Chrome OS Version: 54.0.2822.0
Chrome OS Platform: 8682.0.0.0
Firmware Google_Lulu.6301.136.57


Steps To Reproduce:
(1)Plug in UDL device or DisplayLink USB3 device
(2)Change Display setting to mirror

Expected Result:
UDL or DisplayLink USB3 device is mirroring laptop builtin screen.

Actual Result:
Only mouse cursor is visible on builtin screen. Sometimes builtin screen is freezing and only mouse is working. External udl or DisplayLink USB3 displays are black.
To recover from this it is necessary to unplug udl/evdi device.

How frequently does this problem reproduce? Always

What is the impact to the user, and is there a workaround? If so, what is
it?
No workaround. Displays are black.


Please provide any additional information below. Attach a screen shot or
log if possible.

In dmesg log I see following errors for UDL device:
[  105.195958] [drm:udl_cursor_set] *ERROR* we currently only support 64x64 cursors
[  105.195981] [drm:udl_crtc_cursor_set] *ERROR* Failed to set UDL cursor
or for DisplayLink USB3 device:
[  560.559659] [drm:evdi_cursor_set] *ERROR* we currently only support 64x64 cursors
[  560.559675] evdi: [D] evdi_crtc_cursor_set:223 evdi_crtc_cursor_set unlock
[  560.559690] [drm:evdi_crtc_cursor_set] *ERROR* Failed to set evdi cursor


I have investigated this a bit and unsupported size which desktop tries to set is 256x256. I have modified udl source code to support it as it just matter of buffer change. But it didn't helped. udl_cursor_set operation failed on drm_gem_object_lookup call. It somehow connected with cursor, but not only. I have removed cursor support from the driver and usb display was still black. No errors visible.

It is not regression. 
I believe that I have this issue also on R52 version.

I have tested other mirror scenarios and apart from this case mirror mode is working in different configurations like:
1. Laptop built-in screen closed and mirroring two DisplayLink USB3 devices
2. Laptop built-in screen closed and mirroring external screen connected via udl and DisplayLink USB3 device. One screen is using udl kernel module, and second one is using evdi module.
3. Laptop built-in screen closed. 
   External native monitor is connected via HDMI.
   DisplayLink USB3 device is connected.
   Mirror mode works on both od them.


In the attached file there are drm debug logs gathered during issue reproduction.


 

Deleted: dmesg_chromeos 2.6 MB

dmesg_chromeos 2.6 MB View Download