linux-kernel - Re: [RFC][PATCH 1/3] PM / sleep: Flag to speed up suspend-resume of runtime-suspended devices

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Message-ID: <1516837.oN5cf7KDad@vostro.rjw.lan>
Date:	Thu, 08 May 2014 23:42:01 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Linux PM list <linux-pm@...r.kernel.org>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Aaron Lu <aaron.lu@...el.com>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC][PATCH 1/3] PM / sleep: Flag to speed up suspend-resume of runtime-suspended devices

On Thursday, May 08, 2014 05:20:43 PM Alan Stern wrote:
> On Thu, 8 May 2014, Rafael J. Wysocki wrote:
> 
> > > > Wait a minute.  Following ->runtime_suspend(), you are going to call 
> > > > ->suspend() and then ->runtime_resume()?  That doesn't seem like what 
> > > > you really want; a ->suspend() call should always have a matching 
> > > > ->resume().
> > > 
> > > Yes, it should, but I didn't see any other way to do that.
> > 
> > Actually, that's kind of easy to resolve. :-)
> > 
> > When ->suspend() leaves power.leave_runtime_suspended set, the PM core can
> > simply skip the early/late and noirq callbacks and then call ->resume()
> > that will be responsible for using whatever is necessary to resume the
> > device.
> > 
> > And perhaps the flag should be called something different then, like
> > direct_resume (meaning go directly for ->resume() without executing
> > the intermediate callbacks)?
> 
> In light of what I wrote earlier, it should be okay for the ->prepare() 
> callback to be responsible for setting leave_runtime_suspended.  Then 
> there will be no need to call either ->suspend() or ->resume().

Hmm.  OK, let's try that.

Rafael

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