Re: [PATCH V3 1/3] mmc: core: Add partial initialization support

[Sarthak Garg]

On 10/27/2023 3:23 PM, Ulf Hansson wrote:
> [...]
>
> > > > +{
> > > > +       int err = 0;
> > > > +       struct mmc_card *card = host->card;
> > > > +
> > > > +       mmc_set_bus_width(host, host->cached_ios.bus_width);
> > > > +       mmc_set_timing(host, host->cached_ios.timing);
> > > > +       if (host->cached_ios.enhanced_strobe) {
> > > > +               host->ios.enhanced_strobe = true;
> > > > +               if (host->ops->hs400_enhanced_strobe)
> > > > +                       host->ops->hs400_enhanced_strobe(host, &host->ios);
> > > > +       }
> > > > +       mmc_set_clock(host, host->cached_ios.clock);
> > > > +       mmc_set_bus_mode(host, host->cached_ios.bus_mode);
> > > > +
> > >
> > > Rather than re-using the above APIs and the ->set_ios() callback in
> > > the host, I believe it would be better to add a new host ops to manage
> > > all of the above at once instead. Something along the lines of the
> > > below, would then replace all of the above.
> > >
> > > host->ops->restore_ios(host, &host->cached_ios)
> > > memcpy(&host->ios, &host->cached_ios, sizeof(host->ios));
> > >
> > > Would that make sense to you too?
> >
> >
> > I didn't get this completely. Do you mean that we should implement a new
> > restore_ios callback (e.g. sdhci_restore_ios) similar to sdhci_set_ios
> > and removing all the redundant code from sdhci_set_ios which should
> > achieve the behaviour same as calling all the above mmc_set_* API's ?
>
> Correct. Would it not simply the things in the driver too?
>
> > > > +       if (!mmc_card_hs400es(card) &&
> > > > +                       (mmc_card_hs200(card) || mmc_card_hs400(card))) {
> > > > +               err = mmc_execute_tuning(card);
> > > > +               if (err) {
> > > > +                       pr_err("%s: %s: Tuning failed (%d)\n",
> > > > +                               mmc_hostname(host), __func__, err);
> > >
> > > There is already a print being done in mmc_execute_tuning() at
> > > failure. So, let's drop the above print.
> >
> > Sure will take care in V4.
> >
> > > > +                       goto out;
> > > > +               }
> > > > +       }
> > > > +
> > > > +       err = mmc_test_awake_ext_csd(host);
> > >
> > > Again, I don't get why this is needed, so let's discuss this more.
> >
> > This is just a safety check added because ext_csd has some W/E_P or
> > W/C_P registers which gets reset if any HW reset happens to the card.
> > So this will check for those cases if any other vendor is doing reset as
> > part of suspend and compare a subset of those W/E_P and W/C_P registers
> > and if they are changed then we will bail out of this partial init
> > feature and go for full initialization.
> > We are also fine with removing this function but just added for the
> > above mentioned case.
>
> In that case, I would rather remove it as I think it's superfluous.
>
> More precisely, I would expect that we fail to wake up the card with a
> CMD5 (get an error response for the CMD) if there has been a HW reset
> somewhere done before.
>
> Another reason to *not* read the ext_csd would be to further improve
> the resume time, as reading it takes time too. I would be curious to
> know how much though. :-)
>
> [...]
>
> Kind regards
> Uffe

Hi ulf,

Sorry for the delay but we are seeing some stability issues when testing 
this feature with HS400 cards which I am debugging and may take some 
time and will come back.
Note: This feature is working perfectly fine with HS400ES cards.