linux-kernel - [PATCH] Driver core: leave runtime PM enabled during system shutdown

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Date:	Tue, 6 Dec 2011 10:26:14 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
cc:	NeilBrown <neilb@...e.de>, Ming Lei <tom.leiming@...il.com>,
	Chen Peter-B29397 <B29397@...escale.com>,
	Greg KH <greg@...ah.com>,
	Kernel development list <linux-kernel@...r.kernel.org>,
	Linux-pm mailing list <linux-pm@...r.kernel.org>,
	"hzpeterchen@...il.com" <hzpeterchen@...il.com>,
	Igor Grinberg <grinberg@...pulab.co.il>
Subject: [PATCH] Driver core: leave runtime PM enabled during system shutdown

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 regression on some OMAP systems.

Signed-off-by: Alan Stern <stern@...land.harvard.edu>
Reported-by: NeilBrown <neilb@...e.de>
CC: Chen Peter-B29397 <B29397@...escale.com>

---

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

Index: usb-3.2/drivers/base/core.c
===================================================================
--- usb-3.2.orig/drivers/base/core.c
+++ usb-3.2/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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