TEARING - dreaming of tearfree on lvds with Intel gma950

[whizse]

Of course, see the bug report I mentioned previously.

http://bugs.freedesktop.org/show_bug.cgi?id=19635

[wswartzendruber]

Interesting. Here's what I've found with my system:

UXA+XV - Tears...
UXA+GL - Tears...
EXA+XV - Tears...
EXA+GL - WORKS!!!

I thought DRI2 was supposed to fix this. Instead, it seems that EXA and GL are the only way to get things to stop tearing.

[bridgman]

DRI2 fixes flicker, not tearing. Actually DRI2 + GEM/TTM allows RDR, and RDR fixes flicker. Whatever.

Here's what I think is going on (10,000 foot view) :

- Xv on Intel used to tear, GL on Intel did not tear
- in the process of implementing GEM, sync-to-vblank was temporarily disabled
- GL uses sync-to-vblank to avoid tearing
- UXA is EXA over GEM

so...

EXA+GL always worked, but UXA needs GEM, which in turn seems to "break" GL from a tearing point of view (GL is actually fine, it's the DRM that can't sync to vblank)

This is all based on vague recollections of discussion in IRC that I wasn't really paying attention to, but I *think* it's right. Hopefully someone more familiar with the Intel code will jump in here.

[wswartzendruber]

If that's the case, I'm going to try enabling RDR to see if that fixes it.

EDIT: Wait, don't you mean RandR?

EDIT: Still tears with RandR enabled.

[Gentooer]

If that's the case, I'm going to try enabling RDR to see if that fixes it.

EDIT: Wait, don't you mean RandR?

EDIT: Still tears with RandR enabled.

RDR is "Redirected Direct Rendering". I don't think it's something you can enable/disable, but I'm not really sure.

[bridgman]

Yep, Redirected Direct Rendering. It lets a direct-rendered client (typically 3D, but could be something else) get along with a compositor like Compiz. Without RDR, the compostor and the direct rendered (DRI) app both draw to the same area of the screen, which is why you get flicker.

http://hoegsberg.blogspot.com/2007/08/redirected-direct-rendering.html

http://hoegsberg.blogspot.com/2008/03/i-just-committed-last-bit-of-dri2-work.html

Again, that fixes flicker under Compiz, not tearing. Peversely enough, though, I believe it was the addition of memory management (required by RDR) which resulted in the temporary lost of sync-to-vblank support and the re-introduction of tearing. Some days life just sucks

[wswartzendruber]

I just subscribed to the intel-gfx mailing list, so I'll be sure to let everyone here know what they say.