Comment 0 for bug 1763271

[Impact]
The display becomes black after S3 with the following error messages.

dmesg:
[ 60.546305] [drm:intel_dp_start_link_train [i915]] Link Training failed at link rate = 540000, lane count = 4

Xorg.0.log:
[ 60.748] (EE) modeset(0): failed to set mode: Invalid argument
[ 60.748] (WW) modeset(0): hotplug event: connector 48's link-state is BAD, tried resetting the current mode. You may be left with a black screen if this fails...

[Fix]
Looks like link training fallback fails sometimes with eDP, we need this commit to fix the issue.

commit a306343bcd7df89d9d45a601929e26866e7b7a81 (refs/bisect/bad)
Author: Manasi Navare <email address hidden>
Date: Thu Oct 12 12:13:38 2017 -0700

    drm/i915/edp: Do not do link training fallback or prune modes on EDP

[Regression Potential]
Should be low.
To avoid conflicts, we introduce 4 commits, I'll try explaining them below
fbe0967 drm/i915/edp: Do not do link training fallback or prune modes on EDP
   This is the fix commit and the behavior only changes when DP is eDP, it does nothing if DP is eDP. Should be fine to not do link training fallback and not emit Hotplug Uevent to userspace to start modeset, since its eDP.

b25b806 drm/i915/edp: Allow alternate fixed mode for eDP if available.
   Change the prototype of function "intel_panel_init()" and adding one extra argument, should have small impact on the display.

bf389c7 drm/i915/dp: make is_edp non-static and rename to intel_dp_is_edp
6199c65 drm/i915/dp: rename intel_dp_is_edp to intel_dp_is_port_edp