Bug 92003

Summary: SKL: Display underruns
Product: DRI Reporter: Daniel Drake <dan>
Component: DRM/IntelAssignee: Intel GFX Bugs mailing list <intel-gfx-bugs>
Status: CLOSED FIXED QA Contact: Intel GFX Bugs mailing list <intel-gfx-bugs>
Severity: normal    
Priority: medium CC: intel-gfx-bugs
Version: unspecified   
Hardware: Other   
OS: All   
Whiteboard:
i915 platform: i915 features:

Description Daniel Drake 2015-09-14 17:57:51 UTC 
Every now and then, the display momentarily blinks to black, and the following message appears in the log:

[drm:intel_cpu_fifo_underrun_irq_handler] *ERROR* CPU pipe A FIFO underrun

Reproduced on Linux 4.2 and 4.3-rc1, on a new Skylake laptop with quad-core i5 6200U. The laptop seems rather beefy so I have trouble believing this is a general RAM bandwidth issue.

This is using just the internal laptop display, 1920x1080. Sometimes the problem happens a lot, and sometimes it takes a while. However, I find that I can't complete a grand prix in SuperTuxKart (about 20 mins gameplay) without this happening at least once (usually more times).

I can't reproduce on intel-drm-nightly, however SuperTuxKart gameplay is not as smooth there, every few minutes the display hangs for approximately 1 second, with no messages in the log.

00:02.0 VGA compatible controller: Intel Corporation Device 1916 (rev 07) (prog-if 00 [VGA controller])
	Subsystem: ASUSTeK Computer Inc. Device 1c3d
	Flags: bus master, fast devsel, latency 0, IRQ 123
	Memory at de000000 (64-bit, non-prefetchable) [size=16M]
	Memory at c0000000 (64-bit, prefetchable) [size=256M]
	I/O ports at f000 [size=64]
	Expansion ROM at <unassigned> [disabled]
	Capabilities: [40] Vendor Specific Information: Len=0c <?>
	Capabilities: [70] Express Root Complex Integrated Endpoint, MSI 00
	Capabilities: [ac] MSI: Enable+ Count=1/1 Maskable- 64bit-
	Capabilities: [d0] Power Management version 2
	Capabilities: [100] #1b
	Capabilities: [200] Address Translation Service (ATS)
	Capabilities: [300] #13
	Kernel driver in use: i915
Comment 1 Daniel Drake 2015-09-14 18:04:45 UTC 
Spoke to soon - just reproduced this on drm-intel-nightly.
Comment 2 Daniel Drake 2015-09-23 19:39:00 UTC 
Ping - anything I can do to help?
We also see this on other Skylake laptops.
Comment 3 Jani Nikula 2015-10-30 13:25:01 UTC 
Please try Ville's FIFO underrun elimination series [1] on top of drm-intel-nightly, also available at [2], and report back.

[1] http://mid.gmane.org/1446146763-31821-1-git-send-email-ville.syrjala@linux.intel.com
[2] git://github.com/vsyrjala/linux.git pch_fifo_underrun_fix_4
Comment 4 Daniel Drake 2016-01-19 22:09:13 UTC 
I can reproduce the problem on that github branch, and also in Linux 4.4.
However linus master from today seems fine. Yay!
Comment 5 Jani Nikula 2016-01-21 09:20:38 UTC 
(In reply to Daniel Drake from comment #4)
> I can reproduce the problem on that github branch, and also in Linux 4.4.
> However linus master from today seems fine. Yay!

Great, thanks for testing.
Comment 6 Jari Tahvanainen 2016-10-10 13:09:40 UTC 
Closing resolved+fixed based on verification done by Daniel.

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