hw/ssi/mss-spi.c - third_party/qemu - Git at Google

 /*
  * Block model of SPI controller present in
  * Microsemi's SmartFusion2 and SmartFusion SoCs.
  *
  * Copyright (C) 2017 Subbaraya Sundeep <sundeep.lkml@gmail.com>
  *
  * 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/irq.h"
 #include "hw/ssi/mss-spi.h"
 #include "migration/vmstate.h"
 #include "qemu/log.h"
 #include "qemu/module.h"

 #ifndef MSS_SPI_ERR_DEBUG
 #define MSS_SPI_ERR_DEBUG   0
 #endif

 #define DB_PRINT_L(lvl, fmt, args...) do { \
     if (MSS_SPI_ERR_DEBUG >= lvl) { \
         qemu_log("%s: " fmt "\n", __func__, ## args); \
     } \
 } while (0)

 #define DB_PRINT(fmt, args...) DB_PRINT_L(1, fmt, ## args)

 #define FIFO_CAPACITY         32

 #define R_SPI_CONTROL         0
 #define R_SPI_DFSIZE          1
 #define R_SPI_STATUS          2
 #define R_SPI_INTCLR          3
 #define R_SPI_RX              4
 #define R_SPI_TX              5
 #define R_SPI_CLKGEN          6
 #define R_SPI_SS              7
 #define R_SPI_MIS             8
 #define R_SPI_RIS             9

 #define S_TXDONE             (1 << 0)
 #define S_RXRDY              (1 << 1)
 #define S_RXCHOVRF           (1 << 2)
 #define S_RXFIFOFUL          (1 << 4)
 #define S_RXFIFOFULNXT       (1 << 5)
 #define S_RXFIFOEMP          (1 << 6)
 #define S_RXFIFOEMPNXT       (1 << 7)
 #define S_TXFIFOFUL          (1 << 8)
 #define S_TXFIFOFULNXT       (1 << 9)
 #define S_TXFIFOEMP          (1 << 10)
 #define S_TXFIFOEMPNXT       (1 << 11)
 #define S_FRAMESTART         (1 << 12)
 #define S_SSEL               (1 << 13)
 #define S_ACTIVE             (1 << 14)

 #define C_ENABLE             (1 << 0)
 #define C_MODE               (1 << 1)
 #define C_INTRXDATA          (1 << 4)
 #define C_INTTXDATA          (1 << 5)
 #define C_INTRXOVRFLO        (1 << 6)
 #define C_SPS                (1 << 26)
 #define C_BIGFIFO            (1 << 29)
 #define C_RESET              (1 << 31)

 #define FRAMESZ_MASK         0x3F
 #define FMCOUNT_MASK         0x00FFFF00
 #define FMCOUNT_SHIFT        8
 #define FRAMESZ_MAX          32

 static void txfifo_reset(MSSSpiState *s)
 {
     fifo32_reset(&s->tx_fifo);

     s->regs[R_SPI_STATUS] &= ~S_TXFIFOFUL;
     s->regs[R_SPI_STATUS] |= S_TXFIFOEMP;
 }

 static void rxfifo_reset(MSSSpiState *s)
 {
     fifo32_reset(&s->rx_fifo);

     s->regs[R_SPI_STATUS] &= ~S_RXFIFOFUL;
     s->regs[R_SPI_STATUS] |= S_RXFIFOEMP;
 }

 static void set_fifodepth(MSSSpiState *s)
 {
     unsigned int size = s->regs[R_SPI_DFSIZE] & FRAMESZ_MASK;

     if (size <= 8) {
         s->fifo_depth = 32;
     } else if (size <= 16) {
         s->fifo_depth = 16;
     } else {
         s->fifo_depth = 8;
     }
 }

 static void update_mis(MSSSpiState *s)
 {
     uint32_t reg = s->regs[R_SPI_CONTROL];
     uint32_t tmp;

