On the ODROID-GO Ultra, booting from the SD card fails after a reboot from Linux. Linux sets vddio_c (the SD card vqmmc supply, RK818 LDO9) to 3.0V, the value is kept across the warm reboot, and with U-Boot running the card at 40 MHz, reads fail on some cards. The board then stops at the U-Boot prompt. A cold boot is fine.
Patch 1 adds the missing RK818 LDO9 to the rk8xx regulator driver, and patch 2 uses it to set vddio_c to 3.3V on the ODROID-GO Ultra. Tested on an ODROID-GO Ultra with v2026.07 and a SanDisk Ultra A1 64GB card: 9 reboots from Linux in a row, all booting from SD. The series is rebased on current main and builds with odroid-go-ultra_defconfig. The patches were written with the help of Claude (claude-opus-5-5). Shigeaki Asai (2): power: regulator: rk8xx: add RK818 LDO9 support arm: dts: meson-g12b-odroid-go-ultra-u-boot: set vddio_c to 3.3V .../meson-g12b-odroid-go-ultra-u-boot.dtsi | 8 ++++ drivers/power/regulator/rk8xx.c | 46 +++++++++++++++---- 2 files changed, 44 insertions(+), 10 deletions(-) -- 2.43.0
