drivers/spi/spi_dw.c - third_party/github/zephyrproject-rtos/zephyr - Git at Google

 /* spi_dw.c - Designware SPI driver implementation */

 /*
  * Copyright (c) 2015 Intel Corporation.
  *
  * SPDX-License-Identifier: Apache-2.0
  */

 #include <errno.h>

 #include <kernel.h>
 #include <arch/cpu.h>

 #include <misc/__assert.h>
 #include <board.h>
 #include <device.h>
 #include <init.h>

 #include <sys_io.h>
 #include <clock_control.h>
 #include <misc/util.h>

 #include <spi.h>
 #include <spi_dw.h>

 #ifdef CONFIG_IOAPIC
 #include <drivers/ioapic.h>
 #endif

 #define SYS_LOG_DOMAIN "SPI DW"
 #define SYS_LOG_LEVEL CONFIG_SYS_LOG_SPI_LEVEL
 #include <logging/sys_log.h>

 #if (CONFIG_SYS_LOG_SPI_LEVEL == 4)
 #define DBG_COUNTER_INIT()	\
 	uint32_t __cnt = 0
 #define DBG_COUNTER_INC()	\
 	(__cnt++)
 #define DBG_COUNTER_RESULT()	\
 	(__cnt)
 #else
 #define DBG_COUNTER_INIT() {; }
 #define DBG_COUNTER_INC() {; }
 #define DBG_COUNTER_RESULT() 0
 #endif

 #ifdef SPI_DW_SPI_CLOCK
 #define SPI_DW_CLK_DIVIDER(ssi_clk_hz) \
 		((SPI_DW_SPI_CLOCK / ssi_clk_hz) & 0xFFFF)
 /* provision for soc.h providing a clock that is different than CPU clock */
 #else
 #define SPI_DW_CLK_DIVIDER(ssi_clk_hz) \
 		((CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC / ssi_clk_hz) & 0xFFFF)
 #endif

 static void completed(struct device *dev, int error)
 {
 	const struct spi_dw_config *info = dev->config->config_info;
 	struct spi_dw_data *spi = dev->driver_data;

 	if (error) {
 		goto out;
 	}

 	/*
 	* There are several situations here.
 	* 1. spi_write w rx_buf - need last_tx && rx_buf_len zero to be done.
 	* 2. spi_write w/o rx_buf - only need to determine when write is done.
 	* 3. spi_read - need rx_buf_len zero.
 	*/
 	if (spi->tx_buf && spi->rx_buf) {
 		if (!spi->last_tx || spi->rx_buf_len)
 			return;
 	} else if (spi->tx_buf) {
 		if (!spi->last_tx)
 			return;
 	} else { /* or, spi->rx_buf!=0 */
 		if (spi->rx_buf_len)
 			return;
 	}

 out:
 	/* need to give time for FIFOs to drain before issuing more commands */
 	while (test_bit_sr_busy(info->regs)) {
 	}

 	spi->error = error;

 	/* Disabling interrupts */
 	write_imr(DW_SPI_IMR_MASK, info->regs);
 	/* Disabling the controller */
 	clear_bit_ssienr(info->regs);

 	_spi_control_cs(dev, 0);

 	SYS_LOG_DBG("SPI transaction completed %s error",
 	    error ? "with" : "without");

 	k_sem_give(&spi->device_sync_sem);
 }

 static void push_data(struct device *dev)
 {
 	const struct spi_dw_config *info = dev->config->config_info;
 	struct spi_dw_data *spi = dev->driver_data;
 	uint32_t data = 0;
 	uint32_t f_tx;
 	DBG_COUNTER_INIT();

 	if (spi->rx_buf) {
 		f_tx = DW_SPI_FIFO_DEPTH - read_txflr(info->regs) -
 					read_rxflr(info->regs);
 		if ((int)f_tx < 0) {
 			f_tx = 0; /* if rx-fifo is full, hold off tx */
 		}
 	} else {
 		f_tx = DW_SPI_FIFO_DEPTH - read_txflr(info->regs);
 	}
 	if (f_tx && (spi->tx_buf_len == 0)) {
 		/* room in fifo, yet nothing to send */
 		spi->last_tx = 1; /* setting last_tx indicates TX is done */
 	}
 	while (f_tx) {
 		if (spi->tx_buf && spi->tx_buf_len > 0) {
 			switch (spi->dfs) {
 			case 1:
 				data = UNALIGNED_GET((uint8_t *)(spi->tx_buf));
 				break;
 			case 2:
 				data = UNALIGNED_GET((uint16_t *)(spi->tx_buf));
 				break;
 #ifndef CONFIG_ARC
 			case 4:
 				data = UNALIGNED_GET((uint32_t *)(spi->tx_buf));
 				break;
 #endif
 			}

 			spi->tx_buf += spi->dfs;
 			spi->tx_buf_len--;
 		} else if (spi->rx_buf && spi->rx_buf_len > 0) {
 			/* No need to push more than necessary */
 			if (spi->rx_buf_len - spi->fifo_diff <= 0) {
 				break;
 			}

 			data = 0;
 		} else {
 			/* Nothing to push anymore */
 			break;
 		}

 		write_dr(data, info->regs);
 		f_tx--;
 		spi->fifo_diff++;
 		DBG_COUNTER_INC();
 	}

 	if (spi->last_tx) {
 		write_txftlr(0, info->regs);
 		/* prevents any further interrupts demanding TX fifo fill */
 	}

