tests: dma/chan_blen_transfer: relocate TX and RX buffers

This commit places the chan_blen_transfer DMA test's TX and RX buffers
in a separate file that gets entirely relocated. This ensures that the
buffers reside in the correct memory, without breaking other things
due to relocation of test data/code.

Fixes #75676.

Signed-off-by: Mathieu Choplain <mathieu.choplain@st.com>

Author: Mathieu Choplain

tests/drivers/dma/chan_blen_transfer/CMakeLists.txt

@@ -7,4 +7,6 @@ project(chan_blen_transfer)
 FILE(GLOB app_sources src/*.c)
 target_sources(app PRIVATE ${app_sources})
 
-zephyr_code_relocate(FILES src/test_dma.c LOCATION ${CONFIG_DMA_LOOP_TRANSFER_RELOCATE_SECTION}_RODATA_BSS)
+if (CONFIG_DMA_LOOP_TRANSFER_RELOCATE_SECTION)
+  zephyr_code_relocate(FILES src/test_buffers.c LOCATION ${CONFIG_DMA_LOOP_TRANSFER_RELOCATE_SECTION})
+endif()

tests/drivers/dma/chan_blen_transfer/src/test_buffers.c

@@ -0,0 +1,12 @@
+/*
+ * Copyright (c) 2024 STMicroelectronics
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/kernel.h>
+
+#include "test_buffers.h"
+
+__aligned(32) char tx_data[TEST_BUF_SIZE] = "It is harder to be kind than to be wise........";
+__aligned(32) char rx_data[TEST_BUF_SIZE] = { 0 };

tests/drivers/dma/chan_blen_transfer/src/test_buffers.h

@@ -0,0 +1,12 @@
+/*
+ * Copyright (c) 2024 STMicroelectronics
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <stdint.h>
+
+#define TEST_BUF_SIZE (48)
+
+extern char tx_data[TEST_BUF_SIZE];
+extern char rx_data[TEST_BUF_SIZE];

tests/drivers/dma/chan_blen_transfer/src/test_dma.c

@@ -20,10 +20,7 @@
 #include <zephyr/drivers/dma.h>
 #include <zephyr/ztest.h>
 
-#define RX_BUFF_SIZE (48)
-
-static __aligned(32) char tx_data[] = "It is harder to be kind than to be wise........";
-static __aligned(32) char rx_data[RX_BUFF_SIZE] = { 0 };
+#include "test_buffers.h"
 
 static void test_done(const struct device *dma_dev, void *arg,
 		      uint32_t id, int status)