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: <Pine.LNX.4.44L0.1405081028370.1087-100000@iolanthe.rowland.org>
Date:	Thu, 8 May 2014 10:36:24 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Ulf Hansson <ulf.hansson@...aro.org>
cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	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 Thu, 8 May 2014, Ulf Hansson wrote:

> >> Should we not depend on PM_RUNTIME only? Thus we don't need the new
> >> Kconfig,
> >
> > Well, OK.  I guess we can tolerate one useless statement in rpm_resume()
> > in case CONFIG_PM_SLEEP is unset.

It isn't a big deal.  However, Ulf, you need to understand that this 
API belongs to _both_ PM_SLEEP _and_ PM_RUNTIME.  It doesn't mean 
anything unless both are present.

But as Rafael said, the extra overhead if !CONFIG_PM_SLEEP is minimal.  
(Although I would move the new flag to be next to the other bitflags, 
so that it doesn't add an entire extra word to the dev_pm_info 
structure.)

> >> and then we could rename the new APIs to pm_runtime_* instead.
> >
> > That would just make the name longer - for what value?
> 
> Only "__set_leave_runtime_suspended" will be a bit longer.
> 
> The idea I had was to clearly indicate, these functions is a part of
> PM_RUNTIME API.

Not so.  They are part of both PM_SLEEP and PM_RUNTIME, which means
they are really just part of PM.  You can tell by the fact that they 
are used in both main.c and runtime.c.

Alan Stern

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