soc: renesas: ra: Add battery backup support for RA8 family

Add support for the battery backup (VBAT) functionality on
Renesas RA8 family. This allows the RTC to retain timekeeping
data when the main power supply is lost by switching to the
VBAT domain automatically. This commit add support for these
SoC series: ra8m1, ra8p1, ra8d1

Signed-off-by: Khoa Tran <[email protected]>

Author: khoatranyj

soc/renesas/ra/CMakeLists.txt

@@ -5,4 +5,5 @@
 zephyr_include_directories(common)
 zephyr_include_directories_ifdef(CONFIG_HAS_RENESAS_RA_FSP common_fsp)
 
+add_subdirectory_ifdef(CONFIG_HAS_RENESAS_RA_FSP common_fsp)
 add_subdirectory(${SOC_SERIES})

soc/renesas/ra/Kconfig

@@ -24,4 +24,12 @@ config CPU_HAS_RENESAS_RA_IDAU
 
 rsource "*/Kconfig"
 
+config RENESAS_RA_BATTERY_BACKUP_MANUAL_CONFIGURE
+	bool "VBAT switching manual"
+	default y
+	depends on DT_HAS_RENESAS_RA_BATTERY_BACKUP_ENABLED && $(dt_compat_any_has_prop,$(DT_COMPAT_RENESAS_RA_BATTERY_BACKUP),manual-configure)
+	help
+	  Enable if this SoC's battery backup domain allows switching to VBAT manually.
+	  Leave disabled if switching is automatic.
+
 endif # SOC_FAMILY_RENESAS_RA

soc/renesas/ra/common_fsp/CMakeLists.txt

@@ -0,0 +1,5 @@
+# Copyright (c) 2025 Renesas Electronics Corporation
+# SPDX-License-Identifier: Apache-2.0
+
+zephyr_sources_ifdef(CONFIG_RENESAS_RA_BATTERY_BACKUP_MANUAL_CONFIGURE battery_backup.c)
+zephyr_sources(cold_start.c)

soc/renesas/ra/common_fsp/battery_backup.c

@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) 2025 Renesas Electronics Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+#include "battery_backup.h"
+
+#define VCC_DROP_DETECTION_STABILIZATION_WAIT_TIME_US 20
+#define VBTBPSR_VBPORF_IS_SET                         BIT(0)
+#define VBTBPCR2_VDETLVL_SETTING_NOT_USED             0x6
+
+static uint8_t vbtbpsr_state_at_boot;
+
+bool is_backup_domain_reset_happen(void)
+{
+	return (vbtbpsr_state_at_boot & VBTBPSR_VBPORF_IS_SET);
+}
+
+void battery_backup_init(void)
+{
+#if DT_NODE_HAS_PROP(DT_NODELABEL(battery_backup), switch_threshold)
+	/*  Check VBPORM bit. If VBPORM flag is 0, wait until it changes to 1 */
+	while (R_SYSTEM->VBTBPSR_b.VBPORM == 0) {
+	}
+	vbtbpsr_state_at_boot = R_SYSTEM->VBTBPSR;
+	if (R_SYSTEM->VBTBPSR_b.VBPORF == 1) {
+		R_BSP_RegisterProtectDisable(BSP_REG_PROTECT_OM_LPC_BATT);
+		R_SYSTEM->VBTBPSR_b.VBPORF = 0;
+		R_SYSTEM->VBTBPCR2_b.VDETLVL =
+			DT_ENUM_IDX(DT_NODELABEL(battery_backup), switch_threshold);
+		R_BSP_SoftwareDelay(VCC_DROP_DETECTION_STABILIZATION_WAIT_TIME_US,
+				    BSP_DELAY_UNITS_MICROSECONDS);
+		R_SYSTEM->VBTBPCR2_b.VDETE = 1;
+		R_BSP_RegisterProtectEnable(BSP_REG_PROTECT_OM_LPC_BATT);
+	}
+#else
+	/*  Set the BPWSWSTP bit to 1. The power supply switch is stopped */
+	R_BSP_RegisterProtectDisable(BSP_REG_PROTECT_OM_LPC_BATT);
+	R_SYSTEM->VBTBPCR1_b.BPWSWSTP = 1;
+
+	/* Check VBPORM flag. If VBPORM flag is 0, wait until it changes to 1 */
+	while (R_SYSTEM->VBTBPSR_b.VBPORM == 0) {
+	}
+	vbtbpsr_state_at_boot = R_SYSTEM->VBTBPSR;
+	R_SYSTEM->VBTBPSR_b.VBPORF = 0;
+	R_SYSTEM->VBTBPCR2_b.VDETE = 0;
+	R_SYSTEM->VBTBPCR2_b.VDETLVL = DT_ENUM_IDX_OR(
+		DT_NODELABEL(battery_backup), switch_threshold, VBTBPCR2_VDETLVL_SETTING_NOT_USED);
+	R_BSP_RegisterProtectEnable(BSP_REG_PROTECT_OM_LPC_BATT);
+
+	/* Set the SOSTP bit to 1 regardless of its value. Stop Sub-Clock Oscillator */
+	R_BSP_RegisterProtectDisable(BSP_REG_PROTECT_CGC);
+	R_SYSTEM->SOSCCR_b.SOSTP = 1;
+	R_BSP_RegisterProtectEnable(BSP_REG_PROTECT_CGC);
+#endif /* BATTERY_BACKUP_CONFIGURATION_NOT_USED */
+}

