[i945] underrun on pipe A! prevents Xorg from starting.

[Joe Fry]

I realise that there are a number of bugs referencing an the "underrun on pipe X" issues with the intel driver. My issue doesn't appear to be addressed by any of them that I looked at however.

My issue is that early in the Xorg startup, I begin to get the underruns, and Xorg doesn't start. The attached log file shows what I mean. I have left it for a long time and had nothing more to show but a larger log file.

The system is a Intel Mac Mini Core Duo connected to a Toshiba Regza 42LX196. I have had no issues connecting other computers, with NVidia and ATI video cards, to the same TV. I am running Mythbuntu 8.10 (intrepid) fully patched, and I enabled the backports repo's just to see if there were any updates that helped.

The only other oddity I have noticed is that get-edid tells me "Something special has happened" though I don't suspect it's the display as my other computers seem to work fine with their drivers. I will attach the get-edid output as well.

Thanks!

[lspci]
00:00.0 Host bridge [0600]: Intel Corporation Mobile 945GM/PM/GMS, 943/940GML and 945GT Express Memory Controller Hub [8086:27a0] (rev 03)
     Subsystem: Intel Corporation Device [8086:7270]
00:02.0 VGA compatible controller [0300]: Intel Corporation Mobile 945GM/GMS, 943/940GML Express Integrated Graphics Controller [8086:27a2] (rev 03)
     Subsystem: Intel Corporation Device [8086:7270]

[Joe Fry (joe-thefrys)]

Tested with:

Section "Device"
        Identifier "Configured Video Device"
        Driver "intel"
        Option "FramebufferCompression" "off"
EndSection

No change.

[Geir Ove Myhr (gomyhr)]

Thank you for reporting this bug. Could you check if this is still a problem in Jaunty? (alpha-6 is currently the latest test-release, http://cdimage.ubuntu.com/releases/9.04/). If it is, then we would like the /var/log/Xorg.0.log from there as it contains some extra information.

The get-edid output you uploaded seems fine, but the errors you saw would be written to standard error, not to standard out. If you do `sudo get-edid >get-edid.out 2>get-edid.err`, the get-edid.err file will contain the error message and possibly other suspicious messages.

Finally, we would like a output of `lspci -vvnn` from you.

[Joe Fry (joe-thefrys)]

Looks like the underruns are gone... however the Mac Mini still does not detect the display properly.

I can get it to display at 1080x540i... looks horrible, but it is displayed.

[Bryce Harrington (bryce)]

Joel, can you also update the title please?

On Tue, Mar 31, 2009 at 12:06:03AM -0000, Joe Fry wrote:
> Looks like the underruns are gone... however the Mac Mini still does not
> detect the display properly.
>
> I can get it to display at 1080x540i... looks horrible, but it is
> displayed.
>
>
> ** Attachment added: "Xorg.0.log"
> http://launchpadlibrarian.net/24551956/Xorg.0.log
>
> --
> [i945] underrun on pipe A! prevents Xorg from starting.
> https://bugs.launchpad.net/bugs/328918
> You received this bug notification because you are a member of Ubuntu-X,
> which is subscribed to xserver-xorg-video-intel in ubuntu.

[Geir Ove Myhr (gomyhr)]

And can you also attach the Xorg.0.log from Jaunty? To get the most information out of it, you should add
  Option "ModeDebug" "true"
to you xorg.conf, restart X (by for example logging out and in again) and then grab /var/log/Xorg.0.log.

I suspect the EDID error you get is because the get-edid program doesn't properly support the E-EDID standard. If you run `get-edid | hd` you will see that the second last byte is 01, which means that there is one extension. For most monitors this is 00 (for no extensions) and I guess that maybe get-edid does not support extensions. There is a new version of EDID in the PPA https://launchpad.net/~intuitivenipple/+archive/ppa/ which you may try (see also bug https://bugs.launchpad.net/debian/+bug/242043), but I don't know if this issue addressed here. Anyway, this should be independent of the EDID handling in Xorg.

Also, if you have a ~/.config/monitors.xml, please rename it or delete it as there may be some old resolution settings there.

[Geir Ove Myhr (gomyhr)]

Forgot to say that the ModeDebug line belongs in the "Device" section of your /etc/X11/xorg.conf.

[Carey Underwood (cwillu)]

Some relevant details listed on bug 322959 (Mac Mini under jaunty)

[Bryce Harrington (bryce)]

We're closing this bug since it is has been some time with no response from the original reporter. However, if the issue still exists please feel free to reopen with the requested information. Also, if you could, please test against the latest development version of Ubuntu, since this confirms the bug is one we may be able to pass upstream for help.