Re: [PATCH 2/2] arm: dts: meson-g12b-odroid-go-ultra-u-boot: set vddio_c to 3.3V

["Asai, Shigeaki" <y-asai.0816@docomonet.jp>]

(Resending to the list only; my first reply was rejected by the list
server. Sorry for the duplicate.)

Hi Quentin,

Thank you for the review.

On 10/16/26, Quentin Schulz wrote:
> I'll let Neil decide since he's the maintainer of that code, but I don't
> think this is necessarily correct? The spec specifically allows
> 2.7-3.6V, c.f. https://www.sdcard.org/developers/sd-standard-overview/.
>
> Moreover, RK3399 Puma has 1.8-3.0V only, and it's been working fine for
> years now (though I haven't checked with that SD card specifically).
>
> What happens if you do NOT use the SD in U-Boot at all and boot straight
> to the Linux kernel, is it also broken in the Linux kernel then? If not,
> then your issue is probably not what your tool output and we may have an
> issue elsewhere (possibly in the MMC subsystem for example).

Linux is fine with this card at 3.0V. Linux itself sets vddio_c to
3.0V, and the system runs from the same card (SD high speed, 50MHz)
with no errors in dmesg.

Following your comments, I tested again without this patch, and I can
no longer reproduce the problem. I tried U-Boot 2025.07, 2026.07 and
2026.10, with and without patch 1/2, and three SD cards, including the
one in the commit message. In about 35 reboots from Linux, U-Boot always
read the card and booted the kernel. At the U-Boot prompt after a
reboot, vddio_c was 3.0V and the SD card ran at 40MHz, so the
conditions were the same as in my original report. I do not know what
was different when I saw the failure.

So I agree that 3.0V is probably not the cause, and I will drop this
patch. If I can reproduce the problem again, I will look at it again,
including the MMC side as you suggested.

Neil, sorry for the noise.

Best regards,
Shigeaki Asai

(This reply was written with the help of Claude.)