commit b67d049c870c2b82c2883b0c10a07bc29c4cd598
author Neil Armstrong <narmstrong@baylibre.com> Thu Jun 20 09:00:21 2019 +0000
committer Neil Armstrong <narmstrong@baylibre.com> Fri Jun 21 07:17:06 2019 +0000
tree 1cb0077617acc634bfc9866833227247c4e30178
parent 27cd4805010184f0e9faf712dd0980e8700c26b9

drm_hwcomposer: pre-filter modes provided to HWC2

Currently LocalDisplayAdapter in AOSP filters out similar modes based
on their currently limited supported attributes: width/height/refresh.

This leads to a situation where important modes are discarded, like the
preferred mode and/or the active mode, leading SurfaceFlinger to select
an unwanted and potentially invalid  mode in the list provided by
drm-hwcomposer to HWC2.

Let's pre-filter the modes provided to HWC2 by :
- systematically adding the preferred mode
- systematically adding the current active mode, if different
  from preferred mode
- keeping the interlaced modes filtering-out if no other non-interlace
  modes with same widthXheight exists (for HD-Ready 1080i TVs or CVBS)
- discarding modes if a similar mode with same widthXheight@refresh was
  already selected for HWC2

This mimics the behavior of LocalDisplayAdapter filtering algorithm,
but keeps the important modes from the DRM Point Of View and drops the
duplicate modes while keeping the mode ordering from DRM in account.

This local filtering should ultimately go out when HWC2 can actually
handle mode Attributes to describe Preferred mode, Interlaced, 3D...
and LocalDisplayAdapter uses these Attributes for filtering duplicate
modes.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Tested-by: John Stultz <john.stultz@linaro.org>