[Intel-gfx] Valid DP connection without EDID?

[Dave Airlie]

On Mon, Sep 17, 2012 at 6:16 PM, Takashi Iwai <tiwai at suse.de> wrote:
> Hi Adam,
>
> At Fri, 14 Sep 2012 11:25:03 -0400,
> Adam Jackson wrote:
>>
>> On 9/14/12 10:19 AM, Takashi Iwai wrote:
>> > Hi,
>> >
>> > we've got a machine showing a ghost DP2 output on a docking station.
>> > The docking station has only one DP port and it's connected to DP1.
>> > As a result, we get an DP2 active output containing the bogus VESA
>> > standard modes 1024x768, 800x600, 640x480 although it's not connected
>> > at all.
>> >
>> > Looking a bit deeply on it, it seems that the connector gives actually
>> > the valid DPCD.  So intel_dp_detect() returns
>> > connector_status_connected.  But since there is no real connection,
>> > EDID isn't obtained.  Thus of course no valid modes set.
>>
>> Can you be more specific here?  What DPCD does it return?
>
> It shows "DPCD: 110a820100030181"

I don't see how it can be a floating port if something is answering
DPCD, or how it could be a hardware problem. Like it doesn't seem
likely they terminated the port with a special DP chip.

Though you'd have to decode the DPCD to see what it is.

Dave.