soc/renesas/ra/common_fsp/battery_backup.h

@@ -0,0 +1,16 @@
+/*
+ * Copyright (c) 2025 Renesas Electronics Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#ifndef ZEPHYR_SOC_RENESAS_RA_BATTERY_BACKUP_H_
+#define ZEPHYR_SOC_RENESAS_RA_BATTERY_BACKUP_H_
+
+#include <zephyr/device.h>
+#include <bsp_api.h>
+
+bool is_backup_domain_reset_happen(void);
+void battery_backup_init(void);
+
+#endif /* ZEPHYR_SOC_RENESAS_RA_BATTERY_BACKUP_H_ */

soc/renesas/ra/common_fsp/cold_start.c

@@ -0,0 +1,29 @@
+/*
+ * Copyright (c) 2025 Renesas Electronics Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+#include <zephyr/device.h>
+#include <bsp_api.h>
+#include "cold_start.h"
+
+#define RSTSR2_CWSF_BIT_MASK BIT(0)
+
+static uint8_t rstsr2_state_at_boot;
+
+bool is_power_on_reset_happen(void)
+{
+	return ((rstsr2_state_at_boot & RSTSR2_CWSF_BIT_MASK) == 0);
+}
+
+void cold_start_handler(void)
+{
+	/* Detect power on reset */
+	rstsr2_state_at_boot = R_SYSTEM->RSTSR2;
+	if (R_SYSTEM->RSTSR2_b.CWSF == 0) {
+#if defined(CONFIG_RENESAS_RA_BATTERY_BACKUP_MANUAL_CONFIGURE)
+		battery_backup_init();
+#endif /* CONFIG_RENESAS_RA_BATTERY_BACKUP_MANUAL_CONFIGURE */
+		R_SYSTEM->RSTSR2_b.CWSF = 1;
+	}
+}

soc/renesas/ra/common_fsp/cold_start.h

@@ -0,0 +1,17 @@
+/*
+ * Copyright (c) 2025 Renesas Electronics Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#ifndef ZEPHYR_SOC_RENESAS_RA_COLD_START_H_
+#define ZEPHYR_SOC_RENESAS_RA_COLD_START_H_
+
+#include <zephyr/device.h>
+#include <bsp_api.h>
+#include "battery_backup.h"
+
+bool is_power_on_reset_happen(void);
+void cold_start_handler(void);
+
+#endif /* ZEPHYR_SOC_RENESAS_RA_COLD_START_H_ */

soc/renesas/ra/ra8d1/soc.c

@@ -74,4 +74,6 @@ void soc_early_init_hook(void)
 
 	z_arm_nmi_set_handler(NMI_Handler);
 #endif /* CONFIG_RUNTIME_NMI */
+
+	cold_start_handler();
 }

soc/renesas/ra/ra8d1/soc.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2024 Renesas Electronics Corporation
+ * Copyright (c) 2024-2025 Renesas Electronics Corporation
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -12,5 +12,6 @@
 #define ZEPHYR_SOC_RENESAS_RA8D1_SOC_H_
 
 #include <bsp_api.h>
+#include <cold_start.h>
 
 #endif /* ZEPHYR_SOC_RENESAS_RA8D1_SOC_H_ */

soc/renesas/ra/ra8m1/soc.c

@@ -47,4 +47,6 @@ void soc_early_init_hook(void)
 
 	z_arm_nmi_set_handler(NMI_Handler);
 #endif /* CONFIG_RUNTIME_NMI */
+
+	cold_start_handler();
 }