[Linux-stm32] [PATCH v2 4/5] arm64: dts: st: use sdmmc2 pins_a on stm32mp257f-dk

[Christophe KERELLO]

Hello Mateusz,

On 11/4/26 16:27, Mateusz Nowicki wrote:
> The eMMC of the STM32MP257F-DK was moved to the faster sdmmc2 pins_b
> groups because HS200 at 100 MHz returned corrupted data with pins_a. The
> cause was the delay block, which was used at 100 MHz, not the slew rate
> of the pins. With "mmc: mmci: stm32: use the delay block above 100 MHz
> on stm32mp25 SoC" HS200 works with pins_a at 100 MHz, and at 150 MHz
> with the delay block.
>
> Use pins_a again. Their slower outputs avoid overshoots on the SDMMC2
> clock, which can disturb other blocks such as USB.
>
> Fixes: 94911ce62b45 ("arm64: dts: st: enable eMMC on stm32mp257f-dk")
> Suggested-by: Christophe Kerello<christophe.kerello at foss.st.com>
> Signed-off-by: Mateusz Nowicki<mateusz.nowicki at posteo.net>
> ---
>
> Notes:
>      This needs patch 3 of the series: without it HS200 at 100 MHz loses writes
>      with pins_a. With it, the eMMC of the DK passed every 832 MiB write and
>      read-back run on pins_a at 100 MHz and at 150 MHz (see the cover letter).
>
>   arch/arm64/boot/dts/st/stm32mp257f-dk.dts | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)

Reviewed-by: Christophe Kerello <christophe.kerello at foss.st.com>

Regards,
Christophe Kerello.