     /*
      * form the Control register interrupt enable bits
      * same as RIS, MIS and Interrupt clear registers for simplicity
      */
     tmp = ((reg & C_INTRXOVRFLO) >> 4) | ((reg & C_INTRXDATA) >> 3) |
            ((reg & C_INTTXDATA) >> 5);
     s->regs[R_SPI_MIS] |= tmp & s->regs[R_SPI_RIS];
 }

 static void spi_update_irq(MSSSpiState *s)
 {
     int irq;

     update_mis(s);
     irq = !!(s->regs[R_SPI_MIS]);

     qemu_set_irq(s->irq, irq);
 }

 static void mss_spi_reset(DeviceState *d)
 {
     MSSSpiState *s = MSS_SPI(d);

     memset(s->regs, 0, sizeof s->regs);
     s->regs[R_SPI_CONTROL] = 0x80000102;
     s->regs[R_SPI_DFSIZE] = 0x4;
     s->regs[R_SPI_STATUS] = S_SSEL | S_TXFIFOEMP | S_RXFIFOEMP;
     s->regs[R_SPI_CLKGEN] = 0x7;
     s->regs[R_SPI_RIS] = 0x0;

     s->fifo_depth = 4;
     s->frame_count = 1;
     s->enabled = false;

     rxfifo_reset(s);
     txfifo_reset(s);
 }

 static uint64_t
 spi_read(void *opaque, hwaddr addr, unsigned int size)
 {
     MSSSpiState *s = opaque;
     uint32_t ret = 0;

     addr >>= 2;
     switch (addr) {
     case R_SPI_RX:
         s->regs[R_SPI_STATUS] &= ~S_RXFIFOFUL;
         s->regs[R_SPI_STATUS] &= ~S_RXCHOVRF;
         if (fifo32_is_empty(&s->rx_fifo)) {
             qemu_log_mask(LOG_GUEST_ERROR,
                           "%s: Reading empty RX_FIFO\n",
                           __func__);
         } else {
             ret = fifo32_pop(&s->rx_fifo);
         }
         if (fifo32_is_empty(&s->rx_fifo)) {
             s->regs[R_SPI_STATUS] |= S_RXFIFOEMP;
         }
         break;

     case R_SPI_MIS:
         update_mis(s);
         ret = s->regs[R_SPI_MIS];
         break;

     default:
         if (addr < ARRAY_SIZE(s->regs)) {
             ret = s->regs[addr];
         } else {
             qemu_log_mask(LOG_GUEST_ERROR,
                          "%s: Bad offset 0x%" HWADDR_PRIx "\n", __func__,
                          addr * 4);
             return ret;
         }
         break;
     }

     DB_PRINT("addr=0x%" HWADDR_PRIx " = 0x%" PRIx32, addr * 4, ret);
     spi_update_irq(s);
     return ret;
 }

 static void assert_cs(MSSSpiState *s)
 {
     qemu_set_irq(s->cs_line, 0);
 }

 static void deassert_cs(MSSSpiState *s)
 {
     qemu_set_irq(s->cs_line, 1);
 }

 static void spi_flush_txfifo(MSSSpiState *s)
 {
     uint32_t tx;
     uint32_t rx;
     bool sps = !!(s->regs[R_SPI_CONTROL] & C_SPS);

     /*
      * Chip Select(CS) is automatically controlled by this controller.
      * If SPS bit is set in Control register then CS is asserted
      * until all the frames set in frame count of Control register are
      * transferred. If SPS is not set then CS pulses between frames.
      * Note that Slave Select register specifies which of the CS line
      * has to be controlled automatically by controller. Bits SS[7:1] are for
      * masters in FPGA fabric since we model only Microcontroller subsystem
      * of Smartfusion2 we control only one CS(SS[0]) line.
      */
     while (!fifo32_is_empty(&s->tx_fifo) && s->frame_count) {
         assert_cs(s);

         s->regs[R_SPI_STATUS] &= ~(S_TXDONE | S_RXRDY);

         tx = fifo32_pop(&s->tx_fifo);
         DB_PRINT("data tx:0x%" PRIx32, tx);
         rx = ssi_transfer(s->spi, tx);
         DB_PRINT("data rx:0x%" PRIx32, rx);

