Re: [PATCH 3/5] drm/i915/chv: Set min freq to efficient frequency on chv

Deepak S
2015-03-11T13:56:50Z

On Thursday 26 February 2015 09:42 PM, Chris Wilson wrote:
> On Thu, Feb 26, 2015 at 08:46:56PM +0530, deepak.s@linux.intel.com wrote:
>> From: Deepak S <deepak.s@linux.intel.com>
>>
>> After feedback from the hardware team, now we set the GPU min freq to RPe.
>> If we drop the freq to RPn, we found that the punit was not setting the
>> voltage to Vnn, So recommendation is to set min freq to RPe.
> And does it change the voltage at all?

Yes Voltage does change when we drop to RPe

> Is there really any advantage to
> the extra code on idle?Does efficient_freq really consume less power
> than min_freq when active (assuming a min_freq/efficient_freq busy
> workload i.e. does a workload that would be 100% busy at min_freq
> consume less power when run at efficient_freq)?

The delta voltage usage between RPn and RPe is very small like close to zero.
Also, if we run workload 100% busy at Rpe we get better performance without much of voltage loss right?
btw, Punit expects us to operate between Rpe & RP0.

> -Chris