[Bug 92237] New: Horrible noise via DisplayPort [regression]

Fri Oct 2 02:07:52 PDT 2015

https://bugs.freedesktop.org/show_bug.cgi?id=92237

            Bug ID: 92237
           Summary: Horrible noise via DisplayPort [regression]
           Product: DRI
           Version: DRI git
          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: freedesktop.org at schildbach.de
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

Created attachment 118588
  --> https://bugs.freedesktop.org/attachment.cgi?id=118588&action=edit
output of dmesg

When logging in and my display is extended to two monitors, or switched between
mirror/extended, and also when the screen blanks/sleeps, I get 1-5 seconds of
horrible noise via DisplayPort audio out.

The noise is loud enough to damage ears and loudspeakers, if volume has been
set to a normal listening level.

I bisected the kernel and found this commit to introduce the regression:

commit fdbc3b1f639bb2cbfb32c612b2699e0ba373317d
Author: Jani Nikula <email address hidden>
Date: Tue Nov 12 17:10:13 2013 +0200

    drm/i915/dp: set sink to power down mode on dp disable

To reproduce, make sure to connect some audio equipment to the audio output of
the monitor and make sure you can actually hear audio (e.g. using the sound
tests provided by your distribution). Then switch between mirrored and extended
display mode, or switch resolutions, or make your laptop go to sleep. You
should hear at least a short burst of random static.

WARNING: Do not try reproduce this with headphones, it will damage your ears!

Related Launchpad bug report:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1296224

I'm using a Dell T410s (BIOS 1.50) connected to a Dell U2711 via DisplayPort.

Side note: You asked me to test this on the latest drm-intel-nightly, which
happens to be commit eb69e51 for me. The bug is reproducable there, however in
addition to that the DP signal seems to be unstable. My monitor randomly blanks
from time to time. This report is not about the blanking, rather it's just
about the audio noise.

$ uname -a
Linux darkly 4.3.0-rc3-intel #16 SMP Fri Oct 2 10:01:54 CEST 2015 x86_64 x86_64
x86_64 GNU/Linux
$ uname -m
x86_64
$ uname -r
4.3.0-rc3-intel

$ lspci
00:00.0 Host bridge: Intel Corporation Core Processor DRAM Controller (rev 02)
00:02.0 VGA compatible controller: Intel Corporation Core Processor Integrated
Graphics Controller (rev 02)
00:16.0 Communication controller: Intel Corporation 5 Series/3400 Series
Chipset HECI Controller (rev 06)
00:19.0 Ethernet controller: Intel Corporation 82577LM Gigabit Network
Connection (rev 06)
00:1a.0 USB controller: Intel Corporation 5 Series/3400 Series Chipset USB2
Enhanced Host Controller (rev 06)
00:1b.0 Audio device: Intel Corporation 5 Series/3400 Series Chipset High
Definition Audio (rev 06)
00:1c.0 PCI bridge: Intel Corporation 5 Series/3400 Series Chipset PCI Express
Root Port 1 (rev 06)
00:1c.1 PCI bridge: Intel Corporation 5 Series/3400 Series Chipset PCI Express
Root Port 2 (rev 06)
00:1c.3 PCI bridge: Intel Corporation 5 Series/3400 Series Chipset PCI Express
Root Port 4 (rev 06)
00:1d.0 USB controller: Intel Corporation 5 Series/3400 Series Chipset USB2
Enhanced Host Controller (rev 06)
00:1e.0 PCI bridge: Intel Corporation 82801 Mobile PCI Bridge (rev a6)
00:1f.0 ISA bridge: Intel Corporation 5 Series/3400 Series Chipset LPC
Interface Controller (rev 06)
00:1f.2 SATA controller: Intel Corporation 5 Series/3400 Series Chipset 6 port
SATA AHCI Controller (rev 06)
00:1f.3 SMBus: Intel Corporation 5 Series/3400 Series Chipset SMBus Controller
(rev 06)
00:1f.6 Signal processing controller: Intel Corporation 5 Series/3400 Series
Chipset Thermal Subsystem (rev 06)
03:00.0 Network controller: Intel Corporation Centrino Ultimate-N 6300 (rev 35)
05:00.0 SD Host controller: Ricoh Co Ltd MMC/SD Host Controller (rev 01)
05:00.1 System peripheral: Ricoh Co Ltd R5U2xx (R5U230 / R5U231 / R5U241)
[Memory Stick Host Controller] (rev 01)
ff:00.0 Host bridge: Intel Corporation Core Processor QuickPath Architecture
Generic Non-core Registers (rev 02)
ff:00.1 Host bridge: Intel Corporation Core Processor QuickPath Architecture
System Address Decoder (rev 02)
ff:02.0 Host bridge: Intel Corporation Core Processor QPI Link 0 (rev 02)
ff:02.1 Host bridge: Intel Corporation 1st Generation Core Processor QPI
Physical 0 (rev 02)
ff:02.2 Host bridge: Intel Corporation 1st Generation Core Processor Reserved
(rev 02)
ff:02.3 Host bridge: Intel Corporation 1st Generation Core Processor Reserved
(rev 02)

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