zephyr/drivers/spi/spi_nxp_lpspi/spi_nxp_lpspi.c

/*
 * Copyright 2024-2025 NXP
 *
 * SPDX-License-Identifier: Apache-2.0
 */

#define DT_DRV_COMPAT nxp_lpspi

#include <zephyr/logging/log.h>
LOG_MODULE_DECLARE(spi_lpspi, CONFIG_SPI_LOG_LEVEL);

#include "spi_nxp_lpspi_priv.h"

struct lpspi_driver_data {
	size_t fill_len;
	uint8_t word_size_bytes;
};

static inline uint8_t rx_fifo_cur_len(LPSPI_Type *base)
{
	return (base->FSR & LPSPI_FSR_RXCOUNT_MASK) >> LPSPI_FSR_RXCOUNT_SHIFT;
}

static inline uint8_t tx_fifo_cur_len(LPSPI_Type *base)
{
	return (base->FSR & LPSPI_FSR_TXCOUNT_MASK) >> LPSPI_FSR_TXCOUNT_SHIFT;
}

/* Reads a word from the RX fifo and handles writing it into the RX spi buf */
static inline void lpspi_rx_word_write_bytes(const struct device *dev, size_t offset)
{
	LPSPI_Type *base = (LPSPI_Type *)DEVICE_MMIO_NAMED_GET(dev, reg_base);
	struct lpspi_data *data = dev->data;
	struct lpspi_driver_data *lpspi_data = (struct lpspi_driver_data *)data->driver_data;
	struct spi_context *ctx = &data->ctx;
	uint8_t num_bytes = lpspi_data->word_size_bytes;
	uint8_t *buf = ctx->rx_buf + offset;
	uint32_t word = base->RDR;

	if (!spi_context_rx_buf_on(ctx) && spi_context_rx_on(ctx)) {
		/* receive no actual data if rx buf is NULL */
		return;
	}

	for (uint8_t i = 0; i < num_bytes; i++) {
		buf[i] = (uint8_t)(word >> (BITS_PER_BYTE * i));
	}
}

/* Reads a maximum number of words from RX fifo and writes them to the remainder of the RX buf */
static inline size_t lpspi_rx_buf_write_words(const struct device *dev, uint8_t max_read)
{
	struct lpspi_data *data = dev->data;
	struct lpspi_driver_data *lpspi_data = (struct lpspi_driver_data *)data->driver_data;
	struct spi_context *ctx = &data->ctx;
	size_t buf_len = ctx->rx_len;
	uint8_t words_read = 0;
	size_t offset = 0;

	while (buf_len-- > 0 && max_read-- > 0) {
		lpspi_rx_word_write_bytes(dev, offset);
		offset += lpspi_data->word_size_bytes;
		words_read++;
	}

	return words_read;
}

static inline void lpspi_handle_rx_irq(const struct device *dev)
{
	LPSPI_Type *base = (LPSPI_Type *)DEVICE_MMIO_NAMED_GET(dev, reg_base);
	struct lpspi_data *data = dev->data;
	struct lpspi_driver_data *lpspi_data = (struct lpspi_driver_data *)data->driver_data;
	struct spi_context *ctx = &data->ctx;
	uint8_t rx_fsr = rx_fifo_cur_len(base);
	uint8_t total_words_written = 0;
	uint8_t total_words_read = 0;
	uint8_t words_read;

	base->SR = LPSPI_SR_RDF_MASK;

	LOG_DBG("RX FIFO: %d, RX BUF: %p", rx_fsr, ctx->rx_buf);

	while ((rx_fsr = rx_fifo_cur_len(base)) > 0 && spi_context_rx_on(ctx)) {
		words_read = lpspi_rx_buf_write_words(dev, rx_fsr);
		total_words_read += words_read;
		total_words_written += (spi_context_rx_buf_on(ctx) ? words_read : 0);
		spi_context_update_rx(ctx, lpspi_data->word_size_bytes, words_read);
	}

	LOG_DBG("RX done %d words to spi buf", total_words_written);

	if (spi_context_rx_len_left(ctx) == 0) {
		base->IER &= ~LPSPI_IER_RDIE_MASK;
		base->CR |= LPSPI_CR_RRF_MASK; /* flush rx fifo */
	}
}

