[mga] mode validation seems to treat ModeLines and DDC dtimings differently

[John Steele Scott]

I have been playing with Ubuntu on a test box at home and will soon be putting
it on my main computer. In preparation for this, I attached my main monitor.
After figuring out the magical incantation to reprobe the monitor, I found that
xorg didn't want to run it at native resolution. I knew this from experience
with my main computer, but I never reported it before.

To get it to work, I had to add the following modeline to my xorg.conf in the
Monitor section:
ModeLine "1920x1200" 162.00 1920 1980 2040 2160 1200 1201 1204 1242

And then in my Screen section, I prepended "1920x1200" to each of the "Modes"
entries in the "Display" subsections.

I will attach my Xorg.log; that is where I got the values from for the modeline.
The monitor is connected via the D-SUB VGA connector. This modeline works on
this machine, which has a Matrox G450, and also on my iBook G4, which has a ATI
Radeon Mobility 9200 M9+.

[John Steele Scott (toojays)]

Created an attachment (id=1255)
Xorg.log containing DDC info as reported from my FP231W

If you scroll down to where it says "Supported additional Video Mode" (around
line 435), you see that it contains enough information to construct a working
modeline for 1920x1200. This information is printed whether or not I include
the modeline in my xorg.conf.

But without the modeline, it wouldn't actually run at the resolution, as you
can see, it complains "(WW) (1920x1200,BenQ FP231W) mode clock 162MHz exceeds
DDC maximum 160MHz", but with the modeline it does it anyway, with no apparent
problem.

Presumably the 1920x1080 mode could be achieved as well, but I have not tried
that yet. I can try it if you want, but otherwise I won't bother.

[John Steele Scott (toojays)]

Created an attachment (id=1275)
Xorg.log with DDC info from FP231W, this time on radeon mobility 9200

I've installed Ubuntu on my iBook G4 (Radeon Mobility 9200 M9+) and it exhibits
the same behaviour, so this isn't just limited to the mga driver. Again I have
added the same modeline to make it work.

I have another problem with X on this iBook (flickering panel when using
external display), but I'll file that in another bug later.

[Matt Zimmerman (mdz)]

Please attach the xorg.conf which was autogenerated for you, and the output from
"sudo xresprobe ati"

[John Steele Scott (toojays)]

Okay, I've just installed a fresh breezy preview on this machine. Here's the
output of xresprobe ati:

id: BenQ FP231W
res: 1920x1080 1600x1200 1280x1024 1152x864 1024x768 832x624 800x600 720x400 640x480
freq: 31-80 56-76
disptype: crt

I will attach a new Xorg.log and the autogenerated xorg.conf.

[John Steele Scott (toojays)]

Created an attachment (id=4005)
xorg.conf autogenerated with fresh installed of breezy preview

[John Steele Scott (toojays)]

Created an attachment (id=4006)
Xorg.log for breezy preview (see attachment 4005)

[John Steele Scott (toojays)]

By the way, as well as not showing all the resolutions of this monitor,
xresprobe is saying it's a CRT, when it's actually an LCD panel. Thought I'd
point that out, since I haven't mentioned it in a previous comment.

[John Steele Scott (toojays)]

Daniel, do you need any more info about this? I openned this bug a year ago . . . surely we should aim to get it fixed in Dapper (assuming it's not fixed already . . . maybe it is?).

[Henrik Nilsen Omma (henrik)]

"Daniel, do you need any more info about this? I openned this bug a year ago . . . surely we should aim to get it fixed in Dapper (assuming it's not fixed already . . . maybe it is?)."

Hi John,

Do you have an opportunity to test this machine with Dapper? Perhaps just starting with a live CD? The issue isn't serious enough for us to backport a fix to breezy, but we are still interested to know if it persists in Dapper. Thanks for your help.

- Henrik

[John Steele Scott (toojays)]

The machine with the mga card is attached to a different monitor at the moment. If there's a reason to think that this bug is fixed, I'll make some time to move the machine and test it. But I'm not going to do that just to confirm something we already know.

[Henrik Nilsen Omma (henrik)]

OK, your call obviously, but xorg has changed a significantly from breezy to dapper, so there is a fair chance that any given bug has been fixed along the way. Finding out would help us close it or pursue it further. Thanks.

[Fabio Massimo Di Nitto (fabbione)]

John, i do understand that moving a machine or a monitor is a pain, but it would be nice to know if this bug is still there or not and without your input is quite difficult.

Thanks a lot!
Fabio

[John Steele Scott (toojays)]

My last comment was reflecting my frustration with people doing but triage asking me for the Nth time if a bug has been fixed, when there is no good reason to think that it has been. I have a couple of these bugs which have been open since before Hoary, with no action except from people on triage asking if it is fixed.

