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

 /*
  * Copyright (c) 2023 Rivos Inc.
  *
  * SPDX-License-Identifier: Apache-2.0
  */

 #include <zephyr/logging/log.h>
 LOG_MODULE_REGISTER(spi_opentitan);

 #include "spi_context.h"

 #include <zephyr/device.h>
 #include <zephyr/drivers/spi.h>
 #include <soc.h>
 #include <stdbool.h>

 /* Register offsets within the SPI host register space. */
 #define SPI_HOST_INTR_STATE_REG_OFFSET 0x00
 #define SPI_HOST_INTR_ENABLE_REG_OFFSET 0x04
 #define SPI_HOST_INTR_TEST_REG_OFFSET 0x08
 #define SPI_HOST_ALERT_TEST_REG_OFFSET 0x0c
 #define SPI_HOST_CONTROL_REG_OFFSET 0x10
 #define SPI_HOST_STATUS_REG_OFFSET 0x14
 #define SPI_HOST_CONFIGOPTS_REG_OFFSET 0x18
 #define SPI_HOST_CSID_REG_OFFSET 0x1c
 #define SPI_HOST_COMMAND_REG_OFFSET 0x20
 #define SPI_HOST_RXDATA_REG_OFFSET 0x24
 #define SPI_HOST_TXDATA_REG_OFFSET 0x28
 #define SPI_HOST_ERROR_ENABLE_REG_OFFSET 0x2c
 #define SPI_HOST_ERROR_STATUS_REG_OFFSET 0x30
 #define SPI_HOST_EVENT_ENABLE_REG_OFFSET 0x34

 /* Control register fields. */
 #define SPI_HOST_CONTROL_OUTPUT_EN_BIT BIT(29)
 #define SPI_HOST_CONTROL_SW_RST_BIT BIT(30)
 #define SPI_HOST_CONTROL_SPIEN_BIT BIT(31)

 /* Status register fields. */
 #define SPI_HOST_STATUS_TXQD_MASK GENMASK(7, 0)
 #define SPI_HOST_STATUS_RXQD_MASK GENMASK(15, 8)
 #define SPI_HOST_STATUS_BYTEORDER_BIT BIT(22)
 #define SPI_HOST_STATUS_RXEMPTY_BIT BIT(24)
 #define SPI_HOST_STATUS_ACTIVE_BIT BIT(30)
 #define SPI_HOST_STATUS_READY_BIT BIT(31)

 /* Command register fields. */
 #define SPI_HOST_COMMAND_LEN_MASK GENMASK(8, 0)
 /* "Chip select active after transaction" */
 #define SPI_HOST_COMMAND_CSAAT_BIT BIT(9)
 #define SPI_HOST_COMMAND_SPEED_MASK GENMASK(11, 10)
 #define SPI_HOST_COMMAND_SPEED_STANDARD (0 << 10)
 #define SPI_HOST_COMMAND_SPEED_DUAL (1 << 10)
 #define SPI_HOST_COMMAND_SPEED_QUAD (2 << 10)
 #define SPI_HOST_COMMAND_DIRECTION_MASK GENMASK(13, 12)
 #define SPI_HOST_COMMAND_DIRECTION_RX (0x1 << 12)
 #define SPI_HOST_COMMAND_DIRECTION_TX (0x2 << 12)
 #define SPI_HOST_COMMAND_DIRECTION_BOTH (0x3 << 12)

 /* Configopts register fields. */
 #define SPI_HOST_CONFIGOPTS_CPHA0_BIT BIT(30)
 #define SPI_HOST_CONFIGOPTS_CPOL0_BIT BIT(31)

