_PRESCALER_REGISTER];
    }

    return val;
}

static uint64_t can_btr_pre_write(RegisterInfo  *reg, uint64_t val)
{
    XlnxZynqMPCANState *s = XLNX_ZYNQMP_CAN(reg->opaque);

    /* Only allow writes when in config mode. */
    if (ARRAY_FIELD_EX32(s->regs, SOFTWARE_RESET_REGISTER, CEN)) {
        return s->regs[R_ARBITRATION_PHASE_BIT_TIMING_REGISTER];
    }

    return val;
}

static uint64_t can_tcr_pre_write(RegisterInfo  *reg, uint64_t val)
{
    XlnxZynqMPCANState *s = XLNX_ZYNQMP_CAN(reg->opaque);

    if (FIELD_EX32(val, TIMESTAMP_REGISTER, CTS)) {
        ptimer_transaction_begin(s->can_timer);
        ptimer_set_count(s->can_timer, 0);
        ptimer_transaction_commit(s->can_timer);
    }

    return 0;
}

static void update_rx_fifo(XlnxZynqMPCANState *s, const qemu_can_frame *frame)
{
    bool filter_pass = false;
    uint16_t timestamp = 0;

    /* If no filter is enabled. Message will be stored in FIFO. */
    if (!((ARRAY_FIELD_EX32(s->regs, AFR, UAF1)) |
       (ARRAY_FIELD_EX32(s->regs, AFR, UAF2)) |
       (ARRAY_FIELD_EX32(s->regs, AFR, UAF3)) |
       (ARRAY_FIELD_EX32(s->regs, AFR, UAF4)))) {
        filter_pass = true;
    }

    /*
     * Messages that pass any of the acceptance filters will be stored in
     * the RX FIFO.
     */
    if (ARRAY_FIELD_EX32(s->regs, AFR, UAF1)) {
        uint32_t id_masked = s->regs[R_AFMR1] & frame->can_id;
        uint32_t filter_id_masked = s->regs[R_AFMR1] & s->regs[R_AFIR1];

        if (filter_id_masked == id_masked) {
            filter_pass = true;
        }
    }

    if (ARRAY_FIELD_EX32(s->regs, AFR, UAF2)) {
        uint32_t id_masked = s->regs[R_AFMR2] & frame->can_id;
        uint32_t filter_id_masked = s->regs[R_AFMR2] & s->regs[R_AFIR2];

        if (filter_id_masked == id_masked) {
            filter_pass = true;
        }
    }

    if (ARRAY_FIELD_EX32(s->regs, AFR, UAF3)) {
        uint32_t id_masked = s->regs[R_AFMR3] & frame->can_id;
        uint32_t filter_id_masked = s->regs[R_AFMR3] & s->regs[R_AFIR3];

        if (filter_id_masked == id_masked) {
            filter_pass = true;
        }
    }

    if (ARRAY_FIELD_EX32(s->regs, AFR, UAF4)) {
        uint32_t id_masked = s->regs[R_AFMR4] & frame->can_id;
        uint32_t filter_id_masked = s->regs[R_AFMR4] & s->regs[R_AFIR4];

        if (filter_id_masked == id_masked) {
            filter_pass = true;
        }
    }

    if (!filter_pass) {
        trace_xlnx_can_rx_fifo_filter_reject(frame->can_id, frame->can_dlc);
        return;
    }

    /* Store the message in fifo if it passed through any of the filters. */
    if (filter_pass && frame->can_dlc <= MAX_DLC) {

        if (fifo32_is_full(&s->rx_fifo)) {
            ARRAY_FIELD_DP32(s->regs, INTERRUPT_STATUS_REGISTER, RXOFLW, 1);
        } else {
            timestamp = CAN_TIMER_MAX - ptimer_get_count(s->can_timer);

            fifo32_push(&s->rx_fifo, frame->can_id);

            fifo32_push(&s->rx_fifo, deposit32(0, R_RXFIFO_DLC_DLC_SHIFT,
                                               R_RXFIFO_DLC_DLC_LENGTH,
                                               frame->can_dlc) |
                                     deposit32(0, R_RXFIFO_DLC_RXT_SHIFT,
                                               R_RXFIFO_DLC_RXT_LENGTH,
                                               timestamp));

