[Bug 104054] New: [SKL][DP] HP Lap Dock external display with DisplayPort over USB Type-C input not properly detected

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=104054

            Bug ID: 104054
           Summary: [SKL][DP] HP Lap Dock external display with
                    DisplayPort over USB Type-C input not properly
                    detected
           Product: DRI
           Version: unspecified
          Hardware: Other
                OS: All
            Status: NEW
          Severity: normal
          Priority: medium
         Component: DRM/Intel
          Assignee: intel-gfx-bugs at lists.freedesktop.org
          Reporter: jerome.debretagne at gmail.com
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

-- chipset: Intel HD Graphics 515 (GT2)
-- system architecture: x86_64
-- xserver-xorg-video-intel: 2:2.99.917+git20161206-1
-- xserver-xorg-core: 2:1.19.2-1+deb9u2
-- libdrm-intel1 2.4.74-1
-- kernel version: drm-intel-next-2017-12-01 (commit:
d65efe7c951371fbad2c426b59bbac8bf2e60662)
-- Linux distribution: Debian 9.1 Stretch
-- Machine: Dell Latitude 7275 with an Intel Skylake Core M7-6Y75
-- Display connector: DisplayPort over USB Type-C


When plugging an HP Lap Dock as an external display to my Intel Skylake laptop,
this monitor isn't properly detected and configured to its native 1920x1080
resolution. In fact, the external display ends up rebooting after just a few
seconds; upon a quick reboot, the setup is tried again, triggering another
reboot, etc. in a never-ending loop... This is always reproducible.

It's a bit tricky but it is possible to set it up manually to the minimum
exposed 640x480 resolution at least, by executing an xrandr command at the
right time, just before the displays reboots.

$ xrandr --output DP-1 --mode 640x480
DP-1 connected 640x480+1280+0 (normal left inverted right x axis y axis) 160mm
x 90mm
   1920x1080     60.00 +  59.94
   720x576       50.00
   720x480       60.00    59.94
   640x480       60.00*   59.94

None of the 3 other resolutions exposed by xrandr are working at all when tried
manually, but using 640x480 is stable, allowing to test other configurations.

I'm trying to use this display connected to a Dell Latitude 7275 with an Intel
Core M7-6Y75 /  Intel HD Graphics 515 (GT2). I've been able to check that this
HP Lap Dock can run properly at its native resolution when plugged to other
devices such as phones (LG G5, Microsoft Lumia 950) to rule out issues with the
hardware itself or the connectivity (as I'm using the same USB Type-C to USB
Type-C cable in all cases).

Thanks to randr, I was able to get the EDID info, attached for reference and to
create the corresponding edid.bin file to run parse-edid on it. However, trying
to create corresponding Modelines with xrandr for the 1920x1080 resolution
manually didn't help either.

I'm attaching my dmesg output and Xorg.0.log using a kernel built based on the
very recent drm-intel-next-2017-12-01 tag and with drm.debug=0x06. Let me know
if other inputs would be useful to investigate this issue. Thanks.


P.S. I don't know if that makes a difference but I should mention that this HP
Lap Dock display is somehow unusual, as it only has one DisplayPort over USB
Type-C input. Since there are very few adapters/docks with DisplayPort over USB
Type-C video output, this limits the testing mainly to devices with such USB-C
video ports built-in.

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