Re: [RFC PATCH V2 2/2] mmc: allow card to disable tuning

[Adrian Hunter]

On 7/03/25 19:45, Erick Shepherd wrote:
>> Sorry for the slow reply.
> 
>> I would expect if there was a general problem with DDR50 SD cards,
>> it would have come to light before now.
> 
>> Does the card work with any other host controllers with linux?
> 
>> If it is specific to a particular kind of card, a card quirk
>> could be added, say MMC_QUIRK_BROKEN_DDR50_TUNING
> 
> No worries. I have not tested this with other host controllers but
> can try to get something set up. This issue has only appeared on
> one particular SD card model for us so I would not be surprised if
> the I/O errors we see on subsequent tune requests are specific to this
> card. I can put together a solution using the card quirk you suggested
> if you think that is the best way forward.
> 
> My fix is currently spread across two commits, one to return the error
> code thrown by the tune request timing out, which prevents the card from
> retuning, and this one that prevents the initial card tuning if it has
> already failed. Should both parts be controlled by the new card quirk?

Does it tuning at all?  Maybe MMC_QUIRK_NO_UHS_DDR50_TUNING is a better
name, then at the top of mmc_execute_tuning()

	if ((card->quirks & MMC_QUIRK_NO_UHS_DDR50_TUNING) &&
	    host->ios->timing == MMC_TIMING_UHS_DDR50)
		return 0;