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

[Hans de Goede]

Hi,

On 17-01-18 09:31, Mika Kuoppala wrote:
> 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.

I noticed this patch was lacking the ping Chris' version has. Is that
in the intel_idle driver now ? And did your test kernel have the intel_idle
patch? If not the lack of the ping may be the reason why this patch did not
survive the night.

Regards,

Hans