Re: [PATCH] ufs: core: Fix the UFSHCD_QUIRK_MCQ_BROKEN_RTC implementation

["Peter Wang (王信友)" <peter.wang@mediatek.com>]

On Tue, 2025-10-28 at 06:46 -0700, Bart Van Assche wrote:
> ufshcd_mcq_sqe_search() only searches the submission queue. Examining
> completion queues is not something ufshcd_mcq_sqe_search() must do.
> 
> The UFSHCI driver is based on the assumption that the UFSHCI
> controller
> works correctly and hence passes completions quickly to the host. The
> SCSI core only tries to abort a SCSI command after the SCSI timeout
> has
> expired. The smallest SCSI timeout that can be configured is one
> second.
> This is several orders of magnitude larger than the typical time for
> passing a completion from the UFSHCI to the host. Hence, I think it
> is
> very unlikely that a completion is present in the host controller and
> has not yet reached the host by the time the SCSI core aborts a SCSI
> command.
> 
> Bart.

Hi Bart,

The probability is indeed quite low, but it can still happen,
especially when the timeout is set low. For example, the dev 
command only has 1.5 seconds. Some device dev commands may be
delayed by normal read/write commands and eventually reach 
this timeout.

By the way,
ufshcd_mcq_sqe_search will return true if UFSHCD_QUIRK_MCQ_BROKEN_RTC.
Therefore, this code:

+	if (hba->quirks & UFSHCD_QUIRK_MCQ_BROKEN_RTC)
+		return ufshcd_mcq_sqe_search(hba, hwq, task_tag) ? -
ETIMEDOUT :
+			0;
+

should be equivalent to:

-	if (hba->quirks & UFSHCD_QUIRK_MCQ_BROKEN_RTC)
-		return -ETIMEDOUT;
-

am I right?

Thanks
Peter