linux-kernel - Re: [PATCH] mmc: core: Do not hold re-tuning during CMD6 commands

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Date:   Tue, 28 Mar 2017 10:30:31 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Chaotian Jing <chaotian.jing@...iatek.com>,
        Adrian Hunter <adrian.hunter@...el.com>
Cc:     Matthias Brugger <matthias.bgg@...il.com>,
        Jaehoon Chung <jh80.chung@...sung.com>,
        Shawn Lin <shawn.lin@...k-chips.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        linux-mediatek@...ts.infradead.org,
        srv_heupstream <srv_heupstream@...iatek.com>
Subject: Re: [PATCH] mmc: core: Do not hold re-tuning during CMD6 commands

[...]

>>
>> If there is a problem in __mmc_switch(), let's try to fix it there first.
>>
> Anyway, it is a bug of retry 3 times at max but without check current
> card status and ensure it's in transfer state before next retry.

Correct. Do you want to send a patch that fixes this? Otherwise I can do it...

>> >> > I think the purpose of "re-tune" is trying to cover particular case(eg.
>> >> > voltage fluctuate or EMI or some glitch of host/device which caused CRC
>> >> > error)
>> >>
>> >> No, re-tuning is to compensate for drift caused primarily by temperature change.
>> >>
>> > Yes, by JEDEC spec, temperature change cause timing drift of EMMC
>> > device, but, as you mentioned, maybe I have a hardware problem of host,
>> > but needs Software to cover it. so that we are doing our best to do
>> > re-tune if got CRC error. if could recover it, then  it's better than
>> > system hung.
>>
>> Exactly in what cases do you get CRC errors for CMD6. We need a full
>> cmd log to understand and to help.
>>
>> >> > error) , but in such cases, too many cases are disable re-tune function
>> >> > by mmc_retune_hold(), for example, in this case, if a response CRC error
>> >> > got then we never have chance to recover it. then cause system cannot
>> >> > access emmc or suspend/resume fail.
>> >>
>> >> Maybe you have a hardware problem.
>>
>> There is no way I am going to accept patches touching this part of the
>> mmc core, without providing real evidence for how it solves a problem.
>> To me, it seems like you are applying a workaround for another issue.
>>
>> Again, try to provide us with some more data and logs, then perhaps we
>> can help narrow down the issues.
>>
>> Kind regards
>> Uffe
>
> Below is the fail log of suspend fail.
> the normal command tune result should be 0xffffff9ff, but some time, we
> get the tune result of 0xffffffff, then we choose the 10 as the best
> tune parameter, which is not stable.
> I know that we should focus on why we get the result of 0xffffffff, this
> may be result of device/host timing shifting while tuning. but what I
> want to do is that when get a response CRC error, we can do re-tune to
> recovery it, but not only return the -84 and cause suspend fail
> eventually. if all hardware are perfect, then we don't need the re-tune
> mechanism.

Thanks for elaborating!

Can you please also tell exactly which of the CMD6 commands in the
suspend sequence that is triggering this problem? Cache flush? Power
off notification?

>
> as Adrian's comment, if temperature change at here caused CMD6 response
> CRC error, then how to recovery it ?

So in your case, allowing re-tuning a little longer in __mmc_switch()
solves your problem. Clearly there are cases when we need to prevent
re-tuning when sending CMD6, however maybe not in all cases as we do
today.

For example it seems reasonable to not hold retuning before sending
CMD6 for cache flush, but instead it should be sufficient to hold it
before polling for busy in __mmc_switch().

Adrian, what's your thoughts on this?

>
> [  129.106622]  (0)[96:mmcqd/0]mtk-msdc 11230000.mmc: phase:
> [map:fffff9ff] [maxlen:21] [final:21] -->current result is OK and 21 is
> stable
> [  129.109404]  (0)[96:mmcqd/0]mtk-msdc 11230000.mmc: phase:
> [map:ffffe03f] [maxlen:19] [final:22]
> --------------------> below is next resume and re-init card:
> [  129.778454]  (0)[96:mmcqd/0]mtk-msdc 11230000.mmc: Regulator set
> error -22: 3300000 - 3300000
> [  130.016987]  (0)[96:mmcqd/0]mtk-msdc 11230000.mmc: phase:
> [map:ffffffff] [maxlen:32] [final:10] --> this result if not OK and 10
> is not stable.

As you suspect the tuning didn't work out correctly, then why don't
you retry one more time?

> [  130.019556]  (0)[96:mmcqd/0]mtk-msdc 11230000.mmc: phase:
> [map:ffffc03f] [maxlen:18] [final:23]
> [  130.124279]  (1)[1248:system_server]mmc0: cache flush error -84
> [  130.125058]  (1)[1248:system_server]dpm_run_callback():
> mmc_bus_suspend+0x0/0x4c returns -84
> [  130.126104]  (1)[1248:system_server]PM: Device mmc0:0001 failed to
> suspend: error -84
>
>
>

Kind regards
Uffe