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

[Ulf Hansson]

On Mon, 2 Mar 2020 at 14:11, Faiz Abbas <faiz_abbas@xxxxxx> wrote:
>
> Uffe,
>
> On 26/02/20 8:51 pm, Ulf Hansson wrote:
> > + Anders, Kishon
> >
> > On Tue, 25 Feb 2020 at 17:24, Jon Hunter <jonathanh@xxxxxxxxxx> 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, 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.
> >
> > Comments or other ideas of how to move forward?
> >
>
> Sorry I missed this earlier.
>
> I don't have an X15 with me here but I'm trying to set one up in our
> remote farm. In the meantime, I tried to reproduce this issue on two
> platforms (dra72-evm and am57xx-evm) and wasn't able to see the issue
> because those eMMC's don't even have a cache. I will keep you updated
> when I do get a board with a eMMC that has a cache.
>
> Is there a way to reproduce this CMD6 issue with another operation?

Yes, most definitely.

Let me cook a debug patch for you that should trigger the problem for
another CMD6 operation. I will post something later this evening or in
the mornings (Swedish timezone).

Kind regards
Uffe