[Bug 97878] New: [SKL][REGRESSION][BISECTED] Dropped frames and FIFO underruns when moving mouse across (plane?) boundary

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=97878

            Bug ID: 97878
           Summary: [SKL][REGRESSION][BISECTED] Dropped frames and FIFO
                    underruns when moving mouse across (plane?) boundary
           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: michael at michaelmarley.com
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

Created attachment 126674
  --> https://bugs.freedesktop.org/attachment.cgi?id=126674&action=edit
Output of dmesg with the DRM debugging turned on

After upgrading from kernel 4.7.4 to 4.8-rc7, several frames are dropped
(resulting in jerky graphics and a jerky mouse cursor) when the mouse passes
over a boundary about a hundred pixels from the right side of my left monitor
(DP-1).  Sometimes, especially if the system is under heavy load, a FIFO
underrun on one of the monitors will occur as well.

My system is a Lenovo m900 with a "Intel(R) Core(TM) i5-6500T CPU @ 2.50GHz"
processor.  It is running kernel 4.8.0-040800rc7-lowlatency (as downloaded from
http://kernel.ubuntu.com/~kernel-ppa/mainline/) on Kubuntu 16.10 amd64.  The
system has two monitors, both Dell U2312HMs connected by DisplayPort.  The left
monitor is connected to DP-1 and the right monitor to DP-2.  I have also tried
connecting the monitors using DisplayPort-DVI adapters, but this does not
affect the issue.

I bisected the issue and found that it was introduced with commit
9909113cc48a7ce6e772573e3cc82a3f03ffa8ef
(https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/drivers/gpu/drm/i915?id=9909113cc48a7ce6e772573e3cc82a3f03ffa8ef).
 However, reverting the commit isn't a possibility because that causes severe
problems with mouse cursor updates (a cursor trail getting stuck on the screen
and often flickering rapidly.)

-- 
You are receiving this mail because:
You are the QA Contact for the bug.
You are the assignee 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/20160920/e2da604d/attachment-0001.html>