Bug 20754

Summary: [RV730] Signal out of range at low resolutions with DVI
Product: xorg Reporter: Rüdiger <best-before-31-12-2008>
Component: Driver/RadeonAssignee: xf86-video-ati maintainers <xorg-driver-ati>
Status: RESOLVED FIXED QA Contact: Xorg Project Team <xorg-team>
Severity: normal    
Priority: medium    
Version: 7.3 (2007.09)   
Hardware: x86-64 (AMD64)   
OS: Linux (All)   
Whiteboard:
i915 platform: i915 features:
Attachments:
Description Flags
Xorg.0.log with repeated switches to 800x600 and back to 1280x1024.
none
Xorg.0.log with disabled coherent mode before, while and after modeswitching none

Description Rüdiger 2009-03-19 13:48:42 UTC 
Created attachment 24051 [details] [review]
Xorg.0.log with repeated switches to 800x600 and back to 1280x1024.

When I switch to a resolution below 1024x768, the screen gets blanked and my lcd reports that the incoming signal is out of range. This happens with all radeon and radeonhd drivers which support my Radeon 4670 RV730XT, but only with DVI output, VGA seems ok. It looks like the drivers calculate wrong modes but strangely only at low resolutions. The Option "DefaultTMDSPLL" doesn't help, neither enabled nor disabled.
Comment 1 Alex Deucher 2009-03-19 14:56:20 UTC 
does turning off coherent mode help?
xrandr --output DVI-0 --set coherent_mode 0
Comment 2 Rüdiger 2009-03-19 15:19:11 UTC 
On Thu, 19 Mar 2009 14:56:21 -0700 (PDT)
bugzilla-daemon@freedesktop.org wrote:

> --- Comment #1 from Alex Deucher <agd5f@yahoo.com>  2009-03-19
> 14:56:20 PST --- does turning off coherent mode help?
> xrandr --output DVI-0 --set coherent_mode 0

It doesnt seem to make any difference. Logfile says that coherent
mode is disabled, the screen gets black for a second and then the
lcd again reports "Signal out of range".
Comment 3 Rüdiger 2009-03-19 15:22:23 UTC 
Created attachment 24055 [details]
Xorg.0.log with disabled coherent mode before, while and after modeswitching
Comment 4 Alex Deucher 2009-03-20 10:50:10 UTC 
DVI seems to have issues with low dot clocks on DCE 3.2 display engines.  I've just changed the driver to use the scaler by default instead:
1ddee7cd6fd267b2fc86f21af27c5425eb0835a4

You can also use the scaler on your current driver as follows:
xrandr --output DVI-0 --set scaler <scale type>

where scale type is: full or center or aspect.

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