Bug 84951

Summary: [HSW] fifo underrun error message when waking from suspend
Product: DRI Reporter: pdknsk <pdknsk>
Component: DRM/IntelAssignee: Intel GFX Bugs mailing list <intel-gfx-bugs>
Status: CLOSED DUPLICATE QA Contact: Intel GFX Bugs mailing list <intel-gfx-bugs>
Severity: minor    
Priority: medium CC: intel-gfx-bugs, przanoni, yi.sun
Version: unspecified   
Hardware: x86-64 (AMD64)   
OS: All   
Whiteboard:
i915 platform: i915 features:
Attachments:
Description Flags
dmesg
none
xorg none

Description pdknsk 2014-10-13 06:00:30 UTC 
It seems to have no adverse effect, that I have noticed anyway. Reproduces reliably.

[drm:intel_dp_start_link_train] *ERROR* failed to enable link training
[drm:intel_dp_complete_link_train] *ERROR* failed to start channel equalization
[drm:ivybridge_set_fifo_underrun_reporting] *ERROR* uncleared fifo underrun on pipe A
[drm:ivb_err_int_handler] *ERROR* Pipe A FIFO underrun

This is with an Intel NUC (Haswell) on Ubuntu.
Comment 1 Paulo Zanoni 2014-10-13 12:50:18 UTC 
Please boot with "drm.debug=0xe" as a Kernel parameter (you can pass it from Grub), reproduce the bug, then run "dmesg > dmesg.txt" and attach the file here.
Comment 2 pdknsk 2014-10-14 17:51:03 UTC 
Created attachment 107832 [details]
dmesg
Comment 3 pdknsk 2014-10-14 17:51:21 UTC 
Created attachment 107833 [details]
xorg
Comment 4 pdknsk 2014-10-14 17:52:11 UTC 
I have debugged the problem a bit further. It turns out a certain order of events is necessary to trigger the bug (or at least that's the most reliable way to reproduce).

First, suspend. Next my monitor goes into standby, and after a few minutes turns itself off. Now, wake from suspend. Turn on monitor. If the last two events are reversed, the error does not appear.
Comment 5 Rodrigo Vivi 2015-01-15 18:58:16 UTC 
What kernel version was that? please boot next time with buf_log_len=8M so we have full dmesg.

Could you please try to reproduce with latest drm-intel-nightly from cgit.freedesktop.org/drm-intel. Well since you use Ubuntu one good alternative is ppa's drm-intel-nightly kernel: http://kernel.ubuntu.com/~kernel-ppa/mainline/drm-intel-nightly/current/
Comment 6 pdknsk 2015-01-15 21:39:39 UTC 
That's the complete log with 3.16, just with drm grepped. I tried drm-intel-nightly, the fifo underrun error is missing. Just this.
 
[  195.451488] [drm:intel_dp_start_link_train [i915]] *ERROR* failed to enable link training
[  195.454207] [drm:intel_dp_complete_link_train [i915]] *ERROR* failed to start channel equalization
Comment 7 Rodrigo Vivi 2015-01-22 22:19:46 UTC 

*** This bug has been marked as a duplicate of bug 86478 ***
Comment 8 Jari Tahvanainen 2016-09-28 13:34:08 UTC 
Closing as duplicate of closed+fixed.

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