mmc: tmio_mmc_core: don’t claim spurious interrupts [Linux 5.0]

mmc: tmio_mmc_core: don’t claim spurious interrupts [Linux 5.0]

This Linux kernel change "mmc: tmio_mmc_core: don’t claim spurious interrupts" is included in the Linux 5.0 release. This change is authored by Sergei Shtylyov <sergei.shtylyov [at] cogentembedded.com> on Mon Feb 18 20:45:40 2019 +0300. The commit for this change in Linux stable tree is 5c27ff5 (patch).

mmc: tmio_mmc_core: don't claim spurious interrupts

I have encountered an interrupt storm during the eMMC chip probing (and
the chip finally didn't get detected).  It turned out that U-Boot left
the DMAC interrupts enabled while the Linux driver  didn't use those.
The SDHI driver's interrupt handler somehow assumes that, even if an
SDIO interrupt didn't happen, it should return IRQ_HANDLED.  I think
that if none of the enabled interrupts happened and got handled, we
should return IRQ_NONE -- that way the kernel IRQ code recoginizes
a spurious interrupt and masks it off pretty quickly...

Fixes: 7729c7a232a9 ("mmc: tmio: Provide separate interrupt handlers")
Signed-off-by: Sergei Shtylyov <[email protected]>
Reviewed-by: Wolfram Sang <[email protected]>
Tested-by: Wolfram Sang <[email protected]>
Reviewed-by: Simon Horman <[email protected]>
Cc: [email protected]
Signed-off-by: Ulf Hansson <[email protected]>

There are 11 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 drivers/mmc/host/tmio_mmc_core.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/mmc/host/tmio_mmc_core.c b/drivers/mmc/host/tmio_mmc_core.c
index 085a0fa..41d7972 100644
--- a/drivers/mmc/host/tmio_mmc_core.c
+++ b/drivers/mmc/host/tmio_mmc_core.c
@@ -629,7 +629,7 @@ static bool __tmio_mmc_sdcard_irq(struct tmio_mmc_host *host, int ireg,
    return false;
 }

-static void __tmio_mmc_sdio_irq(struct tmio_mmc_host *host)
+static bool __tmio_mmc_sdio_irq(struct tmio_mmc_host *host)
 {
    struct mmc_host *mmc = host->mmc;
    struct tmio_mmc_data *pdata = host->pdata;
@@ -637,7 +637,7 @@ static void __tmio_mmc_sdio_irq(struct tmio_mmc_host *host)
    unsigned int sdio_status;

    if (!(pdata->flags & TMIO_MMC_SDIO_IRQ))
-       return;
+       return false;

    status = sd_ctrl_read16(host, CTL_SDIO_STATUS);
    ireg = status & TMIO_SDIO_MASK_ALL & ~host->sdio_irq_mask;
@@ -650,6 +650,8 @@ static void __tmio_mmc_sdio_irq(struct tmio_mmc_host *host)

    if (mmc->caps & MMC_CAP_SDIO_IRQ && ireg & TMIO_SDIO_STAT_IOIRQ)
        mmc_signal_sdio_irq(mmc);
+
+   return ireg;
 }

 irqreturn_t tmio_mmc_irq(int irq, void *devid)
@@ -668,9 +670,10 @@ irqreturn_t tmio_mmc_irq(int irq, void *devid)
    if (__tmio_mmc_sdcard_irq(host, ireg, status))
        return IRQ_HANDLED;

-   __tmio_mmc_sdio_irq(host);
+   if (__tmio_mmc_sdio_irq(host))
+       return IRQ_HANDLED;

-   return IRQ_HANDLED;
+   return IRQ_NONE;
 }
 EXPORT_SYMBOL_GPL(tmio_mmc_irq);

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