[Bug 97283] New: drm/i915: Intermittent flicker (bisected)

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=97283

            Bug ID: 97283
           Summary: drm/i915: Intermittent flicker (bisected)
           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: mymailclone at t-online.de
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

Hi!

Noticed an intermittent flicker of the monitor (part goes black for a fraction
of a second) with kernel 4.4.10.

dmesg showed the following messages:

[drm:ironlake_irq_handler [i915]] *ERROR* CPU pipe A FIFO underrun
[drm:ironlake_irq_handler [i915]] *ERROR* PCH transcoder A FIFO underrun


Bisected it to this commit:

> git bisect bad
8e1001c5638e244ab9a2ddddf5466b05ddf6af77 is the first bad commit
commit 8e1001c5638e244ab9a2ddddf5466b05ddf6af77
Author: Shashank Sharma <shashank.sharma at intel.com>
Date:   Thu Apr 21 16:48:32 2016 +0530

    drm/i915: Fake HDMI live status

    commit 60b3143c7cac7e8d2ca65c0b347466c5776395d1 upstream.

    This patch does the following:
    - Fakes live status of HDMI as connected (even if that's not).
      While testing certain (monitor + cable) combinations with
      various intel  platforms, it seems that live status register
      doesn't work reliably on some older devices. So limit the
      live_status check for HDMI detection, only for platforms
      from gen7 onwards.

    V2: restrict faking live_status to certain platforms
    V3: (Ville)
       - keep the debug message for !live_status case
       - fix indentation of comment
       - remove "warning" from the debug message

        (Jani)
       - Change format of fix details in the commit message

    Fixes: 237ed86c693d ("drm/i915: Check live status before reading edid")
    Suggested-by: Ville Syrjala <ville.syrjala at linux.intel.com>
    Signed-off-by: Shashank Sharma <shashank.sharma at intel.com>
    Link:
http://patchwork.freedesktop.org/patch/msgid/1461237606-16491-1-git-send-email-shashank.sharma@intel.com
    Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
    (cherry picked from commit 4f4a8185011773f7520d9916c6857db946e7f9d1)
    Signed-off-by: Jani Nikula <jani.nikula at intel.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>

:040000 040000 6e90ff06fc964d1ddbb57155f8a42b840ea563d9
f76dff57b7ea8aa4d8cd66544eefc0a0b6c37a3d M     drivers
---

Regards!

Jay

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