Bug 27408 - [Intel 915GM][KMS]: Primary and Secondary display blanks in extended desktop mode with Compiz enabled
Summary: [Intel 915GM][KMS]: Primary and Secondary display blanks in extended desktop ...
Alias: None
Product: Mesa
Classification: Unclassified
Component: Drivers/DRI/i915 (show other bugs)
Version: git
Hardware: x86 (IA32) Linux (All)
: high major
Assignee: Chris Wilson
QA Contact:
Depends on:
Reported: 2010-04-01 00:52 UTC by Vance
Modified: 2010-06-13 13:39 UTC (History)
6 users (show)

See Also:
i915 platform:
i915 features:

dmesg with drm.debug=0x07 option (247.11 KB, text/plain)
2010-04-01 00:52 UTC, Vance
lspci (1.56 KB, application/octet-stream)
2010-04-01 01:18 UTC, Vance
Xorg.0.log (16.36 KB, text/plain)
2010-04-01 01:25 UTC, Vance
Screenshot of extended desktop messed up (313.25 KB, image/png)
2010-04-07 06:27 UTC, fangxun
Off-by-one drawrect fix. (1.52 KB, patch)
2010-06-09 00:52 UTC, Chris Wilson
Details | Splinter Review

Description Vance 2010-04-01 00:52:10 UTC
Created attachment 34591 [details]
dmesg with drm.debug=0x07 option

This screen blank issue is experienced on 2.6.33 kernel and extended desktop mode, it wasn't reproduceable in Dual Twin/Clone mode. The only way to work around this is to disable compiz. I was running 1024x768 on both displays so the virtual desktop resolution shouldn't exceed the 2048 limit mentioned in http://bugs.freedesktop.org/show_bug.cgi?id=23718. In any case I am already running mesa 7.7 containing the fix mentioned in that thread.

I also don't see this issue when I'm running a 1024x768 with a 800x600 resolution display in extended mode with compiz enabled.
Comment 1 Vance 2010-04-01 01:18:55 UTC
Created attachment 34592 [details]
Comment 2 Vance 2010-04-01 01:25:03 UTC
Created attachment 34593 [details]
Comment 3 fangxun 2010-04-07 06:27:32 UTC
Created attachment 34762 [details]
Screenshot of extended desktop messed up
Comment 4 fangxun 2010-04-07 06:32:09 UTC
I've seen the similar behavior. Primary and Secondary display get messed up in extended desktop mode with Compiz enabled(see attached sreenshot). It works well with compiz disabled. It wasn't reproduceable in Dual Twin/Clone mode.
Comment 5 Gordon Jin 2010-04-11 18:12:51 UTC
(In reply to comment #3)
> Created an attachment (id=34762) [details]
> Screenshot of extended desktop messed up

Xun, that looks like bug#27449.
Comment 6 Vance 2010-04-25 20:38:44 UTC
I've tried the patch suggested in the previous comment and it did not help to resolve the screen blanking issue once virtual resolution reaches 2048x768.
Comment 7 Chris Wilson 2010-05-31 11:44:23 UTC
compiz blanking on 2048 sounds like we have an off-by-one somewhere. The challenge will be to find the size of the textures and renderbuffers used by compiz for the desktop and check that they are all within the h/w constraints. Hmm, I wonder if Mesa actually enforces this, it would be best starting point to insert traps...
Comment 8 Chris Wilson 2010-06-05 05:35:55 UTC
commit add3260157368458501709d08a3f913ed448234f
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Sat Jun 5 09:33:58 2010 +0100

    i915: Fix off-by-one for drawing rectangle.
    The drawing rectangle is given in *inclusive* pixel values, so the range
    is only [0,2047]. Hence when rendering to a 2048 wide target, such as an
    extended desktop, we would issue an illegal instruction zeroing the draw
      Bug 27408: Primary and Secondary display blanks in extended
                 desktop mode with Compiz enabled
Comment 9 Vance 2010-06-08 19:33:43 UTC
Hi Chris, thanks for the update. Can you provide a link to the patch so I can try it out?
Comment 11 Gordon Jin 2010-06-12 23:53:37 UTC
Chris, your patch works on my side. Can you please cherry-pick it into mesa 7.8 branch? We do need this fix in 7.8.2 release.
Comment 12 Chris Wilson 2010-06-13 13:39:06 UTC
Applied to 7.8 with Eric's blessing.

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