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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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13
drivers/mmc/host/dw_mmc.c
View File

@ -759,6 +759,7 @@ disable:
static int dw_mci_submit_data_dma(struct dw_mci *host, struct mmc_data *data)
{
unsigned long irqflags;
int sg_len;
u32 temp;
@ -795,9 +796,11 @@ static int dw_mci_submit_data_dma(struct dw_mci *host, struct mmc_data *data)
mci_writel(host, CTRL, temp);
/* Disable RX/TX IRQs, let DMA handle it */
spin_lock_irqsave(&host->irq_lock, irqflags);
temp = mci_readl(host, INTMASK);
temp &= ~(SDMMC_INT_RXDR | SDMMC_INT_TXDR);
mci_writel(host, INTMASK, temp);
spin_unlock_irqrestore(&host->irq_lock, irqflags);
host->dma_ops->start(host, sg_len);
@ -806,6 +809,7 @@ static int dw_mci_submit_data_dma(struct dw_mci *host, struct mmc_data *data)
static void dw_mci_submit_data(struct dw_mci *host, struct mmc_data *data)
{
unsigned long irqflags;
u32 temp;
data->error = -EINPROGRESS;
@ -834,9 +838,12 @@ static void dw_mci_submit_data(struct dw_mci *host, struct mmc_data *data)
host->part_buf_count = 0;
mci_writel(host, RINTSTS, SDMMC_INT_TXDR | SDMMC_INT_RXDR);
spin_lock_irqsave(&host->irq_lock, irqflags);
temp = mci_readl(host, INTMASK);
temp |= SDMMC_INT_TXDR | SDMMC_INT_RXDR;
mci_writel(host, INTMASK, temp);
spin_unlock_irqrestore(&host->irq_lock, irqflags);
temp = mci_readl(host, CTRL);
temp &= ~SDMMC_CTRL_DMA_ENABLE;
@ -1284,8 +1291,11 @@ static void dw_mci_enable_sdio_irq(struct mmc_host *mmc, int enb)
{
struct dw_mci_slot *slot = mmc_priv(mmc);
struct dw_mci *host = slot->host;
unsigned long irqflags;
u32 int_mask;
spin_lock_irqsave(&host->irq_lock, irqflags);
/* Enable/disable Slot Specific SDIO interrupt */
int_mask = mci_readl(host, INTMASK);
if (enb)
@ -1293,6 +1303,8 @@ static void dw_mci_enable_sdio_irq(struct mmc_host *mmc, int enb)
else
int_mask &= ~SDMMC_INT_SDIO(slot->sdio_id);
mci_writel(host, INTMASK, int_mask);
spin_unlock_irqrestore(&host->irq_lock, irqflags);
}
static int dw_mci_execute_tuning(struct mmc_host *mmc, u32 opcode)
@ -2661,6 +2673,7 @@ int dw_mci_probe(struct dw_mci *host)
host->quirks = host->pdata->quirks;
spin_lock_init(&host->lock);
spin_lock_init(&host->irq_lock);
INIT_LIST_HEAD(&host->queue);
/*

6
include/linux/mmc/dw_mmc.h
View File

@ -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;