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 +679,80 @@ static int transceive(const struct device *dev,
 
 #ifdef CONFIG_SPI_STM32_DMA
 
+#ifdef CONFIG_SOC_SERIES_STM32H7X
+#define STM32_SPI_GET_MEM_REGION(node_id) 										\
+	{																			\
+		.start = (const void*)DT_REG_ADDR(node_id), 							\
+		.end = (const void*)(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)																\
+		) 																		\
+	},
+
+#define NOCACHE_ID "RAM_NOCACHE"
+#define NOCACHE_ID_LEN sizeof(NOCACHE_ID)
+
+struct spi_stm32_mem_region {
+	const uint8_t *start;
+	const uint8_t *end;
+	const char *region_mpu;
+};
+
+static struct spi_stm32_mem_region stm32_mem_regions[] = {
+	DT_FOREACH_STATUS_OKAY(mmio_sram, STM32_SPI_GET_MEM_REGION)
+};
+
+/*
+ * DMA in H7 must only access non-cacheable RAM regions or it won't work
+ * properly. Use this function to check if the SPI buffers are in a nocache
+ * region.
+ *
+ * Return true if @param{buf} is not within nocache RAM bounds, false
+ * otherwise.
+ *
+ * TODO In H7, DMA can only access certain memory areas regardless of if they
+ * are nocache or not (e.g. SRAM1, SRAM2). It would be good to check this as
+ * well, but different H7 SoCs can access different areas.
+ */
+static bool buf_in_non_cacheable_sram(const uint8_t *buf, size_t size)
+{
+	const size_t mem_regions_cnt =
+		sizeof(stm32_mem_regions) / sizeof(*stm32_mem_regions);
+
+	for (size_t i = 0; i < mem_regions_cnt; i++) {
+		const struct spi_stm32_mem_region* mem_reg = &stm32_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, NOCACHE_ID, NOCACHE_ID_LEN) == 0) {
+			return false;
+		}
+	}
+	return true;
+}
+
+/*
+ * 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 (buf_in_non_cacheable_sram(buf->buf, buf->len)) {
+			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 +797,13 @@ 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 +1096,7 @@ static void spi_stm32_irq_config_func_##id(const struct device *dev)		\
 
 
 
+
 #define STM32_SPI_INIT(id)						\
 STM32_SPI_IRQ_HANDLER_DECL(id);						\
 									\