At Mon, 17 Sep 2012 18:21:47 +1000, Dave Airlie wrote: > > 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. The problem is that you have no DP output there in reality. So, when you plug the docking station, GNOME sets up the screen with a bogus DP output, either in an extended mode with a non-existing screen or a clone mode with a wrong low resolution. > Though you'd have to decode the DPCD to see what it is. Hmm, but isn't it the check of EDID existence enough? Checking DPCD bits might work, but I have no exact spec of DPCD, so no idea whether the above is really wrong or not. thanks, Takashi
