1 files changed, 81 insertions, 10 deletions

diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
index 16516c528a88..50148991f30e 100644
--- a/drivers/mmc/host/dw_mmc.c
+++ b/drivers/mmc/host/dw_mmc.c
@@ -403,6 +403,7 @@ static inline void dw_mci_set_cto(struct dw_mci *host)
 	unsigned int cto_clks;
 	unsigned int cto_div;
 	unsigned int cto_ms;
+	unsigned long irqflags;
 
 	cto_clks = mci_readl(host, TMOUT) & 0xff;
 	cto_div = (mci_readl(host, CLKDIV) & 0xff) * 2;
@@ -413,8 +414,24 @@ static inline void dw_mci_set_cto(struct dw_mci *host)
 	/* add a bit spare time */
 	cto_ms += 10;
 
-	mod_timer(&host->cto_timer,
-		  jiffies + msecs_to_jiffies(cto_ms) + 1);
+	/*
+	 * The durations we're working with are fairly short so we have to be
+	 * extra careful about synchronization here.  Specifically in hardware a
+	 * command timeout is _at most_ 5.1 ms, so that means we expect an
+	 * interrupt (either command done or timeout) to come rather quickly
+	 * after the mci_writel.  ...but just in case we have a long interrupt
+	 * latency let's add a bit of paranoia.
+	 *
+	 * In general we'll assume that at least an interrupt will be asserted
+	 * in hardware by the time the cto_timer runs.  ...and if it hasn't
+	 * been asserted in hardware by that time then we'll assume it'll never
+	 * come.
+	 */
+	spin_lock_irqsave(&host->irq_lock, irqflags);
+	if (!test_bit(EVENT_CMD_COMPLETE, &host->pending_events))
+		mod_timer(&host->cto_timer,
+			jiffies + msecs_to_jiffies(cto_ms) + 1);
+	spin_unlock_irqrestore(&host->irq_lock, irqflags);
 }
 
 static void dw_mci_start_command(struct dw_mci *host,
@@ -429,11 +446,11 @@ static void dw_mci_start_command(struct dw_mci *host,
 	wmb(); /* drain writebuffer */
 	dw_mci_wait_while_busy(host, cmd_flags);
 
+	mci_writel(host, CMD, cmd_flags | SDMMC_CMD_START);
+
 	/* response expected command only */
 	if (cmd_flags & SDMMC_CMD_RESP_EXP)
 		dw_mci_set_cto(host);
-
-	mci_writel(host, CMD, cmd_flags | SDMMC_CMD_START);
 }
 
 static inline void send_stop_abort(struct dw_mci *host, struct mmc_data *data)
@@ -1930,6 +1947,24 @@ static void dw_mci_set_drto(struct dw_mci *host)
 	mod_timer(&host->dto_timer, jiffies + msecs_to_jiffies(drto_ms));
 }
 
+static bool dw_mci_clear_pending_cmd_complete(struct dw_mci *host)
+{
+	if (!test_bit(EVENT_CMD_COMPLETE, &host->pending_events))
+		return false;
+
+	/*
+	 * Really be certain that the timer has stopped.  This is a bit of
+	 * paranoia and could only really happen if we had really bad
+	 * interrupt latency and the interrupt routine and timeout were
+	 * running concurrently so that the del_timer() in the interrupt
+	 * handler couldn't run.
+	 */
+	WARN_ON(del_timer_sync(&host->cto_timer));
+	clear_bit(EVENT_CMD_COMPLETE, &host->pending_events);
+
+	return true;
+}
+
 static void dw_mci_tasklet_func(unsigned long priv)
 {
 	struct dw_mci *host = (struct dw_mci *)priv;
@@ -1956,8 +1991,7 @@ static void dw_mci_tasklet_func(unsigned long priv)
 
 		case STATE_SENDING_CMD11:
 		case STATE_SENDING_CMD:
-			if (!test_and_clear_bit(EVENT_CMD_COMPLETE,
-						&host->pending_events))
+			if (!dw_mci_clear_pending_cmd_complete(host))
 				break;
 
 			cmd = host->cmd;
@@ -2126,8 +2160,7 @@ static void dw_mci_tasklet_func(unsigned long priv)
 			/* fall through */
 
 		case STATE_SENDING_STOP:
-			if (!test_and_clear_bit(EVENT_CMD_COMPLETE,
-						&host->pending_events))
+			if (!dw_mci_clear_pending_cmd_complete(host))
 				break;
 
