[Intel-gfx] [PATCH] drm/i915: add dynamic clock frequency control

[Jesse Barnes]

On Tue, 28 Jul 2009 13:22:35 +0800
Zhenyu Wang <zhenyuw at linux.intel.com> wrote:

> On 2009.07.27 11:55:49 -0700, Jesse Barnes wrote:
> > Arg, here's one w/o the ACPI bit.
> > 
> > >From e9da891a3e8753c4ad49fad29a334499d5bb31a6 Mon Sep 17 00:00:00
> > >2001
> > From: Matthew Garrett <mjg59 at srcf.ucam.org>
> > Date: Mon, 27 Jul 2009 11:39:42 -0700
> > Subject: [PATCH] drm/i915: add dynamic clock frequency control
> > 
> > There are several sources of unnecessary power consumption on Intel
> > graphics systems. The first is the LVDS clock. TFTs don't suffer
> > from persistence issues like CRTs, and so we can reduce the LVDS
> > refresh rate when the screen is idle. It will be automatically
> > upclocked when userspace triggers graphical activity. Beyond that,
> > we can enable memory self refresh. This allows the memory to go
> > into a lower power state when the graphics are idle. Finally, we
> > can drop some clocks on the gpu itself. All of these things can be
> > reenabled between frames when GPU activity is triggered, and so
> > there should be no user visible graphical changes.
> > 
> 
> Jesse, when I was testing this on IGDNG desktop chipset, I encounter 
> freeze in idle with display's DPMS all off. With 'powersave=0' it
> didn't meet the hang. I think some of those regs this one touches
> might not be valid on it, maybe better to exclude it for now.

Oh, thanks for testing.  Should be easy enough to exclude IGDNG...

-- 
Jesse Barnes, Intel Open Source Technology Center