linux-kernel - Re: [GIT PULL] PM updates for 2.6.33

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Message-ID: <20091207061548.GB21451@core.coreip.homeip.net>
Date:	Sun, 6 Dec 2009 22:15:49 -0800
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Arjan van de Ven <arjan@...radead.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	LKML <linux-kernel@...r.kernel.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	pm list <linux-pm@...ts.linux-foundation.org>,
	Alan Stern <stern@...land.harvard.edu>
Subject: Re: [GIT PULL] PM updates for 2.6.33

On Sun, Dec 06, 2009 at 09:31:12PM -0800, Arjan van de Ven wrote:
> On Sun, 6 Dec 2009 18:27:07 -0800
> Dmitry Torokhov <dmitry.torokhov@...il.com> wrote:
> 
> > On Sun, Dec 06, 2009 at 05:18:56PM -0800, Arjan van de Ven wrote:
> > > On Sun, 6 Dec 2009 14:54:48 -0800
> > > Dmitry Torokhov <dmitry.torokhov@...il.com> wrote:
> > > 
> > > > Yes, that's your PS/2 mouse (rather touchpad) and the delay comes
> > > > from device reset (needed by some keyboard controllers - I
> > > > remember HP -or it and keyboard will be dead at resume).
> > > > 
> > > 
> > > btw could we do this reset in an async function call (as long as we
> > > wait for it to complete before we pull the plug finally) ?
> > 
> > It has to complete before we start shutting down i8042, so there are
> > dependencies involved...
> 
> async function calls have 2 methods for synchronization:
> 
> * inside an async function, you can wait for all "earlier" async
>   functions to complete  (async_synchronize_cookie)
> * outside an async function, you can wait for all scheduled async
>   functions to complete (async_synchronize_full)
> 
> so there's two options to use the async code to cut down this time:
> 
> 1) Make both the mouse, keyboard AND the i8042 suspend functions async,
>    and in the i8042 function the code first synchronizes on all previous
>    async work
> 2) only make the mouse and keyboard suspend async, and just wait for all
>    async work in i8042 suspend
> 
> I strongly prefer number 1, in terms of getting the best suspend speed.
> It means that all other suspend code can run in parallel to the whole
> serio/i8042 suspend.
> Option two is simpler, but the delay is in the normal, synchronous path,
> so other suspend code will not run in parallel.
> 
> The good news is that neither is hard for someone familiar with the
> code...
> 

And the bad thing is that violates multiple layers in the kernel.  Atkbd
driver does not have to be using i8042; neither does psmouse. Althtough
they do in 99% of the cases there are other controllers providing the
i8042-style ports. Just grep for SERIO_8042 in drivers/input/serio.

I do not want to hard-code the i8042-psmouse-atkbd dependency.

-- 
Dmitry
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