In this patch enables support for detecting link failures between
PCON and HDMI sink in i915 driver. HDMI link loss indication to
upstream DP source is indicated via IRQ_HPD. This is followed by
reading of HDMI link configuration status (HDMI_TX_LINK_ACTIVE_STATUS).
If the PCON → HDMI 2.1 link status is off; reinitiate frl link
training to recover. Also, report HDMI FRL link error count range for
each individual FRL active lane is indicated by
DOWNSTREAM_HDMI_ERROR_STATUS_LN registers.

v2: Checked for dpcd read and write failures and added debug message.
(Uma Shankar)

v3: Rearranged code to re-start FRL link training or fall back to
TMDS mode.

v4: Resused function to check frl which inturn restarts FRL and
fallback to TMDS mode.
Signed-off-by: Swati Sharma <swati2.sharma@intel.com>
Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Reviewed-by: Uma Shankar <uma.shankar@intel.com> (v2)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201218103723.30844-12-ankit.k.nautiyal@intel.com