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

[Ben Skeggs]

Sorry for the top-posting. Also confirmed on fermi (nvc0).

Ben.

Sent from my iPhone

On 29/12/2010, at 22:26, Francisco Jerez <currojerez at riseup.net> wrote:

> Mario Kleiner <mario.kleiner at tuebingen.mpg.de> writes:
> 
>> On 12/29/2010 10:44 AM, Ben Skeggs wrote:
>>> On Wed, 2010-12-29 at 10:37 +0100, Maarten Maathuis wrote:
>>> [...]
>>>> 
>>>> In my infinite wisdom i swapped the vertical and horizontal regs,
>>>> these are the right ones:
>>>> 
>>>> 0x616340: CRTC0 horizontal scanline (lower 16 bits, upper 16 bits is a
>>>> counter that increments every display cycle)
>>>> 0x616344: CRTC0 vertical scanline (lower 16 bits, upper 16 bits empty)
>>>> 
>>>> 0x616B40: CRTC1 horizontal scanline
>>>> 0x616B44: CRTC1 vertical scanline
>>> Ah, I should've waited 10 minutes before doing the same here.  Ah well,
>>> I can confirm at least on NV84, I can't imagine it differs at all on any
>>> nv50+ board either.
>>> 
> 
> I can confirm those registers are still there on NVA8.
> 
>>> Ben.
>>>> 
>> 
>> Wow, that was fast! Thanks! I'll get some good sleep now and then give
>> it a try on my GF-8800. This is probably also useful to implement the
>> .get_vblank_counter() hook properly. Currently it hooks up to
>> drm_vblank_count() which is problematic, as .get_vblank_counter() is
>> meant to query the hardware for the purpose of reinitializing
>> drm_vblank_count() after a long vblank irq off period.
>> 
>> I'll let you know how it goes, hopefully with some nice patches asap.
>> 
>> If somebody knows about similar NV40 and earlier registers, keep it
>> coming :-)
>> 
> On nv04-nv4x class hardware there's a scanline counter in the lower 12
> bits of 0x600808 (0x602808 for the second CRTC), bit 16 lights up during
> the vblank period.
> 
> I don't think I've ever seen a hardware frame counter there, but they
> might have one. Tracing what the nvidia blob does for SGI_video_sync and
> friends would be your best bet I guess.
> 
>> Is the range from NV_PCRTC0_OFFSET to NV_PCRTC0_OFFSET +
>> NV_PCRTC0_SIZE a good starting point for a search on NV40 and earlier?
>> 
>> thanks,
>> -mario
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