tree f0a8de3546d832459dfaec2051b395fe8d230bd1
parent 0a8174bdf23ad947e85de7cadbaa0e5fd6d6e290
author Angel Pons <th3fanbus@gmail.com> 1614610798 +0100
committer Nico Huber <nico.h@gmx.de> 1620735138 +0000

Add support to switch LSPCON modes

LSPCON is a level shifter and protocol converter chip. It is principally
used to convert DisplayPort into HDMI 2.0, since some Intel iGPUs do not
have native HDMI 2.0 support. The chip defaults to LS mode, in which the
display engine has to generate an HDMI-protocol signal, which the LSPCON
converts from DisplayPort signal levels to HDMI signal levels.

Add code to detect LSPCON chips and put them in protocol-converter mode.
This way, the LSPCON behaves like a regular DisplayPort sink. This needs
to be done before any DPCD accesses, because the LSPCON does not respond
to DPCD accesses in level-shifter mode.

Tested on Purism Librem Mini v1 (WHL-U), HDMI port can now light up.

Change-Id: Idfa9bdff47a6591000cd5092d64a4cd4f8dbdc8d
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/libgfxinit/+/51133
Reviewed-by: Matt DeVillier <matt.devillier@gmail.com>
Reviewed-by: Nico Huber <nico.h@gmx.de>