drivers: retained_mem: retained_mem_zephyr_ram: flush d-cache if enabled

Flush the data cache if cache management is enabled. Flushing the data
cache is required to ensure data retention across system resets.

Signed-off-by: Henrik Brix Andersen <[email protected]>

Author: henrikbrixandersen

drivers/retained_mem/retained_mem_zephyr_ram.c

@@ -7,6 +7,7 @@
 #define DT_DRV_COMPAT zephyr_retained_ram
 
 #include <string.h>
+#include <zephyr/cache.h>
 #include <zephyr/device.h>
 #include <zephyr/devicetree.h>
 #include <zephyr/drivers/retained_mem.h>
@@ -85,27 +86,37 @@ static int zephyr_retained_mem_ram_write(const struct device *dev, off_t offset,
 					 const uint8_t *buffer, size_t size)
 {
 	const struct zephyr_retained_mem_ram_config *config = dev->config;
+	int err = 0;
 
 	zephyr_retained_mem_ram_lock_take(dev);
 
 	memcpy((config->address + offset), buffer, size);
 
+#if defined(CONFIG_CACHE_MANAGEMENT) && defined(CONFIG_DCACHE)
+	err = sys_cache_data_flush_range(config->address + offset, size);
+#endif /* defined(CONFIG_CACHE_MANAGEMENT) && defined(CONFIG_DCACHE) */
+
 	zephyr_retained_mem_ram_lock_release(dev);
 
-	return 0;
+	return err;
 }
 
 static int zephyr_retained_mem_ram_clear(const struct device *dev)
 {
 	const struct zephyr_retained_mem_ram_config *config = dev->config;
+	int err = 0;
 
 	zephyr_retained_mem_ram_lock_take(dev);
 
 	memset(config->address, 0, config->size);
 
+#if defined(CONFIG_CACHE_MANAGEMENT) && defined(CONFIG_DCACHE)
+	err = sys_cache_data_flush_range(config->address, config->size);
+#endif /* defined(CONFIG_CACHE_MANAGEMENT) && defined(CONFIG_DCACHE) */
+
 	zephyr_retained_mem_ram_lock_release(dev);
 
-	return 0;
+	return err;
 }
 
 static DEVICE_API(retained_mem, zephyr_retained_mem_ram_api) = {