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

[Sowjanya Komatineni]

On 3/10/20 2:46 AM, Ulf Hansson wrote:
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>
>
> On Mon, 9 Mar 2020 at 18:33, Sowjanya Komatineni <skomatineni@xxxxxxxxxx> wrote:
> > On 3/6/20 3:14 AM, Ulf Hansson wrote:
> > > External email: Use caution opening links or attachments
> > >
> > >
> > > [...]
> > >
> > > > > > > > > > > > > Actually we always use R1B with CMD6 as per spec.
> > > > > > > > > > > > I fully agree that R1B is preferable, but it's not against the
> > > > > > > > > > > > spec to
> > > > > > > > > > > > send CMD13 to poll for busy.
> > > > > > > > > > > >
> > > > > > > > > > > > Moreover, we need to cope with the scenario when the host has
> > > > > > > > > > > > specified a maximum timeout that isn't sufficiently long enough for
> > > > > > > > > > > > the requested operation. Do you have another proposal for how to
> > > > > > > > > > > > manage this, but disabling MMC_RSP_BUSY?
> > > > > > > > > > > >
> > > > > > > > > > > > Let's assume you driver would get a R1B for the CMD6 (we force it),
> > > > > > > > > > > > then what timeout would the driver be using if we would set
> > > > > > > > > > > > cmd.busy_timeout to 30ms?
> > > > > > Sorry didn't understood clearly. Are you asking with 30s timeout, whats
> > > > > > the data timeout counter used?
> > > > > Yes. It seems like it will pick the maximum, which is 11s?
> > > > yes
> > > Okay, thanks!
> > >
> > > > > > Because of above mentioned issue on our host where CMD interrupt happens
> > > > > > after busy state, poll for busy returns right away as not busy.
> > > > > I see.
> > > > >
> > > > > > So issuing CMD13 after CMD6-R1 followed by busy poll should be working.
> > > > > > But weird that with small delay of 1ms or debug print before CMD13 it
> > > > > > doesn't timeout and works all the time.
> > > > > I have digested the information you provided in these emails. Let me
> > > > > summarize it, to see if I have understood correctly.
> > > > >
> > > > > 1.
> > > > > Your controller can't distinguish between R1 and R1B because of a
> > > > > limitation in the HW. So, in both cases you need to wait for the card
> > > > > to stop signal busy, before the controller can give an IRQ to notify
> > > > > that the R1 response has been received. Correct?
> > > > >
> > > > > In this context, I am wondering if sdhci_send_command(), really
> > > > > conforms to these requirements. For example, depending on if the CMD6
> > > > > has MMC_RSP_BUSY or not, it may pick either SDHCI_CMD_RESP_SHORT or
> > > > > SDHCI_CMD_RESP_SHORT_BUSY.
> > > > >
> > > > > Does this work as expected for your case?
> > > > Design team re-verified internally and bug where HW waits for busy state
> > > > before IRQ is only for R1B and R1 is spec compliant.
> > > >
> > > > So, with R1, CMD complete is generated after response received.
> > > Okay.
> > >
> > > So, the issue we see for CMD6 with R1, is a software problem that we
> > > should be able to fix.
> > >
> > > > With R1B, CMD complete and xfer complete both are generated after
> > > > response received + device busy (max timeout of 11s)
> > > > DATA timeout interrupt will be asserted incase if HW busy detection fails.
> > > >
> > > > With R1B we may see DATA Timeout if operation takes more than max busy
> > > > timeout of 11s.
> > > Okay, I see.
> > >
> > > > > 2.
> > > > > Assuming my interpretation of the above is somewhat correct. Then you
> > > > > always need to set a busy timeout for R1/R1B responses in the
> > > > > controller. The maximum timeout seems to be 11s long. Obviously, this
> > > > > isn't enough for all cases, such as cache flushing and erase, for
> > > > > example. So, what can we do to support a longer timeouts than 11s?
> > > > > Would it be possible to disable the HW timeout, if the requested
> > > > > timeout is longer than 11s and use a SW timeout instead?
> > > > >
> > > > > Kind regards
> > > > > Uffe
> > > > For erase long operations we have register bit to enable for infinite
> > > > busy wait mode where host controller would be monitoring until card is busy.
> > > Alright, that sounds great!
> > >
> > > > But so far for emmc devices we used on our platforms, we haven't seen
> > > > cache flush taking more than 11s.
> > > I understand that 11s is probably fine to use, for most cases.
> > >
> > > However, it's not spec compliant, as for some operations there are
> > > simply no timeout specified. BKOPS, cache flush, sanitize are cases
> > > like this - and then 11s is definitely not sufficient.
> > >
> > > > Will get back on possibility of disabling HW timeout and using SW timeout..
> > > Thanks!
> > >
> > > I would like to get the regression fixed asap, but I also would like
> > > to avoid reverting patches, unless really necessary. May I propose the
> > > following two options.
> > >
> > > 1. Find out why polling with ->card_busy() or CMD13, for a CMD6 with
> > > an R1 response doesn't work - and then fix that behaviour.
> > >
> > > 2. Set the mmc->max_busy_timeout to zero for sdhci-tegra, which makes
> > > the core to always use R1B for CMD6 (and erase). This also means that
> > > when the cmd->busy_timeout becomes longer than 11s, sdhci-tegra must
> > > disable the HW busy timeout and just wait "forever".
> > >
> > > If you decide for 2, you can add the software timeout support on top,
> > > but make that can be considered as a next step of an improvement,
> > > rather than needed as fix. Note that, I believe there are some support
> > > for software timeout already in the sdhci core, maybe you need to
> > > tweak it a bit for your case, I don't know.
> > >
> > > Kind regards
> > > Uffe
> > Hi Uffe
> >
> > Will go with 2nd option and will send patches out when ready.
> Okay, good.
>
> > BTW, Tegra host also supports SDHCI_QUIRK_DATA_TIMEOUT_USES_SDCLK for
> > data timeout based on host clock when using finite mode (HW busy
> > detection based on DATA TIMEOUT count value when cmd operation timeout
> > is < 11s for tegra host).
> >
> > So, looks like we cant set host max_busy_timeout to 0 for Tegra host to
> > force R1B during SWITCH and SLEEP_AWAKE.
> >
> > So, was thinking to introduce host capability MMC_CAP2_LONG_WAIT_HW_BUSY
> > which can be used for hosts supporting long or infinite HW busy wait
> > detection and will update mmc and mmc_ops drivers to not allow convert
> > R1B to R1B for hosts with this capability during SLEEP_AWAKE and SWITCH.
> That seems reasonable, it becomes probably both easier and clearer by
> adding a new host cap.
>
> In any case, let me help out and cook a patch for this for the core
> part (I leave the sdhci change to you). It may be a bit tricky,
> especially since I have currently queued a bunch of new changes for
> v5.7, that enables more users of mmc_poll_for_busy() in the core.
> Maybe I need to temporarily drop them, so we can fix these problems
> first. I will check.
>
> Probably, I would also name the cap MMC_CAP_HW_NEED_RSP_BUSY, as that
> seems to be describing the common problem we have for sdhci
> omap/tegra.
>
> Finally, it seems like MMC_CAP_WAIT_WHILE_BUSY should be set for
> sdhci- tegra, so while at it, perhaps you can cook a patch for that as
> well.
>
> Kind regards
> Uffe

OK, I sent v1 yesterday. Please ignore them then.

Will send out patches only for HW busy wait modes program based on cmd 
timeout and WAIT_WHILE_BUSY enabled.

Thanks

Sowjanya