Nouveau - Dec 2017 - [Bug 104344] New: Display Adapter Chain, Cable Disconnect causes Nouveau crash

https://bugs.freedesktop.org/show_bug.cgi?id=104344

            Bug ID: 104344
           Summary: Display Adapter Chain, Cable Disconnect causes Nouveau
                    crash
           Product: xorg
           Version: unspecified
          Hardware: x86-64 (AMD64)
                OS: Linux (All)
            Status: NEW
          Severity: normal
          Priority: medium
         Component: Driver/nouveau
          Assignee: nouveau at lists.freedesktop.org
          Reporter: mbazzinotti at gmail.com
        QA Contact: xorg-team at lists.x.org

Created attachment 136308
  --> https://bugs.freedesktop.org/attachment.cgi?id=136308&action=edit
collation of syslog grep'd for "nouveau|drm"; includes trace.
there was no
pertinent log info right before the trace occurred.

While experimenting with physical connections to avert Flicker Bug 88272
(https://bugs.freedesktop.org/show_bug.cgi?id=88272)

I found myself using a mini DisplayPort(mDP) adapter which has 3 outputs
(HDMI, DVI, and DP), with its DP output connected to a second DP->DVI
adapter.

Let's call the first adapter A, and the 2nd adapter B. The connections are:


-------  mDP  ---  DP  --- DVI --------- 
Laptop |-----| A |----| B |---| Monitor |
-------       ---      ---     ---------


While connected, display appeared "normal" as per Bug 88272 screen
flicker.
When
I unplugged the DVI cable from adapter B, this trace appeared in the dmesg
attachment. Dmesg Output before the trace was not relevant. This issue can be
reproduced again and again by reconnecting and disconnecting the cable.

This does not crash X. The desktop appears to run just fine, even during the
nouveau crash IIRC. If I was not watching dmesg, I may not have even noticed.

The problem does not happen if unplugging the root adapter from the laptop. I
have not tried unplugging the 2nd adapter to see what happens in that case.

Note: When adapter A is plugged via DVI to monitor directly, unplugging the DVI
cable does not cause a crash; no call stack is outputted to dmesg in this case.

---------
Hardware |
---------
Macbook Pro 5,4 15" mid-2009
Nvidia GeForce 9400m
mini DisplayPort -> "Gigaware" DVI/HDMI/Displayport adapter ->
HP DP>DVI
adapter
Dell LCD Monitor model E2011Hc

--------
Software|
--------
Gentoo Linux 4.12.12. 
x11-base/xorg-server-1.19.5
x11-drivers/xf86-video-nouveau-1.0.15
i3wm
No compositor

kernel command line: ro root=PARTUUID=xxxxxxxx net.ifnames=0

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https://bugs.freedesktop.org/show_bug.cgi?id=104344

mbazzinotti at gmail.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|Display Adapter Chain,      |Display Adapter Chain,
                   |Cable Disconnect causes     |Cable Disconnect causes
                   |Nouveau crash               |Nouveau trace

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https://bugs.freedesktop.org/show_bug.cgi?id=104344

--- Comment #1 from mbazzinotti at gmail.com ---
Ah, it was not a crash! it was the WARN_ON.

I got some more info on what produced the warning
drivers/gpu/drm/nouveau/include/nvkm/subdev/i2c.h:169

inside nvkm_rdaux()
WARN_ON(!ret && size != xfer);

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https://bugs.freedesktop.org/show_bug.cgi?id=104344

Martin Peres <martin.peres at free.fr> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |MOVED

--- Comment #2 from Martin Peres <martin.peres at free.fr> ---
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This bug has been migrated to freedesktop.org's GitLab instance and has been
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https://gitlab.freedesktop.org/xorg/driver/xf86-video-nouveau/issues/392.

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