[Intel-gfx] [PATCH] drm/i915/cnl: WaForceContextSaveRestoreNonCoherent

[Oscar Mateo]

On 09/28/2017 01:56 PM, Oscar Mateo wrote:
>
>
> On 09/28/2017 02:46 AM, Chris Wilson wrote:
>> Stealing the thread for another gem_workarounds conundrum.
>>
>> After a reset, we lose the RING_FORCE_TO_NONPRIV registers. If they
>> where in the context image as we presumed, the values would be retained
>> and they can be read back from before reset, so it's not the case of
>> write-only register!
>>
>> So are they the mythical powercontext but require an LRI after reset to
>> restore the settings for all logical contexts? Or can we make those into
>> regular MMIO?
>> -Chris
>
> I cannot see these in any the context image formats, no matter the 
> GEN, so I suspect they are regular (but privileged) MMIO registers. I 
> think by "These are global registers and power context save/restored" 
> they simply mean that they survive RC6.

And, sure enough, these registers do appear in the "Render Engine Power 
Context" (save/restored by PM), not to be confused with the "Register 
State Context" (the usual HW context)