Re: IVB GPU turbo

[Jesse Barnes <jbarnes@virtuousgeek.org>]

On Thu, 17 May 2012 21:11:45 +0100
Joe Bloggsian <joebloggsian@gmail.com> wrote:

> Hi,
> 
> We are looking at accelerating video operations using 
> vaapi/intel-driver. When using Ivy bridge we believe that the GPU is 
> (almost always) not turboing even when 100% busy doing vaapi video 
> things (e.g. image scaling on EUs or bitstream decode). To determined 
> this we use cat /sys/kernel/debug/dri/0/i915_cur_delayinfo and GPU top 
> (todays IVB fixed vesion). We have tried a variety of IVB parts from 
> 3610QE up to 3770 - all do the same. We've mainly been using kernel 
> 3.2.0-24-generic and libdrm 2.4.32. The same machines turbo correctly 
> when doing equivent things in windows using intel media SDK.
> 
> I get the impression from mailing lists that turbo is known to have 
> driver/sw issues. Can anyone suggest if there is a later kernel/drm 
> version that might improve things? If so where do we find it? This is 
> for evaluation so we're happy to try unstable latest software.

You could try the drm-intel-next branch from Daniel's git tree at
git://people.freedesktop.org/~danvet/drm-intel.

I've definitely seen turbo kick in for gfx workloads, but parts of the
media engine use a different turbo mechanism, so if the current kernel
bits don't work, you could try this:

--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -2439,7 +2439,7 @@ void gen6_enable_rps(struct drm_i915_private *dev_priv)
        I915_WRITE(GEN6_RP_IDLE_HYSTERSIS, 10);
        I915_WRITE(GEN6_RP_CONTROL,
                   GEN6_RP_MEDIA_TURBO |
-                  GEN6_RP_MEDIA_HW_MODE |
+                  GEN6_RP_MEDIA_HW_NORMAL_MODE |
                   GEN6_RP_MEDIA_IS_GFX |
                   GEN6_RP_ENABLE |
                   GEN6_RP_UP_BUSY_AVG |

If that doesn't work, let me know and I'll see what we're missing.

Thanks,
-- 
Jesse Barnes, Intel Open Source Technology Center