Bug 97878

Summary:

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

Product:

DRI

Reporter:

Michael Marley <michael>

Component:

DRM/Intel

Assignee:

cprigent <christophe.prigent>

Status:

CLOSED FIXED

QA Contact:

Intel GFX Bugs mailing list <intel-gfx-bugs>

Severity:

blocker

Priority:

highest

CC:

intel-gfx-bugs

Version:

unspecified

Keywords:

bisected, regression

Hardware:

x86-64 (AMD64)

OS:

Linux (All)

Whiteboard:

i915 platform:

SKL

i915 features:

display/watermark

Attachments:

Description	Flags
Output of dmesg with the DRM debugging turned on	none
Output of dmesg without the DRM debugging enabled, showing a FIFO underrun	none

Description Michael Marley 2016-09-20 19:35:54 UTC

Created attachment 126674 [details]
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.)

Comment 1 Michael Marley 2016-09-20 19:37:03 UTC

Created attachment 126675 [details]
Output of dmesg without the DRM debugging enabled, showing a FIFO underrun

Comment 2 Michael Marley 2016-09-21 11:56:49 UTC

I have tested a drm-intel-next build from yesterday and cannot reproduce the issue there, so it seems that the fix just needs to be applied to Linus's kernel tree.

Comment 3 Michael Marley 2016-09-26 14:01:49 UTC

This still happens with 4.8-rc8.

Comment 4 yann 2016-09-30 09:54:58 UTC

(In reply to Michael Marley from comment #3)
> This still happens with 4.8-rc8.

This should be landing more in incoming 4.9

Comment 5 Jani Saarinen 2016-12-09 10:13:36 UTC

How about now with latest kernel?

Comment 6 Michael Marley 2016-12-09 12:07:08 UTC

Sorry, I forgot to post right after it happened, but this was fixed in a 4.8 point release (4.8.5, maybe?) and stays fixed in 4.9-rc8.  Thanks!

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