Re: sdhci-omap: additional PM issue since 5.16

[Tony Lindgren <tony@atomide.com>]

* Ulf Hansson <ulf.hansson@linaro.org> [250320 08:48]:
> On Thu, 20 Mar 2025 at 05:14, Tony Lindgren <tony@atomide.com> wrote:
> >
> > Hi,
> >
> > * Ulf Hansson <ulf.hansson@linaro.org> [250312 11:56]:
> > > On Fri, 7 Mar 2025 at 05:28, Tony Lindgren <tony@atomide.com> wrote:
> > > > Based on the symptoms, it sounds like there might be a missing flush of
> > > > a posted write in the PM runtime suspend/resume path. This could cause
> > > > something in the sequence happen in the wrong order for some of the
> > > > related surrounding resources like power, clocks or interrupts.
> > >
> > > SDIO is entirely different in this regard compared to eMMC/SD. So if
> > > there are no reports of issues I suggest we keep the SDIO part.
> >
> > Hmm just wondering if you have any guesses what causes the eMMC/SD related
> > PM to break?
> >
> > Regards,
> >
> > Tony
> 
> Well, I have recently been looking a bit closer at the runtime PM
> support of the eMMC/SD card. We seem to have some kind of related
> problems [1], but I am not really sure yet.
> 
> That said, I believe I may have found some *potential* issues and I am
> working on a few patches for it (for the mmc core), I will keep you
> and the people in $subject posted. Although, it's not quite clear to
> me, why these problems have turned up at this point and not a lot
> earlier. I have a feeling there is something that I am missing.
> 
> Also note that, if the problems are sdhci/sdhci-omap specific, it
> becomes a bit more difficult for me to help out.
> 
> Luckily, it seems like David shared a pretty simple script with us,
> which should reproduce the problem in just a few minutes. There are
> also debugfs and the runtime PM-sysfs interface one can use to play
> with the behaviour of MMC_CAP_AGGRESSIVE_PM.

OK thanks for the description. AFAIK this is issue has not been happening
with the eMMC and the old mmc-omap-hs driver. Sounds like the issue might
be also eMMC specific.

Regards,

Tony

> [1]
> https://bugzilla.kernel.org/show_bug.cgi?id=218821
> https://lore.kernel.org/all/CAPDyKFq4-fL3oHeT9phThWQJqzicKeA447WBJUbtcKPhdZ2d1A@mail.gmail.com/T/