[PATCH v4 1/4] mmc: sdhci: fix interrupt storm from card detection

[Philip Rakity]

On Jun 21, 2011, at 9:40 PM, Shawn Guo wrote:

> On Tue, Jun 21, 2011 at 09:05:25AM -0700, Philip Rakity wrote:
>> 
>> On Jun 21, 2011, at 7:41 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>
>>> Tested-by: Arnaud Patard <arnaud.patard at rtp-net.org>
>>> ---
>>> drivers/mmc/host/sdhci.c |   29 +++++++++++++++++++++++++----
>>> 1 files changed, 25 insertions(+), 4 deletions(-)
>>> 
>>> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
>>> index 91d9892..790f959 100644
>>> --- a/drivers/mmc/host/sdhci.c
>>> +++ b/drivers/mmc/host/sdhci.c
>>> @@ -127,11 +127,15 @@ 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, 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;
>>> +
>>> 	if (enable)
>>> 		sdhci_unmask_irqs(host, irqs);
>>> 	else
>>> @@ -2154,13 +2158,30 @@ static irqreturn_t sdhci_irq(int irq, void *dev_id)
>>> 		mmc_hostname(host->mmc), intmask);
>>> 
>>> 	if (intmask & (SDHCI_INT_CARD_INSERT | SDHCI_INT_CARD_REMOVE)) {
>>> +		u32 present = sdhci_readl(host, SDHCI_PRESENT_STATE) &
>>> +			      SDHCI_CARD_PRESENT;
>>> +
>>> +		/*
>>> +		 * There is a observation on i.mx esdhc.  INSERT bit will be
>>> +		 * immediately set again when it gets cleared, if a card is
>>> +		 * inserted.  We have to mask the irq to prevent interrupt
>>> +		 * storm which will freeze the system.  And the REMOVE gets
>>> +		 * the same situation.
>>> +		 *
>>> +		 * More testing are needed here to ensure it works for other
>>> +		 * platforms though.
>>> +		 */
>>> +		sdhci_mask_irqs(host, present ? SDHCI_INT_CARD_INSERT :
>>> +						SDHCI_INT_CARD_REMOVE);
>>> +		sdhci_unmask_irqs(host, present ? SDHCI_INT_CARD_REMOVE :
>>> +						  SDHCI_INT_CARD_INSERT);
>>> +
>> 
>> ====
>>> 		sdhci_writel(host, intmask & (SDHCI_INT_CARD_INSERT |
>>> -			SDHCI_INT_CARD_REMOVE), SDHCI_INT_STATUS);
>>> +			     SDHCI_INT_CARD_REMOVE), SDHCI_INT_STATUS);
>> 
>> ====
>> Please keep the old formatting since code does not change anything.  Makes it easier to find
>> the real change
>> 
> 
> I actually rewrote the body of the if-statement, and fixed one
> indentation in that specific line.

understand -- I'm happy with the results !  
Philip

> 
>>> +		intmask &= ~(SDHCI_INT_CARD_INSERT | SDHCI_INT_CARD_REMOVE);
>>> 		tasklet_schedule(&host->card_tasklet);
>>> 	}
>>> 
>>> -	intmask &= ~(SDHCI_INT_CARD_INSERT | SDHCI_INT_CARD_REMOVE);
>>> -
>>> 	if (intmask & SDHCI_INT_CMD_MASK) {
>>> 		sdhci_writel(host, intmask & SDHCI_INT_CMD_MASK,
>>> 			SDHCI_INT_STATUS);
>>> -- 
>>> 1.7.4.1
>>> 
>> 
>> 
>> Reviewed-by: Philip Rakity <prakity at marvell.com>
>> 
> 
> -- 
> Regards,
> Shawn
>