linux-kernel - [ 08/38] PM / Driver core: leave runtime PM enabled during system shutdown

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Date:	Fri, 16 Mar 2012 16:34:55 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Alan Stern <stern@...land.harvard.edu>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Kostyantyn Shlyakhovoy <x0155534@...com>
Subject: [ 08/38] PM / Driver core: leave runtime PM enabled during system shutdown

3.0-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Alan Stern <stern@...land.harvard.edu>

commit fe6b91f47080eb17d21cbf2a39311877d57f6938 upstream.

Disabling all runtime PM during system shutdown turns out not to be a
good idea, because some devices may need to be woken up from a
low-power state at that time.

The whole point of disabling runtime PM for system shutdown was to
prevent untimely runtime-suspend method calls.  This patch (as1504)
accomplishes the same result by incrementing the usage count for each
device and waiting for ongoing runtime-PM callbacks to finish.  This
is what we already do during system suspend and hibernation, which
makes sense since the shutdown method is pretty much a legacy analog
of the pm->poweroff method.

This fixes a recent regression on some OMAP systems introduced by
commit af8db1508f2c9f3b6e633e2d2d906c6557c617f9 (PM / driver core:
disable device's runtime PM during shutdown).

Reported-and-tested-by: NeilBrown <neilb@...e.de>
Signed-off-by: Alan Stern <stern@...land.harvard.edu>
Acked-by: Greg Kroah-Hartman <gregkh@...e.de>
Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
Cc: Kostyantyn Shlyakhovoy <x0155534@...com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/base/core.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -1743,8 +1743,10 @@ void device_shutdown(void)
 		 */
 		list_del_init(&dev->kobj.entry);
 		spin_unlock(&devices_kset->list_lock);
-		/* Disable all device's runtime power management */
-		pm_runtime_disable(dev);
+
+		/* Don't allow any more runtime suspends */
+		pm_runtime_get_noresume(dev);
+		pm_runtime_barrier(dev);

 		if (dev->bus && dev->bus->shutdown) {
 			dev_dbg(dev, "shutdown\n");

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