[Patch ping #3: anyone interested in making sdhci_irq a bit faster?]
Hi all,
I've discovered that the sdhci_irq() function needlessly iterates re-reading
the interrupt status and doing nothing (until it runs out of max_loops) when
it handles the "Card Interrupt" status in the interrupt status register.
The reason is that the "Card Interrupt" bit is not cleared until the
sdhci_irq() calls mmc_signal_sdio_irq(), so if Card Interrupt was asserted,
re-reading the interrupt status will find this bit set over and over, even if
no other bits are reported.
The fix: ignore Card Interrupt bits in the interrupt status if we already know
that mmc_signal_sdio_irq() is going to be called at the end of sdhci_irq().
Signed-off-by: Alexey Neyman <stilor@xxxxxxx>
commit 7f23315b344ca51ddf22a78f326f88404fa8c81d
Author: Alexey Neyman <stilor@xxxxxxx>
Date: Wed Oct 9 22:23:54 2013 -0700
Avoid a loop in sdhci.c.
diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index 7a7fb4f..a83cd1b 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -2491,6 +2491,14 @@ again:
result = IRQ_HANDLED;
intmask = sdhci_readl(host, SDHCI_INT_STATUS);
+
+ /*
+ * If we know we'll call the driver to signal SDIO IRQ, disregard
+ * further indications of Card Interrupt in the status to avoid a
+ * needless loop.
+ */
+ if (cardint)
+ intmask &= ~SDHCI_INT_CARD_INT;
if (intmask && --max_loops)
goto again;
out:
