[PATCH v3 1/4] mmc: sdhci: fix interrupt storm from card detection

[Shawn Guo]

On Mon, Jun 20, 2011 at 08:59:38AM -0700, Philip Rakity wrote:
> 
> On Jun 20, 2011, at 3:38 AM, Shawn Guo wrote:
> 
> > The issue was initially found by Eric Benard as below.
> > 
> > http://permalink.gmane.org/gmane.linux.ports.arm.kernel/108031
> > 
> > Not sure about other SDHCI based controller, but on Freescale eSDHC,
> > the SDHCI_INT_CARD_INSERT bits will be immediately set again when it
> > gets cleared, if a card is inserted. The driver need to mask the irq
> > to prevent interrupt storm which will freeze the system.  And the
> > SDHCI_INT_CARD_REMOVE gets the same situation.
> > 
> > The patch fixes the problem based on the initial idea from
> > Eric Benard.
> > 
> > Signed-off-by: Shawn Guo <shawn.guo at linaro.org>
> > Cc: Eric Benard <eric at eukrea.com>
> > ---
> > drivers/mmc/host/sdhci.c |   27 +++++++++++++++++++++++----
> > 1 files changed, 23 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> > index 91d9892..d94e2b4 100644
> > --- a/drivers/mmc/host/sdhci.c
> > +++ b/drivers/mmc/host/sdhci.c
> > @@ -127,7 +127,9 @@ static void sdhci_mask_irqs(struct sdhci_host *host, u32 irqs)
> > 
> > static void sdhci_set_card_detection(struct sdhci_host *host, bool enable)
> > {
> > -	u32 irqs = SDHCI_INT_CARD_REMOVE | SDHCI_INT_CARD_INSERT;
> > +	u32 present = sdhci_readl(host, SDHCI_PRESENT_STATE) &
> > +		      SDHCI_CARD_PRESENT;
> > +	u32 irqs = present ? SDHCI_INT_CARD_REMOVE : SDHCI_INT_CARD_INSERT;
> > 
> > 	if (host->quirks & SDHCI_QUIRK_BROKEN_CARD_DETECTION)
> > 		return;
> 
> 
> Accessing off chip registers is slow.  It would be better to check for the quirk first
> and then read the present state register.
> 
> eg
> 	
> 	u32 present;
> 	u32 irqs;	
> 
> > 	if (host->quirks & SDHCI_QUIRK_BROKEN_CARD_DETECTION)
> > 		return;
> 
> >  	present = sdhci_readl(host, SDHCI_PRESENT_STATE) &
> > 		      SDHCI_CARD_PRESENT;
> 
> 
> > 	irqs = present ? SDHCI_INT_CARD_REMOVE : SDHCI_INT_CARD_INSERT;
> 
Makes sense.  Will do.

-- 
Regards,
Shawn