[Intel-gfx] [PATCH 2/2] drm/i915: load a ring frequency scaling table

[Jesse Barnes]

On Mon, 27 Jun 2011 20:40:08 +0100
Chris Wilson <chris at chris-wilson.co.uk> wrote:

> On Fri, 24 Jun 2011 11:13:14 -0700, Jesse Barnes <jbarnes at virtuousgeek.org> wrote:
> > The ring frequency scaling table tells the PCU to treat certain GPU
> > frequencies as if they were a given CPU frequency for purposes of
> > scaling the ring frequency.  Normally the PCU will scale the ring
> > frequency based on the CPU P-state, but with the table present, it will
> > also take the GPU frequency into account.
> 
> So it wasn't picking up max-cpu-freq even though I have CONFIG_CPU_FREQ
> and the various ACPI and Intel cpu drivers.
> 
> Taking a hint from x86/kvm, I used tsc_khz instead of the default 3000.
> 
> nexuiz @10x7  nopatch -> 3000 -> 3300 [tsc_khz]
> uncached:     43.2       44.4    44.8
>      llc:     51.3               52.3
> 
> At max_freq=3000, a cpu busy loop was still able to nudge it up to the
> same speed as using the max_freq=3300 value.

Ok tsc_khz is a good fallback, thanks.

-- 
Jesse Barnes, Intel Open Source Technology Center