 	SYS_LOG_DBG("Pushed: %d", DBG_COUNTER_RESULT());
 }

 static void pull_data(struct device *dev)
 {
 	const struct spi_dw_config *info = dev->config->config_info;
 	struct spi_dw_data *spi = dev->driver_data;
 	uint32_t data = 0;
 	DBG_COUNTER_INIT();

 	while (read_rxflr(info->regs)) {
 		data = read_dr(info->regs);
 		DBG_COUNTER_INC();

 		if (spi->rx_buf && spi->rx_buf_len > 0) {
 			switch (spi->dfs) {
 			case 1:
 				UNALIGNED_PUT(data, (uint8_t *)spi->rx_buf);
 				break;
 			case 2:
 				UNALIGNED_PUT(data, (uint16_t *)spi->rx_buf);
 				break;
 #ifndef CONFIG_ARC
 			case 4:
 				UNALIGNED_PUT(data, (uint32_t *)spi->rx_buf);
 				break;
 #endif
 			}

 			spi->rx_buf += spi->dfs;
 			spi->rx_buf_len--;
 		}

 		spi->fifo_diff--;
 	}

 	if (!spi->rx_buf_len && spi->tx_buf_len < DW_SPI_FIFO_DEPTH) {
 		write_rxftlr(spi->tx_buf_len - 1, info->regs);
 	} else if (read_rxftlr(info->regs) >= spi->rx_buf_len) {
 		write_rxftlr(spi->rx_buf_len - 1, info->regs);
 	}

 	SYS_LOG_DBG("Pulled: %d", DBG_COUNTER_RESULT());
 }

 static inline bool _spi_dw_is_controller_ready(struct device *dev)
 {
 	const struct spi_dw_config *info = dev->config->config_info;

 	if (test_bit_ssienr(info->regs) || test_bit_sr_busy(info->regs)) {
 		return false;
 	}

 	return true;
 }

 static int spi_dw_configure(struct device *dev,
 				struct spi_config *config)
 {
 	const struct spi_dw_config *info = dev->config->config_info;
 	struct spi_dw_data *spi = dev->driver_data;
 	uint32_t flags = config->config;
 	uint32_t ctrlr0 = 0;
 	uint32_t mode;

 	SYS_LOG_DBG("%s: %p (0x%x), %p", __func__, dev, info->regs, config);

 	/* Check status */
 	if (!_spi_dw_is_controller_ready(dev)) {
 		SYS_LOG_DBG("%s: Controller is busy", __func__);
 		return -EBUSY;
 	}

 	/* Word size */
 	ctrlr0 |= DW_SPI_CTRLR0_DFS(SPI_WORD_SIZE_GET(flags));

 	/* Determine how many bytes are required per-frame */
 	spi->dfs = SPI_DFS_TO_BYTES(SPI_WORD_SIZE_GET(flags));

 	/* SPI mode */
 	mode = SPI_MODE(flags);
 	if (mode & SPI_MODE_CPOL) {
 		ctrlr0 |= DW_SPI_CTRLR0_SCPOL;
 	}

 	if (mode & SPI_MODE_CPHA) {
 		ctrlr0 |= DW_SPI_CTRLR0_SCPH;
 	}

 	if (mode & SPI_MODE_LOOP) {
 		ctrlr0 |= DW_SPI_CTRLR0_SRL;
 	}

 	/* Installing the configuration */
 	write_ctrlr0(ctrlr0, info->regs);

 	/*
 	 * Configure the rate. Use this small hack to allow the user to call
 	 * spi_configure() with both a divider (as the driver was initially
 	 * written) and a frequency (as the SPI API suggests to). The clock
 	 * divider is a 16bit value, hence we can fairly, and safely, assume
 	 * that everything above this value is a frequency. The trade-off is
 	 * that if one wants to use a bus frequency of 64kHz (or less), it has
 	 * the use a divider...
 	 */
 	if (config->max_sys_freq > 0xffff) {
 		write_baudr(SPI_DW_CLK_DIVIDER(config->max_sys_freq),
 			    info->regs);
 	} else {
 		write_baudr(config->max_sys_freq, info->regs);
 	}

 	return 0;
 }

 static int spi_dw_slave_select(struct device *dev, uint32_t slave)
 {
 	struct spi_dw_data *spi = dev->driver_data;

 	SYS_LOG_DBG("%s: %p %d", __func__, dev, slave);

 	if (slave == 0 || slave > 16) {
 		return -EINVAL;
 	}

 	spi->slave = 1 << (slave - 1);

 	return 0;
 }

 static int spi_dw_transceive(struct device *dev,
 			     const void *tx_buf, uint32_t tx_buf_len,
 			     void *rx_buf, uint32_t rx_buf_len)
 {
 	const struct spi_dw_config *info = dev->config->config_info;
 	struct spi_dw_data *spi = dev->driver_data;
 	uint32_t rx_thsld = DW_SPI_RXFTLR_DFLT;
 	uint32_t imask;