 #define DT_DRV_COMPAT lowrisc_opentitan_spi

 struct spi_opentitan_data {
 	struct spi_context ctx;
 };

 struct spi_opentitan_cfg {
 	uint32_t base;
 	uint32_t f_input;
 };

 static int spi_config(const struct device *dev, uint32_t frequency,
 		uint16_t operation)
 {
 	const struct spi_opentitan_cfg *cfg = dev->config;

 	uint32_t reg;

 	if (operation & SPI_HALF_DUPLEX) {
 		return -ENOTSUP;
 	}

 	if (SPI_OP_MODE_GET(operation) != SPI_OP_MODE_MASTER) {
 		return -ENOTSUP;
 	}

 	if (operation & SPI_MODE_LOOP) {
 		return -ENOTSUP;
 	}

 	if (SPI_WORD_SIZE_GET(operation) != 8) {
 		return -ENOTSUP;
 	}

 	if (IS_ENABLED(CONFIG_SPI_EXTENDED_MODES) &&
 		(operation & SPI_LINES_MASK) != SPI_LINES_SINGLE) {
 		return -ENOTSUP;
 	}

 	/* Most significant bit always transferred first. */
 	if (operation & SPI_TRANSFER_LSB) {
 		return -ENOTSUP;
 	}

 	/* Set the SPI frequency, polarity, and clock phase in CONFIGOPTS register.
 	 * Applied divider (divides f_in / 2) is CLKDIV register (16 bit) + 1.
 	 */
 	reg = cfg->f_input / 2 / frequency;
 	if (reg > 0xffffu) {
 		reg = 0xffffu;
 	} else if (reg > 0) {
 		reg--;
 	}
 	/* Setup phase */
 	if (operation & SPI_MODE_CPHA) {
 		reg |= SPI_HOST_CONFIGOPTS_CPHA0_BIT;
 	}
 	/* Setup polarity. */
 	if (operation & SPI_MODE_CPOL) {
 		reg |= SPI_HOST_CONFIGOPTS_CPOL0_BIT;
 	}
 	sys_write32(reg, cfg->base + SPI_HOST_CONFIGOPTS_REG_OFFSET);

 	return 0;
 }

 static bool spi_opentitan_rx_available(const struct spi_opentitan_cfg *cfg)
 {
 	/* Rx bytes are available if Tx FIFO is non-empty. */
 	return !(sys_read32(cfg->base + SPI_HOST_STATUS_REG_OFFSET) & SPI_HOST_STATUS_RXEMPTY_BIT);
 }

 static void spi_opentitan_xfer(const struct device *dev, const bool gpio_cs_control)
 {
 	const struct spi_opentitan_cfg *cfg = dev->config;
 	struct spi_opentitan_data *data = dev->data;
 	struct spi_context *ctx = &data->ctx;

 	while (spi_context_tx_on(ctx) || spi_context_rx_on(ctx)) {
 		const size_t segment_len = MAX(ctx->tx_len, ctx->rx_len);
 		uint32_t host_command_reg;

 		/* Setup transaction duplex. */
 		if (!spi_context_tx_on(ctx)) {
 			host_command_reg = SPI_HOST_COMMAND_DIRECTION_RX;
 		} else if (!spi_context_rx_on(ctx)) {
 			host_command_reg = SPI_HOST_COMMAND_DIRECTION_TX;
 		} else {
 			host_command_reg = SPI_HOST_COMMAND_DIRECTION_BOTH;
 		}

 		size_t tx_bytes_to_queue = spi_context_tx_buf_on(ctx) ? ctx->tx_len : 0;

 		/* First place Tx bytes in FIFO, packed four to a word. */
 		while (tx_bytes_to_queue > 0) {
 			uint32_t fifo_word = 0;

 			for (int byte = 0; byte < 4; ++byte) {
 				if (tx_bytes_to_queue == 0) {
 					break;
 				}
 				fifo_word |= *ctx->tx_buf << (8 * byte);
 				spi_context_update_tx(ctx, 1, 1);
 				tx_bytes_to_queue--;
 			}
 			sys_write32(fifo_word, cfg->base + SPI_HOST_TXDATA_REG_OFFSET);
 		}

