Re: [PATCH] mmc: sdhci-of-at91: fix card detect when using runtime PM

[Ludovic Desroches <ludovic.desroches@atmel.com>]

On Thu, Feb 11, 2016 at 04:10:54PM +0100, Ulf Hansson wrote:
> On 11 February 2016 at 14:48, Ludovic Desroches
> <ludovic.desroches@atmel.com> wrote:
> > Add quirk broken card detection to enable card detection polling. It is
> > a short term solution until reworking PM stuff.
> >
> > If the card detect signal is connected to the sdhci controller and not a
> > gpio, when runtime PM suspend happens, we have no way to wake up on a card
> > detect event since these irqs are no more enabled.
> >
> > Signed-off-by: Ludovic Desroches <ludovic.desroches@atmel.com>
> > Fixes: f5f17813ae9b ("mmc: sdhci-of-at91: add PM support")
> > ---
> >  drivers/mmc/host/sdhci-of-at91.c | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/mmc/host/sdhci-of-at91.c b/drivers/mmc/host/sdhci-of-at91.c
> > index 9cb86fb..efec736 100644
> > --- a/drivers/mmc/host/sdhci-of-at91.c
> > +++ b/drivers/mmc/host/sdhci-of-at91.c
> > @@ -45,6 +45,7 @@ static const struct sdhci_ops sdhci_at91_sama5d2_ops = {
> >
> >  static const struct sdhci_pltfm_data soc_data_sama5d2 = {
> >         .ops = &sdhci_at91_sama5d2_ops,
> > +       .quirks = SDHCI_QUIRK_BROKEN_CARD_DETECTION,
> >         .quirks2 = SDHCI_QUIRK2_NEED_DELAY_AFTER_INT_CLK_RST,
> >  };
> >
> > --
> > 2.7.0
> >
> 
> According to the below commit, SDHCI_QUIRK_BROKEN_CARD_DETECTION was
> invented because of unreliable card detection mechanism inside the
> sdhci controller.
> Therefore it required polling to be used, but also to make ->get_cd()
> to always return 1 in these cases.
> 
> Although, as I understand it that's not the case here. You can still
> rely on card detection to work, but as you don't have wakeups you
> can't fully make use of card detect, when combined with runtime PM.
> I am not sure we should add more users of
> SDHCI_QUIRK_BROKEN_CARD_DETECTION, especially since in this case it's
> not reflecting the capability of the hardware.
> 
> Can't we think of another way?

Sorry but I am not sure to understand. In the previous thread, you told
me to use MMC_CAP_NEEDS_POLL which is set if we have
SDHCI_QUIRK_BROKEN_CARD_DETECTION. I was not confortable to do this
because as you say it is not reflecting the capability of the hardware.

Do you mean that I can simply add MMC_CAP_NEEDS_POLL after sdhci_add_host()?

Regards

Ludovic

> 
> Kind regards
> Uffe
> 
> 
> commit 68d1fb7e229c6f95be4fbbe3eb46b24e41184924
> Author: Anton Vorontsov <avorontsov@ru.mvista.com>
> sdhci: Add support for card-detection polling
> 
> This patch adds SDHCI_QUIRK_BROKEN_CARD_DETECTION quirk. When specified,
> sdhci driver will set MMC_CAP_NEEDS_POLL MMC host capability, and won't
> enable card insert/remove interrupts.
> 
> This is needed for hosts with unreliable card detection, such as FSL
> eSDHC. The original eSDHC driver was tring to "debounce" card-detection
> IRQs by reading present state and disabling particular interrupts. But
> with this debouncing scheme I noticed that sometimes we miss card
> insertion/removal events.
> 
> Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
> Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>