 	SYS_LOG_DBG("%s: %p, %p, %u, %p, %u",
 	    __func__, dev, tx_buf, tx_buf_len, rx_buf, rx_buf_len);

 	/* Check status */
 	if (!_spi_dw_is_controller_ready(dev)) {
 		SYS_LOG_DBG("%s: Controller is busy", __func__);
 		return -EBUSY;
 	}

 	/* Set buffers info */
 	spi->tx_buf = tx_buf;
 	spi->tx_buf_len = tx_buf_len/spi->dfs;
 	spi->rx_buf = rx_buf;
 	if (rx_buf) {
 		spi->rx_buf_len = rx_buf_len/spi->dfs;
 	} else {
 		spi->rx_buf_len = 0; /* must be zero if no buffer */
 	}
 	spi->fifo_diff = 0;
 	spi->last_tx = 0;

 	/* Tx Threshold */
 	write_txftlr(DW_SPI_TXFTLR_DFLT, info->regs);

 	/* Does Rx thresholds needs to be lower? */
 	if (spi->rx_buf_len && spi->rx_buf_len < DW_SPI_FIFO_DEPTH) {
 		rx_thsld = spi->rx_buf_len - 1;
 	} else if (!spi->rx_buf_len && spi->tx_buf_len < DW_SPI_FIFO_DEPTH) {
 		rx_thsld = spi->tx_buf_len - 1;
 		/* TODO: why? */
 	}

 	write_rxftlr(rx_thsld, info->regs);

 	/* Slave select */
 	write_ser(spi->slave, info->regs);

 	_spi_control_cs(dev, 1);

 	/* Enable interrupts */
 	imask = DW_SPI_IMR_UNMASK;
 	if (!rx_buf) {
 		/* if there is no rx buffer, keep all rx interrupts masked */
 		imask &= DW_SPI_IMR_MASK_RX;
 	}

 	write_imr(imask, info->regs);

 	/* Enable the controller */
 	set_bit_ssienr(info->regs);

 	k_sem_take(&spi->device_sync_sem, K_FOREVER);

 	if (spi->error) {
 		spi->error = 0;
 		return -EIO;
 	}

 	return 0;
 }

 void spi_dw_isr(void *arg)
 {
 	struct device *dev = (struct device *)arg;
 	const struct spi_dw_config *info = dev->config->config_info;
 	uint32_t error = 0;
 	uint32_t int_status;

 	int_status = read_isr(info->regs);

 	SYS_LOG_DBG("SPI int_status 0x%x - (tx: %d, rx: %d)",
 	    int_status, read_txflr(info->regs), read_rxflr(info->regs));

 	if (int_status & DW_SPI_ISR_ERRORS_MASK) {
 		error = 1;
 		goto out;
 	}

 	if (int_status & DW_SPI_ISR_RXFIS) {
 		pull_data(dev);
 	}

 	if (int_status & DW_SPI_ISR_TXEIS) {
 		push_data(dev);
 	}

 out:
 	clear_interrupts(info->regs);
 	completed(dev, error);
 }

 static const struct spi_driver_api dw_spi_api = {
 	.configure = spi_dw_configure,
 	.slave_select = spi_dw_slave_select,
 	.transceive = spi_dw_transceive,
 };

 int spi_dw_init(struct device *dev)
 {
 	const struct spi_dw_config *info = dev->config->config_info;
 	struct spi_dw_data *spi = dev->driver_data;

 	_clock_config(dev);
 	_clock_on(dev);

 #if 0 /* TODO: Not correct version for every target. Don't check. */
 #ifndef CONFIG_SOC_QUARK_SE_C1000_SS
 	if (read_ssi_comp_version(info->regs) != DW_SSI_COMP_VERSION) {
 		dev->driver_api = NULL;
 		_clock_off(dev);
 		return -EPERM;
 	}
 #endif
 #endif

 	info->config_func();

 	k_sem_init(&spi->device_sync_sem, 0, UINT_MAX);

 	_spi_config_cs(dev);

 	/* Masking interrupt and making sure controller is disabled */
 	write_imr(DW_SPI_IMR_MASK, info->regs);
 	clear_bit_ssienr(info->regs);

 	SYS_LOG_DBG("Designware SPI driver initialized on device: %p", dev);

 	return 0;
 }


 #ifdef CONFIG_SPI_0
 void spi_config_0_irq(void);

 struct spi_dw_data spi_dw_data_port_0;

 const struct spi_dw_config spi_dw_config_0 = {
 	.regs = SPI_DW_PORT_0_REGS,
 #ifdef CONFIG_SPI_DW_CLOCK_GATE
 	.clock_data = UINT_TO_POINTER(CONFIG_SPI_0_CLOCK_GATE_SUBSYS),
 #endif /* CONFIG_SPI_DW_CLOCK_GATE */
 #ifdef CONFIG_SPI_DW_CS_GPIO
 	.cs_gpio_name = CONFIG_SPI_0_CS_GPIO_PORT,
 	.cs_gpio_pin = CONFIG_SPI_0_CS_GPIO_PIN,
 #endif
 	.config_func = spi_config_0_irq
 };

