linux-kernel - Re: LKFT: arm x15: mmc1: cache flush error -110

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Date:   Wed, 26 Feb 2020 17:04:54 +0000
From:   Jon Hunter <jonathanh@...dia.com>
To:     Ulf Hansson <ulf.hansson@...aro.org>,
        Faiz Abbas <faiz_abbas@...com>,
        Bitan Biswas <bbiswas@...dia.com>
CC:     Sowjanya Komatineni <skomatineni@...dia.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Naresh Kamboju <naresh.kamboju@...aro.org>,
        "Jens Axboe" <axboe@...nel.dk>,
        Alexei Starovoitov <ast@...nel.org>,
        linux-block <linux-block@...r.kernel.org>,
        <lkft-triage@...ts.linaro.org>,
        open list <linux-kernel@...r.kernel.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>,
        John Stultz <john.stultz@...aro.org>,
        Thierry Reding <treding@...dia.com>,
        Anders Roxell <anders.roxell@...aro.org>,
        Kishon <kishon@...com>
Subject: Re: LKFT: arm x15: mmc1: cache flush error -110


On 26/02/2020 15:21, Ulf Hansson wrote:
> + Anders, Kishon
> 
> On Tue, 25 Feb 2020 at 17:24, Jon Hunter <jonathanh@...dia.com> wrote:
>>
>>
>> On 25/02/2020 14:26, Ulf Hansson wrote:
>>
>> ...
>>
>>> However, from the core point of view, the response is still requested,
>>> only that we don't want the driver to wait for the card to stop
>>> signaling busy. Instead we want to deal with that via "polling" from
>>> the core.
>>>
>>> This is a rather worrying behaviour, as it seems like the host driver
>>> doesn't really follow this expectations from the core point of view.
>>> And mmc_flush_cache() is not the only case, as we have erase, bkops,
>>> sanitize, etc. Are all these working or not really well tested?
>>
>> I don't believe that they are well tested. We have a simple test to
>> mount an eMMC partition, create a file, check the contents, remove the
>> file and unmount. The timeouts always occur during unmounting.
>>
>>> Earlier, before my three patches, if the provided timeout_ms parameter
>>> to __mmc_switch() was zero, which was the case for
>>> mmc_mmc_flush_cache() - this lead to that __mmc_switch() simply
>>> ignored validating host->max_busy_timeout, which was wrong. In any
>>> case, this also meant that an R1B response was always used for
>>> mmc_flush_cache(), as you also indicated above. Perhaps this is the
>>> critical part where things can go wrong.
>>>
>>> BTW, have you tried erase commands for sdhci tegra driver? If those
>>> are working fine, do you have any special treatments for these?
>>
>> That I am not sure, but I will check.
> 
> Great, thanks. Looking forward to your report.

So no I don't believe that we have explicitly tried erase commands and
no there is nothing special that we are doing for erase.

> So, from my side, me and Anders Roxell, have been collaborating on
> testing the behaviour on a TI Beagleboard x15 (remotely with limited
> debug options), which is using the sdhci-omap variant. I am trying to
> get hold of an Nvidia jetson-TX2, but not found one yet. These are the
> conclusions from the observed behaviour on the Beagleboard for the
> CMD6 cache flush command.
> 
> First, the reported host->max_busy_timeout is 2581 (ms) for the
> sdhci-omap driver in this configuration.
> 
> 1. As we all know by now, the cache flush command (CMD6) fails with
> -110 currently. This is when MMC_CACHE_FLUSH_TIMEOUT_MS is set to 30 *
> 1000 (30s), which means __mmc_switch() drops the MMC_RSP_BUSY flag
> from the command.
> 
> 2. Changing the MMC_CACHE_FLUSH_TIMEOUT_MS to 2000 (2s), means that
> the MMC_RSP_BUSY flag becomes set by __mmc_switch, because of the
> timeout_ms parameter is less than max_busy_timeout (2000 <  2581).
> Then everything works fine.
> 
> 3. Updating the code to again use 30s as the
> MMC_CACHE_FLUSH_TIMEOUT_MS, but instead forcing the MMC_RSP_BUSY to be
> set, even when the timeout_ms becomes greater than max_busy_timeout.
> This also works fine.
> 
> Clearly this indicates a problem that I think needs to be addressed in
> the sdhci driver. However, of course I can revert the three discussed
> patches to fix the problem, but that would only hide the issues and I
> am sure we would then get back to this issue, sooner or later.
> 
> To fix the problem in the sdhci driver, I would appreciate if someone
> from TI and Nvidia can step in to help, as I don't have the HW on my
> desk.

OK, let me check to see who can help from our side.

Cheers
Jon

-- 
nvpublic