[Intel-gfx] [PATCH RFC] drm/i915/vlv: Ramp up gpu freq gradually

[Mika Kuoppala]

Chris Wilson <chris at chris-wilson.co.uk> writes:

> Quoting Mika Kuoppala (2018-01-16 15:21:16)
>> There is a suspicion that with aggressive upclocking, power rail
>> voltage fluctuations can disrupt c state transition, leading
>> to system hang.
>> 
>> When upclocking with 4 cpu Baytrails, bring up cpus to c1 and then
>> go through bins gradually towards target frequency to give leeway
>> for hw.
>> 
>> We go towards requested frequency on 1 millisecond intervals. For
>> each 1 millisecond, we increase the frequency by half of bins
>> that are in between current frequency and target.
>
> Either this is good for everyone or it is not. Doing more punit accesses
> seems counter productive though, and adds 8ms to the initial request?

Wanted to see if it is not punit access in itself but voltage rampup. We
can forget this patch as atleast with these values as it didn't survive
night.

-Mika