 		/* Keep CS asserted if another Tx segment remains or if two more Rx
 		 * segments remain (because we will handle one Rx segment after the
 		 * forthcoming transaction).
 		 */
 		if (ctx->tx_count > 0 || ctx->rx_count > 1)  {
 			host_command_reg |= SPI_HOST_COMMAND_CSAAT_BIT;
 		}
 		/* Segment length field holds COMMAND.LEN + 1. */
 		host_command_reg |= segment_len - 1;

 		/* Issue transaction. */
 		sys_write32(host_command_reg, cfg->base + SPI_HOST_COMMAND_REG_OFFSET);

 		size_t rx_bytes_to_read = spi_context_rx_buf_on(ctx) ? ctx->rx_len : 0;

 		/* Read from Rx FIFO as required. */
 		while (rx_bytes_to_read > 0) {
 			while (!spi_opentitan_rx_available(cfg)) {
 				;
 			}
 			uint32_t rx_word = sys_read32(cfg->base +
 				SPI_HOST_RXDATA_REG_OFFSET);
 			for (int byte = 0; byte < 4; ++byte) {
 				if (rx_bytes_to_read == 0) {
 					break;
 				}
 				*ctx->rx_buf = (rx_word >> (8 * byte)) & 0xff;
 				spi_context_update_rx(ctx, 1, 1);
 				rx_bytes_to_read--;
 			}
 		}
 	}

 	/* Deassert the CS line if required. */
 	if (gpio_cs_control) {
 		spi_context_cs_control(ctx, false);
 	}

 	spi_context_complete(ctx, dev, 0);
 }

 static int spi_opentitan_init(const struct device *dev)
 {
 	const struct spi_opentitan_cfg *cfg = dev->config;
 	struct spi_opentitan_data *data = dev->data;
 	int err;

 	/* Place SPI host peripheral in reset and wait for reset to complete. */
 	sys_write32(SPI_HOST_CONTROL_SW_RST_BIT,
 		cfg->base + SPI_HOST_CONTROL_REG_OFFSET);
 	while (sys_read32(cfg->base + SPI_HOST_STATUS_REG_OFFSET)
 			& (SPI_HOST_STATUS_ACTIVE_BIT | SPI_HOST_STATUS_TXQD_MASK |
 				SPI_HOST_STATUS_RXQD_MASK)) {
 		;
 	}
 	/* Clear reset and enable SPI host peripheral. */
 	sys_write32(SPI_HOST_CONTROL_OUTPUT_EN_BIT | SPI_HOST_CONTROL_SPIEN_BIT,
 		cfg->base + SPI_HOST_CONTROL_REG_OFFSET);

 	err = spi_context_cs_configure_all(&data->ctx);
 	if (err < 0) {
 		return err;
 	}

 	/* Make sure the context is unlocked */
 	spi_context_unlock_unconditionally(&data->ctx);
 	return 0;
 }

 static int spi_opentitan_transceive(const struct device *dev,
 			  const struct spi_config *config,
 			  const struct spi_buf_set *tx_bufs,
 			  const struct spi_buf_set *rx_bufs)
 {
 	int rc = 0;
 	bool gpio_cs_control = false;
 	struct spi_opentitan_data *data = dev->data;

 	/* Lock the SPI Context */
 	spi_context_lock(&data->ctx, false, NULL, NULL, config);

 	/* Configure the SPI bus */
 	data->ctx.config = config;
 	rc = spi_config(dev, config->frequency, config->operation);
 	if (rc < 0) {
 		spi_context_release(&data->ctx, rc);
 		return rc;
 	}

 	spi_context_buffers_setup(&data->ctx, tx_bufs, rx_bufs, 1);

 	/* Assert the CS line. HW will always assert the CS pin identified by CSID
 	 * (default CSID: 0), so GPIO CS control will work in addition to HW
 	 * asserted (and presumably ignored) CS.
 	 */
 	if (config->cs) {
 		gpio_cs_control = true;
 		spi_context_cs_control(&data->ctx, true);
 	}

