mmc: Add quirk to disable DDR50 tuning

[erickshepherdNI]

Adds the MMC_QUIRK_NO_UHS_DDR50_TUNING quirk and updates
mmc_execute_tuning() to return 0 if that quirk is set. This fixes an
issue on certain Swissbit SD cards that do not support DDR50 tuning
where tuning requests caused I/O errors to be thrown.

WI#2805437

Testing

Built the kernel and confirmed that the SD card attempts to tune but is stopped by the new change. No I/O errors were thrown.

[chaitu236]

Changes lgtm. But please add WI# to PR description and rebase to latest nilrt/master/6.6.

Btw, did you end up testing on other controllers? What were the findings?

[erickshepherdNI]

Changes lgtm. But please add WI# to PR description and rebase to latest nilrt/master/6.6.

Btw, did you end up testing on other controllers? What were the findings?

I updated the PR description and rebased the changes. as far as other testing, I was not able to reproduce the issue on a 9034 with the same Swissbit card. I'd be curious to test on more hardware configurations but this change should be ok since the card doesn't support tuning anyway.

[chaitu236]

Changes lgtm. But please add WI# to PR description and rebase to latest nilrt/master/6.6.
Btw, did you end up testing on other controllers? What were the findings?

I updated the PR description and rebased the changes. as far as other testing, I was not able to reproduce the issue on a 9034 with the same Swissbit card. I'd be curious to test on more hardware configurations but this change should be ok since the card doesn't support tuning anyway.

I see. Did we get the info about it's tuning support from it's manual/manufacturer?

[erickshepherdNI]

Changes lgtm. But please add WI# to PR description and rebase to latest nilrt/master/6.6.
Btw, did you end up testing on other controllers? What were the findings?

I updated the PR description and rebased the changes. as far as other testing, I was not able to reproduce the issue on a 9034 with the same Swissbit card. I'd be curious to test on more hardware configurations but this change should be ok since the card doesn't support tuning anyway.

I see. Did we get the info about it's tuning support from it's manual/manufacturer?

I dug up the exact card model and spec sheet when I started working on this and confirmed that the card was built to the 3.0 SD spec that does not support DDR50 tuning. I can find the documentation again and attach it to the work item. It would probably be good to have for future reference.

[gratian]

Looks good. Just a nitpick on the comment being too general to be useful.

Also looks like check-patch flagged an indentation warning (see the 'Checks' tab in the PR).

[chaitu236]

@erickshepherdNI can this be closed?