            /* First 32 bit of the data. */
            fifo32_push(&s->rx_fifo, deposit32(0, R_TXFIFO_DATA1_DB3_SHIFT,
                                               R_TXFIFO_DATA1_DB3_LENGTH,
                                               frame->data[0]) |
                                     deposit32(0, R_TXFIFO_DATA1_DB2_SHIFT,
                                               R_TXFIFO_DATA1_DB2_LENGTH,
                                               frame->data[1]) |
                                     deposit32(0, R_TXFIFO_DATA1_DB1_SHIFT,
                                               R_TXFIFO_DATA1_DB1_LENGTH,
                                               frame->data[2]) |
                                     deposit32(0, R_TXFIFO_DATA1_DB0_SHIFT,
                                               R_TXFIFO_DATA1_DB0_LENGTH,
                                               frame->data[3]));
            /* Last 32 bit of the data. */
            fifo32_push(&s->rx_fifo, deposit32(0, R_TXFIFO_DATA2_DB7_SHIFT,
                                               R_TXFIFO_DATA2_DB7_LENGTH,
                                               frame->data[4]) |
                                     deposit32(0, R_TXFIFO_DATA2_DB6_SHIFT,
                                               R_TXFIFO_DATA2_DB6_LENGTH,
                                               frame->data[5]) |
                                     deposit32(0, R_TXFIFO_DATA2_DB5_SHIFT,
                                               R_TXFIFO_DATA2_DB5_LENGTH,
                                               frame->data[6]) |
                                     deposit32(0, R_TXFIFO_DATA2_DB4_SHIFT,
                                               R_TXFIFO_DATA2_DB4_LENGTH,
                                               frame->data[7]));

            ARRAY_FIELD_DP32(s->regs, INTERRUPT_STATUS_REGISTER, RXOK, 1);
            trace_xlnx_can_rx_data(frame->can_id, frame->can_dlc,
                                   frame->data[0], frame->data[1],
                                   frame->data[2], frame->data[3],
                                   frame->data[4], frame->data[5],
                                   frame->data[6], frame->data[7]);
        }

        can_update_irq(s);
    }
}

static uint64_t can_rxfifo_pre_read(RegisterInfo *reg, uint64_t val)
{
    XlnxZynqMPCANState *s = XLNX_ZYNQMP_CAN(reg->opaque);

    if (!fifo32_is_empty(&s->rx_fifo)) {
        val = fifo32_pop(&s->rx_fifo);
    } else {
        ARRAY_FIELD_DP32(s->regs, INTERRUPT_STATUS_REGISTER, RXUFLW, 1);
    }

    can_update_irq(s);
    return val;
}

static void can_filter_enable_post_write(RegisterInfo *reg, uint64_t val)
{
    XlnxZynqMPCANState *s = XLNX_ZYNQMP_CAN(reg->opaque);

    if (ARRAY_FIELD_EX32(s->regs, AFR, UAF1) &&
        ARRAY_FIELD_EX32(s->regs, AFR, UAF2) &&
        ARRAY_FIELD_EX32(s->regs, AFR, UAF3) &&
        ARRAY_FIELD_EX32(s->regs, AFR, UAF4)) {
        ARRAY_FIELD_DP32(s->regs, STATUS_REGISTER, ACFBSY, 1);
    } else {
        ARRAY_FIELD_DP32(s->regs, STATUS_REGISTER, ACFBSY, 0);
    }
}

static uint64_t can_filter_mask_pre_write(RegisterInfo *reg, uint64_t val)
{
    XlnxZynqMPCANState *s = XLNX_ZYNQMP_CAN(reg->opaque);
    uint32_t reg_idx = (reg->access->addr) / 4;
    uint32_t filter_number = (reg_idx - R_AFMR1) / 2;

