[Bug 99448] New: HDMI Output Fault - Unstable Display (drm_dp_dpcd_access Error in dmesg).

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=99448

            Bug ID: 99448
           Summary: HDMI Output Fault - Unstable Display
                    (drm_dp_dpcd_access Error in dmesg).
           Product: DRI
           Version: unspecified
          Hardware: x86-64 (AMD64)
                OS: Linux (All)
            Status: NEW
          Severity: normal
          Priority: medium
         Component: DRM/Intel
          Assignee: intel-gfx-bugs at lists.freedesktop.org
          Reporter: synup at tiscali.co.uk
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org
     i915 platform: SNB
     i915 features: display/HDMI

Created attachment 129021
  --> https://bugs.freedesktop.org/attachment.cgi?id=129021&action=edit
Archive of files containing configuration and log information (see description
for details).

[i915][SNB]
This issue is occurring after a restart while the LightDM logon screen is
displayed prior to any attempt to actually logon.  I am seeing the display
blink intermittently (i.e. the display momentarily goes blank and then
returns).  In my experience this issue is repeatable.  The time interval
between blinks is variable.  The display continues to blink even after logon.

In order to reproduce this issue I am using the following configuration:
- Ubuntu 16.04.1 installed from ISO image (no updates applied from the Ubuntu
repository).
- TV display connected via HDMI connection (no other displays connected).

This issue occurs with the v4.4 Linux kernel from the DVD image.  In an attempt
to further investigate this issue I have experimented with other Linux kernels
from http://kernel.ubuntu.com/~kernel-ppa/mainline/.  The issue still exists
with Linux kernel v4.9.4.  With this kernel the display blinks several times
(say 10) within a couple of minutes of a restart.  I have gathered some
configuration and log information which I hope will help you understand the
issue and hopefully suggest a fix/workaround.

In addition I have tried older Linux kernels and in my experience the most
recent kernel that does NOT exhibit this issue is v4.2.8-ckt13.  I have
gathered some configuration and log information when testing with this kernel
as well.

I am attaching two sets of files containing configuration and log information
when testing with v4.9.4 (display issue exists) and v4.2.8-ckt13 (display issue
does NOT exist).  The names of these attachments are prefixed with the relevant
Linux kernel version.  The information gathered covers:
- dmesg output with drm.debug=0xe.
- dmidecode output for hardware information.
- an Intel Register Dump.
- uname output.
- a VBIOS dump.
- xrandr output.

I am currently using the same hardware with a Windows based Media Centre and am
having no display issues, from this I am concluding that I do not have an
underlying hardware related issue.  I am aiming to replace Windows with Linux
and this is how I have discovered this display blinking issue.

Please let me know if further information is required.  I am keen to help but I
am new to Linux so may need more detailed instructions than experienced
contributors.

-- 
You are receiving this mail because:
You are the assignee for the bug.
You are the QA Contact for the bug.
You are on the CC list for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.freedesktop.org/archives/intel-gfx-bugs/attachments/20170118/41e60d6b/attachment.html>