[ltp] Re: Blanking out when driving QHD 2560x1440 cheap panels with the displayport

James Macpherson linux-thinkpad@linux-thinkpad.org
Fri, 07 Mar 2014 10:32:50 +1100

Hi Ruben,

I've been using my X220 for well over a year with the same resolution
(2560x1440) Dell screen, using what was a cheap (but annoyingly short)
displayport cable.  I have this next to a rotated 1680x1050 Dell panel
driven from the VGA port, so I'd suggest the hardware itself is more
than capable enough.  Neither panel is laggy (I can fullscreen video on
either).  Plugging both cables in disables the inbuilt Lenovo screen. 
Audio even works over the displayport and headphone socket in the monitor.

I'm currently on Ubuntu 13.04 (3.8.0-35-generic), and the only thing
that's non-standard from a Ubuntu perspective is that I run the Gnome
shell on GDM from the gnome-team PPA, rather than the default
unity/lightdm thing that came with.

DP1 connected 2560x1440+0+0 (normal left inverted right x axis y axis)
597mm x 336mm
VGA1 connected 1050x1680+2560+0 left (normal left inverted right x axis
y axis) 434mm x 270mm

I didn't have to do anything special to get it all working, so I don't
have any handy tips but I'm happy to check version numbers on drivers,
hardware etc. if it's useful to you.  Let me know!

One of the links you posted was about driving two such panels from a
dock with multiple displayport outputs, which is a lot more pixels than
you're looking at, so I'd disregard that.  The arch linux post though
talked about using a different driver, the version I have is:

Seems to me like the panel is doing something slightly nonstandard that
your windows driver doesn't care about but is tripping something in the
linux driver if the Intel/Lenovo hardware's clearly up to driving it.



On 07/03/14 05:45, Rubin Abdi wrote:
> Rubin Abdi wrote, On 2014-03-06 10:43:
>> Through the suggestion of this thread...
>> https://bbs.archlinux.org/viewtopic.php?id=175868
>> ...I've stuck xorg into UXA mode. That's slightly helped as it takes
>> slightly longer before the display craps about, but by a minute or two.
>> Other than that thread and attached bug I really haven't seen any other
>> references of folks having this problem.
> I take that back, there's also this thread...
> https://01.org/linuxgraphics/node/161