i915 display driver causes crash back to login window

[Amos Shapira]

I've just installed Ubuntu 14.04 server on Dell Latitude E7440 and then installed Cinnamon 2.4.5 on top of it. The laptop has an external monitor connected through Display Port and a docking station.

On the first day the system worked perfectly.

On the second day, the system booted to the login screen (leaving the external screen empty but otherwise seemed to be under X11's control), it then let me type my username and password but then X exits, shows a bit of VT1 with errors then gets back to the login page.

I found the following error in /var/log/kern.log:

[drm:intel_dp_complete_link_train] ERROR failed to train DP, aborting

I found a page which claims to solve this error for 12.04 in the second comment in https://www.libreoffice.org/bugzilla/show_bug.cgi?id=73694#c2.

I found that the file linux-source-3.13.0/drivers/gpu/drm/i915/intel_dp.c, which is included in the tar file /usr/src/linux-source-3.13.0.tar.bz2 (also copied in /usr/src/linux-source-3.13.0/linux-source-3.13.0.tar.bz2), from the kernel source package "linux-source-3.13.0", contains the pre-patch lines mentioned in the fix above.

Would you please consider including this fix in the Ubuntu kernel?

Thanks,

--Amos

For completeness, the patch pointed to from the link above is:

Link: https://www.libreoffice.org/bugzilla/attachment.cgi?id=92231

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 8f17f8fbd0b1..5631cfb874db 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -847,8 +847,8 @@ intel_dp_compute_config(struct intel_encoder *encoder,
   mode_rate = intel_dp_link_required(adjusted_mode->crtc_clock,
          bpp);

- for (clock = 0; clock <= max_clock; clock++) {
- for (lane_count = 1; lane_count <= max_lane_count; lane_count <<= 1) {
+ for (lane_count = 1; lane_count <= max_lane_count; lane_count <<= 1) {
+ for (clock = 0; clock <= max_clock; clock++) {
     link_clock = drm_dp_bw_code_to_link_rate(bws[clock]);
     link_avail = intel_dp_max_data_rate(link_clock,
             lane_count);

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: xorg 1:7.7+1ubuntu8
ProcVersionSignature: Ubuntu 3.13.0-43.72-generic 3.13.11.11
Uname: Linux 3.13.0-43-generic x86_64
ApportVersion: 2.14.1-0ubuntu3.6
Architecture: amd64
CurrentDesktop: X-Cinnamon
Date: Wed Dec 17 12:57:10 2014
InstallationDate: Installed on 2014-12-15 (1 days ago)
InstallationMedia: Ubuntu-Server 14.04.1 LTS "Trusty Tahr" - Release amd64 (20140722.3)
SourcePackage: xorg
Symptom: display
Title: Xorg crash
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[penalvch (penalvch)]

Amos Shapira, this bug was reported a while ago and there hasn't been any activity in it recently. We were wondering if this is still an issue? If so, could you please test for this with the latest development release of Ubuntu? ISO images are available from http://cdimage.ubuntu.com/daily-live/current/ .

If it remains an issue, could you please run the following command in the development release from a Terminal as it will automatically gather and attach updated debug information to this report:

apport-collect -p xorg 1403275

Please ensure you have xdiagnose installed, and that you click the Yes button for attaching additional debugging information.

As well, given the information from the prior release is already available, testing a release prior to the development one would not be helpful.

Thank you for your understanding.

Helpful bug reporting tips:
https://wiki.ubuntu.com/ReportingBugs

[Vladimír Kriška (ujovlado)]

Hi there,

I think this is something more "global" - I mean it affects whole system, not only part when you're going back to login window.

For example, this happens every time I connect external monitor through DP. Of course, I cannot extend desktop to this monitor. Looks like monitor is detected, bot due to mentioned error "not trained" ...

A minute ago, I tried daily build as you recommend and error is still there.

[penalvch (penalvch)]

Vladimír Kriška, it would help immensely if you filed a new report via a terminal:
ubuntu-bug xorg

Please feel free to subscribe me to it.

[Vladimír Kriška (ujovlado)]

Hi Christopher, I've already reported it to kernel intel-gfx-bugs. Should i report it to Xorg too?

[Launchpad Janitor (janitor)]

[Expired for xorg (Ubuntu) because there has been no activity for 60 days.]