Revert "drm/i915: Fix DP-MST crtc_mask"
authorVille Syrjälä <ville.syrjala@linux.intel.com>
Tue, 3 Sep 2019 15:40:18 +0000 (18:40 +0300)
committerVille Syrjälä <ville.syrjala@linux.intel.com>
Wed, 4 Sep 2019 15:46:40 +0000 (18:46 +0300)
commite838bfa8e170415fa3cc8e83ecb171e809c0c422
tree38f3a7b9ddcd05355d74084ea249b6210ee9099a
parent9d7b01e93526efe79dbf75b69cc5972b5a4f7b37
Revert "drm/i915: Fix DP-MST crtc_mask"

This reverts commit 4eaceea3a00f8e936a7f48dcd0c975a57f88930f.

Several userspace clients (modesetting ddx and mutter+wayland at least)
handle encoder.possible_crtcs incorrectly. What they essentially do is
the following:

possible_crtcs = ~0;
for_each_possible_encoder(connector)
possible_crtcs &= encoder->possible_crtcs;

Ie. they calculate the intersection of the possible_crtcs
for the connector when they really should be calculating the
union instead.

In our case each MST encoder now has just one unique bit set,
and so the intersection is always zero. The end result is that
MST connectors can't be lit up because no crtc can be found to
drive them.

I've submitted a fix for the modesetting ddx [1], and complained
on #wayland about mutter, so hopefully the situation will improve
in the future. In the meantime we have regression, and so must go
back to the old way of misconfiguring possible_crtcs in the kernel.

[1] https://gitlab.freedesktop.org/xorg/xserver/merge_requests/277

Cc: Jonas Ådahl <jadahl@gmail.com>
Cc: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=111507
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190903154018.26357-1-ville.syrjala@linux.intel.com
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
drivers/gpu/drm/i915/display/intel_dp_mst.c