drivers: retained_mem: enable retained_mem for esp32 paltforms

Enables retained_mem on esp32 platforms using RTCRAM

Signed-off-by: Marcio Ribeiro <[email protected]>

Author: wmrsouza

boards/espressif/esp32s3_devkitc/esp32s3_devkitc_procpu.yaml

@@ -17,4 +17,5 @@ supported:
   - pwm
   - dma
   - input
+  - retained_mem
 vendor: espressif

dts/xtensa/espressif/esp32s3/esp32s3_common.dtsi

@@ -161,6 +161,18 @@
 			#mbox-cells = <1>;
 		};
 
+		rtcram_slow: memory@50000000 {
+			compatible = "zephyr,memory-region", "mmio-sram";
+			reg = <0x50000000 DT_SIZE_K(8)>;
+			zephyr,memory-region = "RTCRAM_SLOW";
+		};
+
+		rtcram_fast: memory@600fe000 {
+			compatible = "zephyr,memory-region", "mmio-sram";
+			reg = <0x600fe000 DT_SIZE_K(8)>;
+			zephyr,memory-region = "RTCRAM_FAST";
+		};
+
 		intc: interrupt-controller@600c2000 {
 			#interrupt-cells = <3>;
 			#address-cells = <0>;

soc/espressif/esp32s3/default.ld

@@ -95,7 +95,7 @@ MEMORY
 #endif
 
   /* RTC fast memory (executable). Persists over deep sleep. */
-  rtc_iram_seg(RWX): org = 0x600fe000, len = 0x2000 - CONFIG_RESERVE_RTC_MEM
+  rtc_iram_seg(RWX): org = RCTRAM_FAST_START, len = RCTRAM_FAST_SIZE - CONFIG_RESERVE_RTC_MEM
 
   /* We reduced the size of rtc_iram_seg by CONFIG_RESERVE_RTC_MEM value.
    * It reserves the amount of RTC fast memory that we use for this memory segment.
@@ -105,12 +105,12 @@ MEMORY
    * The aim of this is to keep data that will not be moved around and have a fixed address.
    */
 #if (CONFIG_RESERVE_RTC_MEM > 0)
-  rtc_reserved_seg(RW): org = 0x600fe000 + 0x2000 - CONFIG_RESERVE_RTC_MEM,
+  rtc_reserved_seg(RW): org = RCTRAM_FAST_START + RCTRAM_FAST_SIZE - CONFIG_RESERVE_RTC_MEM,
                         len = CONFIG_RESERVE_RTC_MEM
 #endif
 
   /* RTC slow memory (data accessible). Persists over deep sleep. */
-  rtc_slow_seg(RW): org = 0x50000000, len = 0x2000
+  rtc_slow_seg(RW): org = RCTRAM_SLOW_START, len = RCTRAM_SLOW_SIZE
 
 #ifdef CONFIG_GEN_ISR_TABLES
   IDT_LIST(RW): org = 0x3ebfe010, len = 0x2000

soc/espressif/esp32s3/memory.h

@@ -18,6 +18,12 @@
 #define SRAM2_USER_DRAM_START (SRAM2_DRAM_START + CONFIG_ESP32S3_DATA_CACHE_SIZE)
 #define SRAM2_USER_DRAM_SIZE  (SRAM2_SIZE - CONFIG_ESP32S3_DATA_CACHE_SIZE)
 
+#define RCTRAM_SLOW_START     DT_REG_ADDR(DT_NODELABEL(rtcram_slow))
+#define RCTRAM_SLOW_SIZE      DT_REG_SIZE(DT_NODELABEL(rtcram_slow))
+
+#define RCTRAM_FAST_START     DT_REG_ADDR(DT_NODELABEL(rtcram_fast))
+#define RCTRAM_FAST_SIZE      DT_REG_SIZE(DT_NODELABEL(rtcram_fast))
+
 /** Simplified memory map for the bootloader.
  *  Make sure the bootloader can load into main memory without overwriting itself.
  *

tests/drivers/retained_mem/api/boards/esp32s3_devkitc_procpu.overlay

@@ -0,0 +1,30 @@
+/*
+ * Copyright (c) 2025 Espressif Systems (Shanghai) Co., Ltd.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/ {
+	memory@600fff00 {
+		compatible = "zephyr,memory-region", "mmio-sram";
+		reg = <0x600fff00 0x100>;
+		zephyr,memory-region = "RTCRAM_FAST_RETAINEDMEM";
+		status = "okay";
+
+		retainedmem0: retainedmem {
+			compatible = "zephyr,retained-ram";
+			status = "okay";
+		};
+	};
+
+	aliases {
+		retainedmemtestdevice = &retainedmem0;
+	};
+};
+
+&rtcram_fast {
+	/* Shrink rtcram_fast size to avoid overlap with retained memory region:
+	 * 8KB - 256 = 0x1f00
+	 */
+	reg = <0x600fe000 0x1f00>;
+};

tests/drivers/retained_mem/api/testcase.yaml

@@ -6,6 +6,7 @@ tests:
       - retained_mem
   drivers.retained_mem.api.ram:
     platform_allow:
+      - esp32s3_devkitc/esp32s3/procpu
       - qemu_cortex_m3
       - nrf5340dk/nrf5340/cpuapp
       - nrf54h20dk/nrf54h20/cpuapp