drivers: retained_mem: Add RAM driver

Adds a non-initialised RAM-based retained memory driver.

Signed-off-by: Jamie McCrae <jamie.mccrae@nordicsemi.no>

drivers/retained_mem/CMakeLists.txt

@@ -2,3 +2,4 @@
 
 zephyr_library()
 zephyr_library_sources_ifdef(CONFIG_RETAINED_MEM_NRF_GPREGRET retained_mem_nrf_gpregret.c)
+zephyr_library_sources_ifdef(CONFIG_RETAINED_MEM_ZEPHYR_RAM   retained_mem_zephyr_ram.c)

drivers/retained_mem/Kconfig

@@ -21,4 +21,6 @@ source "subsys/logging/Kconfig.template.log_config"
 
 source "drivers/retained_mem/Kconfig.nrf"
 
+source "drivers/retained_mem/Kconfig.zephyr"
+
 endif # RETAINED_MEM

drivers/retained_mem/Kconfig.zephyr

@@ -0,0 +1,9 @@
+# Copyright (c) 2023 Nordic Semiconductor ASA
+# SPDX-License-Identifier: Apache-2.0
+
+config RETAINED_MEM_ZEPHYR_RAM
+	bool "Generic Zephyr RAM retained memory driver"
+	default y
+	depends on DT_HAS_ZEPHYR_RETAINED_RAM_ENABLED
+	help
+	  Enable driver for retained memory in RAM.

drivers/retained_mem/retained_mem_zephyr_ram.c

@@ -0,0 +1,139 @@
+/*
+ * Copyright (c) 2023, Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#define DT_DRV_COMPAT zephyr_retained_ram
+
+#include <string.h>
+#include <zephyr/device.h>
+#include <zephyr/devicetree.h>
+#include <zephyr/drivers/retained_mem.h>
+#include <zephyr/kernel.h>
+#include <zephyr/sys/util.h>
+#include <zephyr/logging/log.h>
+
+LOG_MODULE_REGISTER(retained_mem_zephyr_ram, CONFIG_RETAINED_MEM_LOG_LEVEL);
+
+#ifdef CONFIG_MULTITHREADING
+struct zephyr_retained_mem_ram_data {
+	struct k_mutex lock;
+};
+#endif
+
+struct zephyr_retained_mem_ram_config {
+	uint8_t *address;
+	size_t size;
+};
+
+static inline void zephyr_retained_mem_ram_lock_take(const struct device *dev)
+{
+#ifdef CONFIG_MULTITHREADING
+	struct zephyr_retained_mem_ram_data *data = dev->data;
+
+	k_mutex_lock(&data->lock, K_FOREVER);
+#else
+	ARG_UNUSED(dev);
+#endif
+}
+
+static inline void zephyr_retained_mem_ram_lock_release(const struct device *dev)
+{
+#ifdef CONFIG_MULTITHREADING
+	struct zephyr_retained_mem_ram_data *data = dev->data;
+
+	k_mutex_unlock(&data->lock);
+#else
+	ARG_UNUSED(dev);
+#endif
+}
+
+static int zephyr_retained_mem_ram_init(const struct device *dev)
+{
+#ifdef CONFIG_MULTITHREADING
+	struct zephyr_retained_mem_ram_data *data = dev->data;
+
+	k_mutex_init(&data->lock);
+#endif
+
+	return 0;
+}
+
+static ssize_t zephyr_retained_mem_ram_size(const struct device *dev)
+{
+	const struct zephyr_retained_mem_ram_config *config = dev->config;
+
+	return (ssize_t)config->size;
+}
+
+static int zephyr_retained_mem_ram_read(const struct device *dev, off_t offset, uint8_t *buffer,
+					size_t size)
+{
+	const struct zephyr_retained_mem_ram_config *config = dev->config;
+
+	zephyr_retained_mem_ram_lock_take(dev);
+
+	memcpy(buffer, (config->address + offset), size);
+
+	zephyr_retained_mem_ram_lock_release(dev);
+
+	return 0;
+}
+
+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;
+
+	zephyr_retained_mem_ram_lock_take(dev);
+
+	memcpy((config->address + offset), buffer, size);
+
+	zephyr_retained_mem_ram_lock_release(dev);
+
+	return 0;
+}
+
+static int zephyr_retained_mem_ram_clear(const struct device *dev)
+{
+	const struct zephyr_retained_mem_ram_config *config = dev->config;
+
+	zephyr_retained_mem_ram_lock_take(dev);
+
+	memset(config->address, 0, config->size);
+
+	zephyr_retained_mem_ram_lock_release(dev);
+
+	return 0;
+}
+
+static const struct retained_mem_driver_api zephyr_retained_mem_ram_api = {
+	.size = zephyr_retained_mem_ram_size,
+	.read = zephyr_retained_mem_ram_read,
+	.write = zephyr_retained_mem_ram_write,
+	.clear = zephyr_retained_mem_ram_clear,
+};
+
+#define ZEPHYR_RETAINED_MEM_RAM_DEVICE(inst)							\
+	IF_ENABLED(CONFIG_MULTITHREADING,							\
+		   (static struct zephyr_retained_mem_ram_data					\
+		    zephyr_retained_mem_ram_data_##inst;)					\
+	)											\
+	static const struct zephyr_retained_mem_ram_config					\
+			zephyr_retained_mem_ram_config_##inst = {				\
+		.address = (uint8_t *)DT_REG_ADDR(DT_PARENT(DT_INST(inst, DT_DRV_COMPAT))),	\
+		.size = DT_REG_SIZE(DT_PARENT(DT_INST(inst, DT_DRV_COMPAT))),			\
+	};											\
+	DEVICE_DT_INST_DEFINE(inst,								\
+			      &zephyr_retained_mem_ram_init,					\
+			      NULL,								\
+			      COND_CODE_1(CONFIG_MULTITHREADING,				\
+					  (&zephyr_retained_mem_ram_data_##inst), (NULL)	\
+			      ),								\
+			      &zephyr_retained_mem_ram_config_##inst,				\
+			      POST_KERNEL,							\
+			      CONFIG_RETAINED_MEM_INIT_PRIORITY,				\
+			      &zephyr_retained_mem_ram_api);
+
+DT_INST_FOREACH_STATUS_OKAY(ZEPHYR_RETAINED_MEM_RAM_DEVICE)

dts/bindings/retained_mem/zephyr,retained-ram.yaml

@@ -0,0 +1,8 @@
+# Copyright (c) 2023 Nordic Semiconductor ASA
+# SPDX-License-Identifier: Apache-2.0
+
+description: Unitialised RAM-based retained memory area.
+
+compatible: "zephyr,retained-ram"
+
+include: base.yaml