[Nouveau] [PATCH 3/3] dri2: Fixes to swap scheduling, especially for copy-swaps.

[Francisco Jerez]

Francisco Jerez <currojerez at riseup.net> writes:

> Mario Kleiner <mario.kleiner at tuebingen.mpg.de> writes:
>
>> On 09/09/2011 11:14 PM, Francisco Jerez wrote:
>>> Mario Kleiner<mario.kleiner at tuebingen.mpg.de>  writes:
>>>
>>>>[...]
>>>> Is the blip operation started at leading edge of the vblank interval?
>>>> Or anywhere inside the vblank interval (level triggered)? Are such
>>>> blits submitted on a separate fifo (or even dma engine?) in the gpu to
>>>> avoid stalling the rest of the command stream until vblank?
>>>
>>> It depends, right now we have two completely different implementations
>>> and we use one or the other depending on the card generation:
>>>
>>> On nv11-nv4x, we use the PGRAPH vsync methods (0x120-0x134), that means
>>> it's the drawing engine that waits. Basically you have a counter that's
>>> incremented by a CRTC of your choice when it reaches a scanline range of
>>> your choice, wrapping around at a configurable value; you can put the
>>> drawing engine to sleep until the counter reaches a given value. Right
>>> now we make it wait until somewhere between vdisplay-3 and vdisplay-1
>>> before going on with the swap.
>>>
>>
>> Interesting, thanks for the explanation. Maybe that counter could also
>> be used to implement a hardware vblank counter on pre-NV50?

I forgot to answer to this question... Not really, these counters are
(IIRC) only 3 bits wide, and they need PGRAPH intervention to get
incremented, so they're quite useless for anything more sophisticated
than what we're doing right now.

>>[...]
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