[Bug 100572] [SKL dmc] Headless mode media transcoding is 20-30% slower comparing to connected monitor use case

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=100572

--- Comment #22 from Sunil Kamath <sunil.kamath at intel.com> ---
>> Some details and further tests to be tried are:
>> 
>> Though by avoiding DMC fw load, issue is going away issue is not lilted just
>> to DMC fw. (proved by other tests results)
>
>Which results are you referring to? So far I haven't been able to reproduce the performance regression without the DMC loaded. But yeah, it is possible it >is an driver - firmware interaction of some sorts.
I am referring to results with “i915.disable_power_wells=0”.
>
>> Real way to address this is to gracefully handle power infra change for a
>> headless system.
>> 
>> “i915.disable_power_wells=0” fixes performance issue on DP too?
>
>It fixes the issue in headless mode and headless mode cannot have DP connected so not sure what you mean by this?

Here im referring to comment #19. If the same scenario is tested with
i915.disable_power_wells=0. But I got further clarity in below comments from
you.
>
>What Dmitry observed in #19 is that forcing the DP connector on hasn't got the same workaround effect as forcing the HDMI on does. As far as I could see, >there is some difference in the display code paths, where forcing the DP on does not actually turn on the power well(s). Contrary to forcing the HDMI >connector to on which does this. There is also a difference in system behaviour depending on presence or absence of fbcon, but this is just a secondary >effect of modeset happening or not when the connector is forced.

This is the area where I was seeking efforts from Imre – to clarify further on
power infrastructure handling for headless-system.

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