spi: rtio: Add default iodev_submit handler

To emulate SPI RTIO behavior for drivers that do not have native
support yet.

Signed-off-by: Luis Ubieda <[email protected]>

drivers/spi/Kconfig

@@ -32,6 +32,7 @@ config SPI_RTIO
 	bool "RTIO support [EXPERIMENTAL]"
 	select EXPERIMENTAL
 	select RTIO
+	select RTIO_WORKQ
 	help
 	  This option enables the RTIO API calls. RTIO support is
 	  experimental as the API itself is unstable.

drivers/spi/spi_rtio.c

@@ -1,11 +1,108 @@
 /*
  * Copyright (c) 2023 Intel Corporation
+ * Copyright (c) 2024 Croxel Inc
  *
  * SPDX-License-Identifier: Apache-2.0
  */
 
+#include <zephyr/kernel.h>
 #include <zephyr/drivers/spi.h>
+#include <zephyr/rtio/work.h>
+
+#include <zephyr/logging/log.h>
+LOG_MODULE_DECLARE(spi_rtio, CONFIG_SPI_LOG_LEVEL);
 
 const struct rtio_iodev_api spi_iodev_api = {
 	.submit = spi_iodev_submit,
 };
+
+static void spi_rtio_iodev_default_submit_sync(struct rtio_iodev_sqe *iodev_sqe)
+{
+	struct spi_dt_spec *dt_spec = iodev_sqe->sqe.iodev->data;
+	const struct device *dev = dt_spec->bus;
+	int err = 0;
+
+	LOG_DBG("Sync RTIO work item for: %p", (void *)dev);
+
+	/** Take care of Multi-submissions transactions in the same context.
+	 * This guarantees that linked items will be consumed in the expected
+	 * order, regardless pending items in the workqueue.
+	 */
+	struct rtio_iodev_sqe *txn_head = iodev_sqe;
+	struct rtio_iodev_sqe *txn_curr = iodev_sqe;
+
+	do {
+		struct rtio_sqe *sqe = &txn_curr->sqe;
+		struct spi_buf tx_buf = {0};
+		struct spi_buf_set tx_buf_set = {
+			.buffers = &tx_buf,
+		};
+
+		struct spi_buf rx_buf = {0};
+		struct spi_buf_set rx_buf_set = {
+			.buffers = &rx_buf,
+		};
+
+		LOG_DBG("Preparing transfer: %p", txn_curr);
+
+		switch (sqe->op) {
+		case RTIO_OP_RX:
+			rx_buf.buf = sqe->rx.buf;
+			rx_buf.len = sqe->rx.buf_len;
+			rx_buf_set.count = 1;
+			break;
+		case RTIO_OP_TX:
+			tx_buf.buf = (uint8_t *)sqe->tx.buf;
+			tx_buf.len = sqe->tx.buf_len;
+			tx_buf_set.count = 1;
+			break;
+		case RTIO_OP_TINY_TX:
+			tx_buf.buf = (uint8_t *)sqe->tiny_tx.buf;
+			tx_buf.len = sqe->tiny_tx.buf_len;
+			tx_buf_set.count = 1;
+			break;
+		case RTIO_OP_TXRX:
+			rx_buf.buf = sqe->txrx.rx_buf;
+			rx_buf.len = sqe->txrx.buf_len;
+			tx_buf.buf = (uint8_t *)sqe->txrx.tx_buf;
+			tx_buf.len = sqe->txrx.buf_len;
+			rx_buf_set.count = 1;
+			tx_buf_set.count = 1;
+			break;
+		default:
+			LOG_ERR("Invalid op code %d for submission %p\n", sqe->op, (void *)sqe);
+			err = -EIO;
+			break;
+		}
+
+		if (!err) {
+			struct spi_buf_set *tx_buf_ptr = tx_buf_set.count > 0 ? &tx_buf_set : NULL;
+			struct spi_buf_set *rx_buf_ptr = rx_buf_set.count > 0 ? &rx_buf_set : NULL;
+
+			err = spi_transceive_dt(dt_spec, tx_buf_ptr, rx_buf_ptr);
+
+			/* NULL if this submission is not a transaction */
+			txn_curr = rtio_txn_next(txn_curr);
+		}
+	} while (err >= 0 && txn_curr != NULL);
+
+	if (err < 0) {
+		LOG_ERR("Transfer failed: %d", err);
+		rtio_iodev_sqe_err(txn_head, err);
+	} else {
+		LOG_DBG("Transfer OK: %d", err);
+		rtio_iodev_sqe_ok(txn_head, err);
+	}
+}
+
+void spi_rtio_iodev_default_submit(const struct device *dev,
+				   struct rtio_iodev_sqe *iodev_sqe)
+{
+	LOG_DBG("Executing fallback for dev: %p, sqe: %p", (void *)dev, (void *)iodev_sqe);
+
+	struct rtio_work_req *req = rtio_work_req_alloc();
+
+	__ASSERT_NO_MSG(req);
+
+	rtio_work_req_submit(req, iodev_sqe, spi_rtio_iodev_default_submit_sync);
+}

include/zephyr/drivers/spi/rtio.h

@@ -0,0 +1,19 @@
+/*
+ * Copyright (c) 2024 Croxel, Inc.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#ifndef ZEPHYR_DRIVERS_SPI_RTIO_H_
+#define ZEPHYR_DRIVERS_SPI_RTIO_H_
+
+/**
+ * @brief Fallback SPI RTIO submit implementation.
+ *
+ * Default RTIO SPI implementation for drivers who do no yet have
+ * native support. For details, see @ref spi_iodev_submit.
+ */
+void spi_rtio_iodev_default_submit(const struct device *dev,
+				   struct rtio_iodev_sqe *iodev_sqe);
+
+#endif /* ZEPHYR_DRIVERS_SPI_RTIO_H_ */