Re: [PATCH] mmc: dw_mmc: Wait for data transfer after response errors

Enric Balletbo Serra
2016-03-31T06:39:35Z

2016-03-31 4:03 GMT+02:00 Jaehoon Chung <jh80.chung@samsung.com>:
> On 03/31/2016 02:16 AM, Enric Balletbo Serra wrote:
>> 2016-03-24 17:22 GMT+01:00 Russell King - ARM Linux <linux@arm.linux.org.uk>:
>>> On Thu, Mar 24, 2016 at 09:06:45AM -0700, Doug Anderson wrote:
>>>> Russell,
>>> ...
>>>> Presumably this is similar to what you saw: the host saw the CRC error
>>>> but the card knew nothing about it. Sending the stop command during
>>>> this time confused the card. Presumably the card was in transfer
>>>> state during this time?
>>>
>>> If the card was in transfer state for a command which expects a stop
>>> command, and that stop command was issued after the card entered
>>> the transfer state, then I'd expect the card to handle it... though
>>> there's always the firmware bug issue.
>>>
>>> If the card hadn't entered transfer state at the time the stop command
>>> was issued.. I think that's more likely to hit card firmware issues.
>>>
>>> With the tuning commands, there's another case you can hit though:
>>> the data transfer may have completed before you get around to sending
>>> the stop command.
>>>
>>> That's why, for sdhci, I came to the conclusion that waiting for the
>>> data transfer to complete or timeout was the best solution for SDHCI.
>>>
>>
>> In fact I only saw the problem with dw_mmc-exynos, on dw_mmc-rockchip
>> it doesn't happen because it enables the DW_MCI_QUIRK_BROKEN_DTO
>> behaviour. What does this is use a kernel timer to signal when DTO
>> interrupt does NOT come. Note that if I disable this quirk I can also
>> saw the problem on rockchip.
>
> Did you see the problem with exynos? Could you share which exynos chip you use?
> Then i can check this with all exynos.
>

Applying this patch I saw the problem with peach-pi, exynos 58000.

>>
>>> Maybe, if sending a STOP command does cause card firmware issues, then:
>>>
>>> 1) it provides evidence that trying to send a stop command on response
>>> CRC error is the wrong thing to do (it was talked about making SDHCI
>>> do this.)
>>>
>>
>> Seems the same here, so guess is the wrong thing to do.
>>
>>> 2) it suggests that the solution I came up with for SDHCI is the better
>>> solution, rather than trying to immediately recover the situation by
>>> sending a STOP command.
>>>
>>
>> I'm wondering if just enable this quirk on exynos too is the proper
>> solution. Unfortunately I don't have enough documentation to check
>> differences between those controllers.
>> Also will really help have access to some hardware that uses
>> dw_mmc-pltfm to check if, like on exynos, same issue is triggered.
>> Anyone with the hardware who can do some tests?
>
> I want to remove all quirks for dwmmc controller. (in progressing with Shawn.)
>

Nice, do you have a work-in-progress repository? Maybe I can help
testing the patches.

>>
>>
>>> Maybe dw-mmc can do something similar, but with the lack of data transfer
>>> timeout, maybe it's possible to do something with a kernel timer instead,
>>> and check what the hardware is doing after a response CRC error?
>>>
>>> --
>>> RMK's Patch system: http://www.arm.linux.org.uk/developer/patches/
>>> FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
>>> according to speedtest.net.
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>>
>