Re: [PATCH v2 3/5] mmc: tegra: implement UHS tuning

[Jon Hunter <jonathanh-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>]

On 29/03/16 17:37, Jon Hunter wrote:
> Hi Lucas,
> 
> On 22/12/15 18:41, Lucas Stach wrote:
>> This implements the UHS tuning sequence in a similar way to the one
>> contained in the TRM. It deviates in the way how to check if the tap
>> value is passing, by using the common Linux MMC function, which does
>> not only check for data CRC errors, but also if the received block
>> pattern is correct.
>>
>> Signed-off-by: Lucas Stach <dev-8ppwABl0HbeELgA04lAiVw@public.gmane.org>
> 
> I have been investigating a hang that occurs randomly during
> system-suspend on Tegra124 Jetson TK1 (I have also reproduced the
> problem on Tegra124 Nyan Big as well) with -next. The problem does not
> occur on every suspend transition but if I execute 100 transitions I
> will typically see it at some point. For example ...
> 
> count=0; while [ $count -lt 100 ]; do rtcwake -d rtc0 -m mem -s 3; echo
> Suspend iteration $count; count=`expr $count + 1`; done
> 
> I was able to bisect this problem down to RMK's commit 71fcbda0fcdd
> (“mmc: sdhci: fix command response CRC error handling”). However,
> looking at RMK's change, I believe that this commit is not the problem
> but has exposed a problem with the tegra SDHCI driver.
> 
> When the hang occurs I always see the following when starting the
> suspend sequence and after which the system continues to suspend but
> never exits suspend:
> 
> 	mmc0: Timeout waiting for hardware interrupt.
> 
> The above message is a symptom of RMK's commit and I have found that
> when I see this, it always occurs during tegra_sdhci_execute_tuning()
> because sometimes we get a CRC error.

For completeness, when disabling the UHS modes for Tegra, I no longer
see the hang during suspend (because the execute_tuning() is not called).

Cheers
Jon