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Date: Tue, 15 Oct 2013 15:39:22 -0700
From: Doug Anderson <dianders@...omium.org>
To: Chris Ball <cjb@...top.org>
Cc: Jaehoon Chung <jh80.chung@...sung.com>,
Seungwon Jeon <tgih.jun@...sung.com>,
James Hogan <james.hogan@...tec.com>,
Grant Grundler <grundler@...omium.org>,
Alim Akhtar <alim.akhtar@...sung.com>,
Abhilash Kesavan <a.kesavan@...sung.com>,
Tomasz Figa <tomasz.figa@...il.com>,
Olof Johansson <olof@...om.net>,
Sonny Rao <sonnyrao@...omium.org>,
Bing Zhao <bzhao@...vell.com>,
Doug Anderson <dianders@...omium.org>,
linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] 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 <bzhao@...vell.com>
Signed-off-by: Doug Anderson <dianders@...omium.org>
---
drivers/mmc/host/dw_mmc.c | 13 +++++++++++++
include/linux/mmc/dw_mmc.h | 6 ++++++
2 files changed, 19 insertions(+)
diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
index 1b75816..b810654 100644
--- a/drivers/mmc/host/dw_mmc.c
+++ b/drivers/mmc/host/dw_mmc.c
@@ -657,6 +657,7 @@ disable:
static int dw_mci_submit_data_dma(struct dw_mci *host, struct mmc_data *data)
{
+ unsigned long irqflags;
int sg_len;
u32 temp;
@@ -693,9 +694,11 @@ 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->intmask_lock, irqflags);
temp = mci_readl(host, INTMASK);
temp &= ~(SDMMC_INT_RXDR | SDMMC_INT_TXDR);
mci_writel(host, INTMASK, temp);
+ spin_unlock_irqrestore(&host->intmask_lock, irqflags);
host->dma_ops->start(host, sg_len);
@@ -704,6 +707,7 @@ 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;
@@ -732,9 +736,12 @@ 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->intmask_lock, irqflags);
temp = mci_readl(host, INTMASK);
temp |= SDMMC_INT_TXDR | SDMMC_INT_RXDR;
mci_writel(host, INTMASK, temp);
+ spin_unlock_irqrestore(&host->intmask_lock, irqflags);
temp = mci_readl(host, CTRL);
temp &= ~SDMMC_CTRL_DMA_ENABLE;
@@ -1089,8 +1096,11 @@ 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->intmask_lock, irqflags);
+
/* Enable/disable Slot Specific SDIO interrupt */
int_mask = mci_readl(host, INTMASK);
if (enb)
@@ -1098,6 +1108,8 @@ static void dw_mci_enable_sdio_irq(struct mmc_host *mmc, int enb)
else
int_mask &= ~SDMMC_INT_SDIO(slot->id);
mci_writel(host, INTMASK, int_mask);
+
+ spin_unlock_irqrestore(&host->intmask_lock, irqflags);
}
static int dw_mci_execute_tuning(struct mmc_host *mmc, u32 opcode)
@@ -2500,6 +2512,7 @@ int dw_mci_probe(struct dw_mci *host)
host->quirks = host->pdata->quirks;
spin_lock_init(&host->lock);
+ spin_lock_init(&host->intmask_lock);
INIT_LIST_HEAD(&host->queue);
/*
diff --git a/include/linux/mmc/dw_mmc.h b/include/linux/mmc/dw_mmc.h
index 6ce7d2c..002ab56 100644
--- a/include/linux/mmc/dw_mmc.h
+++ b/include/linux/mmc/dw_mmc.h
@@ -102,6 +102,11 @@ struct mmc_data;
* @cur_slot, @mrq and @state. These must always be updated
* at the same time while holding @lock.
*
+ * @intmask_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.
@@ -121,6 +126,7 @@ struct mmc_data;
*/
struct dw_mci {
spinlock_t lock;
+ spinlock_t intmask_lock;
void __iomem *regs;
struct scatterlist *sg;
--
1.8.4
--
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