         if (fifo32_num_used(&s->rx_fifo) == s->fifo_depth) {
             s->regs[R_SPI_STATUS] |= S_RXCHOVRF;
             s->regs[R_SPI_RIS] |= S_RXCHOVRF;
         } else {
             fifo32_push(&s->rx_fifo, rx);
             s->regs[R_SPI_STATUS] &= ~S_RXFIFOEMP;
             if (fifo32_num_used(&s->rx_fifo) == (s->fifo_depth - 1)) {
                 s->regs[R_SPI_STATUS] |= S_RXFIFOFULNXT;
             } else if (fifo32_num_used(&s->rx_fifo) == s->fifo_depth) {
                 s->regs[R_SPI_STATUS] |= S_RXFIFOFUL;
             }
         }
         s->frame_count--;
         if (!sps) {
             deassert_cs(s);
         }
     }

     if (!s->frame_count) {
         s->frame_count = (s->regs[R_SPI_CONTROL] & FMCOUNT_MASK) >>
                             FMCOUNT_SHIFT;
         deassert_cs(s);
         s->regs[R_SPI_RIS] |= S_TXDONE | S_RXRDY;
         s->regs[R_SPI_STATUS] |= S_TXDONE | S_RXRDY;
    }
 }

 static void spi_write(void *opaque, hwaddr addr,
             uint64_t val64, unsigned int size)
 {
     MSSSpiState *s = opaque;
     uint32_t value = val64;

     DB_PRINT("addr=0x%" HWADDR_PRIx " =0x%" PRIx32, addr, value);
     addr >>= 2;

     switch (addr) {
     case R_SPI_TX:
         /* adding to already full FIFO */
         if (fifo32_num_used(&s->tx_fifo) == s->fifo_depth) {
             break;
         }
         s->regs[R_SPI_STATUS] &= ~S_TXFIFOEMP;
         fifo32_push(&s->tx_fifo, value);
         if (fifo32_num_used(&s->tx_fifo) == (s->fifo_depth - 1)) {
             s->regs[R_SPI_STATUS] |= S_TXFIFOFULNXT;
         } else if (fifo32_num_used(&s->tx_fifo) == s->fifo_depth) {
             s->regs[R_SPI_STATUS] |= S_TXFIFOFUL;
         }
         if (s->enabled) {
             spi_flush_txfifo(s);
         }
         break;

     case R_SPI_CONTROL:
         s->regs[R_SPI_CONTROL] = value;
         if (value & C_BIGFIFO) {
             set_fifodepth(s);
         } else {
             s->fifo_depth = 4;
         }
         s->enabled = value & C_ENABLE;
         s->frame_count = (value & FMCOUNT_MASK) >> FMCOUNT_SHIFT;
         if (value & C_RESET) {
             mss_spi_reset(DEVICE(s));
         }
         break;

     case R_SPI_DFSIZE:
         if (s->enabled) {
             break;
         }
         /*
          * [31:6] bits are reserved bits and for future use.
          * [5:0] are for frame size. Only [5:0] bits are validated
          * during write, [31:6] bits are untouched.
          */
         if ((value & FRAMESZ_MASK) > FRAMESZ_MAX) {
             qemu_log_mask(LOG_GUEST_ERROR, "%s: Incorrect size %u provided."
                          "Maximum frame size is %u\n",
                          __func__, value & FRAMESZ_MASK, FRAMESZ_MAX);
             break;
         }
         s->regs[R_SPI_DFSIZE] = value;
         break;

     case R_SPI_INTCLR:
         s->regs[R_SPI_INTCLR] = value;
         if (value & S_TXDONE) {
             s->regs[R_SPI_RIS] &= ~S_TXDONE;
         }
         if (value & S_RXRDY) {
             s->regs[R_SPI_RIS] &= ~S_RXRDY;
         }
         if (value & S_RXCHOVRF) {
             s->regs[R_SPI_RIS] &= ~S_RXCHOVRF;
         }
         break;

     case R_SPI_MIS:
     case R_SPI_STATUS:
     case R_SPI_RIS:
             qemu_log_mask(LOG_GUEST_ERROR,
                          "%s: Write to read only register 0x%" HWADDR_PRIx "\n",
                          __func__, addr * 4);
         break;

     default:
         if (addr < ARRAY_SIZE(s->regs)) {
             s->regs[addr] = value;
         } else {
             qemu_log_mask(LOG_GUEST_ERROR,
                          "%s: Bad offset 0x%" HWADDR_PRIx "\n", __func__,
                          addr * 4);
         }
         break;
     }