 	/* Perform transfer */
 	spi_opentitan_xfer(dev, gpio_cs_control);

 	rc = spi_context_wait_for_completion(&data->ctx);

 	spi_context_release(&data->ctx, rc);

 	return rc;
 }

 #ifdef CONFIG_SPI_ASYNC
 static int spi_opentitan_transceive_async(const struct device *dev,
 					const struct spi_config *spi_cfg,
 					const struct spi_buf_set *tx_bufs,
 					const struct spi_buf_set *rx_bufs,
 					spi_callback_t cb,
 					void *userdata)
 {
 	return -ENOTSUP;
 }
 #endif

 static int spi_opentitan_release(const struct device *dev,
 			   const struct spi_config *config)
 {
 	struct spi_opentitan_data *data = dev->data;

 	spi_context_unlock_unconditionally(&data->ctx);
 	return 0;
 }

 /* Device Instantiation */

 static const struct spi_driver_api spi_opentitan_api = {
 	.transceive = spi_opentitan_transceive,
 #ifdef CONFIG_SPI_ASYNC
 	.transceive_async = spi_opentitan_transceive_async,
 #endif
 	.release = spi_opentitan_release,
 };

 #define SPI_INIT(n) \
 	static struct spi_opentitan_data spi_opentitan_data_##n = { \
 		SPI_CONTEXT_INIT_LOCK(spi_opentitan_data_##n, ctx), \
 		SPI_CONTEXT_INIT_SYNC(spi_opentitan_data_##n, ctx), \
 		SPI_CONTEXT_CS_GPIOS_INITIALIZE(DT_DRV_INST(n), ctx)	\
 	}; \
 	static struct spi_opentitan_cfg spi_opentitan_cfg_##n = { \
 		.base = DT_INST_REG_ADDR(n), \
 		.f_input = DT_INST_PROP(n, clock_frequency), \
 	}; \
 	DEVICE_DT_INST_DEFINE(n, \
 			spi_opentitan_init, \
 			NULL, \
 			&spi_opentitan_data_##n, \
 			&spi_opentitan_cfg_##n, \
 			POST_KERNEL, \
 			CONFIG_SPI_INIT_PRIORITY, \
 			&spi_opentitan_api);

 DT_INST_FOREACH_STATUS_OKAY(SPI_INIT)
	/*
	* Copyright (c) 2023 Rivos Inc.
	*
	* SPDX-License-Identifier: Apache-2.0
	*/

	#include <zephyr/logging/log.h>
	LOG_MODULE_REGISTER(spi_opentitan);

	#include "spi_context.h"

	#include <zephyr/device.h>
	#include <zephyr/drivers/spi.h>
	#include <soc.h>
	#include <stdbool.h>

	/* Register offsets within the SPI host register space. */
	#define SPI_HOST_INTR_STATE_REG_OFFSET 0x00
	#define SPI_HOST_INTR_ENABLE_REG_OFFSET 0x04
	#define SPI_HOST_INTR_TEST_REG_OFFSET 0x08
	#define SPI_HOST_ALERT_TEST_REG_OFFSET 0x0c
	#define SPI_HOST_CONTROL_REG_OFFSET 0x10
	#define SPI_HOST_STATUS_REG_OFFSET 0x14
	#define SPI_HOST_CONFIGOPTS_REG_OFFSET 0x18
	#define SPI_HOST_CSID_REG_OFFSET 0x1c
	#define SPI_HOST_COMMAND_REG_OFFSET 0x20
	#define SPI_HOST_RXDATA_REG_OFFSET 0x24
	#define SPI_HOST_TXDATA_REG_OFFSET 0x28
	#define SPI_HOST_ERROR_ENABLE_REG_OFFSET 0x2c
	#define SPI_HOST_ERROR_STATUS_REG_OFFSET 0x30
	#define SPI_HOST_EVENT_ENABLE_REG_OFFSET 0x34

	/* Control register fields. */
	#define SPI_HOST_CONTROL_OUTPUT_EN_BIT BIT(29)
	#define SPI_HOST_CONTROL_SW_RST_BIT BIT(30)
	#define SPI_HOST_CONTROL_SPIEN_BIT BIT(31)