/* constructs the next word from the buffer */
static inline uint32_t lpspi_next_tx_word(const struct device *dev, const uint8_t *buf,
					  int offset, size_t max_bytes)
{
	const uint8_t *byte = buf + offset;
	uint32_t next_word = 0;

	for (uint8_t i = 0; i < max_bytes; i++) {
		next_word |= byte[i] << (BITS_PER_BYTE * i);
	}

	return next_word;
}

/* fills the TX fifo with specified amount of data from the specified buffer */
static inline void lpspi_fill_tx_fifo(const struct device *dev, const uint8_t *buf,
				      size_t buf_len, size_t fill_len)
{
	LPSPI_Type *base = (LPSPI_Type *)DEVICE_MMIO_NAMED_GET(dev, reg_base);
	struct lpspi_data *data = dev->data;
	struct lpspi_driver_data *lpspi_data = (struct lpspi_driver_data *)data->driver_data;
	uint8_t word_size = lpspi_data->word_size_bytes;
	size_t buf_remaining_bytes = buf_len * word_size;
	size_t offset = 0;
	uint32_t next_word;
	uint32_t next_word_bytes;

	for (int word_count = 0; word_count < fill_len; word_count++) {
		next_word_bytes = MIN(word_size, buf_remaining_bytes);
		next_word = lpspi_next_tx_word(dev, buf, offset, next_word_bytes);
		base->TDR = next_word;
		offset += word_size;
		buf_remaining_bytes -= word_size;
	}

	LOG_DBG("Filled TX FIFO to %d words (%d bytes)", lpspi_data->fill_len, offset);
}

/* just fills TX fifo with the specified amount of NOPS */
static void lpspi_fill_tx_fifo_nop(const struct device *dev, size_t fill_len)
{
	LPSPI_Type *base = (LPSPI_Type *)DEVICE_MMIO_NAMED_GET(dev, reg_base);

	for (int i = 0; i < fill_len; i++) {
		base->TDR = 0;
	}

	LOG_DBG("Filled TX fifo with %d NOPs", fill_len);
}

/* handles refilling the TX fifo from empty */
static void lpspi_next_tx_fill(const struct device *dev)
{
	const struct lpspi_config *config = dev->config;
	struct lpspi_data *data = dev->data;
	struct lpspi_driver_data *lpspi_data = (struct lpspi_driver_data *)data->driver_data;
	struct spi_context *ctx = &data->ctx;
	size_t fill_len;
	size_t actual_filled = 0;

	fill_len = MIN(ctx->tx_len, config->tx_fifo_size);

	const struct spi_buf *current_buf = ctx->current_tx;
	const uint8_t *cur_buf_pos = ctx->tx_buf;
	size_t cur_buf_len_left = ctx->tx_len;
	size_t bufs_left = ctx->tx_count;

	while (fill_len > 0) {
		size_t next_buf_fill = MIN(cur_buf_len_left, fill_len);

		if (cur_buf_pos == NULL) {
			lpspi_fill_tx_fifo_nop(dev, next_buf_fill);
		} else {
			lpspi_fill_tx_fifo(dev, cur_buf_pos,
						current_buf->len, next_buf_fill);
		}

		fill_len -= next_buf_fill;
		cur_buf_pos += next_buf_fill;

		/* in the case where we just filled as much as we could from the current buffer,
		 * this logic while wrong should have no effect, since fill_len will be 0,
		 * so I choose not to make the code extra complex
		 */
		bufs_left--;
		if (bufs_left > 0) {
			current_buf += 1;
			cur_buf_len_left = current_buf->len;
			cur_buf_pos = current_buf->buf;
		} else {
			fill_len = 0;
		}

		actual_filled += next_buf_fill;
	}

	lpspi_data->fill_len = actual_filled;
}

static inline void lpspi_handle_tx_irq(const struct device *dev)
{
	LPSPI_Type *base = (LPSPI_Type *)DEVICE_MMIO_NAMED_GET(dev, reg_base);
	struct lpspi_data *data = dev->data;
	struct lpspi_driver_data *lpspi_data = (struct lpspi_driver_data *)data->driver_data;
	struct spi_context *ctx = &data->ctx;

	while (spi_context_tx_on(ctx) && lpspi_data->fill_len > 0) {
		size_t this_buf_words_sent = MIN(lpspi_data->fill_len, ctx->tx_len);

		spi_context_update_tx(ctx, lpspi_data->word_size_bytes, this_buf_words_sent);
		lpspi_data->fill_len -= this_buf_words_sent;
	}

	base->SR = LPSPI_SR_TDF_MASK;