     spi_update_irq(s);
 }

 static const MemoryRegionOps spi_ops = {
     .read = spi_read,
     .write = spi_write,
     .endianness = DEVICE_NATIVE_ENDIAN,
     .valid = {
         .min_access_size = 1,
         .max_access_size = 4
     }
 };

 static void mss_spi_realize(DeviceState *dev, Error **errp)
 {
     MSSSpiState *s = MSS_SPI(dev);
     SysBusDevice *sbd = SYS_BUS_DEVICE(dev);

     s->spi = ssi_create_bus(dev, "spi");

     sysbus_init_irq(sbd, &s->irq);
     ssi_auto_connect_slaves(dev, &s->cs_line, s->spi);
     sysbus_init_irq(sbd, &s->cs_line);

     memory_region_init_io(&s->mmio, OBJECT(s), &spi_ops, s,
                           TYPE_MSS_SPI, R_SPI_MAX * 4);
     sysbus_init_mmio(sbd, &s->mmio);

     fifo32_create(&s->tx_fifo, FIFO_CAPACITY);
     fifo32_create(&s->rx_fifo, FIFO_CAPACITY);
 }

 static const VMStateDescription vmstate_mss_spi = {
     .name = TYPE_MSS_SPI,
     .version_id = 1,
     .minimum_version_id = 1,
     .fields = (VMStateField[]) {
         VMSTATE_FIFO32(tx_fifo, MSSSpiState),
         VMSTATE_FIFO32(rx_fifo, MSSSpiState),
         VMSTATE_UINT32_ARRAY(regs, MSSSpiState, R_SPI_MAX),
         VMSTATE_END_OF_LIST()
     }
 };

 static void mss_spi_class_init(ObjectClass *klass, void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(klass);

     dc->realize = mss_spi_realize;
     dc->reset = mss_spi_reset;
     dc->vmsd = &vmstate_mss_spi;
 }

 static const TypeInfo mss_spi_info = {
     .name           = TYPE_MSS_SPI,
     .parent         = TYPE_SYS_BUS_DEVICE,
     .instance_size  = sizeof(MSSSpiState),
     .class_init     = mss_spi_class_init,
 };

 static void mss_spi_register_types(void)
 {
     type_register_static(&mss_spi_info);
 }

 type_init(mss_spi_register_types)
	/*
	* Block model of SPI controller present in
	* Microsemi's SmartFusion2 and SmartFusion SoCs.
	*
	* Copyright (C) 2017 Subbaraya Sundeep <sundeep.lkml@gmail.com>
	*
	* 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/irq.h"
	#include "hw/ssi/mss-spi.h"
	#include "migration/vmstate.h"
	#include "qemu/log.h"
	#include "qemu/module.h"

	#ifndef MSS_SPI_ERR_DEBUG
	#define MSS_SPI_ERR_DEBUG 0
	#endif

	#define DB_PRINT_L(lvl, fmt, args...) do { \
	if (MSS_SPI_ERR_DEBUG >= lvl) { \
	qemu_log("%s: " fmt "\n", __func__, ## args); \
	} \
	} while (0)

	#define DB_PRINT(fmt, args...) DB_PRINT_L(1, fmt, ## args)

	#define FIFO_CAPACITY 32

	#define R_SPI_CONTROL 0
	#define R_SPI_DFSIZE 1
	#define R_SPI_STATUS 2
	#define R_SPI_INTCLR 3
	#define R_SPI_RX 4
	#define R_SPI_TX 5
	#define R_SPI_CLKGEN 6
	#define R_SPI_SS 7
	#define R_SPI_MIS 8
	#define R_SPI_RIS 9

	#define S_TXDONE (1 << 0)
	#define S_RXRDY (1 << 1)
	#define S_RXCHOVRF (1 << 2)
	#define S_RXFIFOFUL (1 << 4)
	#define S_RXFIFOFULNXT (1 << 5)
	#define S_RXFIFOEMP (1 << 6)
	#define S_RXFIFOEMPNXT (1 << 7)
	#define S_TXFIFOFUL (1 << 8)
	#define S_TXFIFOFULNXT (1 << 9)
	#define S_TXFIFOEMP (1 << 10)
	#define S_TXFIFOEMPNXT (1 << 11)
	#define S_FRAMESTART (1 << 12)
	#define S_SSEL (1 << 13)
	#define S_ACTIVE (1 << 14)

