Bug 45968 - [RADEON:KMS:RS780:HD3200] l 2560x1440 detected by monitor as 1280x1440, every second pixel missing
Summary: [RADEON:KMS:RS780:HD3200] l 2560x1440 detected by monitor as 1280x1440, every...
Status: RESOLVED NOTOURBUG
Alias: None
Product: DRI
Classification: Unclassified
Component: DRM/Radeon (show other bugs)
Version: unspecified
Hardware: Other Linux (All)
: medium normal
Assignee: Default DRI bug account
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Reported: 2012-02-12 15:39 UTC by Tobias Diedrich
Modified: 2012-02-14 10:04 UTC (History)
0 users

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Attachments
Xorg log (66.27 KB, text/plain)
2012-02-13 08:12 UTC, Tobias Diedrich 		no flags Details
xrandr --verbose output (4.99 KB, text/plain)
2012-02-13 08:13 UTC, Tobias Diedrich 		no flags Details
dmesg output (66.73 KB, text/plain)
2012-02-13 08:16 UTC, Tobias Diedrich 		no flags Details
video bios rom (58.50 KB, application/octet-stream)
2012-02-13 08:18 UTC, Tobias Diedrich 		no flags Details
View All

Description Tobias Diedrich 2012-02-12 15:39:22 UTC 
My new monitors native resolution is 2560x1440 which requires dual-link.
I'm using the DVI-Cable that came with the monitor.
KMS/Xorg claims to have set the resolution to 2560x1440.

Debian/unstable
Linux 3.3.0-rc3 (built from source)
libdrm 2.4.31-0 (built from source)
xserver-xorg              1:7.6+11 
xserver-xorg-video-radeon 1:6.14.3-2 (tried building from source, had the same problem)
Gigabyte GA-MA78GPM-DS2H

As a workaround, custom 2560x1440@30 and 2560x1440@24 modelines work, but seems very suboptimal...
Comment 1 Alex Deucher 2012-02-13 05:27:57 UTC 
Please attach your xorg log, dmesg output, and xrandr --verbose output.
Comment 2 Tobias Diedrich 2012-02-13 08:12:35 UTC 
Created attachment 56974 [details]
Xorg log
Comment 3 Tobias Diedrich 2012-02-13 08:13:07 UTC 
Created attachment 56975 [details]
xrandr --verbose output
Comment 4 Tobias Diedrich 2012-02-13 08:16:57 UTC 
Created attachment 56977 [details]
dmesg output
Comment 5 Tobias Diedrich 2012-02-13 08:18:44 UTC 
Created attachment 56979 [details]
video bios rom
Comment 6 Alex Deucher 2012-02-13 08:22:51 UTC 
Does it work ok with a pre3.3 kernel (e.g., 3.2, 3.1, etc.)?  If so, does reverting this commit fix the issue?

http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=commitdiff;h=9aa59993e226af94088adaee993eb8cfd33ae295
Comment 7 Tobias Diedrich 2012-02-13 08:27:05 UTC 
(In reply to comment #6)
> Does it work ok with a pre3.3 kernel (e.g., 3.2, 3.1, etc.)?  If so, does reverting this commit fix the issue?
> 
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=commitdiff;h=9aa59993e226af94088adaee993eb8cfd33ae295

It didn't work with 3.2.4, which is why tried 3.3-rc.
Comment 8 Tobias Diedrich 2012-02-13 08:28:23 UTC 
(In reply to comment #7)
> (In reply to comment #6)
> > Does it work ok with a pre3.3 kernel (e.g., 3.2, 3.1, etc.)?  If so, does reverting this commit fix the issue?
> > 
> > http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=commitdiff;h=9aa59993e226af94088adaee993eb8cfd33ae295
> 
> It didn't work with 3.2.4, which is why tried 3.3-rc.

Looking at the mentioned patch I should actually retry HDMI, which with 3.2.4 only supported up to 1920xsomething
Comment 9 Tobias Diedrich 2012-02-14 03:00:35 UTC 
FWIW using HDMI on 3.3-rc I can go up to 2560x1440@48, but 2560x1440@60 is above the 340MHz pixelclock limit for one link.

I installed XP yesterday and found that it shows the same problem with dual-link not working properly, so this seems to be just a case of bad HW.
Comment 10 Alex Deucher 2012-02-14 06:01:56 UTC 
Seems like the oem may not have wired up the DVI port correctly for duallink.
Comment 11 Roland Scheidegger 2012-02-14 10:04:35 UTC 
(In reply to comment #9)
> FWIW using HDMI on 3.3-rc I can go up to 2560x1440@48, but 2560x1440@60 is above the 340MHz pixelclock limit for one link.

I'm surprised this old hw supports 340Mhz pixelclock on hdmi, I thought only Tahiti could do that, and monitors wouldn't support it neither typically (though I know some hw tolerates overclocking tmds quite well).
In any case 2560x1440@60Hz should be clearly below 340Mhz with reduced blanking (around 250Mhz).

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