    /* modify an acceptance filter, the corresponding UAF bit should be '0'. */
    if (!(s->regs[R_AFR] & (1 << filter_number))) {
        s->regs[reg_idx] = val;

        trace_xlnx_can_filter_mask_pre_write(filter_number, s->regs[reg_idx]);
    } else {
        g_autofree char *path = object_get_canonical_path(OBJECT(s));

        qemu_log_mask(LOG_GUEST_ERROR, "%s: Acceptance filter %d"
                      " mask is not set as corresponding UAF bit is not 0.\n",
                      path, filter_number + 1);
    }

    return s->regs[reg_idx];
}

static uint64_t can_filter_id_pre_write(RegisterInfo *reg, uint64_t val)
{
    XlnxZynqMPCANState *s = XLNX_ZYNQMP_CAN(reg->opaque);
    uint32_t reg_idx = (reg->access->addr) / 4;
    uint32_t filter_number = (reg_idx - R_AFIR1) / 2;

    if (!(s->regs[R_AFR] & (1 << filter_number))) {
        s->regs[reg_idx] = val;

        trace_xlnx_can_filter_id_pre_write(filter_number, s->regs[reg_idx]);
    } else {
        g_autofree char *path = object_get_canonical_path(OBJECT(s));

        qemu_log_mask(LOG_GUEST_ERROR, "%s: Acceptance filter %d"
                      " id is not set as corresponding UAF bit is not 0.\n",
                      path, filter_number + 1);
    }

    return s->regs[reg_idx];
}

static void can_tx_post_write(RegisterInfo *reg, uint64_t val)
{
    XlnxZynqMPCANState *s = XLNX_ZYNQMP_CAN(reg->opaque);

    bool is_txhpb = reg->access->addr > A_TXFIFO_DATA2;

    bool initiate_transfer = (reg->access->addr == A_TXFIFO_DATA2) ||
                             (reg->access->addr == A_TXHPB_DATA2);

    Fifo32 *f = is_txhpb ? &s->txhpb_fifo : &s->tx_fifo;

    if (!fifo32_is_full(f)) {
        fifo32_push(f, val);
    } else {
        g_autofree char *path = object_get_canonical_path(OBJECT(s));

        qemu_log_mask(LOG_GUEST_ERROR, "%s: TX FIFO is full.\n", path);
    }

    /* Initiate the message send if TX register is written. */
    if (initiate_transfer &&
        ARRAY_FIELD_EX32(s->regs, SOFTWARE_RESET_REGISTER, CEN)) {
        transfer_fifo(s, f);
    }

