[Bug 88590] [hsw ult dp-to-vga] embedded DP-to-VGA output only works once

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=88590

Lucas Nussbaum <lucas at lucas-nussbaum.net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEEDINFO                    |NEW

--- Comment #9 from Lucas Nussbaum <lucas at lucas-nussbaum.net> ---
(In reply to Jani Nikula from comment #8)
> Please try v3.19-rc1 or later, or try cherry-picking
> 
> commit 19a93f042fc241ecdf98543cedfe7c171f8cdf53
> Author: Dave Airlie <airlied at redhat.com>
> Date:   Wed Nov 26 13:13:09 2014 +1000
> 
>     drm/dp: retry AUX transactions 32 times (v1.1)
> 
> to v3.18. The above commit is marked cc: stable, so it should eventually get
> backported to stable kernels. It should give the DP downstream a little more
> slack in responding; the legacy analog things may need that.

Hi,

I tried with 3.19.0-rc5, and the problem still occurs. I'm adding the dmesg
output with drm.debug=0x06

Some more information:
There are two Ubuntu bug reports where users complain about the same problem
(or at least some of the
posters do -- others are commenting about seemingly unrelated issues)
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1300914
https://bugs.launchpad.net/ubuntu/+source/libdrm/+bug/1411552

Comment 13 describes exactly the behaviour I'm seeing:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1300914/comments/13

Changing window manager (from GNOME to OpenBox) changes the behaviour:
- with OpenBox, switching to a TTY and then switching back to X "fixes"
  the problem.
- with GNOME, it does not.

However, I confirm that suspending/resuming "fixes" the problem (even with 
GNOME).

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