nanopi-r76s: fix SD boot and storage stability on eMMC-less units (#9908)

* nanopi-r76s: build u-boot with the SD boost to fix no-UART SD boot

eMMC-less units printed nothing on serial and would not boot from SD:
the binman u-boot-rockchip.bin image omits the Rockchip SD boost the
BootROM needs. Assemble idbloader.img through boot_merger so the boost
is included, writing idbloader and u-boot.itb at the standard offsets.

Signed-off-by: SuperKali <hello@superkali.me>

* nanopi-r76s: drop sdmmc0_pwren pinctrl to fix SD SDR104 instability

The SD node inherited the SoC default pinctrl, which claims the card
power-enable pin and lets the controller power-cycle the card during
error recovery, causing an endless SDR104 re-tune loop and I/O errors.
Drop that pin from the SD pinctrl, as Rockchip did upstream for rk3576.

Signed-off-by: SuperKali <hello@superkali.me>

---------

Signed-off-by: SuperKali <hello@superkali.me>

Author: SuperKali

config/boards/nanopi-r76s.conf

@@ -31,15 +31,14 @@ function post_family_config__nanopi_r76s_use_mainline_uboot() {
 	declare -g BOOTPATCHDIR="v2026.04"
 	unset BOOT_FDT_FILE
 
-	# Don't set BOOTDIR, allow shared U-Boot source directory for disk space efficiency
-	declare -g UBOOT_TARGET_MAP="BL31=${RKBIN_DIR}/${BL31_BLOB} ROCKCHIP_TPL=${RKBIN_DIR}/${DDR_BLOB};;u-boot-rockchip.bin"
+	# boot_merger (uboot_custom_postprocess) injects the rk3576 SD boost; binman's u-boot-rockchip.bin lacks it
+	declare -g UBOOT_TARGET_MAP="BL31=${RKBIN_DIR}/${BL31_BLOB} ROCKCHIP_TPL=${RKBIN_DIR}/${DDR_BLOB};;idbloader.img u-boot.itb"
 
-	# Disable stuff from rockchip64_common; we're using binman here which does all the work already
-	unset uboot_custom_postprocess write_uboot_platform write_uboot_platform_mtd # disable stuff from rockchip64_common; we're using binman here which does all the work already
+	unset write_uboot_platform write_uboot_platform_mtd
 
-	# Just use the binman-provided u-boot-rockchip.bin, which is ready-to-go
 	function write_uboot_platform() {
-		dd "if=$1/u-boot-rockchip.bin" "of=$2" bs=32k seek=1 conv=notrunc status=none
+		dd "if=$1/idbloader.img" "of=$2" seek=64    conv=notrunc status=none
+		dd "if=$1/u-boot.itb"    "of=$2" seek=16384 conv=notrunc status=none
 	}
 }
 

patch/kernel/archive/rockchip64-6.18/dt/rk3576-nanopi-r76s.dts

@@ -793,6 +793,8 @@
 	vmmc-supply = <&vcc_3v3_s3>;
 	vqmmc-supply = <&vccio_sd_s0>;
 	pinctrl-names = "default";
+	/* drop sdmmc0_pwren from SoC default pinctrl: unstable SDR104 re-init */
+	pinctrl-0 = <&sdmmc0_clk &sdmmc0_cmd &sdmmc0_det &sdmmc0_bus4>;
 	status = "okay";
 };
 

patch/kernel/archive/rockchip64-7.0/dt/rk3576-nanopi-r76s.dts

@@ -793,6 +793,8 @@
 	vmmc-supply = <&vcc_3v3_s3>;
 	vqmmc-supply = <&vccio_sd_s0>;
 	pinctrl-names = "default";
+	/* drop sdmmc0_pwren from SoC default pinctrl: unstable SDR104 re-init */
+	pinctrl-0 = <&sdmmc0_clk &sdmmc0_cmd &sdmmc0_det &sdmmc0_bus4>;
 	status = "okay";
 };
 

patch/kernel/archive/rockchip64-7.1/dt/rk3576-nanopi-r76s.dts

@@ -793,6 +793,8 @@
 	vmmc-supply = <&vcc_3v3_s3>;
 	vqmmc-supply = <&vccio_sd_s0>;
 	pinctrl-names = "default";
+	/* drop sdmmc0_pwren from SoC default pinctrl: unstable SDR104 re-init */
+	pinctrl-0 = <&sdmmc0_clk &sdmmc0_cmd &sdmmc0_det &sdmmc0_bus4>;
 	status = "okay";
 };