Created attachment 111358 [details]
error message when unplugging VGA cable in 3.13.0-38 kernel

The difference with -34 is that in -34 there are two FIFO underrun errors with Pipe B and Pipe A in `drm:gen8_irq_handler`, which doesn't exist in -38.

Created attachment 111502 [details]
error message when unplugging VGA cable in 3.13.0-34 kernel

Same contents. Only edit out host information.

*** Bug 88590 has been marked as a duplicate of this bug. ***

We seem to have neglected this bug. Apologies.

Is this still an issue with latest kernels?

Bug scrub:
Assigned to Christophe, to confirm if reproduced or not with fresh setup.

Hi Phidias Chiang(In reply to Phidias Chiang from comment #0)
> Created attachment 111357 [details]
> error message when unplugging VGA cable in 3.13.0-34 kernel
> 
> [Summary]
> Hot unplug VGA EFP from docking then plug in, find EFP cannot be detected
> any more.
> 
> [Steps]
> 1. Boot up the system with docking
> 2. Plug the VGA port
> 3. Fn+F4 to trigger the external monitor display
> 4. Unplug the VGA port and replug again
> 5. Check the external monitor
> 
> [Expected results]
> 1. External monitor still can display.
> 
> [Actual results]
> 1. External monitor can't display.
> 
> [linux-3.13.0-34-generic]
> After unplugging VGA and replugging back, system is blocked
> when executing `cat /sys/class/drm/card0-DP-2/status`.
> Test with Fn+F4 or running `xrandr` at the moment system hangs.
> 
> [linux-3.13.0-38]
> After detaching DP and connection VGA,
> it probes and outputs to external monitor correctly,
> but if unplug VGA and replug again it failed
> (disconnected in /sys/class/drm/card0-DP-2/status)

Hi Phidias Chiang :

I've check this issue with the following platform with latest drm-intel-nightly and drm-intel-testing kernels with a miniDP to VGA dongle (because BDW-U nuc doest has VGA port) follow your exacts steps and i couldn't find the issue, so could you provide a full dmesg (adding this to your grub initcall_debug drm.debug=0xe) and xrandr output for both cases where you plug and unplug the VGA please as well the kernel version (uname -r) ?


Hardware Configuration : BDW-U Nuc
----------------------------------
CPU : Intel(R) Core(TM) i7-5557U CPU @ 3.10GHz
GPU : Intel Corporation Broadwell-U Integrated Graphics
Memory ram : 8 GB
Dongle : miniDP to VGA (StarTech E328232)

Software Configuration :
---------------------------------
Ubuntu 14.04.03 x86_64
Xserver : 1.17.4  (commit : 2c7fa2a)
libdrm : 2.4.65 (commit :c349616)
Xf86-video-intel : 2.99.917 (commit : baec802)
Mesa : 11.0.4 (commit : 31bf247)
Libva : 1.6.1 (commit : 613eb96)
Intel-driver : 1.6.1 (commit : 35858c6)
Cairo : 1.14.4 (commit : 0317ee7)
BIOS : 5.6


Kernel : latest drm-intel-testing (4.3.0-rc6-testing)
commit 87074657f22e38163e712ca417e1a398d00096b6
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Fri Oct 23 11:56:52 2015 +0200

Kernel : latest drm-intel-nightly: 2015y-11m-06d-12h-48m-02s UTC integration manifest
commit a3b0dec82fdb59c629c4fb9847245b80b0cf69dd
Author: Jani Nikula <jani.nikula@intel.com>
Date:   Fri Nov 6 14:48:23 2015 +0200

Additional notes : 
plug / unplug miniDP to VGA dongle (10 times) and the issue isn't present

Hi Phidias,
We don't have your Laptop, docking station and screen and are not able to reproduce your problem, this bug could be specific to your environment.

Another possibility for you is to update your kernel to a fresh one from this tree: http://cgit.freedesktop.org/drm-intel/, it could solve your problem.
To install the kernel:
git clone git://anongit.freedesktop.org/drm-intel
cd drm-intel
cp /boot/config* .config
make
make modules
sudo make modules_install
sudo make install

I close the bug. Feel free to re-open it if needed. If you re-open it, some logs could be useful for investigation, please follow this guide: https://01.org/linuxgraphics/documentation/how-report-bugs

So closed