Commit 28fd00d4 authored Dec 22, 2011 by Lin Ming Committed by Jeff Garzik Jan 08, 2012

[SCSI] runtime resume parent for child's system-resume



[Patch description from Alan Stern]

If a child device was runtime-suspended when a system suspend began,
then there will be nothing to prevent its parent from
runtime-suspending as soon as it is woken up during the system resume.
Then when the time comes to resume the child, the resume will fail
because the parent is already back at low power.

On the other hand, there are some devices which should remain at low
power across an entire suspend-resume cycle.  The details depend on the
device and the platform.

This suggests that the PM core is not the right place to solve the
problem. One possible solution is for the subsystem or device driver
to call pm_runtime_get_sync(dev->parent) at the start of the
system-resume procedure and pm_runtime_put_sync(dev->parent) at the
end.

Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

parent 17ab594f

drivers/scsi/scsi_pm.c

+10 −1

Original line number	Diff line number	Diff line
		@@ -72,8 +72,17 @@ static int scsi_bus_resume_common(struct device *dev)
		{
		int err = 0;

		if (scsi_is_sdev_device(dev))
		if (scsi_is_sdev_device(dev)) {
		/*
		* Parent device may have runtime suspended as soon as
		* it is woken up during the system resume.
		*
		* Resume it on behalf of child.
		*/
		pm_runtime_get_sync(dev->parent);
		err = scsi_dev_type_resume(dev);
		pm_runtime_put_sync(dev->parent);
		}

		if (err == 0) {
		pm_runtime_disable(dev);

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