Comment 65 for bug 755841
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#65 |
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bbfa235
(Get the code!)
> Dmitry, do you have any tips for installing the Intel source code and hacking
> on it?
The problem I tried to solve is more complicated. Compiz uses other stuff for vertical sync. Using compiz vsync + video wait for scan line may give unpredictable results. Probably, it will tear even harder (like with radeon fglrx driver). So, solving the problem this way is not a good idea (it means don't care about this patch).
By the way, Eric Anholt from intel-gfx mailing list gave me the following answer why my patch doesn't work:
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You can't wait_for_event on scanlines in the BLT ring, so you'd want the
swap to be done using the 3D engine and have it preceded by a wait for
scanline there (if it works).
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I dig through the specs and found that all commands actually executed from one ring buffer and each certain command comes to the corresponding ring which actually executes it. Moreover, the similar code used to work in the similar place. So the problem is in hardware, I think.
The another possible solution may be to add overlay support for SandyBridge (putOverlayImage). It will solve tearing problem but, unfortunately, only for non-composite display.