	if (!spi_context_tx_on(ctx)) {
		base->IER &= ~LPSPI_IER_TDIE_MASK;
		return;
	}

	lpspi_next_tx_fill(data->dev);
}

static inline void lpspi_end_xfer(const struct device *dev)
{
	LPSPI_Type *base = (LPSPI_Type *)DEVICE_MMIO_NAMED_GET(dev, reg_base);
	const struct lpspi_config *config = dev->config;
	struct lpspi_data *data = dev->data;
	struct spi_context *ctx = &data->ctx;

	spi_context_complete(ctx, dev, 0);
	NVIC_ClearPendingIRQ(config->irqn);
	if (!(ctx->config->operation & SPI_HOLD_ON_CS)) {
		base->TCR &= ~(LPSPI_TCR_CONT_MASK | LPSPI_TCR_CONTC_MASK);
	}
	lpspi_wait_tx_fifo_empty(dev);
	spi_context_cs_control(ctx, false);
	spi_context_release(&data->ctx, 0);
}

static void lpspi_isr(const struct device *dev)
{
	LPSPI_Type *base = (LPSPI_Type *)DEVICE_MMIO_NAMED_GET(dev, reg_base);
	const struct lpspi_config *config = dev->config;
	struct lpspi_data *data = dev->data;
	struct lpspi_driver_data *lpspi_data = (struct lpspi_driver_data *)data->driver_data;
	struct spi_context *ctx = &data->ctx;
	uint32_t status_flags = base->SR;

	if (status_flags & LPSPI_SR_RDF_MASK) {
		lpspi_handle_rx_irq(dev);
	}

	if (status_flags & LPSPI_SR_TDF_MASK) {
		lpspi_handle_tx_irq(dev);
	}

	if (spi_context_tx_on(ctx)) {
		return;
	}

	if (spi_context_rx_on(ctx)) {
		size_t rx_fifo_len = rx_fifo_cur_len(base);
		size_t expected_rx_left = rx_fifo_len < ctx->rx_len ? ctx->rx_len - rx_fifo_len : 0;
		size_t max_fill = MIN(expected_rx_left, config->rx_fifo_size);
		size_t tx_current_fifo_len = tx_fifo_cur_len(base);

		size_t fill_len = tx_current_fifo_len < ctx->rx_len ?
					max_fill - tx_current_fifo_len : 0;

		lpspi_fill_tx_fifo_nop(dev, fill_len);
		lpspi_data->fill_len = fill_len;
	}

	if (spi_context_rx_len_left(ctx) == 1 && (LPSPI_VERID_MAJOR(base->VERID) < 2)) {
		/* Due to stalling behavior on older LPSPI,
		 * need to end xfer in order to get last bit clocked out on bus.
		 */
		base->TCR |= LPSPI_TCR_CONT_MASK;
	} else if (spi_context_rx_len_left(ctx) == 0) {
		lpspi_end_xfer(dev);
	}
}

static int transceive(const struct device *dev, const struct spi_config *spi_cfg,
		      const struct spi_buf_set *tx_bufs, const struct spi_buf_set *rx_bufs,
		      bool asynchronous, spi_callback_t cb, void *userdata)
{
	LPSPI_Type *base = (LPSPI_Type *)DEVICE_MMIO_NAMED_GET(dev, reg_base);
	struct lpspi_data *data = dev->data;
	struct lpspi_driver_data *lpspi_data = (struct lpspi_driver_data *)data->driver_data;
	struct spi_context *ctx = &data->ctx;
	int ret = 0;

	spi_context_lock(&data->ctx, asynchronous, cb, userdata, spi_cfg);

	lpspi_data->word_size_bytes =
		DIV_ROUND_UP(SPI_WORD_SIZE_GET(spi_cfg->operation), BITS_PER_BYTE);
	if (lpspi_data->word_size_bytes > 4) {
		LOG_ERR("Maximum 4 byte word size");
		ret = -EINVAL;
		goto error;
	}

	spi_context_buffers_setup(ctx, tx_bufs, rx_bufs, lpspi_data->word_size_bytes);

	ret = spi_mcux_configure(dev, spi_cfg);
	if (ret) {
		goto error;
	}

	base->CR |= LPSPI_CR_RTF_MASK | LPSPI_CR_RRF_MASK; /* flush fifos */
	base->IER = 0;                                     /* disable all interrupts */
	base->FCR = 0;                                     /* set watermarks to 0 */
	base->SR |= LPSPI_INTERRUPT_BITS;