	#define C_ENABLE (1 << 0)
	#define C_MODE (1 << 1)
	#define C_INTRXDATA (1 << 4)
	#define C_INTTXDATA (1 << 5)
	#define C_INTRXOVRFLO (1 << 6)
	#define C_SPS (1 << 26)
	#define C_BIGFIFO (1 << 29)
	#define C_RESET (1 << 31)

	#define FRAMESZ_MASK 0x3F
	#define FMCOUNT_MASK 0x00FFFF00
	#define FMCOUNT_SHIFT 8
	#define FRAMESZ_MAX 32

	static void txfifo_reset(MSSSpiState *s)
	{
	fifo32_reset(&s->tx_fifo);

	s->regs[R_SPI_STATUS] &= ~S_TXFIFOFUL;
	s->regs[R_SPI_STATUS] \|= S_TXFIFOEMP;
	}

	static void rxfifo_reset(MSSSpiState *s)
	{
	fifo32_reset(&s->rx_fifo);

	s->regs[R_SPI_STATUS] &= ~S_RXFIFOFUL;
	s->regs[R_SPI_STATUS] \|= S_RXFIFOEMP;
	}

	static void set_fifodepth(MSSSpiState *s)
	{
	unsigned int size = s->regs[R_SPI_DFSIZE] & FRAMESZ_MASK;

	if (size <= 8) {
	s->fifo_depth = 32;
	} else if (size <= 16) {
	s->fifo_depth = 16;
	} else {
	s->fifo_depth = 8;
	}
	}

	static void update_mis(MSSSpiState *s)
	{
	uint32_t reg = s->regs[R_SPI_CONTROL];
	uint32_t tmp;

	/*
	* form the Control register interrupt enable bits
	* same as RIS, MIS and Interrupt clear registers for simplicity
	*/
	tmp = ((reg & C_INTRXOVRFLO) >> 4) \| ((reg & C_INTRXDATA) >> 3) \|
	((reg & C_INTTXDATA) >> 5);
	s->regs[R_SPI_MIS] \|= tmp & s->regs[R_SPI_RIS];
	}

	static void spi_update_irq(MSSSpiState *s)
	{
	int irq;

	update_mis(s);
	irq = !!(s->regs[R_SPI_MIS]);

	qemu_set_irq(s->irq, irq);
	}

	static void mss_spi_reset(DeviceState *d)
	{
	MSSSpiState *s = MSS_SPI(d);

	memset(s->regs, 0, sizeof s->regs);
	s->regs[R_SPI_CONTROL] = 0x80000102;
	s->regs[R_SPI_DFSIZE] = 0x4;
	s->regs[R_SPI_STATUS] = S_SSEL \| S_TXFIFOEMP \| S_RXFIFOEMP;
	s->regs[R_SPI_CLKGEN] = 0x7;
	s->regs[R_SPI_RIS] = 0x0;

	s->fifo_depth = 4;
	s->frame_count = 1;
	s->enabled = false;

	rxfifo_reset(s);
	txfifo_reset(s);
	}

	static uint64_t
	spi_read(void *opaque, hwaddr addr, unsigned int size)
	{
	MSSSpiState *s = opaque;
	uint32_t ret = 0;

	addr >>= 2;
	switch (addr) {
	case R_SPI_RX:
	s->regs[R_SPI_STATUS] &= ~S_RXFIFOFUL;
	s->regs[R_SPI_STATUS] &= ~S_RXCHOVRF;
	if (fifo32_is_empty(&s->rx_fifo)) {
	qemu_log_mask(LOG_GUEST_ERROR,
	"%s: Reading empty RX_FIFO\n",
	__func__);
	} else {
	ret = fifo32_pop(&s->rx_fifo);
	}
	if (fifo32_is_empty(&s->rx_fifo)) {
	s->regs[R_SPI_STATUS] \|= S_RXFIFOEMP;
	}
	break;

	case R_SPI_MIS:
	update_mis(s);
	ret = s->regs[R_SPI_MIS];
	break;

	default:
	if (addr < ARRAY_SIZE(s->regs)) {
	ret = s->regs[addr];
	} else {
	qemu_log_mask(LOG_GUEST_ERROR,
	"%s: Bad offset 0x%" HWADDR_PRIx "\n", __func__,
	addr * 4);
	return ret;
	}
	break;
	}

