[ltp] DisplayPort on the T500

[Frank Myhr]

Hi Mircea,

Unfortunately, it seems that Linux users of ThinkPads with switchable
graphics are between a rock and hard place when it comes to digital
video output (DVI or DisplayPort):


Alex Deucher wrote:
> On Tue, Sep 1, 2009 at 3:49 AM, Mircea
> Gherzan<mgherzan@anaconda.cs.pub.ro> wrote:
>> Hello,
>>
>> Did anyone manage to get the DisplayPort output working? The T500
>> (2082-6PG) sports the following ("switchable graphics"):
> You might try a newer intel driver.  DP should be working.

I don't think the Intel GPU is even connected to the digital video
outputs on switchable GPU models:

According to:
http://www-307.ibm.com/pc/support/site.wss/document.do?lndocid=MIGR-70495#e2

'DVI and DisplayPort digital graphics output ports are not supported in
"Energy Savings" mode.
This is the expected behavior of the Switchable Graphics architecture.
The discrete graphics adapter must be active to use a digital graphics
output port.'


>> With the Radeon (driver 1.2.5-1 from Debian Sid and "Discrete
>> graphics" in the BIOS) I get "DVI-D_1 disconnected" in xrandr.
> 
> radeonhd does not support displayport yet.  The radeon driver has
> experimental support on the displayport branch of git:
> http://cgit.freedesktop.org/xorg/driver/xf86-video-ati/log/?h=displayport
> However, it's not working 100% yet.

Looks like further development of radeonhd is your only hope for using
DisplayPort on your T500 with switchable graphics.


Best regards,
Frank