	LOG_DBG("Starting LPSPI transfer");
	spi_context_cs_control(ctx, true);

	base->CR |= LPSPI_CR_MEN_MASK;

	/* keep the chip select asserted until the end of the zephyr xfer by using
	 * continunous transfer mode. If SPI_HOLD_ON_CS is requested, we need
	 * to also set CONTC in order to continue the previous command to keep CS
	 * asserted.
	 */
	if (spi_cfg->operation & SPI_HOLD_ON_CS || base->TCR & LPSPI_TCR_CONTC_MASK) {
		base->TCR |= LPSPI_TCR_CONTC_MASK | LPSPI_TCR_CONT_MASK;
	} else {
		base->TCR |= LPSPI_TCR_CONT_MASK;
	}
	/* tcr is written to tx fifo */
	lpspi_wait_tx_fifo_empty(dev);

	/* start the transfer sequence which are handled by irqs */
	lpspi_next_tx_fill(dev);

	base->IER |= LPSPI_IER_TDIE_MASK | LPSPI_IER_RDIE_MASK;

	ret = spi_context_wait_for_completion(ctx);
	if (ret >= 0) {
		return ret;
	}

error:
	spi_context_release(ctx, ret);
	return ret;
}

static int lpspi_transceive_sync(const struct device *dev, const struct spi_config *spi_cfg,
				    const struct spi_buf_set *tx_bufs,
				    const struct spi_buf_set *rx_bufs)
{
	return transceive(dev, spi_cfg, tx_bufs, rx_bufs, false, NULL, NULL);
}

#ifdef CONFIG_SPI_ASYNC
static int lpspi_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 transceive(dev, spi_cfg, tx_bufs, rx_bufs, true, cb, userdata);
}
#endif /* CONFIG_SPI_ASYNC */

static DEVICE_API(spi, lpspi_driver_api) = {
	.transceive = lpspi_transceive_sync,
#ifdef CONFIG_SPI_ASYNC
	.transceive_async = lpspi_transceive_async,
#endif
#ifdef CONFIG_SPI_RTIO
	.iodev_submit = spi_rtio_iodev_default_submit,
#endif
	.release = spi_lpspi_release,
};

static int lpspi_init(const struct device *dev)
{
	LPSPI_Type *base = (LPSPI_Type *)DEVICE_MMIO_NAMED_GET(dev, reg_base);
	struct lpspi_data *data = dev->data;
	int err = 0;

	err = spi_nxp_init_common(dev);
	if (err) {
		return err;
	}

	/* Starting config should be master with active low CS, to make sure
	 * the CS lines are configured properly at init for the most common use
	 * cases. This can be changed later on transceive call if user specifies
	 * different spi configuration.
	 */
	base->CFGR1 |= LPSPI_CFGR1_MASTER_MASK;
	base->CFGR1 &= ~LPSPI_CFGR1_PCSPOL_MASK;

	spi_context_unlock_unconditionally(&data->ctx);

	return 0;
}

#define LPSPI_INIT(n)                                                                              \
	SPI_NXP_LPSPI_COMMON_INIT(n)                                                               \
	SPI_LPSPI_CONFIG_INIT(n)                                                              \
                                                                                                   \
	static struct lpspi_driver_data lpspi_##n##_driver_data;                                   \
                                                                                                   \
	static struct lpspi_data lpspi_data_##n = {                                             \
		SPI_NXP_LPSPI_COMMON_DATA_INIT(n)                                                  \
		.driver_data = &lpspi_##n##_driver_data,                                           \
	};                                                                                         \
                                                                                                   \
	SPI_DEVICE_DT_INST_DEFINE(n, lpspi_init, NULL, &lpspi_data_##n,                            \
				  &lpspi_config_##n, POST_KERNEL, CONFIG_SPI_INIT_PRIORITY,     \
				  &lpspi_driver_api);

#define SPI_LPSPI_INIT_IF_DMA(n) IF_DISABLED(SPI_NXP_LPSPI_HAS_DMAS(n), (LPSPI_INIT(n)))

#define SPI_LPSPI_INIT(n)                                                                     \
	COND_CODE_1(CONFIG_SPI_MCUX_LPSPI_DMA,				   \
						(SPI_LPSPI_INIT_IF_DMA(n)), (LPSPI_INIT(n)))

DT_INST_FOREACH_STATUS_OKAY(SPI_LPSPI_INIT)