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mmc: dw_mmc: Protect read-modify-write of INTMASK with a lock

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We're running into cases where our enabling of the SDIO interrupt in
dw_mmc doesn't actually take effect.  Specifically, adding patch like
this:

 +++ b/drivers/mmc/host/dw_mmc.c
 @@ -1076,6 +1076,9 @@ static void dw_mci_enable_sdio_irq(struct mmc_host *mmc, int enb)

      mci_writel(host, INTMASK,
           (int_mask | SDMMC_INT_SDIO(slot->id)));
 +    int_mask = mci_readl(host, INTMASK);
 +    if (!(int_mask & SDMMC_INT_SDIO(slot->id)))
 +      dev_err(&mmc->class_dev, "failed to enable sdio irq\n");
    } else {

...actually triggers the error message.  That's because the
dw_mci_enable_sdio_irq() unsafely does a read-modify-write of the
INTMASK register.

We can't just use the standard host->lock since that lock is not irq
safe and mmc_signal_sdio_irq() (called from interrupt context) calls
dw_mci_enable_sdio_irq().  Add a new irq-safe lock to protect INTMASK.

An alternate solution to this is to punt mmc_signal_sdio_irq() to the
tasklet and then protect INTMASK modifications by the standard host
lock.  This seemed like a bit more of a high-latency change.

Reported-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: Doug Anderson <dianders@chromium.org>
Reviewed-by: James Hogan <james.hogan@imgtec.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
This commit is contained in:
Doug Anderson
2014-12-02 15:42:47 -08:00
committed by Ulf Hansson
parent b24c8b2601
commit f8c58c1136
2 changed files with 19 additions and 0 deletions
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6
include/linux/mmc/dw_mmc.h
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@@ -106,6 +106,11 @@ struct mmc_data;
* @cur_slot, @mrq and @state. These must always be updated
* at the same time while holding @lock.
*
* @irq_lock is an irq-safe spinlock protecting the INTMASK register
* to allow the interrupt handler to modify it directly. Held for only long
* enough to read-modify-write INTMASK and no other locks are grabbed when
* holding this one.
*
* The @mrq field of struct dw_mci_slot is also protected by @lock,
* and must always be written at the same time as the slot is added to
* @queue.
@@ -125,6 +130,7 @@ struct mmc_data;
*/
struct dw_mci {
spinlock_t lock;
spinlock_t irq_lock;
void __iomem *regs;
struct scatterlist *sg;