On 16 January 2017 at 04:48, Dong Aisheng <dongas86@xxxxxxxxx> wrote:
> Hi Ulf,
>
> On Fri, Jan 13, 2017 at 7:05 PM, Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote:
>> Regressions for not being able to detect an eMMC HS DDR mode card has been
>> reported for the sdhci-esdhc-imx driver, but potentially other sdhci
>> variants may suffer from the similar problem.
>>
>> The commit e173f8911f09 ("mmc: core: Update CMD13 polling policy when
>> switch to HS DDR mode"), is causing the problem. It seems that change moved
>> one step to far, regarding changing the host's timing before polling for a
>> busy card.
>>
>> To fix this, let's move back to the behaviour when the host's timing is
>> updated after the polling, but before the switch status is fetched and
>> validated.
>>
>> In cases when polling with CMD13, we keep validating the switch status at
>> each attempt. However, to align with the other card busy detections
>> mechanism, let's fetch and validate the switch status also after the host's
>> timing is updated.
>>
>> Reported-by: Clemens Gruber <clemens.gruber@xxxxxxxxxxxx>
>> Reported-by: Gary Bisson <gary.bisson@xxxxxxxxxxxxxxxxxxx>
>> Fixes: e173f8911f09 ("mmc: core: Update CMD13 polling policy when switch..")
>> Cc: Shawn Lin <shawn.lin@xxxxxxxxxxxxxx>
>> Cc: Dong Aisheng <aisheng.dong@xxxxxxx>
>> Cc: Haibo Chen <haibo.chen@xxxxxxx>
>> Signed-off-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
>
> Thanks for the fix.
>
> Reviewed-by: Dong Aisheng <aisheng.dong@xxxxxxx>
Thanks for reviewing!
>
> BTW, i wonder if we could then remove the CMD13 Polling method or give a
> temporarily WARN_ONCE to indicate OBSOLETED using and force all hosts
> to provide card_busy() callback.
> Then we can permanently fix the potential timing mismatch issue.
In the end it seems like the issue is host specific. I have
successfully used CM13 polling on my ux500 board (mmci.c, with some
hacks to force CMD13).
If we see any further issues, perhaps we should invent a new host cap,
which forbids the CMD13 polling and then those host drivers that has
issues, can set it. Wouldn't that be okay for you?
[...]
Kind regards
Uffe
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