 DEVICE_AND_API_INIT(spi_dw_port_0, CONFIG_SPI_0_NAME, spi_dw_init,
 		    &spi_dw_data_port_0, &spi_dw_config_0,
 		    POST_KERNEL, CONFIG_SPI_INIT_PRIORITY,
 		    &dw_spi_api);

 void spi_config_0_irq(void)
 {
 #ifdef CONFIG_SPI_DW_INTERRUPT_SINGLE_LINE
 	IRQ_CONNECT(SPI_DW_PORT_0_IRQ, CONFIG_SPI_0_IRQ_PRI,
 		    spi_dw_isr, DEVICE_GET(spi_dw_port_0), SPI_DW_IRQ_FLAGS);
 	irq_enable(SPI_DW_PORT_0_IRQ);
 	_spi_int_unmask(SPI_DW_PORT_0_INT_MASK);
 #else /* SPI_DW_INTERRUPT_SEPARATED_LINES */
 	IRQ_CONNECT(IRQ_SPI0_RX_AVAIL, CONFIG_SPI_0_IRQ_PRI,
 		    spi_dw_isr, DEVICE_GET(spi_dw_port_0), SPI_DW_IRQ_FLAGS);
 	IRQ_CONNECT(IRQ_SPI0_TX_REQ, CONFIG_SPI_0_IRQ_PRI,
 		    spi_dw_isr, DEVICE_GET(spi_dw_port_0), SPI_DW_IRQ_FLAGS);
 	IRQ_CONNECT(IRQ_SPI0_ERR_INT, CONFIG_SPI_0_IRQ_PRI,
 		    spi_dw_isr, DEVICE_GET(spi_dw_port_0), SPI_DW_IRQ_FLAGS);

 	irq_enable(IRQ_SPI0_RX_AVAIL);
 	irq_enable(IRQ_SPI0_TX_REQ);
 	irq_enable(IRQ_SPI0_ERR_INT);

 	_spi_int_unmask(SPI_DW_PORT_0_RX_INT_MASK);
 	_spi_int_unmask(SPI_DW_PORT_0_TX_INT_MASK);
 	_spi_int_unmask(SPI_DW_PORT_0_ERROR_INT_MASK);
 #endif
 }
 #endif /* CONFIG_SPI_0 */
 #ifdef CONFIG_SPI_1
 void spi_config_1_irq(void);

 struct spi_dw_data spi_dw_data_port_1;

 static const struct spi_dw_config spi_dw_config_1 = {
 	.regs = SPI_DW_PORT_1_REGS,
 #ifdef CONFIG_SPI_DW_CLOCK_GATE
 	.clock_data = UINT_TO_POINTER(CONFIG_SPI_1_CLOCK_GATE_SUBSYS),
 #endif /* CONFIG_SPI_DW_CLOCK_GATE */
 #ifdef CONFIG_SPI_DW_CS_GPIO
 	.cs_gpio_name = CONFIG_SPI_1_CS_GPIO_PORT,
 	.cs_gpio_pin = CONFIG_SPI_1_CS_GPIO_PIN,
 #endif
 	.config_func = spi_config_1_irq
 };

 DEVICE_AND_API_INIT(spi_dw_port_1, CONFIG_SPI_1_NAME, spi_dw_init,
 		    &spi_dw_data_port_1, &spi_dw_config_1,
 		    POST_KERNEL, CONFIG_SPI_INIT_PRIORITY,
 		    &dw_spi_api);

 void spi_config_1_irq(void)
 {
 #ifdef CONFIG_SPI_DW_INTERRUPT_SINGLE_LINE
 	IRQ_CONNECT(SPI_DW_PORT_1_IRQ, CONFIG_SPI_1_IRQ_PRI,
 		    spi_dw_isr, DEVICE_GET(spi_dw_port_1), SPI_DW_IRQ_FLAGS);
 	irq_enable(SPI_DW_PORT_1_IRQ);
 	_spi_int_unmask(SPI_DW_PORT_1_INT_MASK);
 #else /* SPI_DW_INTERRUPT_SEPARATED_LINES */
 	IRQ_CONNECT(IRQ_SPI1_RX_AVAIL, CONFIG_SPI_1_IRQ_PRI,
 		    spi_dw_isr, DEVICE_GET(spi_dw_port_1), SPI_DW_IRQ_FLAGS);
 	IRQ_CONNECT(IRQ_SPI1_TX_REQ, CONFIG_SPI_1_IRQ_PRI,
 		    spi_dw_isr, DEVICE_GET(spi_dw_port_1), SPI_DW_IRQ_FLAGS);
 	IRQ_CONNECT(IRQ_SPI1_ERR_INT, CONFIG_SPI_1_IRQ_PRI,
 		    spi_dw_isr, DEVICE_GET(spi_dw_port_1), SPI_DW_IRQ_FLAGS);

 	irq_enable(IRQ_SPI1_RX_AVAIL);
 	irq_enable(IRQ_SPI1_TX_REQ);
 	irq_enable(IRQ_SPI1_ERR_INT);

