[PATCH] rockchip: rock-4c-plus: Configure IO domains in SPL

[Shigeaki Asai <asai.6265@gmail.com>]

From: Shigeaki Asai <y-asai.0816@docomonet.jp>

On the ROCK 4C+, nothing is printed on the debug UART after a cold
boot until U-Boot proper configures the regulators, so the TPL and
SPL output is lost.

The IO domains of UART2 (APIO4) and PMUIO2 are supplied by
vcc_3v0_s0, which is LDO7 of the RK809. This LDO comes up at 1.8V
at power-on (measured on the UART TX pin). U-Boot proper later sets
it to 3.0V and configures the IO domains to match.

Enable the PMIC, regulator and IO domain drivers in SPL, and add
bootph-pre-ram to the related nodes. The IO domain driver then sets
vcc_3v0_s0 to 3.0V and configures the IO domains early in SPL.

With this, the output is visible from SPL on a cold boot. The TPL
output is still not visible.

Tested on ROCK 4C+ V1.41.

This patch was written with the help of Claude (claude-opus-5-5).

Signed-off-by: Shigeaki Asai <y-asai.0816@docomonet.jp>
---
Tested on top of the series "ram: rk3399: Fix LPDDR4 tRFCab for
high-density devices", because this board does not boot without it:
https://lore.kernel.org/all/20261101185441.755448-1-asai.6265@gmail.com/

 arch/arm/dts/rk3399-rock-4c-plus-u-boot.dtsi | 32 ++++++++++++++++++++
 configs/rock-4c-plus-rk3399_defconfig        |  7 +++++
 2 files changed, 39 insertions(+)

diff --git a/arch/arm/dts/rk3399-rock-4c-plus-u-boot.dtsi b/arch/arm/dts/rk3399-rock-4c-plus-u-boot.dtsi
index 7a6af430a6f..6094cda551a 100644
--- a/arch/arm/dts/rk3399-rock-4c-plus-u-boot.dtsi
+++ b/arch/arm/dts/rk3399-rock-4c-plus-u-boot.dtsi
@@ -49,3 +49,35 @@
 &vdd_log {
 	regulator-init-microvolt = <950000>;
 };
+
+&i2c0 {
+	bootph-pre-ram;
+};
+
+&i2c0_xfer {
+	bootph-pre-ram;
+};
+
+&pcfg_pull_none {
+	bootph-pre-ram;
+};
+
+&rk809 {
+	bootph-pre-ram;
+
+	regulators {
+		bootph-pre-ram;
+	};
+};
+
+&vcc_3v0_s0 {
+	bootph-pre-ram;
+};
+
+&io_domains {
+	bootph-pre-ram;
+};
+
+&pmu_io_domains {
+	bootph-pre-ram;
+};
diff --git a/configs/rock-4c-plus-rk3399_defconfig b/configs/rock-4c-plus-rk3399_defconfig
index 0f6bdfdfb06..d3870586cf7 100644
--- a/configs/rock-4c-plus-rk3399_defconfig
+++ b/configs/rock-4c-plus-rk3399_defconfig
@@ -9,6 +9,7 @@ CONFIG_DEFAULT_DEVICE_TREE="rockchip/rk3399-rock-4c-plus"
 CONFIG_DM_RESET=y
 CONFIG_ROCKCHIP_RK3399=y
 CONFIG_ROCKCHIP_SPI_IMAGE=y
+CONFIG_SPL_DRIVERS_MISC=y
 CONFIG_TARGET_ROCKPI4_RK3399=y
 CONFIG_SYS_LOAD_ADDR=0x800800
 CONFIG_SF_DEFAULT_BUS=1
@@ -24,6 +25,8 @@ CONFIG_DEFAULT_FDT_FILE="rockchip/rk3399-rock-4c-plus.dtb"
 CONFIG_DISPLAY_BOARDINFO_LATE=y
 CONFIG_SPL_MAX_SIZE=0x40000
 # CONFIG_SPL_RAW_IMAGE_SUPPORT is not set
+CONFIG_SPL_I2C=y
+CONFIG_SPL_POWER=y
 CONFIG_SPL_SPI_LOAD=y
 CONFIG_SYS_SPI_U_BOOT_OFFS=0xE0000
 CONFIG_SPL_ATF_NO_PLATFORM_PARAM=y
@@ -48,6 +51,7 @@ CONFIG_ROCKCHIP_GPIO=y
 CONFIG_SYS_I2C_ROCKCHIP=y
 CONFIG_LED=y
 CONFIG_LED_GPIO=y
+CONFIG_SPL_ROCKCHIP_IODOMAIN=y
 CONFIG_MMC_DW=y
 CONFIG_MMC_DW_ROCKCHIP=y
 CONFIG_MMC_SDHCI=y
@@ -65,7 +69,10 @@ CONFIG_PHY_REALTEK=y
 CONFIG_PHY_ROCKCHIP_INNO_USB2=y
 CONFIG_PHY_ROCKCHIP_TYPEC=y
 CONFIG_PMIC_RK8XX=y
+CONFIG_SPL_PMIC_RK8XX=y
+CONFIG_SPL_DM_REGULATOR=y
 CONFIG_REGULATOR_RK8XX=y
+CONFIG_SPL_REGULATOR_RK8XX=y
 CONFIG_PWM_ROCKCHIP=y
 CONFIG_RAM_ROCKCHIP_LPDDR4=y
 CONFIG_BAUDRATE=1500000
-- 
2.43.0