drm/tegra: dp: Add DisplayPort link training helper

Add a helper that will perform link training as described in the
DisplayPort specification.

Signed-off-by: Thierry Reding <treding@nvidia.com>

drm/tegra: dp: Add support for eDP link rates

Parses additional link rates from DPCD if the sink supports eDP 1.4.

Signed-off-by: Thierry Reding <treding@nvidia.com>

drm/tegra: dp: Add drm_dp_link_choose() helper

This helper chooses an appropriate configuration, according to the
bitrate requirements of the video mode and the capabilities of the
DisplayPort sink.

Signed-off-by: Thierry Reding <treding@nvidia.com>

drm/tegra: dp: Read AUX read interval from DPCD

Store the AUX read interval from DPCD, so that it can be used to wait
for the durations given in the specification during link training.

Signed-off-by: Thierry Reding <treding@nvidia.com>

drm/tegra: dp: Read eDP version from DPCD

If the sink supports eDP, read the eDP revision from it's DPCD.

Signed-off-by: Thierry Reding <treding@nvidia.com>

drm/tegra: dp: Read alternate scrambler reset capability from sink

Parse from the sink capabilities whether or not the eDP alternate
scrambler reset value of 0xfffe is supported.

Signed-off-by: Thierry Reding <treding@nvidia.com>

drm/tegra: dp: Read channel coding capability from sink

Parse from the sink capabilities whether or not it supports ANSI 8B/10B
channel coding as specified in ANSI X3.230-1994, clause 11.

Signed-off-by: Thierry Reding <treding@nvidia.com>

drm/tegra: dp: Read TPS3 capability from sink

The TPS3 capability can be exposed by DP 1.2 and later sinks if they
support the alternative training pattern for channel equalization.

Signed-off-by: Thierry Reding <treding@nvidia.com>

drm/tegra: dp: Read fast training capability from link

While probing the DisplayPort link, query the fast training capability.
If supported, drivers can use the fast link training sequence instead of
the more involved full link training sequence.

Signed-off-by: Thierry Reding <treding@nvidia.com>

drm/tegra: dp: Turn link capabilities into booleans

Rather than storing capabilities as flags in an integer, use a separate
boolean per capability. This simplifies the code that checks for these
capabilities.

Signed-off-by: Thierry Reding <treding@nvidia.com>

drm/tegra: dp: Track link capabilities alongside settings

Store capabilities in max_* fields and add separate fields for the
currently selected settings.

Signed-off-by: Thierry Reding <treding@nvidia.com>

drm/tegra: Add missing kerneldoc for struct drm_dp_link

The drm_dp_link structure tracks capabilities on the DP link. Add some
kerneldoc to explain what each of its fields means.

Signed-off-by: Thierry Reding <treding@nvidia.com>

drm/tegra: Move drm_dp_link helpers to Tegra DRM

During the discussion of patches that enhance the drm_dp_link helpers it
was concluded that these helpers aren't very useful to begin with. After
all other drivers have been converted not to use these helpers anymore,
move these helpers into the last remaining user: Tegra DRM.

If at some point these helpers are deemed more widely useful, they can
be moved out into the DRM DP helpers again.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20191021143437.1477719-14-thierry.reding@gmail.com