[Bug 95141] [BYT] Displayport signals stay on after monitor is unplugged

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=95141

XiongZhang <xiong.y.zhang at intel.com> changed:

           What    |Removed                     |Added
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                 CC|                            |xiong.y.zhang at intel.com

--- Comment #4 from XiongZhang <xiong.y.zhang at intel.com> ---
Created attachment 123288
  --> https://bugs.freedesktop.org/attachment.cgi?id=123288&action=edit
4530.displayport.bmp-344x509.jpg

So on the 4.2 drm/i915 that the laramie image is using, it is getting 50-70mv
on most pins (except 3.29v on HPD) on boot, then it is clear the lines stay on
after hooking up a dp monitor and unplugging it. I'm using the attached diagram
to know which pin is which.

One thing I noticed is ML_Lane3 is off when its never been plugged in but it
stays on also after plugging in and unplugging also.

some examples on 4.2:

on boot
50mv-70 on pin 1
50mv-70 on pin 3
0 on on pin 5
20mv on on pin 7
70mv on on pin 9
0 on pin 12
120 on pin 15
3.29v on 18 (HPD)

after plugging and unplugging a dp monitor
240mv on pin 1
130mv on pin 3
230mv on pin 4
220mv on pin 6
40mv on pin 7
130mv on pin 9
120mv on pin 10
214mv on pin 12
3.29V on pin 18 (HPD)

On the Xenial stock 4.4 kernel the lines are powered up all of the time after
boot and have similar values to the above post unplugging values. The same is
true on 20160426 drm-intel-nightly. The eDP internal monitor does not work on
that drm-intel-nightly but the DP still works and it is obvious the ports are
powered on all of the time. I tried with an ivybridge system and the lines are
powered all of the time there too on a 4.4 kernel.

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