linux-kernel - Re: [PATCH 2/3] [SCSI]: runtime resume parent for child's system-resume

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Date:	Thu, 15 Dec 2011 02:31:52 +0800
From:	Lin Ming <ming.m.lin@...el.com>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Jeff Garzik <jgarzik@...ox.com>,
	James Bottomley <JBottomley@...allels.com>,
	Tejun Heo <tj@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-ide@...r.kernel.org" <linux-ide@...r.kernel.org>,
	"linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>
Subject: Re: [PATCH 2/3] [SCSI]: runtime resume parent for child's
 system-resume

On Thu, 2011-12-15 at 00:51 +0800, Alan Stern wrote:
> On Wed, 14 Dec 2011, Lin Ming wrote:
> 
> > On Wed, Dec 14, 2011 at 11:18 AM, Lin Ming <ming.m.lin@...el.com> wrote:
> > > [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.
> > >
> > > Signed-off-by: Lin Ming <ming.m.lin@...el.com>
> > 
> > Hi Alan,
> > 
> > May I add your SOB?
> 
> You can add: Acked-by: Alan Stern <stern@...land.harvard.edu>
> 
> Did you test this?  Does it do what you want?

Yes, I have tested this and it fixes the problem.

Thanks.

> 
> Alan Stern
> 


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