[Bug 94985] New: [HSW] Severe screen flickering on external monitor after i915.enable_psr=1

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=94985

            Bug ID: 94985
           Summary: [HSW] Severe screen flickering on external monitor
                    after i915.enable_psr=1
           Product: DRI
           Version: XOrg git
          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: pinguin255 at gmail.com
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

Created attachment 123021
  --> https://bugs.freedesktop.org/attachment.cgi?id=123021&action=edit
dmesg

Kernel: 4.6.0-040600rc3-generic
Architecture: x86_64
Distribution: Ubuntu 14.04 trusty
Machine: Thinkpad T440p
Connector: VGA

I was trying to find a way for my Haswell system (Thinkpad T440p, 20AN0034RT,
i5-4300M) to enter deeper power-saving package states (below pc3) and it turned
out, that after following actions system indeed goes to pc7:
1. Setting i915.enable_psr=1
2. Setting SATA link_power_management_policy to min_power

But immediately after applying these settings the problem occurs. External VGA
monitor is no longer usable, as it starts flickering constantly every second
during idling. However, when some activity occurs (video playback or some CPU
intensive task, for example) flickering stops. Main screen screen is flickering
too, but not so hard and is effectively usable as it just becomes black only
for a fraction of second and rarely. As in 4.6 PSR is planned to be set enabled
by default I decided to report this.

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