Since you asked, Fabio, I have gone to the effort of putting a fresh install of Dapper Beta 2 on this machine.

This is perhaps an improvement over previous versions. One of the widescreen modes (1920x1080) has been detected somehow and put in the xorg.conf. Unfortunately this mode is not used, and cannot be selected.

xrandr lists the following modes available:
toojays@ubuntu:~$ xrandr
 SZ: Pixels Physical Refresh
*0 1600 x 1200 ( 502mm x 311mm ) *60
 1 1280 x 1024 ( 502mm x 311mm ) 75 60
 2 1152 x 864 ( 502mm x 311mm ) 75
 3 1024 x 768 ( 502mm x 311mm ) 75 70 60
 4 832 x 624 ( 502mm x 311mm ) 75
 5 800 x 600 ( 502mm x 311mm ) 75 72 60 56
 6 640 x 480 ( 502mm x 311mm ) 75 73 60
 7 1400 x 1050 ( 502mm x 311mm ) 70 60
 8 1440 x 900 ( 502mm x 311mm ) 60
 9 1280 x 960 ( 502mm x 311mm ) 60
 10 1280 x 800 ( 502mm x 311mm ) 60
 11 1280 x 768 ( 502mm x 311mm ) 60
 12 960 x 600 ( 502mm x 311mm ) 60
 13 840 x 525 ( 502mm x 311mm ) 60
 14 700 x 525 ( 502mm x 311mm ) 70 60
 15 640 x 512 ( 502mm x 311mm ) 75 60
 16 720 x 450 ( 502mm x 311mm ) 60
 17 640 x 400 ( 502mm x 311mm ) 60
 18 576 x 432 ( 502mm x 311mm ) 75
 19 640 x 384 ( 502mm x 311mm ) 60
 20 512 x 384 ( 502mm x 311mm ) 75 70 60
 21 416 x 312 ( 502mm x 311mm ) 75
 22 400 x 300 ( 502mm x 311mm ) 75 72 60 56
 23 320 x 240 ( 502mm x 311mm ) 75 73 60
Current rotation - normal
Current reflection - none
Rotations possible - normal
Reflections possible - none

Also of note is that the optimum native resolution on this monitor (1920x1200) has not been specified in the file.

[John Steele Scott (toojays)]

Here's the associated log file. Notice that the mode information for the widescreen modes is listed under "Supported additional Video Mode".

[John Steele Scott (toojays)]

Transposing the information about additional video modes from the Xorg.log gives me the following modelines:

        ModeLine "1920x1080" 160.90 1920 1980 2040 2160 1080 1081 1084 1234
        ModeLine "1920x1200" 160.90 1920 1980 2040 2160 1200 1201 1204 1242

Adding these to the monitor section of my xorg.conf allows me to use these two extra modes.

[S.R.Parda (linux-qbox)]

I had a similar problem in Ubuntu Edgy.
So I don't want to add a new bug, and subscribe to this bug.

I have a Radeon X300 card with a 30" LCD TV Videoseven LTV30C, the native LCD resolution is 1280x768.
But 1280x1024 is the maximum resolution reported and was detected OK and worked fine with a fresh install (automatically selected as the default resolution).
The problem is with the native resolution 1280x768: It was detected Ok as a possible resolution (an advance in comparison with previous ubuntu versions), but timings were not OK, so screen flashes.

Reading the X log, I see the additional mode data reported by the monitor. It is ok and works fine if used in a Modeline.

I think this is a bug (or an additional requirement) that the timings of additional modes reported by the monitor would be used if they are not, or revised if they are used incorrectly.

I build and sell computers and try people use Linux, but the first thing a person see is the screen. I thing it is very important a robust screen detection.
I use 3 widescreen monitors (17" laptop 1920x1200, 19" Wide 1400x900, and 30" Wide 1280x768), with different resolutions and in the last two I needed to edit the config manually.

I am commited to help to make better the user experience, I am used to make installations in different kinds of hardware, so I can report about fresh installations without problem.

Thank You

[Bryce Harrington (bryce)]

It's been a long time since the last comment to this bug report. Is this bug still a problem with current -mga? It would be great if someone could re-test against Jaunty (or Intrepid at least).

With how much the xserver has changed since this bug was originally reported, I'm wondering if this bug is out of date now.

[John Steele Scott (toojays)]

I can't test this, I don't believe I have that hardware anymore.

[Bryce Harrington (bryce)]

Okay, thanks for letting me know. Since the hardware is no longer available for doing troubleshooting with, we'll have to close the bug for now. However please feel free to reopen if you or anyone else has the same HW and can reproduce this issue using the latest development version of Ubuntu and is willing to do some troubleshooting with it.