[Intel-gfx] [PATCH 08/24] drm/i915: Do not add planes from intel_atomic_setup_scalers.

[Maarten Lankhorst]

Op 05-06-15 om 21:05 schreef Konduru, Chandra:
>>>>>>>> @@ -396,6 +377,24 @@ int intel_atomic_setup_scalers(struct
>> drm_device
>>>>>>> *dev,
>>>>>>>>  		}
>>>>>>>>  	}
>>>>>>>>
>>>>>>>> +	/* plane not part of mask must leave hq mode? */
>>>>>>>> +	if (num_scalers_need > 1 && scaler_state->scalers[0].in_use &&
>>>>>>>> +	    scaler_state->scalers[0].mode == PS_SCALER_MODE_HQ) {
>>>>>>>> +		scaler_state->scalers[0].mode =
>> PS_SCALER_MODE_DYN;
>>>>>>>> +
>>>>>>>> +		intel_crtc->atomic.skl_update_scaler0 =
>>>>>>>> +			PS_SCALER_EN | PS_SCALER_MODE_DYN;
>>>>>>>> +	}
>>>>>>>> +
>>>>>>>> +	/* plane not part of mask can enter hq mode? */
>>>>>>>> +	if (num_scalers_need == 1 && scaler_state->scalers[0].in_use
>> &&
>>>>>>>> +	    intel_crtc->pipe != PIPE_C && scaler_state->scalers[0].mode
>> !=
>>>>>>> PS_SCALER_MODE_HQ) {
>>>>>>>> +		scaler_state->scalers[0].mode =
>> PS_SCALER_MODE_HQ;
>>>>>>>> +
>>>>>>>> +		intel_crtc->atomic.skl_update_scaler0 =
>>>>>>>> +			PS_SCALER_EN | PS_SCALER_MODE_HQ;
>>>>>>>> +	}
>>>>>>>> +
>>>>>>> I don't have access to the hw spec at the moment; is scaler #0 the only
>>>>>>> one that can ever go into HQ mode?
>>>>>> Yes
>>>>>>
>>>>>>> If there isn't a hardware
>>>>>>> requirement about this, then it seems like we're missing the case where
>>>>>>> planes A and B get scalers 0 and 1.  Then plane A (and thus scaler 0) is
>>>>>>> disabled, which should allow scaler 1 to go into HQ mode.
>>>>>> In this case, scaler 0 to be allocated to plane B to operate in HQ mode.
>>>>> Is it really bad to keep it on scaler 1 for a while until the next time the plane
>> is
>>>>> added?
>>>>>
>>>>>>> I guess it's not immediately clear to me why we need to not pull the
>>>>>>> other planes into the transaction.  Is this just to avoid doing some
>>>>>>> extra work for a plane that hasn't changed, or does it cause a problem
>>>>>>> somehow?
>>>>>> Per atomic design, unchanged planes can be added to transaction.
>>>>>> And scaler implementation is using this design feature.
>>>>>> Not sure what the issue here, but we need this feature continue
>>>>>> to available.
>>>>>>
>>>>> Unchanged planes can be added, but this could pull in a primary plane,
>> which
>>>>> would need
>>>>> to set atomic.wait_for_flips then. I can do that as special case when adding
>> a
>>>>> plane if
>>>>> that's preferred.
>>>> Here primary plane can get added if that is the only plane using scaler which
>>>> isn't part of the transaction. But here addition of primary plane isn't adding
>>>> or changing its FB. So why it needs to set atomic.wait_for_flips?
>>> In the atomic case, intel_check_primary_plane() sets
>>> atomic.wait_for_flips if the primary plane is part of the original
>>> transaction (no matter what about the primary plane is changing).
>>> However if we pull in the primary plane via
>>> intel_atomic_setup_scalers(), that gets called after we've finished
>>> checking all of the planes (that were originally part of the
>>> transaction), so I don't think wait_for_flips will get set in that case.
>>> So I think pulling in the plane as Chandra was will still avoid an
>>> unnecessary wait.  Even though it's in the transaction, I believe the
>>> 'check' step is bypassed (which means we need to be careful about doing
>>> stuff like this if it could affect derived state...but I think in this
>>> case it's safe).
>>>
>>> N.B.  The wait we're talking about here will only be triggered when a
>>> SKL or BXT platform disables a "sprite" plane (thus triggering the
>>> primary's scaler to switch to HQ mode) while there's a pending legacy
>>> pageflip on the primary plane.  I don't think we have a userspace today
>>> that can trigger this...Weston won't use sprites at all in a non-atomic
>>> manner and although SNA has an Xv sprite adapter, it won't ever be
>>> performing scaling of the primary plane afaik.
>> Correct. The wait will be a nop if there are no legacy page flips. But for
>> completeness sake I included it. :-)
> So you will be keeping current code to add plane as-is and let respective 
> update_plane function take care of updating scaler quality instead 
> of the above update_scaler0?
>
Yes, see "[PATCH v2 08/27] drm/i915: Move scaler setup to check crtc function, v2."