	/* Status register fields. */
	#define SPI_HOST_STATUS_TXQD_MASK GENMASK(7, 0)
	#define SPI_HOST_STATUS_RXQD_MASK GENMASK(15, 8)
	#define SPI_HOST_STATUS_BYTEORDER_BIT BIT(22)
	#define SPI_HOST_STATUS_RXEMPTY_BIT BIT(24)
	#define SPI_HOST_STATUS_ACTIVE_BIT BIT(30)
	#define SPI_HOST_STATUS_READY_BIT BIT(31)

	/* Command register fields. */
	#define SPI_HOST_COMMAND_LEN_MASK GENMASK(8, 0)
	/* "Chip select active after transaction" */
	#define SPI_HOST_COMMAND_CSAAT_BIT BIT(9)
	#define SPI_HOST_COMMAND_SPEED_MASK GENMASK(11, 10)
	#define SPI_HOST_COMMAND_SPEED_STANDARD (0 << 10)
	#define SPI_HOST_COMMAND_SPEED_DUAL (1 << 10)
	#define SPI_HOST_COMMAND_SPEED_QUAD (2 << 10)
	#define SPI_HOST_COMMAND_DIRECTION_MASK GENMASK(13, 12)
	#define SPI_HOST_COMMAND_DIRECTION_RX (0x1 << 12)
	#define SPI_HOST_COMMAND_DIRECTION_TX (0x2 << 12)
	#define SPI_HOST_COMMAND_DIRECTION_BOTH (0x3 << 12)

	/* Configopts register fields. */
	#define SPI_HOST_CONFIGOPTS_CPHA0_BIT BIT(30)
	#define SPI_HOST_CONFIGOPTS_CPOL0_BIT BIT(31)

	#define DT_DRV_COMPAT lowrisc_opentitan_spi

	struct spi_opentitan_data {
	struct spi_context ctx;
	};

	struct spi_opentitan_cfg {
	uint32_t base;
	uint32_t f_input;
	};

	static int spi_config(const struct device *dev, uint32_t frequency,
	uint16_t operation)
	{
	const struct spi_opentitan_cfg *cfg = dev->config;

	uint32_t reg;

	if (operation & SPI_HALF_DUPLEX) {
	return -ENOTSUP;
	}

	if (SPI_OP_MODE_GET(operation) != SPI_OP_MODE_MASTER) {
	return -ENOTSUP;
	}

	if (operation & SPI_MODE_LOOP) {
	return -ENOTSUP;
	}

	if (SPI_WORD_SIZE_GET(operation) != 8) {
	return -ENOTSUP;
	}

	if (IS_ENABLED(CONFIG_SPI_EXTENDED_MODES) &&
	(operation & SPI_LINES_MASK) != SPI_LINES_SINGLE) {
	return -ENOTSUP;
	}

	/* Most significant bit always transferred first. */
	if (operation & SPI_TRANSFER_LSB) {
	return -ENOTSUP;
	}

	/* Set the SPI frequency, polarity, and clock phase in CONFIGOPTS register.
	* Applied divider (divides f_in / 2) is CLKDIV register (16 bit) + 1.
	*/
	reg = cfg->f_input / 2 / frequency;
	if (reg > 0xffffu) {
	reg = 0xffffu;
	} else if (reg > 0) {
	reg--;
	}
	/* Setup phase */
	if (operation & SPI_MODE_CPHA) {
	reg \|= SPI_HOST_CONFIGOPTS_CPHA0_BIT;
	}
	/* Setup polarity. */
	if (operation & SPI_MODE_CPOL) {
	reg \|= SPI_HOST_CONFIGOPTS_CPOL0_BIT;
	}
	sys_write32(reg, cfg->base + SPI_HOST_CONFIGOPTS_REG_OFFSET);

