linux-kernel - Re: Any SYSRQ key to force mode switch to console mode when using KMS?

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Date:	Tue, 21 Sep 2010 15:10:33 -0700
From:	Randy Dunlap <randy.dunlap@...cle.com>
To:	Uwe Bonnes <bon@...ktron.ikp.physik.tu-darmstadt.de>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: Any SYSRQ key to force mode switch to console mode when using
 KMS?

On Wed, 15 Sep 2010 19:40:37 +0200 Uwe Bonnes wrote:

> Hello,
> 
> is there any SYSRQ key that forces the video system to console mode,
> especially when using KMS and allows to work on. 

sysrq-v help message says:

force-fb(V) = "Restore framebuffer console"

> Since going to KMS on a Thinkpad R50 with ATI Radeon RV250 via going from
> Opensuse-11.2 to Opensuse-11.3 I experience frequent situations where I am
> left with a black screen, with only ALT-SYSREQ-C switching the screen back
> on and hard reboot as only chance to escape that situation.
> 
> Situations that result in a black screen are:
> 
> * Going with the mouse over the NOSCRIPT buttom in firefox. Load goes up and
> screen goes black after some seconds. xorg.log ends with "Backtrace", but no
> backtrace output...
> 
> * Calling pm-hibernate on a system that has hibernated before. First
>   pm-hibernate/wake-up-per power buttom sequence is successfull.
> 
> Disabling KMS results in very slow "kaffeine" full screen output...
> 
> pm-hibernate and firefox/noscript worked pre-KMS on opensuse-11.2.
> 
> Some traces of other people hitting the NOSCRIPT xorg crash and others
> hitting the black unresponsive screen with KMS on RV250 are
> found on the net, but I didn't find a conclusive resolution.
> 
> Opensuse default kernel and the recent Opensuse 2.6.36-rc3 kernel-of-the day
> were tested with no difference
> 
> Thanks
> 
> PS: I only follow linux-kernel via gmane.org, so if you need fast feedback,
> please CC me. 

---
~Randy
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