[RFC/PATCH] mmc: core: Signal wakeup event at card insert/removal

[Ulf Hansson <ulf.hansson@linaro.org>]

We want to give user space provision to fully consume a card
insert/remove event, when the event was caused by a wakeup irq.

By signaling the wakeup event for a time of 5 s for devices configured
as wakeup capable, we likely will be prevent a sleep long enough to let
user space consume the event.

To enable this feature, host drivers must thus configure their devices
as wakeup capable.

This is a reworked implementation of the old wakelocks for the mmc
subsystem, originally authored by Colin Cross and San Mehat for the
Android kernel. Zoran Markovic shall also be given cred for recently
re-trying to upstream this feature.

Cc: San Mehat <san@google.com>
Cc: Colin Cross <ccross@android.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Zoran Markovic <zoran.markovic@linaro.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
---

This patch has just been compile tested, since I at very moment did not
have a good board to test it on. I am working on that.

Any help in testing this patch is thus greatly appreciated. While
testing also don't forget to enable the host device as wakeup capable.
Use "device_init_wakeup" from the host probe function.

---
 drivers/mmc/core/core.c |   39 +++++++++++++++++++++++++++------------
 1 file changed, 27 insertions(+), 12 deletions(-)

diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index bf18b6b..3e8229e 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -23,6 +23,7 @@
 #include <linux/log2.h>
 #include <linux/regulator/consumer.h>
 #include <linux/pm_runtime.h>
+#include <linux/pm_wakeup.h>
 #include <linux/suspend.h>
 #include <linux/fault-inject.h>
 #include <linux/random.h>
@@ -1723,6 +1724,28 @@ void mmc_detach_bus(struct mmc_host *host)
 	mmc_bus_put(host);
 }
 
+static void _mmc_detect_change(struct mmc_host *host, unsigned long delay,
+				bool cd_irq)
+{
+#ifdef CONFIG_MMC_DEBUG
+	unsigned long flags;
+	spin_lock_irqsave(&host->lock, flags);
+	WARN_ON(host->removed);
+	spin_unlock_irqrestore(&host->lock, flags);
+#endif
+
+	/*
+	 * If the device is configured as wakeup, we prevent a new sleep for
+	 * 5 s to give provision for user space to consume the event.
+	 */
+	if (cd_irq && !(host->caps & MMC_CAP_NEEDS_POLL) &&
+		device_can_wakeup(mmc_dev(host)))
+		pm_wakeup_event(mmc_dev(host), 5000);
+
+	host->detect_change = 1;
+	mmc_schedule_delayed_work(&host->detect, delay);
+}
+
 /**
  *	mmc_detect_change - process change of state on a MMC socket
  *	@host: host which changed state.
@@ -1735,16 +1758,8 @@ void mmc_detach_bus(struct mmc_host *host)
  */
 void mmc_detect_change(struct mmc_host *host, unsigned long delay)
 {
-#ifdef CONFIG_MMC_DEBUG
-	unsigned long flags;
-	spin_lock_irqsave(&host->lock, flags);
-	WARN_ON(host->removed);
-	spin_unlock_irqrestore(&host->lock, flags);
-#endif
-	host->detect_change = 1;
-	mmc_schedule_delayed_work(&host->detect, delay);
+	_mmc_detect_change(host, delay, true);
 }
-
 EXPORT_SYMBOL(mmc_detect_change);
 
 void mmc_init_erase(struct mmc_card *card)
@@ -2423,7 +2438,7 @@ int mmc_detect_card_removed(struct mmc_host *host)
 			 * rescan handle the card removal.
 			 */
 			cancel_delayed_work(&host->detect);
-			mmc_detect_change(host, 0);
+			_mmc_detect_change(host, 0, false);
 		}
 	}
 
@@ -2505,7 +2520,7 @@ void mmc_start_host(struct mmc_host *host)
 		mmc_power_off(host);
 	else
 		mmc_power_up(host);
-	mmc_detect_change(host, 0);
+	_mmc_detect_change(host, 0, false);
 }
 
 void mmc_stop_host(struct mmc_host *host)
@@ -2724,7 +2739,7 @@ int mmc_pm_notify(struct notifier_block *notify_block,
 		spin_lock_irqsave(&host->lock, flags);
 		host->rescan_disable = 0;
 		spin_unlock_irqrestore(&host->lock, flags);
-		mmc_detect_change(host, 0);
+		_mmc_detect_change(host, 0, false);
 
 	}
 
-- 
1.7.9.5