Bug 32527

Summary: Blanked screen with 2.6.37-rc6, -rc5 works OK (bisected to 541cc966915b6756e54c20eebe60ae957afdb537)
Product: DRI Reporter: Alex Villacís Lasso <avillaci>
Component: DRM/IntelAssignee: Chris Wilson <chris>
Status: CLOSED FIXED QA Contact:
Severity: normal    
Priority: medium CC: jbarnes
Version: unspecifiedKeywords: regression
Hardware: x86-64 (AMD64)   
OS: Linux (All)   
Whiteboard:
i915 platform: i915 features:
Attachments:
Description Flags
lspci -vvvv on the affected machine.
none
Kernel configuration used to compile affected kernel none

Description Alex Villacís Lasso 2010-12-20 07:47:04 UTC 
Created attachment 41300 [details]
lspci -vvvv on the affected machine.

All mentioned computers run Fedora 14 x86_64 with KMS.

On my work machine with an Intel graphics chipset and a flat panel with working
EDID, vanilla kernels 2.6.37-rc6 and 2.6.37-rc5 works OK.

On my home machine, with a somewhat different Intel graphics chipset, and a
flat panel that does *not* report EDID information, 2.6.37-rc5 works OK but
2.6.37-rc6 blanks the KMS display on boot. I get the "no signal" message on the
panel instead of a working display. I was able to bisect this to the following
commit:

commit 541cc966915b6756e54c20eebe60ae957afdb537
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Mon Dec 6 11:24:07 2010 +0000

    drm: Don't try and disable an encoder that was never enabled

    Prevents code that assumes that the encoder is active when asked to be
    disabled from dying a horrible death.

    Reported-by: Daniel Vetter <daniel.vetter@ffwll.ch>
    Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
    Signed-off-by: Dave Airlie <airlied@redhat.com>

When I revert this commit, the problem goes away in my home machine.
Comment 1 Alex Villacís Lasso 2010-12-20 07:47:53 UTC 
Created attachment 41301 [details]
Kernel configuration used to compile affected kernel
Comment 2 Alex Villacís Lasso 2010-12-20 07:48:30 UTC 
Related kernel bug is https://bugzilla.kernel.org/show_bug.cgi?id=25312
Comment 3 Chris Wilson 2010-12-22 04:51:26 UTC 
Upstream, airlied/drm-fixes:

commit 92971021c632876108ea2e06290a56a9157578f5
Author: Dave Airlie <airlied@redhat.com>
Date:   Tue Dec 21 12:47:56 2010 +1000

    Revert "drm: Don't try and disable an encoder that was never enabled"
    
    This reverts commit 541cc966915b6756e54c20eebe60ae957afdb537.
    
    Wei Yonjun reported this caused a regression against Intel VGA hotplug
    on his G33 hw.
    
    Signed-off-by: Dave Airlie <airlied@redhat.com>
Comment 4 Jari Tahvanainen 2016-11-03 11:55:04 UTC 
Closing resolved+fixed. Revert done as suggested by reporter, (CommitDate: Wed Dec 22 2010)

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