    can_update_irq(s);
}

static const RegisterAccessInfo can_regs_info[] = {
    {   .name = "SOFTWARE_RESET_REGISTER",
        .addr = A_SOFTWARE_RESET_REGISTER,
        .rsvd = 0xfffffffc,
        .pre_write = can_srr_pre_write,
    },{ .name = "MODE_SELECT_REGISTER",
        .addr = A_MODE_SELECT_REGISTER,
        .rsvd = 0xfffffff8,
        .pre_write = can_msr_pre_write,
    },{ .name = "ARBITRATION_PHASE_BAUD_RATE_PRESCALER_REGISTER",
        .addr = A_ARBITRATION_PHASE_BAUD_RATE_PRESCALER_REGISTER,
        .rsvd = 0xffffff00,
        .pre_write = can_brpr_pre_write,
    },{ .name = "ARBITRATION_PHASE_BIT_TIMING_REGISTER",
        .addr = A_ARBITRATION_PHASE_BIT_TIMING_REGISTER,
        .rsvd = 0xfffffe00,
        .pre_write = can_btr_pre_write,
    },{ .name = "ERROR_COUNTER_REGISTER",
        .addr = A_ERROR_COUNTER_REGISTER,
        .rsvd = 0xffff0000,
        .ro = 0xffffffff,
    },{ .name = "ERROR_STATUS_REGISTER",
        .addr = A_ERROR_STATUS_REGISTER,
        .rsvd = 0xffffffe0,
        .w1c = 0x1f,
    },{ .name = "STATUS_REGISTER",  .addr = A_STATUS_REGISTER,
        .reset = 0x1,
        .rsvd = 0xffffe000,
        .ro = 0x1fff,
    },{ .name = "INTERRUPT_STATUS_REGISTER",
        .addr = A_INTERRUPT_STATUS_REGISTER,
        .reset = 0x6000,
        .rsvd = 0xffff8000,
        .ro = 0x7fff,
    },{ .name = "INTERRUPT_ENABLE_REGISTER",
        .addr = A_INTERRUPT_ENABLE_REGISTER,
        .rsvd = 0xffff8000,
        .post_write = can_ier_post_write,
    },{ .name = "INTERRUPT_CLEAR_REGISTER",
        .addr = A_INTERRUPT_CLEAR_REGISTER,
        .rsvd = 0xffff8000,
        .pre_write = can_icr_pre_write,
    },{ .name = "TIMESTAMP_REGISTER",
        .addr = A_TIMESTAMP_REGISTER,
        .rsvd = 0xfffffffe,
        .pre_write = can_tcr_pre_write,
    },{ .name = "WIR",  .addr = A_WIR,
        .reset = 0x3f3f,
        .rsvd = 0xffff0000,
    },{ .name = "TXFIFO_ID",  .addr = A_TXFIFO_ID,
        .post_write = can_tx_post_write,
    },{ .name = "TXFIFO_DLC",  .addr = A_TXFIFO_DLC,
        .rsvd = 0xfffffff,
        .post_write = can_tx_post_write,
    },{ .name = "TXFIFO_DATA1",  .addr = A_TXFIFO_DATA1,
        .post_write = can_tx_post_write,
    },{ .name = "TXFIFO_DATA2",  .addr = A_TXFIFO_DATA2,
        .post_write = can_tx_post_write,
    },{ .name = "TXHPB_ID",  .addr = A_TXHPB_ID,
        .post_write = can_tx_post_write,
    },{ .name = "TXHPB_DLC",  .addr = A_TXHPB_DLC,
        .rsvd = 0xfffffff,
        .post_write = can_tx_post_write,
    },{ .name = "TXHPB_DATA1",  .addr = A_TXHPB_DATA1,
        .post_write = can_tx_post_write,
    },{ .name = "TXHPB_DATA2",  .addr = A_TXHPB_DATA2,
        .post_write = can_tx_post_write,
    },{ .name = "RXFIFO_ID",  .addr = A_RXFIFO_ID,
        .ro = 0xffffffff,
        .post_read = can_rxfifo_pre_read,
    },{ .name = "RXFIFO_DLC",  .addr = A_RXFIFO_DLC,
        .rsvd = 0xfff0000,
        .post_read = can_rxfifo_pre_read,
    },{ .name = "RXFIFO_DATA1",  .addr = A_RXFIFO_DATA1,
        .post_read = can_rxfifo_pre_read,
    },{ .name = "RXFIFO_DATA2",  .addr = A_RXFIFO_DATA2,
        .post_read = can_rxfifo_pre_read,
    },{ .name = "AFR",  .addr = A_AFR,
        .rsvd = 0xfffffff0,
        .post_write = can_filter_enable_post_write,
    },{ .name = "AFMR1",  .addr = A_AFMR1,
        .pre_write = can_filter_mask_pre_write,
    },{ .name = "AFIR1",  .addr = A_AFIR1,
        .pre_write = can_filter_id_pre_write,
    },{ .name = "AFMR2",  .addr = A_AFMR2,
        .pre_write = can_filter_mask_pre_write,
    },{ .name = "AFIR2",  .addr = A_AFIR2,
        .pre_write = can_filter_id_pre_write,
    },{ .name = "AFMR3",  .addr = A_AFMR3,
        .pre_write = can_filter_mask_pre_write,
    },{ .name = "AFIR3",  .addr = A_AFIR3,
        .pre_write = can_filter_id_pre_write,
    },{ .name = "AFMR4",  .addr = A_AFMR4,
        .pre_write = can_filter_mask_pre_write,
    },{ .name = "AFIR4",  .addr = A_AFIR4,
        .pre_write = can_filter_id_pre_write,
    }
};

static void xlnx_zynqmp_can_ptimer_cb(void *opaque)
{
    /* No action required on the timer rollover. */
}

static const MemoryRegionOps can_ops = {
    .read = register_read_memory,
    .write = register_write_memory,
    .endianness = DEVICE_LITTLE_ENDIAN,
    .valid = {
        .min_access_size = 4,
        .max_access_size = 4,
    },
};

static void xlnx_zynqmp_can_reset_init(Object *obj, ResetType type)
{
    XlnxZynqMPCANState *s = XLNX_ZYNQMP_CAN(obj);
    unsigned int i;

    for (i = R_RXFIFO_ID; i < ARRAY_SIZE(s->reg_info); ++i) {
        register_reset(&s->reg_info[i]);
    }

    ptimer_transaction_begin(s->can_timer);
    ptimer_set_count(s->can_timer, 0);
    ptimer_transaction_commit(s->can_timer);
}

static void xlnx_zynqmp_can_reset_hold(Object *obj)
{
    XlnxZynqMPCANState *s = XLNX_ZYNQMP_CAN(obj);
    unsigned int i;

    for (i = 0; i < R_RXFIFO_ID; ++i) {
        register_reset(&s->reg_info[i]);
    }