	DB_PRINT("addr=0x%" HWADDR_PRIx " = 0x%" PRIx32, addr * 4, ret);
	spi_update_irq(s);
	return ret;
	}

	static void assert_cs(MSSSpiState *s)
	{
	qemu_set_irq(s->cs_line, 0);
	}

	static void deassert_cs(MSSSpiState *s)
	{
	qemu_set_irq(s->cs_line, 1);
	}

	static void spi_flush_txfifo(MSSSpiState *s)
	{
	uint32_t tx;
	uint32_t rx;
	bool sps = !!(s->regs[R_SPI_CONTROL] & C_SPS);

	/*
	* Chip Select(CS) is automatically controlled by this controller.
	* If SPS bit is set in Control register then CS is asserted
	* until all the frames set in frame count of Control register are
	* transferred. If SPS is not set then CS pulses between frames.
	* Note that Slave Select register specifies which of the CS line
	* has to be controlled automatically by controller. Bits SS[7:1] are for
	* masters in FPGA fabric since we model only Microcontroller subsystem
	* of Smartfusion2 we control only one CS(SS[0]) line.
	*/
	while (!fifo32_is_empty(&s->tx_fifo) && s->frame_count) {
	assert_cs(s);

	s->regs[R_SPI_STATUS] &= ~(S_TXDONE \| S_RXRDY);

	tx = fifo32_pop(&s->tx_fifo);
	DB_PRINT("data tx:0x%" PRIx32, tx);
	rx = ssi_transfer(s->spi, tx);
	DB_PRINT("data rx:0x%" PRIx32, rx);

	if (fifo32_num_used(&s->rx_fifo) == s->fifo_depth) {
	s->regs[R_SPI_STATUS] \|= S_RXCHOVRF;
	s->regs[R_SPI_RIS] \|= S_RXCHOVRF;
	} else {
	fifo32_push(&s->rx_fifo, rx);
	s->regs[R_SPI_STATUS] &= ~S_RXFIFOEMP;
	if (fifo32_num_used(&s->rx_fifo) == (s->fifo_depth - 1)) {
	s->regs[R_SPI_STATUS] \|= S_RXFIFOFULNXT;
	} else if (fifo32_num_used(&s->rx_fifo) == s->fifo_depth) {
	s->regs[R_SPI_STATUS] \|= S_RXFIFOFUL;
	}
	}
	s->frame_count--;
	if (!sps) {
	deassert_cs(s);
	}
	}

	if (!s->frame_count) {
	s->frame_count = (s->regs[R_SPI_CONTROL] & FMCOUNT_MASK) >>
	FMCOUNT_SHIFT;
	deassert_cs(s);
	s->regs[R_SPI_RIS] \|= S_TXDONE \| S_RXRDY;
	s->regs[R_SPI_STATUS] \|= S_TXDONE \| S_RXRDY;
	}
	}

	static void spi_write(void *opaque, hwaddr addr,
	uint64_t val64, unsigned int size)
	{
	MSSSpiState *s = opaque;
	uint32_t value = val64;

	DB_PRINT("addr=0x%" HWADDR_PRIx " =0x%" PRIx32, addr, value);
	addr >>= 2;

	switch (addr) {
	case R_SPI_TX:
	/* adding to already full FIFO */
	if (fifo32_num_used(&s->tx_fifo) == s->fifo_depth) {
	break;
	}
	s->regs[R_SPI_STATUS] &= ~S_TXFIFOEMP;
	fifo32_push(&s->tx_fifo, value);
	if (fifo32_num_used(&s->tx_fifo) == (s->fifo_depth - 1)) {
	s->regs[R_SPI_STATUS] \|= S_TXFIFOFULNXT;
	} else if (fifo32_num_used(&s->tx_fifo) == s->fifo_depth) {
	s->regs[R_SPI_STATUS] \|= S_TXFIFOFUL;
	}
	if (s->enabled) {
	spi_flush_txfifo(s);
	}
	break;

	case R_SPI_CONTROL:
	s->regs[R_SPI_CONTROL] = value;
	if (value & C_BIGFIFO) {
	set_fifodepth(s);
	} else {
	s->fifo_depth = 4;
	}
	s->enabled = value & C_ENABLE;
	s->frame_count = (value & FMCOUNT_MASK) >> FMCOUNT_SHIFT;
	if (value & C_RESET) {
	mss_spi_reset(DEVICE(s));
	}
	break;