	return 0;
	}

	static bool spi_opentitan_rx_available(const struct spi_opentitan_cfg *cfg)
	{
	/* Rx bytes are available if Tx FIFO is non-empty. */
	return !(sys_read32(cfg->base + SPI_HOST_STATUS_REG_OFFSET) & SPI_HOST_STATUS_RXEMPTY_BIT);
	}

	static void spi_opentitan_xfer(const struct device *dev, const bool gpio_cs_control)
	{
	const struct spi_opentitan_cfg *cfg = dev->config;
	struct spi_opentitan_data *data = dev->data;
	struct spi_context *ctx = &data->ctx;

	while (spi_context_tx_on(ctx) \|\| spi_context_rx_on(ctx)) {
	const size_t segment_len = MAX(ctx->tx_len, ctx->rx_len);
	uint32_t host_command_reg;

	/* Setup transaction duplex. */
	if (!spi_context_tx_on(ctx)) {
	host_command_reg = SPI_HOST_COMMAND_DIRECTION_RX;
	} else if (!spi_context_rx_on(ctx)) {
	host_command_reg = SPI_HOST_COMMAND_DIRECTION_TX;
	} else {
	host_command_reg = SPI_HOST_COMMAND_DIRECTION_BOTH;
	}

	size_t tx_bytes_to_queue = spi_context_tx_buf_on(ctx) ? ctx->tx_len : 0;

	/* First place Tx bytes in FIFO, packed four to a word. */
	while (tx_bytes_to_queue > 0) {
	uint32_t fifo_word = 0;

	for (int byte = 0; byte < 4; ++byte) {
	if (tx_bytes_to_queue == 0) {
	break;
	}
	fifo_word \|= ctx->tx_buf << (8 byte);
	spi_context_update_tx(ctx, 1, 1);
	tx_bytes_to_queue--;
	}
	sys_write32(fifo_word, cfg->base + SPI_HOST_TXDATA_REG_OFFSET);
	}

	/* Keep CS asserted if another Tx segment remains or if two more Rx
	* segments remain (because we will handle one Rx segment after the
	* forthcoming transaction).
	*/
	if (ctx->tx_count > 0 \|\| ctx->rx_count > 1) {
	host_command_reg \|= SPI_HOST_COMMAND_CSAAT_BIT;
	}
	/* Segment length field holds COMMAND.LEN + 1. */
	host_command_reg \|= segment_len - 1;

	/* Issue transaction. */
	sys_write32(host_command_reg, cfg->base + SPI_HOST_COMMAND_REG_OFFSET);

	size_t rx_bytes_to_read = spi_context_rx_buf_on(ctx) ? ctx->rx_len : 0;

	/* Read from Rx FIFO as required. */
	while (rx_bytes_to_read > 0) {
	while (!spi_opentitan_rx_available(cfg)) {
	;
	}
	uint32_t rx_word = sys_read32(cfg->base +
	SPI_HOST_RXDATA_REG_OFFSET);
	for (int byte = 0; byte < 4; ++byte) {
	if (rx_bytes_to_read == 0) {
	break;
	}
	ctx->rx_buf = (rx_word >> (8 byte)) & 0xff;
	spi_context_update_rx(ctx, 1, 1);
	rx_bytes_to_read--;
	}
	}
	}

	/* Deassert the CS line if required. */
	if (gpio_cs_control) {
	spi_context_cs_control(ctx, false);
	}

	spi_context_complete(ctx, dev, 0);
	}

	static int spi_opentitan_init(const struct device *dev)
	{
	const struct spi_opentitan_cfg *cfg = dev->config;
	struct spi_opentitan_data *data = dev->data;
	int err;

