[PATCH 10/23] mmc: core: disable auto retune during card detection process

[Dong Aisheng]

On Thu, Apr 28, 2016 at 10:04:34AM +0300, Adrian Hunter wrote:
> On 24/04/16 13:47, Dong Aisheng wrote:
> > On Fri, Apr 22, 2016 at 8:48 PM, Adrian Hunter <adrian.hunter at intel.com> wrote:
> >> On 15/04/16 20:29, Dong Aisheng wrote:
> >>> During card detection process, mmc core may sends commands
> >>> to detect if card is still exist in mmc_rescan for removable
> >>> card which may trigger mmc retuning process after a bit time
> >>> of runtime pm suspend.
> >>> Obviously this retuning process is meaningless for card remove
> >>> case, so we disable mmc_retune in mmc_detect_change() for it.
> >>> For card insert case, the mmc_retune will be enabled normally
> >>> in its card initialization process later in mmc_execute_tuning().
> >>> So disable it at first has no side effection.
> >>
> >> We don't assume that the card has been removed, which is why we send
> >> commands to find out if it is still there.  If it is still there, this
> >> change will have incorrectly disabled re-tuning.
> >>
> > 
> > Do you mean the 'fake' card remove interrupt like caused by glitch?
> 
> Sure
> 
> > Yes, if that the card is still exist and re-tuning is wrongly disabled.
> > 
> > So we could re-enable re-tuning for this special case?
> > Something like:
> > diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> > index 41b1e76..e1990a8 100644
> > --- a/drivers/mmc/core/core.c
> > +++ b/drivers/mmc/core/core.c
> > @@ -2607,6 +2607,8 @@ void mmc_rescan(struct work_struct *work)
> > 
> >         /* if there still is a card present, stop here */
> >         if (host->bus_ops != NULL) {
> > +               if (tuning_is_enabled_before())
> > +                       mmc_retune_enable(host);
> >                 mmc_bus_put(host);
> >                 goto out;
> >         }
> > 
> > 
> >> Do you have an actual problem with the way it works now?
> >>
> > 
> > No actual problems now.
> 
> So let's not spend time on it.
> 
> > I just observe a lot tuning commands keep sending although the card is already
> > removed which seems a bit meaningless.
> > And most tuning execution process is executed with sin_lock_irqsave, i'm not
> > sure if the mass tuning commands may affect the system when CPU is busy.
> > What do you think?
> 
> sdhci spin lock is unlocked while waiting for tuning commands.
> 

It's 40 commands continuously and only cmd transfer time is unlocked.

Hmm.. I can't sure it's no affection.
e.g we did have customers reporting cd plug in/out causing jitters
when system is busy playing audio or video.
Maybe we need to do those tests.

Anyway, what's your point to keep sending tuning commands after card
is already removed?

Regards
Dong Aisheng

> > 
> > Regards
> > Dong Aisheng
> > 
> >>>
> >>> CC: stable <stable at vger.kernel.org>
> >>> Signed-off-by: Dong Aisheng <aisheng.dong at nxp.com>
> >>> ---
> >>>  drivers/mmc/core/core.c | 1 +
> >>>  1 file changed, 1 insertion(+)
> >>>
> >>> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> >>> index 52bfaf0..76d0802 100644
> >>> --- a/drivers/mmc/core/core.c
> >>> +++ b/drivers/mmc/core/core.c
> >>> @@ -1888,6 +1888,7 @@ static void _mmc_detect_change(struct mmc_host *host, unsigned long delay,
> >>>               pm_wakeup_event(mmc_dev(host), 5000);
> >>>
> >>>       host->detect_change = 1;
> >>> +     mmc_retune_disable(host);
> >>>       mmc_schedule_delayed_work(&host->detect, delay);
> >>>  }
> >>>
> >>>
> >>
> > 
> 
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