EDID does not allow LCD widescreen configuration

[Chascon]

Ubuntu has new strict EDID guidelines that does not allow LCD widescreen configuration.

Symptoms:
Constant flickering on and off of screen content, including distortion similar to a bad tv reception.

The screen is a LCD Citizen C19604HD that should run 1440x 900 at 60 Hz (as per manual), which apparently does not have proper EDID. I should note this setup had no problems prior, until tty1 started to complain about a bad EDID checksum during 12.10 beta.

Fix:
Attempting to set my own xorg.conf evoked a message about running in low graphics mode. It asked if I wanted to (re)configure. I confirmed, after which I no longer needed xorg,conf, nor presumably Option "IgnoreEDID" "on" in xorg.conf which made xorg sessions usable.

What should happen
The system should be self-healing. The user should not have to grapple with xorg.conf (for hours or days on end with unfamiliar concepts [EDID] and work-arounds), and even less after all that time and effort just to have the system say, "Hey, I don't like what you're doing. Here, let me do it.". This (self-repair) hook should be invoked sooner in the trouble shooting process.

See related problem about
https://bugs.launchpad.net/ubuntu/+source/xorg/+bug/1047146

[Chascon (chascone)]

After the system configured itself, it still boots into 1224 x 768 (4:3), which makes real estate go off-screen at the right and bottom, affecting both lightdm and the desktop environment. See my bug report at https://bugs.launchpad.net/lightdm/+bug/1047140

Solution:
I've had to force the resolution with the following.
xrandr --newmode "1440x900_60.00" 106.47 1440 1520 1672 1904 900 901 904 932 +HSync +VSync
xrandr --addmode DVI-0 1440x900_60.00
xrandr --output DVI-0 --mode 1440x900_60.00

In place of the first line, the following also has worked for me --something I just got off the net, if I recall.
xrandr --newmode "1440x900_60.00" 106.50 1440 1528 1672 1904 900 903 909 934 -hsync +vsync

Now, I've had to automate it by placing that into ~/.xprofile

Results:
- X starts with the native mode 1440x 900 at 60 Hz, or just shy of 60, 59 if I recall. It blanks out black once or twice though.
- lightdm sometimes entirely fits onto the physical screen, sometimes it doesn't.
- It takes "forever" to reach lightdm. Might this be the EDID issue, causing a delay while Ubuntu decides how to treat my LCD screen? I've run various diagnostics and my HD is fine, only one fan is out, which is noted by the Apple diagnostic. This MacBook Pro used to boot fine with prior versions of Ubuntu which didn't have this TFT issue.

Expected results:
I guess it goes without saying that the expected results should be that the system should auto-configure itself so as to not require user intervention. And it should not go into an episodic and alternating blanking loop.

Comments:
I've had the same issue with another (LCD?) monitor on another Ubuntu 120.10 beta install, and I've had to resort to the same fix. Info to come. So I suspect that this is a LCD problem or one of just having low tolerance for defective EDID.

[Rolf Leggewie (r0lf)]

Thank you for your report. I sense there may be more than issue here. First question, are you connecting over VGA or HDMI?

[Rolf Leggewie (r0lf)]

We're closing this bug since it is has been some time with no response from the original bug reporter. However, if the issue still exists in the latest development version of Ubuntu and you are the original reporter please feel free to reopen with the requested information. If you are not the original reporter, please don't reopen this one but instead file a new bug and reference this one.

[Chascon (chascone)]

@Rolf

I'm connecting via VGA. In truth, my macbook pro has a HDMI, and it came with a " HDMI to VGA" adaptor. So my monitor receives a VGA signal, in the end.

[Chascon (chascone)]

I know this bug report has been closed but I'd still like to leave a record for myself and for any other having the same problems.

@Rolf
You might have been right about there being more than one issue at play here. Since reporting this, I've had to stop using lightdm because of it sending me into low graphics mode ("message about running in low graphics mode" in original report).

 I found out that lightdm's greeter is defined in /etc/lightdm/lightdm.conf and as of recent:

greeter-session=unity-greeter

I investigated further and realized that there is also a lightdm-gtk-greeter. I installed it and changed the above file to reflect:

greeter-session=lightdm-gtk-greeter

Result
No more being thrown into low graphics mode. And lightdm seems less buggy than GDM.

I still use ~/.xprofile as defined in my previous comment. I'm not sure if it's still helping out at the moment, but it's still there, as a fall back if things break, usually during major upgrades.

No xorg.conf is being used.

[Chascon (chascone)]

So being sent into low graphics mode would be one problem and the screen overshooting (low tolerance for defective EDID) would be another, the prior being solved and the later to be seen in 13.04.

[Chascon (chascone)]

I came across another fix, when changing the greeter stopped working. For those who removed Unity, removing it sometimes uninstalls unity-greeter and reinstalling it installs a whole lot of stuff some of which fixed my low resolution issue. For some reason the other greeters don't work.