mmc: sdhci: fix interrupt storm from card detection

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@linaro.org>
Cc: Eric Benard <eric@eukrea.com>
Tested-by: Arnaud Patard <arnaud.patard@rtp-net.org>
Signed-off-by: Chris Ball <cjb@laptop.org>

1 files changed, 25 insertions, 4 deletions

diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index 58d5436ff64..aa25eae6540 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);
+                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);