drivers: stm32: SPI: Check that SPI buffers are in a nocache region

DMA only works with non-cached memory regions in H7. Check them
and return an error if they don't match this condition.

Signed-off-by: Daniel Gaston Ochoa <[email protected]>

drivers/spi/spi_ll_stm32.c

@@ -679,6 +679,33 @@ static int transceive(const struct device *dev,
 
 #ifdef CONFIG_SPI_STM32_DMA
 
+#ifdef CONFIG_SOC_SERIES_STM32H7X
+
+static struct dma_mem_region stm32_mem_regions[] = {
+	DT_FOREACH_STATUS_OKAY(mmio_sram, DT_GET_MEM_REGION)
+};
+
+/*
+ * Checks that all buffers in `bufs` are in a valid area to be used
+ * with DMA.
+ *
+ */
+static bool all_bufs_in_valid_dma_ram(const struct spi_buf_set *bufs)
+{
+	for (size_t i = 0; i < bufs->count; i++) {
+		const struct spi_buf *buf = &bufs->buffers[i];
+
+		if (dma_buf_in_non_cacheable_sram(
+					buf->buf, buf->len,
+					stm32_mem_regions,
+					sizeof(stm32_mem_regions) / sizeof(*stm32_mem_regions))) {
+			return false;
+		}
+	}
+	return true;
+}
+#endif /* CONFIG_SOC_SERIES_STM32H7X */
+
 static int wait_dma_rx_tx_done(const struct device *dev)
 {
 	struct spi_stm32_data *data = dev->data;
@@ -723,6 +750,13 @@ static int transceive_dma(const struct device *dev,
 		return -ENOTSUP;
 	}
 
+#ifdef CONFIG_SOC_SERIES_STM32H7X
+	if ((tx_bufs != NULL && !all_bufs_in_valid_dma_ram(tx_bufs)) ||
+		(rx_bufs != NULL && !all_bufs_in_valid_dma_ram(rx_bufs))) {
+		return -EFAULT;
+	}
+#endif /* CONFIG_SOC_SERIES_STM32H7X */
+
 	spi_context_lock(&data->ctx, asynchronous, cb, userdata, config);
 
 	k_sem_reset(&data->status_sem);
@@ -1015,6 +1049,7 @@ static void spi_stm32_irq_config_func_##id(const struct device *dev)		\
 
 
 
+
 #define STM32_SPI_INIT(id)						\
 STM32_SPI_IRQ_HANDLER_DECL(id);						\
 									\

include/zephyr/drivers/dma.h

@@ -13,6 +13,8 @@
 #ifndef ZEPHYR_INCLUDE_DRIVERS_DMA_H_
 #define ZEPHYR_INCLUDE_DRIVERS_DMA_H_
 
+#include <string.h>
+
 #include <zephyr/kernel.h>
 #include <zephyr/device.h>
 
@@ -256,6 +258,50 @@ struct dma_context {
 /* magic code to identify context content */
 #define DMA_MAGIC 0x47494749
 
+/* Inidicates that a ram region is nocache. */
+/* TODO Obtained from zephyr,memory-region.yaml. This should be defined in
+ * just one place.
+ */
+#define MEM_NOCACHE_ATTR "RAM_NOCACHE"
+
+/**
+ * @brief Container for MMIO SRAM information specified in devicetree
+ *
+ * This type contains pointers to the begin and end of the memory region and
+ * a string that specifies such region's properties.
+ *
+ */
+struct dma_mem_region {
+	const uint8_t *start;
+	const uint8_t *end;
+	const char *region_mpu;
+};
+
+/**
+ * @brief Can be used to initialize a @see{struct dma_mem_region}.
+ *
+ * @param node_id Node ID of the memory region declared in device tree from
+ * which the information will be obtained.
+ *
+ * @example
+ *
+ *		struct dma_mem_region mem_r = {
+ *			DT_GET_MEM_REGION(DT_NODELABEL(<node_label>))
+ *		};
+ *
+ */
+#define DT_GET_MEM_REGION(node_id)                                              \
+	{                                                                           \
+		.start = (const uint8_t *)DT_REG_ADDR(node_id),                         \
+		.end =                                                                  \
+			(const uint8_t *)(DT_REG_ADDR(node_id) + DT_REG_SIZE(node_id)),     \
+		.region_mpu = COND_CODE_1(                                              \
+			DT_NODE_HAS_PROP(node_id, zephyr_memory_region_mpu),                \
+			(DT_PROP(node_id, zephyr_memory_region_mpu)),                       \
+			(NULL)                                                              \
+		)                                                                       \
+	},
+
 /**
  * @cond INTERNAL_HIDDEN
  *
@@ -684,6 +730,36 @@ static inline uint32_t dma_burst_index(uint32_t burst)
 	return find_msb_set(burst);
 }
 
+/**
+ * Return true if buf is in a nocache memory region
+ * among mem_regions.
+ *
+ * @param buf Buffer to be checked
+ * @param size Size of the buffer above
+ * @param mem_regions Memory regions agaisnt which buf will be checked.
+ * @param mem_regions_cnt Number of memory regions
+ */
+static inline bool dma_buf_in_non_cacheable_sram(
+			const uint8_t *buf,
+			size_t size,
+			struct dma_mem_region mem_regions[],
+			size_t mem_regions_cnt)
+{
+	for (size_t i = 0; i < mem_regions_cnt; i++) {
+		const struct dma_mem_region *mem_reg = &mem_regions[i];
+		const char *reg_mpu = mem_reg->region_mpu;
+
+		const bool buf_within_bounds =
+			(buf >= mem_reg->start) && ((buf + size) <= mem_reg->end);
+		if (buf_within_bounds &&
+			reg_mpu != NULL &&
+			strncmp(reg_mpu, MEM_NOCACHE_ATTR, sizeof(MEM_NOCACHE_ATTR)) == 0) {
+			return false;
+		}
+	}
+	return true;
+}
+
 /**
  * Get the device tree property describing the buffer address alignment
  *