linux-kernel - Radeon HD 6290 screen goes black at KMS

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Date:	Mon, 20 Oct 2014 15:09:26 +0200
From:	Marcin Szewczyk <kernel@...ny.org>
To:	linux-kernel@...r.kernel.org
Subject: Radeon HD 6290 screen goes black at KMS

Hi,

I have a DFI OT951-D board and sometimes the screen connected to the
DisplayPort-0 (LVDS) goes black at the moment of radeon's Kernel Mode
Setting. Sometimes I am able to turn it on again after X11 starts using
two commands (referenced as xrandr workaround below):

  xrandr --output DisplayPort-0 --off
  xrandr --output DisplayPort-0 --mode 1920x1080

The workaround helps sometimes with radeon but makes it worse with
fglrx.

Fglrx fails sometimes at early boot but mostly after xrandr.

The adapter as described by lspci:

  00:01.0 VGA compatible controller: Advanced Micro Devices [AMD] nee ATI Wrestler [Radeon HD 6290]

Even when the screen remains black xrandr reports the screen as turned
on.

Some statistics. 120 samples. Numbers below mean the number of times the
screen remained black after the system finished booting:

  Debian with 3.2.54 kernel with X11
    radeon w/  workaround   |  5
    radeon w/o workaround   | 40
    fglrx  w/  workaround   | 25
    fglrx  w/o workaround   | 10

  Arch with 3.16.3 kernel without X11
    radeon w/o workaround   | 35

I attach dmesg output (with drm.debug=0xe) from one successful boot and
a unsuccessful one (both without the workaround). Unfortunately I do not
see much of a difference between them.

Please, help.

-- 
Marcin Szewczyk                       http://wodny.org
mailto:Marcin.Szewczyk@...ny.borg  <- remove b / usuń b
xmpp:wodny@...ntu.pl                  xmpp:wodny@...ster.pl

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