[Intel-gfx] Why idle_freq is set to RPn and not RPe

[Chris Wilson]

On Wed, Dec 30, 2015 at 04:09:46PM +0530, Kamble, Sagar A wrote:
>    Turbo frequency range is Rpe to Rp0 when GPU is active as, on workload
>    submission frequency is taken to Rpe.
> 
>    Does the HW require us to drop to RPn before entering RC6?
>    If we can enter RC6 even with other frequencies I think we can keep
>    running at Rpe on Idle.

Remember that we quite frequently prevent the hardware going into RC6,
and that it has been known for the hardware to fail to enter RC6 itself
(through driver error or whatnot). Going to the extreme, why wouldn't
you set Rp0 on idle, since that will give the best restart latency?
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre