Bug 97878 - [SKL][REGRESSION][BISECTED] Dropped frames and FIFO underruns when moving mouse across (plane?) boundary
Summary: [SKL][REGRESSION][BISECTED] Dropped frames and FIFO underruns when moving mou...
Status: CLOSED FIXED
Alias: None
Product: DRI
Classification: Unclassified
Component: DRM/Intel (show other bugs)
Version: unspecified
Hardware: x86-64 (AMD64) Linux (All)
: highest blocker
Assignee: cprigent
QA Contact: Intel GFX Bugs mailing list
URL:
Whiteboard:
Keywords: bisected, regression
Depends on:
Blocks:
 
Reported: 2016-09-20 19:35 UTC by Michael Marley
Modified: 2016-12-09 13:01 UTC (History)
1 user (show)

See Also:
i915 platform: SKL
i915 features: display/watermark

Attachments
Output of dmesg with the DRM debugging turned on (1001.14 KB, text/x-log)
2016-09-20 19:35 UTC, Michael Marley 		no flags Details
Output of dmesg without the DRM debugging enabled, showing a FIFO underrun (56.30 KB, text/plain)
2016-09-20 19:37 UTC, Michael Marley 		no flags Details
View All

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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