 	_spi_int_unmask(SPI_DW_PORT_1_RX_INT_MASK);
 	_spi_int_unmask(SPI_DW_PORT_1_TX_INT_MASK);
 	_spi_int_unmask(SPI_DW_PORT_1_ERROR_INT_MASK);
 #endif
 }
 #endif /* CONFIG_SPI_1 */
	/* spi_dw.c - Designware SPI driver implementation */

	/*
	* Copyright (c) 2015 Intel Corporation.
	*
	* SPDX-License-Identifier: Apache-2.0
	*/

	#include <errno.h>

	#include <kernel.h>
	#include <arch/cpu.h>

	#include <misc/__assert.h>
	#include <board.h>
	#include <device.h>
	#include <init.h>

	#include <sys_io.h>
	#include <clock_control.h>
	#include <misc/util.h>

	#include <spi.h>
	#include <spi_dw.h>

	#ifdef CONFIG_IOAPIC
	#include <drivers/ioapic.h>
	#endif

	#define SYS_LOG_DOMAIN "SPI DW"
	#define SYS_LOG_LEVEL CONFIG_SYS_LOG_SPI_LEVEL
	#include <logging/sys_log.h>

	#if (CONFIG_SYS_LOG_SPI_LEVEL == 4)
	#define DBG_COUNTER_INIT() \
	uint32_t __cnt = 0
	#define DBG_COUNTER_INC() \
	(__cnt++)
	#define DBG_COUNTER_RESULT() \
	(__cnt)
	#else
	#define DBG_COUNTER_INIT() {; }
	#define DBG_COUNTER_INC() {; }
	#define DBG_COUNTER_RESULT() 0
	#endif

	#ifdef SPI_DW_SPI_CLOCK
	#define SPI_DW_CLK_DIVIDER(ssi_clk_hz) \
	((SPI_DW_SPI_CLOCK / ssi_clk_hz) & 0xFFFF)
	/* provision for soc.h providing a clock that is different than CPU clock */
	#else
	#define SPI_DW_CLK_DIVIDER(ssi_clk_hz) \
	((CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC / ssi_clk_hz) & 0xFFFF)
	#endif

	static void completed(struct device *dev, int error)
	{
	const struct spi_dw_config *info = dev->config->config_info;
	struct spi_dw_data *spi = dev->driver_data;

	if (error) {
	goto out;
	}

	/*
	* There are several situations here.
	* 1. spi_write w rx_buf - need last_tx && rx_buf_len zero to be done.
	* 2. spi_write w/o rx_buf - only need to determine when write is done.
	* 3. spi_read - need rx_buf_len zero.
	*/
	if (spi->tx_buf && spi->rx_buf) {
	if (!spi->last_tx \|\| spi->rx_buf_len)
	return;
	} else if (spi->tx_buf) {
	if (!spi->last_tx)
	return;
	} else { /* or, spi->rx_buf!=0 */
	if (spi->rx_buf_len)
	return;
	}

	out:
	/* need to give time for FIFOs to drain before issuing more commands */
	while (test_bit_sr_busy(info->regs)) {
	}

	spi->error = error;

	/* Disabling interrupts */
	write_imr(DW_SPI_IMR_MASK, info->regs);
	/* Disabling the controller */
	clear_bit_ssienr(info->regs);

	_spi_control_cs(dev, 0);

	SYS_LOG_DBG("SPI transaction completed %s error",
	error ? "with" : "without");

	k_sem_give(&spi->device_sync_sem);
	}

	static void push_data(struct device *dev)
	{
	const struct spi_dw_config *info = dev->config->config_info;
	struct spi_dw_data *spi = dev->driver_data;
	uint32_t data = 0;
	uint32_t f_tx;
	DBG_COUNTER_INIT();

	if (spi->rx_buf) {
	f_tx = DW_SPI_FIFO_DEPTH - read_txflr(info->regs) -
	read_rxflr(info->regs);
	if ((int)f_tx < 0) {
	f_tx = 0; /* if rx-fifo is full, hold off tx */
	}
	} else {
	f_tx = DW_SPI_FIFO_DEPTH - read_txflr(info->regs);
	}
	if (f_tx && (spi->tx_buf_len == 0)) {
	/* room in fifo, yet nothing to send */
	spi->last_tx = 1; /* setting last_tx indicates TX is done */
	}
	while (f_tx) {
	if (spi->tx_buf && spi->tx_buf_len > 0) {
	switch (spi->dfs) {
	case 1:
	data = UNALIGNED_GET((uint8_t *)(spi->tx_buf));
	break;
	case 2:
	data = UNALIGNED_GET((uint16_t *)(spi->tx_buf));
	break;
	#ifndef CONFIG_ARC
	case 4:
	data = UNALIGNED_GET((uint32_t *)(spi->tx_buf));
	break;
	#endif
	}

	spi->tx_buf += spi->dfs;
	spi->tx_buf_len--;
	} else if (spi->rx_buf && spi->rx_buf_len > 0) {
	/* No need to push more than necessary */
	if (spi->rx_buf_len - spi->fifo_diff <= 0) {
	break;
	}

	data = 0;
	} else {
	/* Nothing to push anymore */
	break;
	}

	write_dr(data, info->regs);
	f_tx--;
	spi->fifo_diff++;
	DBG_COUNTER_INC();
	}

	if (spi->last_tx) {
	write_txftlr(0, info->regs);
	/* prevents any further interrupts demanding TX fifo fill */
	}

