[Nouveau] CRTC video scanout position for high precision vblank timestamping?

[Mario Kleiner]

On 12/29/2010 10:35 AM, Maarten Maathuis wrote:
> I found these by simply dumping the entire range modesetting related
> registers. At the time they didn't help me (the issue of swapbuffers
> remains unsolved on this generation of hardware, it didn't interest me
> *that* much). I don't know what exactly you are doing, but a lot of
> stuff is done through pushbuffers (even modesetting) so there are no
> "instant" registers that i know of.
>

Oh, it's about precisely timestamping when a scanout starts (at end of 
vblank) and when exactly a bufferswap completed - when the post-swap 
frontbuffer starts to scan out. This commit gives the background info:

<http://git.kernel.org/?p=linux/kernel/git/airlied/drm-2.6.git;a=commit;h=27641c3f003e7f3b6585c01d8a788883603eb262>

This is what it looks like in the i915 kms, to be implemented very 
similar in nouveau kms:

<http://git.kernel.org/?p=linux/kernel/git/airlied/drm-2.6.git;a=commit;h=0af7e4dff50454905092d468e91c1ef92e10e6b4>

-mario