	/* Place SPI host peripheral in reset and wait for reset to complete. */
	sys_write32(SPI_HOST_CONTROL_SW_RST_BIT,
	cfg->base + SPI_HOST_CONTROL_REG_OFFSET);
	while (sys_read32(cfg->base + SPI_HOST_STATUS_REG_OFFSET)
	& (SPI_HOST_STATUS_ACTIVE_BIT \| SPI_HOST_STATUS_TXQD_MASK \|
	SPI_HOST_STATUS_RXQD_MASK)) {
	;
	}
	/* Clear reset and enable SPI host peripheral. */
	sys_write32(SPI_HOST_CONTROL_OUTPUT_EN_BIT \| SPI_HOST_CONTROL_SPIEN_BIT,
	cfg->base + SPI_HOST_CONTROL_REG_OFFSET);

	err = spi_context_cs_configure_all(&data->ctx);
	if (err < 0) {
	return err;
	}

	/* Make sure the context is unlocked */
	spi_context_unlock_unconditionally(&data->ctx);
	return 0;
	}

	static int spi_opentitan_transceive(const struct device *dev,
	const struct spi_config *config,
	const struct spi_buf_set *tx_bufs,
	const struct spi_buf_set *rx_bufs)
	{
	int rc = 0;
	bool gpio_cs_control = false;
	struct spi_opentitan_data *data = dev->data;

	/* Lock the SPI Context */
	spi_context_lock(&data->ctx, false, NULL, NULL, config);

	/* Configure the SPI bus */
	data->ctx.config = config;
	rc = spi_config(dev, config->frequency, config->operation);
	if (rc < 0) {
	spi_context_release(&data->ctx, rc);
	return rc;
	}

	spi_context_buffers_setup(&data->ctx, tx_bufs, rx_bufs, 1);

	/* Assert the CS line. HW will always assert the CS pin identified by CSID
	* (default CSID: 0), so GPIO CS control will work in addition to HW
	* asserted (and presumably ignored) CS.
	*/
	if (config->cs) {
	gpio_cs_control = true;
	spi_context_cs_control(&data->ctx, true);
	}

	/* Perform transfer */
	spi_opentitan_xfer(dev, gpio_cs_control);

	rc = spi_context_wait_for_completion(&data->ctx);

	spi_context_release(&data->ctx, rc);

	return rc;
	}

	#ifdef CONFIG_SPI_ASYNC
	static int spi_opentitan_transceive_async(const struct device *dev,
	const struct spi_config *spi_cfg,
	const struct spi_buf_set *tx_bufs,
	const struct spi_buf_set *rx_bufs,
	spi_callback_t cb,
	void *userdata)
	{
	return -ENOTSUP;
	}
	#endif

	static int spi_opentitan_release(const struct device *dev,
	const struct spi_config *config)
	{
	struct spi_opentitan_data *data = dev->data;

	spi_context_unlock_unconditionally(&data->ctx);
	return 0;
	}

	/* Device Instantiation */

	static const struct spi_driver_api spi_opentitan_api = {
	.transceive = spi_opentitan_transceive,
	#ifdef CONFIG_SPI_ASYNC
	.transceive_async = spi_opentitan_transceive_async,
	#endif
	.release = spi_opentitan_release,
	};

	#define SPI_INIT(n) \
	static struct spi_opentitan_data spi_opentitan_data_##n = { \
	SPI_CONTEXT_INIT_LOCK(spi_opentitan_data_##n, ctx), \
	SPI_CONTEXT_INIT_SYNC(spi_opentitan_data_##n, ctx), \
	SPI_CONTEXT_CS_GPIOS_INITIALIZE(DT_DRV_INST(n), ctx) \
	}; \
	static struct spi_opentitan_cfg spi_opentitan_cfg_##n = { \
	.base = DT_INST_REG_ADDR(n), \
	.f_input = DT_INST_PROP(n, clock_frequency), \
	}; \
	DEVICE_DT_INST_DEFINE(n, \
	spi_opentitan_init, \
	NULL, \
	&spi_opentitan_data_##n, \
	&spi_opentitan_cfg_##n, \
	POST_KERNEL, \
	CONFIG_SPI_INIT_PRIORITY, \
	&spi_opentitan_api);

	DT_INST_FOREACH_STATUS_OKAY(SPI_INIT)