[PATCH 3/4] mmc: dw_mmc: absorb CMD11 timeout into the central watchdog

[Shawn Lin]

The voltage switch (CMD11) keeps its dedicated 500ms deadline, but it
is now just another arm of the central watchdog; cmd11_timer is
deleted.  The synthesized payload is identical to what the command leg
watchdog produces (cmd_status = RTO plus EVENT_CMD_COMPLETE), so the
request state machine cannot tell the difference.

Behavior notes for review:

  * The extra jiffy in the legacy '500ms + 1' arming was pure jiffies
    rollover paranoia and disappears together with the jiffies math.
  * Since patch 1 arms the regular command watch on every RESP_EXP
    command -- including voltage switches -- the subsequent arm here
    replaces it, as documented there.  For a genuinely stuck CMD11 the
    abort latency therefore becomes exactly 500ms instead of racing
    min(cto_ms, 500ms) between two timers as before; the reported
    error (-ETIMEDOUT either way) is unchanged.
  * dw_mci_cmd_interrupt() already delivers the watched events under
    irq_lock on any completion path, so the former out-of-lock
    timer_delete() next to the VOLT_SWITCH branch simply goes away.

No functional change intended.

Signed-off-by: Shawn Lin <shawn.lin@xxxxxxxxxxxxxx>
---

 drivers/mmc/host/dw_mmc.c | 30 ++++--------------------------
 drivers/mmc/host/dw_mmc.h |  3 ---
 2 files changed, 4 insertions(+), 29 deletions(-)

diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
index 31cf728..6852c05 100644
--- a/drivers/mmc/host/dw_mmc.c
+++ b/drivers/mmc/host/dw_mmc.c
@@ -1393,17 +1393,16 @@ static void dw_mci_start_request(struct dw_mci *host, struct mmc_command *cmd)
 		/*
 		 * Databook says to fail after 2ms w/ no response, but evidence
 		 * shows that sometimes the cmd11 interrupt takes over 130ms.
-		 * We'll set to 500ms, plus an extra jiffy just in case jiffies
-		 * is just about to roll over.
+		 * We'll set to 500ms.
 		 *
 		 * We do this whole thing under spinlock and only if the
 		 * command hasn't already completed (indicating the irq
 		 * already ran so we don't want the timeout).
 		 */
 		spin_lock_irqsave(&host->irq_lock, irqflags);
-		if (!test_bit(EVENT_CMD_COMPLETE, &host->pending_events))
-			mod_timer(&host->cmd11_timer,
-				jiffies + msecs_to_jiffies(500) + 1);
+		dw_mci_wd_arm(host, 500, DW_MCI_WD_CMD_EVENTS,
+			      DW_MCI_WD_CMD_EVENTS,
+			      BIT(STATE_SENDING_CMD11));
 		spin_unlock_irqrestore(&host->irq_lock, irqflags);
 	}
 
@@ -2784,15 +2783,9 @@ static irqreturn_t dw_mci_interrupt(int irq, void *dev_id)
 			mci_writel(host, RINTSTS, SDMMC_INT_VOLT_SWITCH);
 			pending &= ~SDMMC_INT_VOLT_SWITCH;
 
-			/*
-			 * Hold the lock; we know cmd11_timer can't be kicked
-			 * off after the lock is released, so safe to delete.
-			 */
 			spin_lock(&host->irq_lock);
 			dw_mci_cmd_interrupt(host, pending);
 			spin_unlock(&host->irq_lock);
-
-			timer_delete(&host->cmd11_timer);
 		}
 
 		if (pending & DW_MCI_CMD_ERROR_FLAGS) {
@@ -3112,20 +3105,6 @@ static void dw_mci_init_dma(struct dw_mci *host)
 	host->use_dma = TRANS_MODE_PIO;
 }
 
-static void dw_mci_cmd11_timer(struct timer_list *t)
-{
-	struct dw_mci *host = timer_container_of(host, t, cmd11_timer);
-
-	if (host->state != STATE_SENDING_CMD11) {
-		dev_warn(host->dev, "Unexpected CMD11 timeout\n");
-		return;
-	}
-
-	host->cmd_status = SDMMC_INT_RTO;
-	set_bit(EVENT_CMD_COMPLETE, &host->pending_events);
-	queue_work(system_bh_wq, &host->bh_work);
-}
-
 static int dw_mci_parse_dt(struct dw_mci *host)
 {
 	struct device *dev = host->dev;
@@ -3275,7 +3254,6 @@ int dw_mci_probe(struct dw_mci *host)
 
 	hrtimer_setup(&host->wd_timer, dw_mci_watchdog_fn, CLOCK_MONOTONIC,
 		      HRTIMER_MODE_REL);
-	timer_setup(&host->cmd11_timer, dw_mci_cmd11_timer, 0);
 
 	spin_lock_init(&host->lock);
 	spin_lock_init(&host->irq_lock);
diff --git a/drivers/mmc/host/dw_mmc.h b/drivers/mmc/host/dw_mmc.h
index 7af2b45..7b70392 100644
--- a/drivers/mmc/host/dw_mmc.h
+++ b/drivers/mmc/host/dw_mmc.h
@@ -127,7 +127,6 @@ struct dw_mci_dma_slave {
  *	time so that the state machine can synthesize an error.
  * @wd_events: pending_events bits still awaited by the armed watch.
  * @wd_states: host->state values for which the armed watch is valid.
- * @cmd11_timer: Timer for SD3.0 voltage switch over scheme.
  * @mmc: The mmc_host representing this dw_mci.
  * @flags: Random state bits associated with the host.
  * @ctype: Card type for this host.
@@ -242,8 +241,6 @@ struct dw_mci {
 	unsigned long		wd_events;
 	unsigned long		wd_states;
 
-	struct timer_list       cmd11_timer;
-
 #ifdef CONFIG_FAULT_INJECTION
 	struct fault_attr	fail_data_crc;
 	struct hrtimer		fault_timer;
-- 
2.7.4