linux-kernel - Re: [PATCH] DRM / radeon / PM: Do not evict VRAM during freeze phase of hibernation

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Message-Id: <201006190123.00694.rjw@sisk.pl>
Date:	Sat, 19 Jun 2010 01:23:00 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Dave Airlie <airlied@...hat.com>
Cc:	linux-kernel@...r.kernel.org,
	"dri-devel" <dri-devel@...ts.freedesktop.org>,
	linux-pm@...ts.linux-foundation.org,
	Alex Deucher <alexdeucher@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ondrej Zary <linux@...nbow-software.org>
Subject: Re: [PATCH] DRM / radeon / PM: Do not evict VRAM during freeze phase of hibernation

On Friday, June 18, 2010, Dave Airlie wrote:
> On Fri, 2010-06-18 at 22:21 +0200, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rjw@...k.pl>
> > 
> > I have recently noticed a 55 sec. delay during the "device freeze"
> > phase of hibernation on my test-bed HP nx6325.  Due to the 100%
> > reproducibility of it I was able to narrow it down to
> > radeon_suspend_kms() and then it turned out that the delay occured
> > somewhere in radeon_bo_evict_vram().  However, it doesn't seem really
> > necessary or even very useful to me to evict VRAM at this particular
> > point, because we're going to create an image and bring the device
> > back to the fully functional state in a little while.  Thus, I think
> > the VRAM evicition can be skipped for state.event == PM_EVENT_FREEZE,
> > which makes the delay go away.
> 
> I'm not 100% sure of the hibernate sequencing and its early in the
> morning, but we want to evict VRAM before image building so we can have
> the contents of VRAM in the image so we can restore them on resume. Does
> this just avoid evicting them a second time after we created the image?

No, it's the first time, before creating the image, but I didn't seen any
difference on resume with and without the patch, so I thought it was a good
idea. :-)

If you don't like it, though, I guess it will be necessary to find the root
cause of the delay.

Rafael
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