[Bug 38689] Black xorg screen with kernels newer than 2.6.34.x

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=38689

--- Comment #10 from Javier Marcet <jmarcet at gmail.com> 2011-06-27 07:06:42 PDT ---
(In reply to comment #9)
> (In reply to comment #8)
> > The only application running is XBMC, with no even a windows manager.

> > I use xinit, with an empty .xinitrc and launch xbmc in full screen mode.

> (In the future, please include this kind of information in bug reports; this
> isn't exactly a standard setup)

Yeah, I know it is not standard at all, a completely custom Gentoo HTPC/NAS.

I tried to include everything I could think of but I was pretty sure I would
forget something.

> Does setting the environment variable vblank_mode=0 for xbmc work around the
> problem?

Both ways are successful.

I had just compiled a new 2.6.35.9 with KMS_DRIVER_MINOR set to 3 and it works
fine that way.
Right now I booted from a previously compiled 2.6.39.1, setting the env
vblank_mode to 0
and it also works fine.

I understand we are disabling the sync extension, are we?
Or does the vlank_mode=0 do anything else?

I am now checking how well video plays.

On 2.6.39.1 with vblank_mode=0 video playback is quite worse than I was used
to. There is no tearing, but there is some kind of blockiness in the animation.

On 2.6.35.9 with KMS_DRIVER_MINOR=3 video is almost like in not sync enabled
kernels although there
is still some blockiness, not as noticeable as in the other kernel though
(vblank_mode is not set).

You'll tell me whether we dig further to find if I can use the sync extension
on this card or I shall
force the older kms driver minor.

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