[Bug 111507] Unable to detect monitor modes connected to a TB16 Dell dock

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=111507

--- Comment #31 from Stanislav Lisovskiy <stanislav.lisovskiy at intel.com> ---
I think I have found something interesting. For DP-1 connector ocassionally
despite received hotplug event intel_dp_detect function seems to exit
prematurely. 

Like normally it should look like this:

[ 1244.458373] [drm:intel_dp_detect [i915]] [CONNECTOR:100:DP-1]
[ 1244.459728] [drm:intel_dp_read_dpcd [i915]] DPCD: 12 14 c4 00 00 05 01 83 02
00 00 00 00 00 02
[ 1244.461024] [drm:drm_dp_read_desc [drm_kms_helper]] DP branch: OUI 90-cc-24
dev-ID SYNA30 HW-rev 1.0 SW-rev 3.10 quirks 0x0000
[ 1244.463838] [drm:intel_dp_print_rates [i915]] source rates: 162000, 216000,
270000, 324000, 432000, 540000
[ 1244.463858] [drm:intel_dp_print_rates [i915]] sink rates: 162000, 270000,
540000
[ 1244.463875] [drm:intel_dp_print_rates [i915]] common rates: 162000, 270000,
540000
[ 1244.465111] [drm:intel_dp_detect [i915]] MST support? port C: yes, sink:
yes, modparam: yes

However in the log "dmesg with drm.debug=0x1e when plugging the dock usb type-c
cable a single time" the last hotplug event for DP-1 looks like this:

[ 1245.482006] [drm:i915_hotplug_work_func [i915]] Connector DP-1 (pin 5)
received hotplug event.
[ 1245.482093] [drm:intel_dp_detect [i915]] [CONNECTOR:92:DP-1]

So not even showing sink rates means that it was determined as disconnected and
intel_dp_read_dpcd probably failed.
However this port was already disconnected before in the log:

[ 1244.181015] [drm:i915_hotplug_work_func [i915]] running encoder hotplug
functions
[ 1244.181148] [drm:i915_hotplug_work_func [i915]] Connector DP-1 (pin 5)
received hotplug event.
[ 1244.181272] [drm:intel_dp_detect [i915]] [CONNECTOR:92:DP-1]
[ 1244.181769] [drm:intel_dp_detect [i915]] MST device may have disappeared 1
vs 1
[ 1244.181983] [drm:intel_power_well_enable [i915]] enabling DC off
[ 1244.182402] [drm:gen9_set_dc_state [i915]] Setting DC state from 02 to 00
[ 1244.182951] [drm:intel_power_well_enable [i915]] enabling power well 2
[ 1244.191512] [drm:intel_dp_aux_xfer [i915]] dp_aux_ch timeout status
0x7d4003ff
 ...
[ 1244.445543] [drm:intel_dp_aux_xfer [i915]] dp_aux_ch timeout status
0x7d4003ff
[ 1244.454008] [drm:intel_dp_aux_xfer [i915]] dp_aux_ch timeout status
0x7d4003ff
[ 1244.454017] [drm:drm_dp_dpcd_access [drm_kms_helper]] Too many retries,
giving up. First error: -110

Which makes this all look a little suspicious.

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