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

[Zhenyu Wang]

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.

-- 
Open Source Technology Center, Intel ltd.

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