 			/* CMD error in data command */
@@ -2600,6 +2633,7 @@ static irqreturn_t dw_mci_interrupt(int irq, void *dev_id)
 	struct dw_mci *host = dev_id;
 	u32 pending;
 	struct dw_mci_slot *slot = host->slot;
+	unsigned long irqflags;
 
 	pending = mci_readl(host, MINTSTS); /* read-only mask reg */
 
@@ -2607,8 +2641,6 @@ static irqreturn_t dw_mci_interrupt(int irq, void *dev_id)
 		/* Check volt switch first, since it can look like an error */
 		if ((host->state == STATE_SENDING_CMD11) &&
 		    (pending & SDMMC_INT_VOLT_SWITCH)) {
-			unsigned long irqflags;
-
 			mci_writel(host, RINTSTS, SDMMC_INT_VOLT_SWITCH);
 			pending &= ~SDMMC_INT_VOLT_SWITCH;
 
@@ -2624,11 +2656,15 @@ static irqreturn_t dw_mci_interrupt(int irq, void *dev_id)
 		}
 
 		if (pending & DW_MCI_CMD_ERROR_FLAGS) {
+			spin_lock_irqsave(&host->irq_lock, irqflags);
+
 			del_timer(&host->cto_timer);
 			mci_writel(host, RINTSTS, DW_MCI_CMD_ERROR_FLAGS);
 			host->cmd_status = pending;
 			smp_wmb(); /* drain writebuffer */
 			set_bit(EVENT_CMD_COMPLETE, &host->pending_events);
+
+			spin_unlock_irqrestore(&host->irq_lock, irqflags);
 		}
 
 		if (pending & DW_MCI_DATA_ERROR_FLAGS) {
@@ -2668,8 +2704,12 @@ static irqreturn_t dw_mci_interrupt(int irq, void *dev_id)
 		}
 
 		if (pending & SDMMC_INT_CMD_DONE) {
+			spin_lock_irqsave(&host->irq_lock, irqflags);
+
 			mci_writel(host, RINTSTS, SDMMC_INT_CMD_DONE);
 			dw_mci_cmd_interrupt(host, pending);
+
+			spin_unlock_irqrestore(&host->irq_lock, irqflags);
 		}
 
 		if (pending & SDMMC_INT_CD) {
@@ -2943,7 +2983,35 @@ static void dw_mci_cmd11_timer(unsigned long arg)
 static void dw_mci_cto_timer(unsigned long arg)
 {
 	struct dw_mci *host = (struct dw_mci *)arg;
+	unsigned long irqflags;
+	u32 pending;
+
+	spin_lock_irqsave(&host->irq_lock, irqflags);
 
+	/*
+	 * If somehow we have very bad interrupt latency it's remotely possible
+	 * that the timer could fire while the interrupt is still pending or
+	 * while the interrupt is midway through running.  Let's be paranoid
+	 * and detect those two cases.  Note that this is paranoia is somewhat
+	 * justified because in this function we don't actually cancel the
+	 * pending command in the controller--we just assume it will never come.
+	 */
+	pending = mci_readl(host, MINTSTS); /* read-only mask reg */
+	if (pending & (DW_MCI_CMD_ERROR_FLAGS | SDMMC_INT_CMD_DONE)) {
+		/* The interrupt should fire; no need to act but we can warn */
+		dev_warn(host->dev, "Unexpected interrupt latency\n");
+		goto exit;
+	}
+	if (test_bit(EVENT_CMD_COMPLETE, &host->pending_events)) {
+		/* Presumably interrupt handler couldn't delete the timer */
+		dev_warn(host->dev, "CTO timeout when already completed\n");
+		goto exit;
+	}
+
+	/*
+	 * Continued paranoia to make sure we're in the state we expect.
+	 * This paranoia isn't really justified but it seems good to be safe.
+	 */
 	switch (host->state) {
 	case STATE_SENDING_CMD11:
 	case STATE_SENDING_CMD:
@@ -2962,6 +3030,9 @@ static void dw_mci_cto_timer(unsigned long arg)
 			 host->state);
 		break;
 	}
+
+exit:
+	spin_unlock_irqrestore(&host->irq_lock, irqflags);
 }
 
 static void dw_mci_dto_timer(unsigned long arg)