On Tue, Sep 02, 2014 at 02:15:39PM +1000, Dave Airlie wrote:
On 2 September 2014 14:05, Theodore Ts'o tytso@mit.edu wrote:
I recently upgraded to v3.17-rc3, and on my Lenovo T540p, I can no longer see the my Dell 30" monitor when it is connected via the docking station using a Displayport connector. This worked using 3.16 kernel.
If I connect to the monitor using the mini-display, by passing the docking station, things work fine (but of course it's annoying not to be able to use the docking station).
Is this a known problem? This is not the first time that we've had regressions with this docking station. It's vaguely reminsicent of
https://bugs.freedesktop.org/show_bug.cgi?id=71267Except the system isn't hanging; it's just not seeing the monitor at all.
Have you the Dell 30" set to Displayport 1.2 enabled mode?
No, it DP 1.2 was disabled. If I enable it, it breaks things when I try connecting via the MiniDP port (bypassing the dock), and it is still broken when I try to talk via the DisplayPort in the dock.
If I disable DP 1.2 again, it works via the MiniDP port, but if I try to connect through the dock (which has a DP Hub which I believe is MST/DP 1.2 capable), it is still broken.
It does seem that this might be related to 3.17-rc3 trying to talk DP 1.2 if it is available, since I can't control what the DP hub in the docking station advertises --- is there a commit or some kind of hack I can try to force talking to the DP hub using DP 1.1?
- Ted