[Bug 111271] Black stripe on screen with MGAG200 (PowerEdge R320) and modesetting

[bugzilla-daemon at bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=111271

Ville Syrjala <ville.syrjala at linux.intel.com> changed:

           What    |Removed                     |Added
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                 CC|                            |ville.syrjala at linux.intel.c
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--- Comment #4 from Ville Syrjala <ville.syrjala at linux.intel.com> ---
commit 9125e6186822b2698da17690416cd1b55c030115
Author: Ville Syrjälä <ville.syrjala at linux.intel.com>
Date:   Mon Jun 3 16:10:40 2013 +0300

    drm: Add drm_plane_force_disable()

just moves code around. So can't see how it could be related to this.

Well, actually it does add a plane->fb NULL check, so I suppose that could be
somehow related if something else is buggy and clears plane->fb while the plane
is still enabled. But actually, the mgag200 driver doesn't even do planes (nor
is the hardware even capable of turning off the primary plane independent of
the crtc) so not sure why this would have anything to do with the problem.

Without a picture it's a bit hard to know, but black horizontal lines at the
left edge of the screen has a feel of underruns. I have seen such things plenty
of times on my G550 when using the video overlay with eg. 1920x1080 mode with
reduced blanking, if the overlay is postioned too close to the left edge of the
screen. It's possible the hw cursor might suffer from similar issues.

Looking at the driver the hiprilvl computations seem a bit dubious at best.
Possibly by tweaking that stuff it might be possible to eliminate the
underruns, but no guarantees.

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