[Bug 94103] New: [i915] External monitors lose connection after suspend, or don't return from sleep

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=94103

            Bug ID: 94103
           Summary: [i915] External monitors lose connection after
                    suspend, or don't return from sleep
           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: dy at drexel.edu
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

Created attachment 121690
  --> https://bugs.freedesktop.org/attachment.cgi?id=121690&action=edit
short

This is on a Dell XPS 9333 (Haswell) with a mini-displayport to dual HDMI hub.

Linux version 4.5.0-040500rc3-generic (kernel at gomeisa) (gcc version 5.2.1
20151010 (Ubuntu 5.2.1-22ubuntu2) ) #201602071930 SMP Mon Feb 8 00:34:43 UTC
2016
Distro: Ubuntu 15.10
x86_64
Also affects mainline Ubuntu kernel 4.2.0-27-generic.

When entering display standby (either by timeout or xset dpms force off) , one
of three things happens:
1) After 30s, the monitors come back on by themselves, one monitor goes to
low-resolution or is disabled.

or, 2) Monitor configuration stays the same, but on resume, the two externals
fail to resume from standby state. Note that xrandr reports the same
configuration as before, and the mouse can be moved to the (still blank)
monitors.

or, 3) Resume from standby within 10 seconds and the issue doesn't occur.

The workaround is to unplug/replug the mini-DP. Sometimes this results in hang
or X restarting.

Additionally, one of the monitors occasionally (~30 minutes) blanks for a
half-second, and comes back.

This issue occurs regardless of one or two monitors on the hub, or two entirely
different monitors. It didn't occur with a non-MST, single miniDP to HDMI.

I have tested the hub with another XPS 9333 running windows, and the issue
doesn't occur.

Attached logs: short - for case (3) above
longresume-blanked - for case (2) above
what was left of the system log - freeze
all with drm.debug=14 switch

I'll test with drm-intel-nightly again in a few.

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