Re: [PATCH] allow 945 to control self refresh automatically

From: Jesse Barnes <jbarnes@virtuousgeek.org>
To: Chris Wilson <chris@chris-wilson.co.uk>
Cc: intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH] allow 945 to control self refresh automatically
Date: Mon, 3 Jan 2011 11:41:02 -0800	[thread overview]
Message-ID: <20110103114102.6f16a70b@jbarnes-desktop> (raw)
In-Reply-To: <849307$b0cd6l@azsmga001.ch.intel.com>

On Mon, 03 Jan 2011 19:33:05 +0000
Chris Wilson <chris@chris-wilson.co.uk> wrote:

> On Mon,  3 Jan 2011 13:28:56 -0500, Alexander Lam <lambchop468@gmail.com> wrote:
> > I changed 945's self refresh to work without the need for the driver to
> > enable/disable self refresh manually based on the idle state of the gpu.
> > This is much better than enabling/disabling self refresh for various
> > reasons, including staying in a lower power state for more time and
> > avoiding the need for cpu cycles.
> > 
> > Something must have been fixed in the driver between the initial
> > implementation of 945 self refresh and now.
> > (maybe 944001201ca0196bcdb088129e5866a9f379d08c: drm/i915: enable low
> > power render writes on GEN3 hardware?)
> 
> Considering that there is no rationale in the git history as why it was
> done manually, maybe you could explain the reason why it could not have
> been automatically before? Was it simply causing hangs? Do you have any
> measurements that show power/performance impacts of the switch?

Yes, it would hang before, but only on some platforms.  It's likely
related to the low power render writes issue...

-- 
Jesse Barnes, Intel Open Source Technology Center