	case R_SPI_DFSIZE:
	if (s->enabled) {
	break;
	}
	/*
	* [31:6] bits are reserved bits and for future use.
	* [5:0] are for frame size. Only [5:0] bits are validated
	* during write, [31:6] bits are untouched.
	*/
	if ((value & FRAMESZ_MASK) > FRAMESZ_MAX) {
	qemu_log_mask(LOG_GUEST_ERROR, "%s: Incorrect size %u provided."
	"Maximum frame size is %u\n",
	__func__, value & FRAMESZ_MASK, FRAMESZ_MAX);
	break;
	}
	s->regs[R_SPI_DFSIZE] = value;
	break;

	case R_SPI_INTCLR:
	s->regs[R_SPI_INTCLR] = value;
	if (value & S_TXDONE) {
	s->regs[R_SPI_RIS] &= ~S_TXDONE;
	}
	if (value & S_RXRDY) {
	s->regs[R_SPI_RIS] &= ~S_RXRDY;
	}
	if (value & S_RXCHOVRF) {
	s->regs[R_SPI_RIS] &= ~S_RXCHOVRF;
	}
	break;

	case R_SPI_MIS:
	case R_SPI_STATUS:
	case R_SPI_RIS:
	qemu_log_mask(LOG_GUEST_ERROR,
	"%s: Write to read only register 0x%" HWADDR_PRIx "\n",
	__func__, addr * 4);
	break;

	default:
	if (addr < ARRAY_SIZE(s->regs)) {
	s->regs[addr] = value;
	} else {
	qemu_log_mask(LOG_GUEST_ERROR,
	"%s: Bad offset 0x%" HWADDR_PRIx "\n", __func__,
	addr * 4);
	}
	break;
	}

	spi_update_irq(s);
	}

	static const MemoryRegionOps spi_ops = {
	.read = spi_read,
	.write = spi_write,
	.endianness = DEVICE_NATIVE_ENDIAN,
	.valid = {
	.min_access_size = 1,
	.max_access_size = 4
	}
	};

	static void mss_spi_realize(DeviceState dev, Error *errp)
	{
	MSSSpiState *s = MSS_SPI(dev);
	SysBusDevice *sbd = SYS_BUS_DEVICE(dev);

	s->spi = ssi_create_bus(dev, "spi");

	sysbus_init_irq(sbd, &s->irq);
	ssi_auto_connect_slaves(dev, &s->cs_line, s->spi);
	sysbus_init_irq(sbd, &s->cs_line);

	memory_region_init_io(&s->mmio, OBJECT(s), &spi_ops, s,
	TYPE_MSS_SPI, R_SPI_MAX * 4);
	sysbus_init_mmio(sbd, &s->mmio);

	fifo32_create(&s->tx_fifo, FIFO_CAPACITY);
	fifo32_create(&s->rx_fifo, FIFO_CAPACITY);
	}

	static const VMStateDescription vmstate_mss_spi = {
	.name = TYPE_MSS_SPI,
	.version_id = 1,
	.minimum_version_id = 1,
	.fields = (VMStateField[]) {
	VMSTATE_FIFO32(tx_fifo, MSSSpiState),
	VMSTATE_FIFO32(rx_fifo, MSSSpiState),
	VMSTATE_UINT32_ARRAY(regs, MSSSpiState, R_SPI_MAX),
	VMSTATE_END_OF_LIST()
	}
	};

	static void mss_spi_class_init(ObjectClass klass, void data)
	{
	DeviceClass *dc = DEVICE_CLASS(klass);

	dc->realize = mss_spi_realize;
	dc->reset = mss_spi_reset;
	dc->vmsd = &vmstate_mss_spi;
	}

	static const TypeInfo mss_spi_info = {
	.name = TYPE_MSS_SPI,
	.parent = TYPE_SYS_BUS_DEVICE,
	.instance_size = sizeof(MSSSpiState),
	.class_init = mss_spi_class_init,
	};

	static void mss_spi_register_types(void)
	{
	type_register_static(&mss_spi_info);
	}

	type_init(mss_spi_register_types)