	SYS_LOG_DBG("Pushed: %d", DBG_COUNTER_RESULT());
	}

	static void pull_data(struct device *dev)
	{
	const struct spi_dw_config *info = dev->config->config_info;
	struct spi_dw_data *spi = dev->driver_data;
	uint32_t data = 0;
	DBG_COUNTER_INIT();

	while (read_rxflr(info->regs)) {
	data = read_dr(info->regs);
	DBG_COUNTER_INC();

	if (spi->rx_buf && spi->rx_buf_len > 0) {
	switch (spi->dfs) {
	case 1:
	UNALIGNED_PUT(data, (uint8_t *)spi->rx_buf);
	break;
	case 2:
	UNALIGNED_PUT(data, (uint16_t *)spi->rx_buf);
	break;
	#ifndef CONFIG_ARC
	case 4:
	UNALIGNED_PUT(data, (uint32_t *)spi->rx_buf);
	break;
	#endif
	}

	spi->rx_buf += spi->dfs;
	spi->rx_buf_len--;
	}

	spi->fifo_diff--;
	}

	if (!spi->rx_buf_len && spi->tx_buf_len < DW_SPI_FIFO_DEPTH) {
	write_rxftlr(spi->tx_buf_len - 1, info->regs);
	} else if (read_rxftlr(info->regs) >= spi->rx_buf_len) {
	write_rxftlr(spi->rx_buf_len - 1, info->regs);
	}

	SYS_LOG_DBG("Pulled: %d", DBG_COUNTER_RESULT());
	}

	static inline bool _spi_dw_is_controller_ready(struct device *dev)
	{
	const struct spi_dw_config *info = dev->config->config_info;

	if (test_bit_ssienr(info->regs) \|\| test_bit_sr_busy(info->regs)) {
	return false;
	}

	return true;
	}

	static int spi_dw_configure(struct device *dev,
	struct spi_config *config)
	{
	const struct spi_dw_config *info = dev->config->config_info;
	struct spi_dw_data *spi = dev->driver_data;
	uint32_t flags = config->config;
	uint32_t ctrlr0 = 0;
	uint32_t mode;

	SYS_LOG_DBG("%s: %p (0x%x), %p", __func__, dev, info->regs, config);

	/* Check status */
	if (!_spi_dw_is_controller_ready(dev)) {
	SYS_LOG_DBG("%s: Controller is busy", __func__);
	return -EBUSY;
	}

	/* Word size */
	ctrlr0 \|= DW_SPI_CTRLR0_DFS(SPI_WORD_SIZE_GET(flags));

	/* Determine how many bytes are required per-frame */
	spi->dfs = SPI_DFS_TO_BYTES(SPI_WORD_SIZE_GET(flags));

	/* SPI mode */
	mode = SPI_MODE(flags);
	if (mode & SPI_MODE_CPOL) {
	ctrlr0 \|= DW_SPI_CTRLR0_SCPOL;
	}

	if (mode & SPI_MODE_CPHA) {
	ctrlr0 \|= DW_SPI_CTRLR0_SCPH;
	}

	if (mode & SPI_MODE_LOOP) {
	ctrlr0 \|= DW_SPI_CTRLR0_SRL;
	}

	/* Installing the configuration */
	write_ctrlr0(ctrlr0, info->regs);

	/*
	* Configure the rate. Use this small hack to allow the user to call
	* spi_configure() with both a divider (as the driver was initially
	* written) and a frequency (as the SPI API suggests to). The clock
	* divider is a 16bit value, hence we can fairly, and safely, assume
	* that everything above this value is a frequency. The trade-off is
	* that if one wants to use a bus frequency of 64kHz (or less), it has
	* the use a divider...
	*/
	if (config->max_sys_freq > 0xffff) {
	write_baudr(SPI_DW_CLK_DIVIDER(config->max_sys_freq),
	info->regs);
	} else {
	write_baudr(config->max_sys_freq, info->regs);
	}

	return 0;
	}

	static int spi_dw_slave_select(struct device *dev, uint32_t slave)
	{
	struct spi_dw_data *spi = dev->driver_data;

	SYS_LOG_DBG("%s: %p %d", __func__, dev, slave);

	if (slave == 0 \|\| slave > 16) {
	return -EINVAL;
	}

	spi->slave = 1 << (slave - 1);

	return 0;
	}

	static int spi_dw_transceive(struct device *dev,
	const void *tx_buf, uint32_t tx_buf_len,
	void *rx_buf, uint32_t rx_buf_len)
	{
	const struct spi_dw_config *info = dev->config->config_info;
	struct spi_dw_data *spi = dev->driver_data;
	uint32_t rx_thsld = DW_SPI_RXFTLR_DFLT;
	uint32_t imask;

