Re: [PATCH 1/4] arm64: dts: renesas: rzt2h-n2h-evk: Add ramp delay for SD0 card regulator

[Geert Uytterhoeven]

On Sat, 24 Jan 2026 at 00:00, Prabhakar <prabhakar.csengg@xxxxxxxxx> wrote:
> From: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
>
> Add a ramp delay of 60 uV/us to the vqmmc_sdhi0 voltage regulator to
> fix UHS-I SD card detection failures.
>
> Measurements on CN78 pin 4 showed the actual voltage ramp time to be
> 21.86ms when switching between 3.3V and 1.8V. A 25ms ramp delay has
> been configured to provide adequate margin. The calculation is based
> on the voltage delta of 1.5V (3.3V - 1.8V):
>   1500000 uV / 60 uV/us = 25000 us (25ms)
>
> Prior to this patch, UHS-I cards failed to initialize with:
>
>   [   32.723914] mmc0: error -110 whilst initialising SD card
>
> After this patch, UHS-I cards are properly detected on SD0:
>
>   [   28.379122] mmc0: new UHS-I speed SDR104 SDXC card at address aaaa
>   [   28.387239] mmcblk0: mmc0:aaaa SR64G 59.5 GiB
>
> Fixes: d065453e5ee09("arm64: dts: renesas: rzt2h-rzn2h-evk: Enable SD card slot")
> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>

Reviewed-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
i.e. will queue in renesas-fixes for v7.0.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds