From f8c58c1136349fdfa9b605c501f2f911622d3a9a Mon Sep 17 00:00:00 2001 From: Doug Anderson Date: Tue, 2 Dec 2014 15:42:47 -0800 Subject: mmc: dw_mmc: Protect read-modify-write of INTMASK with a lock 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 Signed-off-by: Doug Anderson Reviewed-by: James Hogan Signed-off-by: Ulf Hansson --- include/linux/mmc/dw_mmc.h | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'include/linux') diff --git a/include/linux/mmc/dw_mmc.h b/include/linux/mmc/dw_mmc.h index 42b724e8d503..471fb3116dbe 100644 --- a/include/linux/mmc/dw_mmc.h +++ b/include/linux/mmc/dw_mmc.h @@ -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; -- cgit v1.2.3