[Bug 104054] [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

--- Comment #39 from Jérôme de Bretagne <jerome.debretagne at gmail.com> ---
As requested, Rodrigo and Lakshmi, here is the scenario I've run through for
the updated logs I've just shared. I've let the laptop boot without the HP Lap
Dock plugged at first, I've logged into my Gnome session and only then I've
plugged this external display to DP-1.

In terms of time stamps, I've taken a video with a timer started close to the
initial boot (right after grub) to better measure. Here are the main events:

1/ the HP Lap Dock is plugged at around 26-27s

I think visible in the logs at:
[   26.577340] [drm:gen8_de_irq_handler [i915]] hotplug event received, stat
0x00200000, dig 0x10101012, pins 0x00000020
[   26.577402] [drm:intel_hpd_irq_handler [i915]] digital hpd port B - long
[   26.577457] [drm:intel_hpd_irq_handler [i915]] Received HPD interrupt on PIN
5 - cnt: 0
[   26.577586] [drm:intel_dp_hpd_pulse [i915]] got hpd irq on port B - long
[   26.577661] [drm:i915_hotplug_work_func [i915]] running encoder hotplug
functions
[   26.577721] [drm:i915_hotplug_work_func [i915]] Connector DP-1 (pin 5)
received hotplug event.
[   26.577777] [drm:intel_dp_detect [i915]] [CONNECTOR:78:DP-1]

and for the USB side of things right after at:
[   27.229828] usb 3-1.4: New USB device found, idVendor=03f0, idProduct=0c56,
bcdDevice= 0.00
[   27.229837] usb 3-1.4: New USB device strings: Mfr=1, Product=2,
SerialNumber=0
[   27.229842] usb 3-1.4: Product: HP Elite x3 Lap Dock


2/ the HP Lap Doc reboots at around 44-45s, so after 18s being plugged in, so
displaying the HP boot logo.

In the logs, I believe it is around:
[   45.472235] [drm:i915_hotplug_work_func [i915]] Connector DP-1 (pin 5)
received hotplug event.
[   45.472263] [drm:intel_dp_detect [i915]] [CONNECTOR:78:DP-1]
[   45.472299] [drm:intel_encoder_hotplug [i915]] [CONNECTOR:78:DP-1] status
updated from connected to disconnected

Surprisingly, the USB events are  visible even earlier:
[   40.013014] usb 3-1.4: New USB device found, idVendor=03f0, idProduct=0c56,
bcdDevice= 0.00
[   40.013017] usb 3-1.4: New USB device strings: Mfr=1, Product=2,
SerialNumber=0
[   40.013018] usb 3-1.4: Product: HP Elite x3 Lap Dock


3/ It takes a few seconds for the display to restart, showing the screen
offering either wireless or wired connectivity at around 54s, and the screen
goes black when trying to connect over USB Type-C at 56s.

However, in the logs, I can see events much earlier right after the reboots,
such as:

[   47.050905] [drm:i915_hotplug_work_func [i915]] Connector DP-1 (pin 5)
received hotplug event.
[   47.050930] [drm:intel_dp_detect [i915]] [CONNECTOR:78:DP-1]
[   47.050952] [drm:intel_power_well_enable [i915]] enabling power well 2
[   47.053624] [drm:intel_dp_read_dpcd [i915]] DPCD: 12 14 81 01 21 11 01 80 00
00 04 00 00 00 02
[   47.057861] [drm:intel_dp_print_rates [i915]] source rates: 162000, 216000,
270000, 324000, 432000, 540000
[   47.057883] [drm:intel_dp_print_rates [i915]] sink rates: 162000, 270000,
540000
[   47.057902] [drm:intel_dp_print_rates [i915]] common rates: 162000, 270000,
540000


4/ Finally, I get a second reboot at 1min12s / 1min13s with the HP boot logo
being displayed again, at which time I unplug the USB Type-C cable from the
laptop to end the loop.


I hope this gives you enough input to better analyze what could be going wrong
from these logs.

Thanks, Jérôme

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