	SYS_LOG_DBG("%s: %p, %p, %u, %p, %u",
	__func__, dev, tx_buf, tx_buf_len, rx_buf, rx_buf_len);

	/* Check status */
	if (!_spi_dw_is_controller_ready(dev)) {
	SYS_LOG_DBG("%s: Controller is busy", __func__);
	return -EBUSY;
	}

	/* Set buffers info */
	spi->tx_buf = tx_buf;
	spi->tx_buf_len = tx_buf_len/spi->dfs;
	spi->rx_buf = rx_buf;
	if (rx_buf) {
	spi->rx_buf_len = rx_buf_len/spi->dfs;
	} else {
	spi->rx_buf_len = 0; /* must be zero if no buffer */
	}
	spi->fifo_diff = 0;
	spi->last_tx = 0;

	/* Tx Threshold */
	write_txftlr(DW_SPI_TXFTLR_DFLT, info->regs);

	/* Does Rx thresholds needs to be lower? */
	if (spi->rx_buf_len && spi->rx_buf_len < DW_SPI_FIFO_DEPTH) {
	rx_thsld = spi->rx_buf_len - 1;
	} else if (!spi->rx_buf_len && spi->tx_buf_len < DW_SPI_FIFO_DEPTH) {
	rx_thsld = spi->tx_buf_len - 1;
	/* TODO: why? */
	}

	write_rxftlr(rx_thsld, info->regs);

	/* Slave select */
	write_ser(spi->slave, info->regs);

	_spi_control_cs(dev, 1);

	/* Enable interrupts */
	imask = DW_SPI_IMR_UNMASK;
	if (!rx_buf) {
	/* if there is no rx buffer, keep all rx interrupts masked */
	imask &= DW_SPI_IMR_MASK_RX;
	}

	write_imr(imask, info->regs);

	/* Enable the controller */
	set_bit_ssienr(info->regs);

	k_sem_take(&spi->device_sync_sem, K_FOREVER);

	if (spi->error) {
	spi->error = 0;
	return -EIO;
	}

	return 0;
	}

	void spi_dw_isr(void *arg)
	{
	struct device dev = (struct device )arg;
	const struct spi_dw_config *info = dev->config->config_info;
	uint32_t error = 0;
	uint32_t int_status;

	int_status = read_isr(info->regs);

	SYS_LOG_DBG("SPI int_status 0x%x - (tx: %d, rx: %d)",
	int_status, read_txflr(info->regs), read_rxflr(info->regs));

	if (int_status & DW_SPI_ISR_ERRORS_MASK) {
	error = 1;
	goto out;
	}

	if (int_status & DW_SPI_ISR_RXFIS) {
	pull_data(dev);
	}

	if (int_status & DW_SPI_ISR_TXEIS) {
	push_data(dev);
	}

	out:
	clear_interrupts(info->regs);
	completed(dev, error);
	}

	static const struct spi_driver_api dw_spi_api = {
	.configure = spi_dw_configure,
	.slave_select = spi_dw_slave_select,
	.transceive = spi_dw_transceive,
	};

	int spi_dw_init(struct device *dev)
	{
	const struct spi_dw_config *info = dev->config->config_info;
	struct spi_dw_data *spi = dev->driver_data;

	_clock_config(dev);
	_clock_on(dev);

	#if 0 /* TODO: Not correct version for every target. Don't check. */
	#ifndef CONFIG_SOC_QUARK_SE_C1000_SS
	if (read_ssi_comp_version(info->regs) != DW_SSI_COMP_VERSION) {
	dev->driver_api = NULL;
	_clock_off(dev);
	return -EPERM;
	}
	#endif
	#endif

	info->config_func();

	k_sem_init(&spi->device_sync_sem, 0, UINT_MAX);

	_spi_config_cs(dev);

	/* Masking interrupt and making sure controller is disabled */
	write_imr(DW_SPI_IMR_MASK, info->regs);
	clear_bit_ssienr(info->regs);

	SYS_LOG_DBG("Designware SPI driver initialized on device: %p", dev);

	return 0;
	}


	#ifdef CONFIG_SPI_0
	void spi_config_0_irq(void);

	struct spi_dw_data spi_dw_data_port_0;

	const struct spi_dw_config spi_dw_config_0 = {
	.regs = SPI_DW_PORT_0_REGS,
	#ifdef CONFIG_SPI_DW_CLOCK_GATE
	.clock_data = UINT_TO_POINTER(CONFIG_SPI_0_CLOCK_GATE_SUBSYS),
	#endif /* CONFIG_SPI_DW_CLOCK_GATE */
	#ifdef CONFIG_SPI_DW_CS_GPIO
	.cs_gpio_name = CONFIG_SPI_0_CS_GPIO_PORT,
	.cs_gpio_pin = CONFIG_SPI_0_CS_GPIO_PIN,
	#endif
	.config_func = spi_config_0_irq
	};

