[PATCH 1/2] mmc: detect illegal command response in SPI mode

[Peng Fan]

On Sun, Jun 14, 2026 at 02:04:37AM +0200, Mart?? Alonso wrote:
>At idle state, prior initialization, MMC cards (not SD) will respond
>with illegal command to anything other than CMD1 (MMC_SEND_OP_COND) and
>CMD58 (MMC_READ_OCR). The MMC driver initially sends CMD8
>(SD_SEND_IF_COND) to check for an SD card, but this needs to return an
>error, if not an SD card, so it can later check for an MMC card with
>CMD1 (MMC_SEND_OP_COND).

CMD8 is supported in SD 2.0+, so this might break SD 1.0.

>
>Additionally, CMD55 + ACMD41 (SD_APP_SEND_OP_COND) can be skipped if
>CMD8 (SD_SEND_IF_COND) already failed.
>

Regards
Peng