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From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
To: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Alan Stern <stern@rowland.harvard.edu>,
        Linux PM list <linux-pm@vger.kernel.org>,
        ACPI Devel Maling List <linux-acpi@vger.kernel.org>,
        Aaron Lu <aaron.lu@intel.com>,
        Mika Westerberg <mika.westerberg@linux.intel.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Kevin Hilman <khilman@linaro.org>
Subject: Re: [RFC][PATCH 2/3] PM / sleep: Mechanism to avoid resuming runtime-suspended devices unnecessarily
Date: Thu, 15 May 2014 14:55:49 +0200
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On Thursday, May 15, 2014 02:06:59 PM Ulf Hansson wrote:
> > Do we want to allow ->prepare() to return > 0 if the device isn't
> > runtime suspended?  If we do then non-suspended devices may be a common
> > case.  We should then avoid the extra overhead of disable + enable.
> > So I would write:
> >
> >         if (dev->power.direct_complete) {
> >                 if (pm_runtime_status_suspended(dev)) {
> >                         pm_runtime_disable(dev);
> >                         if (dev->power.disable_depth == 1
> >                             && pm_runtime_status_suspended(dev))
> >                                 goto Complete;
> >                         pm_runtime_enable(dev);
> >                 }
> >                 dev->power.direct_complete = false;
> >         }
> >
> 
> I am wondering whether the above pm_runtime_disable|enable actually
> belongs better in driver/subsystem in favour of the PM core?

No, it doesn't.

> Doesn't the driver/subsystem anyway needs to be on top of what goes
> on? Typically, while runtime PM has been disabled, that might affect
> it's wakeup handling? Or this case are already handled due to other
> circumstances?

Yes, that's the case.

Thanks!

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.