	DEVICE_AND_API_INIT(spi_dw_port_0, CONFIG_SPI_0_NAME, spi_dw_init,
	&spi_dw_data_port_0, &spi_dw_config_0,
	POST_KERNEL, CONFIG_SPI_INIT_PRIORITY,
	&dw_spi_api);

	void spi_config_0_irq(void)
	{
	#ifdef CONFIG_SPI_DW_INTERRUPT_SINGLE_LINE
	IRQ_CONNECT(SPI_DW_PORT_0_IRQ, CONFIG_SPI_0_IRQ_PRI,
	spi_dw_isr, DEVICE_GET(spi_dw_port_0), SPI_DW_IRQ_FLAGS);
	irq_enable(SPI_DW_PORT_0_IRQ);
	_spi_int_unmask(SPI_DW_PORT_0_INT_MASK);
	#else /* SPI_DW_INTERRUPT_SEPARATED_LINES */
	IRQ_CONNECT(IRQ_SPI0_RX_AVAIL, CONFIG_SPI_0_IRQ_PRI,
	spi_dw_isr, DEVICE_GET(spi_dw_port_0), SPI_DW_IRQ_FLAGS);
	IRQ_CONNECT(IRQ_SPI0_TX_REQ, CONFIG_SPI_0_IRQ_PRI,
	spi_dw_isr, DEVICE_GET(spi_dw_port_0), SPI_DW_IRQ_FLAGS);
	IRQ_CONNECT(IRQ_SPI0_ERR_INT, CONFIG_SPI_0_IRQ_PRI,
	spi_dw_isr, DEVICE_GET(spi_dw_port_0), SPI_DW_IRQ_FLAGS);

	irq_enable(IRQ_SPI0_RX_AVAIL);
	irq_enable(IRQ_SPI0_TX_REQ);
	irq_enable(IRQ_SPI0_ERR_INT);

	_spi_int_unmask(SPI_DW_PORT_0_RX_INT_MASK);
	_spi_int_unmask(SPI_DW_PORT_0_TX_INT_MASK);
	_spi_int_unmask(SPI_DW_PORT_0_ERROR_INT_MASK);
	#endif
	}
	#endif /* CONFIG_SPI_0 */
	#ifdef CONFIG_SPI_1
	void spi_config_1_irq(void);

	struct spi_dw_data spi_dw_data_port_1;

	static const struct spi_dw_config spi_dw_config_1 = {
	.regs = SPI_DW_PORT_1_REGS,
	#ifdef CONFIG_SPI_DW_CLOCK_GATE
	.clock_data = UINT_TO_POINTER(CONFIG_SPI_1_CLOCK_GATE_SUBSYS),
	#endif /* CONFIG_SPI_DW_CLOCK_GATE */
	#ifdef CONFIG_SPI_DW_CS_GPIO
	.cs_gpio_name = CONFIG_SPI_1_CS_GPIO_PORT,
	.cs_gpio_pin = CONFIG_SPI_1_CS_GPIO_PIN,
	#endif
	.config_func = spi_config_1_irq
	};

	DEVICE_AND_API_INIT(spi_dw_port_1, CONFIG_SPI_1_NAME, spi_dw_init,
	&spi_dw_data_port_1, &spi_dw_config_1,
	POST_KERNEL, CONFIG_SPI_INIT_PRIORITY,
	&dw_spi_api);

	void spi_config_1_irq(void)
	{
	#ifdef CONFIG_SPI_DW_INTERRUPT_SINGLE_LINE
	IRQ_CONNECT(SPI_DW_PORT_1_IRQ, CONFIG_SPI_1_IRQ_PRI,
	spi_dw_isr, DEVICE_GET(spi_dw_port_1), SPI_DW_IRQ_FLAGS);
	irq_enable(SPI_DW_PORT_1_IRQ);
	_spi_int_unmask(SPI_DW_PORT_1_INT_MASK);
	#else /* SPI_DW_INTERRUPT_SEPARATED_LINES */
	IRQ_CONNECT(IRQ_SPI1_RX_AVAIL, CONFIG_SPI_1_IRQ_PRI,
	spi_dw_isr, DEVICE_GET(spi_dw_port_1), SPI_DW_IRQ_FLAGS);
	IRQ_CONNECT(IRQ_SPI1_TX_REQ, CONFIG_SPI_1_IRQ_PRI,
	spi_dw_isr, DEVICE_GET(spi_dw_port_1), SPI_DW_IRQ_FLAGS);
	IRQ_CONNECT(IRQ_SPI1_ERR_INT, CONFIG_SPI_1_IRQ_PRI,
	spi_dw_isr, DEVICE_GET(spi_dw_port_1), SPI_DW_IRQ_FLAGS);

	irq_enable(IRQ_SPI1_RX_AVAIL);
	irq_enable(IRQ_SPI1_TX_REQ);
	irq_enable(IRQ_SPI1_ERR_INT);

	_spi_int_unmask(SPI_DW_PORT_1_RX_INT_MASK);
	_spi_int_unmask(SPI_DW_PORT_1_TX_INT_MASK);
	_spi_int_unmask(SPI_DW_PORT_1_ERROR_INT_MASK);
	#endif
	}
	#endif /* CONFIG_SPI_1 */