    /*
     * Reset FIFOs when CAN model is reset. This will clear the fifo writes
     * done by post_write which gets called from register_reset function,
     * post_write handle will not be able to trigger tx because CAN will be
     * disabled when software_reset_register is cleared first.
     */
    fifo32_reset(&s->rx_fifo);
    fifo32_reset(&s->tx_fifo);
    fifo32_reset(&s->txhpb_fifo);
}

static bool xlnx_zynqmp_can_can_receive(CanBusClientState *client)
{
    XlnxZynqMPCANState *s = container_of(client, XlnxZynqMPCANState,
                                         bus_client);

    if (ARRAY_FIELD_EX32(s->regs, SOFTWARE_RESET_REGISTER, SRST)) {
        g_autofree char *path = object_get_canonical_path(OBJECT(s));

        qemu_log_mask(LOG_GUEST_ERROR, "%s: Controller is in reset state.\n",
                      path);
        return false;
    }

    if ((ARRAY_FIELD_EX32(s->regs, SOFTWARE_RESET_REGISTER, CEN)) == 0) {
        g_autofree char *path = object_get_canonical_path(OBJECT(s));

        qemu_log_mask(LOG_GUEST_ERROR, "%s: Controller is disabled. Incoming"
                      " messages will be discarded.\n", path);
        return false;
    }

    return true;
}

static ssize_t xlnx_zynqmp_can_receive(CanBusClientState *client,
                               const qemu_can_frame *buf, size_t buf_size) {
    XlnxZynqMPCANState *s = container_of(client, XlnxZynqMPCANState,
                                         bus_client);
    const qemu_can_frame *frame = buf;

    if (buf_size <= 0) {
        g_autofree char *path = object_get_canonical_path(OBJECT(s));

        qemu_log_mask(LOG_GUEST_ERROR, "%s: Error in the data received.\n",
                      path);
        return 0;
    }

    if (ARRAY_FIELD_EX32(s->regs, STATUS_REGISTER, SNOOP)) {
        /* Snoop Mode: Just keep the data. no response back. */
        update_rx_fifo(s, frame);
    } else if ((ARRAY_FIELD_EX32(s->regs, STATUS_REGISTER, SLEEP))) {
        /*
         * XlnxZynqMPCAN is in sleep mode. Any data on bus will bring it to wake
         * up state.
         */
        can_exit_sleep_mode(s);
        update_rx_fifo(s, frame);
    } else if ((ARRAY_FIELD_EX32(s->regs, STATUS_REGISTER, SLEEP)) == 0) {
        update_rx_fifo(s, frame);
    } else {
        /*
         * XlnxZynqMPCAN will not participate in normal bus communication
         * and will not receive any messages transmitted by other CAN nodes.
         */
        trace_xlnx_can_rx_discard(s->regs[R_STATUS_REGISTER]);
    }

    return 1;
}

static CanBusClientInfo can_xilinx_bus_client_info = {
    .can_receive = xlnx_zynqmp_can_can_receive,
    .receive = xlnx_zynqmp_can_receive,
};

static int xlnx_zynqmp_can_connect_to_bus(XlnxZynqMPCANState *s,
                                          CanBusState *bus)
{
    s->bus_client.info = &can_xilinx_bus_client_info;

    if (can_bus_insert_client(bus, &s->bus_client) < 0) {
        return -1;
    }
    return 0;
}

static void xlnx_zynqmp_can_realize(DeviceState *dev, Error **errp)
{
    XlnxZynqMPCANState *s = XLNX_ZYNQMP_CAN(dev);

    if (s->canbus) {
        if (xlnx_zynqmp_can_connect_to_bus(s, s->canbus) < 0) {
            g_autofree char *path = object_get_canonical_path(OBJECT(s));

            error_setg(errp, "%s: xlnx_zynqmp_can_connect_to_bus"
                       " failed.", path);
            return;
        }
    }

