[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

Manasi <manasi.d.navare at intel.com> changed:

           What    |Removed                     |Added
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                 CC|                            |manasi.d.navare at intel.com

--- Comment #7 from Manasi <manasi.d.navare at intel.com> ---
In order to reproduce the bug, I did some PHY testing here on my system with
drm-intel-nightly (kernel 4.6.0-rc4). I hooked up the HPD and data lines to 
the oscilloscope to see the signal levels after the DP monitor is disconnected.
And I saw that signal levels were as low as -1mv after the DP monitor is
disconnected. Also the HPD signal is 0V DC on the DP disconnect. So I am not
able to reproduce the issue that you are seeing.
For me to root cause this bug, I would need the following information from you:
- Could you also hook up the data signals to the oscilloscope and verify if
there is any signal on those lines after the DP monitor is disconnected.
- From the data you provided, it is strange that the HPD signal is 3.29V on 
boot. Was this system booted with DP connected? How did you measure this
electrical signal level? 
- If the DP is not connected on boot and you plug it in later, does the DP
monitor display it properly and it works?
- Could you send separate dmesg logs for :
     Boot without DP connected
     Then dmesg -c to clear dmesg
     Plug in DP cable and collect logs
     dmesg -c
     Unplug and collect logs
- Please send the picture of the motherboard to see the connections of the HPD
pin on the motherboard. Also send us the schematics of the same if you have.

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