Bug 90220 - Black screen with KMS on powerpc iBook
Summary: Black screen with KMS on powerpc iBook
Status: NEW
Alias: None
Product: xorg
Classification: Unclassified
Component: Driver/Radeon (show other bugs)
Version: unspecified
Hardware: PowerPC Linux (All)
: medium major
Assignee: xf86-video-ati maintainers
QA Contact: Xorg Project Team
URL: https://bugs.debian.org/683796
Depends on:
Reported: 2015-04-28 23:00 UTC by Dan DeVoto
Modified: 2016-04-14 07:12 UTC (History)
1 user (show)

See Also:
i915 platform:
i915 features:

dmesg output (30.81 KB, text/plain)
2015-04-28 23:00 UTC, Dan DeVoto
no flags Details
output of cat /var/Xorg.0.log (33.06 KB, text/plain)
2015-04-28 23:01 UTC, Dan DeVoto
no flags Details
output of lspci -vvv (4.63 KB, text/plain)
2015-04-28 23:02 UTC, Dan DeVoto
no flags Details

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Description Dan DeVoto 2015-04-28 23:00:21 UTC
Created attachment 115416 [details]
dmesg output

In Debian Jessie, I get a black screen booting with KMS enabled.  The backlight remains lit, but the screen displays as black.  It happens on boot up about when these lines appear:

[   16.797096] [drm] Initialized drm 1.1.0 20060810
[   18.117763] [drm] radeon kernel modesetting enabled.

From then on I can log in blind, and I'm running pbbuttonsd so the brightness keys can dim or brighten the screen, but it always remains black.  Switching to a console also gives me a black screen.

Adding the kernel parameters video=offb:off radeon.modeset=1 radeon.agpmode=-1 changed nothing.

This isn't a new problem, I've had it in previous Debian releases, but I hope someone might take a crack at this.  Right now the only workaround is to disable KMS and work with a very slow desktop (and no mplayer or vlc fullscreen upscaling).

This is on an G3 iBook (M8603LL/A - PowerBook4,3 - A1007)


Comment 1 Dan DeVoto 2015-04-28 23:01:29 UTC
Created attachment 115417 [details]
output of cat /var/Xorg.0.log
Comment 2 Dan DeVoto 2015-04-28 23:02:18 UTC
Created attachment 115418 [details]
output of lspci -vvv
Comment 3 Dan DeVoto 2015-07-27 06:03:57 UTC
Oddly, screen mirroring works perfectly.  The external monitor shows my desktop as intended, but the iBook's screen remains bleak, I mean, black.

I also generated a xorg.conf file to disable acceleration, but it didn't help.
Comment 4 Michel Dänzer 2015-07-30 02:49:58 UTC
This line in dmesg indicates a problem with the dot clock:

[drm:drm_calc_timestamping_constants] *ERROR* crtc 14: Can't calculate constants, dotclock = 0!
Comment 5 Mathieu Malaterre 2016-04-14 07:12:40 UTC
The issue:

[drm:drm_calc_timestamping_constants] *ERROR* crtc 14: Can't calculate constants, dotclock = 0!

can also be seen here:


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