    /* Create RX FIFO, TXFIFO, TXHPB storage. */
    fifo32_create(&s->rx_fifo, RXFIFO_SIZE);
    fifo32_create(&s->tx_fifo, RXFIFO_SIZE);
    fifo32_create(&s->txhpb_fifo, CAN_FRAME_SIZE);

    /* Allocate a new timer. */
    s->can_timer = ptimer_init(xlnx_zynqmp_can_ptimer_cb, s,
                               PTIMER_POLICY_LEGACY);

    ptimer_transaction_begin(s->can_timer);

    ptimer_set_freq(s->can_timer, s->cfg.ext_clk_freq);
    ptimer_set_limit(s->can_timer, CAN_TIMER_MAX, 1);
    ptimer_run(s->can_timer, 0);
    ptimer_transaction_commit(s->can_timer);
}

static void xlnx_zynqmp_can_init(Object *obj)
{
    XlnxZynqMPCANState *s = XLNX_ZYNQMP_CAN(obj);
    SysBusDevice *sbd = SYS_BUS_DEVICE(obj);

    RegisterInfoArray *reg_array;

    memory_region_init(&s->iomem, obj, TYPE_XLNX_ZYNQMP_CAN,
                        XLNX_ZYNQMP_CAN_R_MAX * 4);
    reg_array = register_init_block32(DEVICE(obj), can_regs_info,
                               ARRAY_SIZE(can_regs_info),
                               s->reg_info, s->regs,
                               &can_ops,
                               XLNX_ZYNQMP_CAN_ERR_DEBUG,
                               XLNX_ZYNQMP_CAN_R_MAX * 4);

    memory_region_add_subregion(&s->iomem, 0x00, &reg_array->mem);
    sysbus_init_mmio(sbd, &s->iomem);
    sysbus_init_irq(SYS_BUS_DEVICE(obj), &s->irq);
}

static const VMStateDescription vmstate_can = {
    .name = TYPE_XLNX_ZYNQMP_CAN,
    .version_id = 1,
    .minimum_version_id = 1,
    .fields = (VMStateField[]) {
        VMSTATE_FIFO32(rx_fifo, XlnxZynqMPCANState),
        VMSTATE_FIFO32(tx_fifo, XlnxZynqMPCANState),
        VMSTATE_FIFO32(txhpb_fifo, XlnxZynqMPCANState),
        VMSTATE_UINT32_ARRAY(regs, XlnxZynqMPCANState, XLNX_ZYNQMP_CAN_R_MAX),
        VMSTATE_PTIMER(can_timer, XlnxZynqMPCANState),
        VMSTATE_END_OF_LIST(),
    }
};

static Property xlnx_zynqmp_can_properties[] = {
    DEFINE_PROP_UINT32("ext_clk_freq", XlnxZynqMPCANState, cfg.ext_clk_freq,
                       CAN_DEFAULT_CLOCK),
    DEFINE_PROP_LINK("canbus", XlnxZynqMPCANState, canbus, TYPE_CAN_BUS,
                     CanBusState *),
    DEFINE_PROP_END_OF_LIST(),
};

static void xlnx_zynqmp_can_class_init(ObjectClass *klass, void *data)
{
    DeviceClass *dc = DEVICE_CLASS(klass);
    ResettableClass *rc = RESETTABLE_CLASS(klass);

    rc->phases.enter = xlnx_zynqmp_can_reset_init;
    rc->phases.hold = xlnx_zynqmp_can_reset_hold;
    dc->realize = xlnx_zynqmp_can_realize;
    device_class_set_props(dc, xlnx_zynqmp_can_properties);
    dc->vmsd = &vmstate_can;
}

static const TypeInfo can_info = {
    .name          = TYPE_XLNX_ZYNQMP_CAN,
    .parent        = TYPE_SYS_BUS_DEVICE,
    .instance_size = sizeof(XlnxZynqMPCANState),
    .class_init    = xlnx_zynqmp_can_class_init,
    .instance_init = xlnx_zynqmp_can_init,
};

static void can_register_types(void)
{
    type_register_static(&can_info);
}

type_init(can_register_types)