On Tue, 08 Dec 2020, Ankit Nautiyal ankit.k.nautiyal@intel.com wrote:
This patch series attempts to add support for a DP-HDMI2.1 Protocol Convertor. The VESA spec for the HDMI2.1 PCON are proposed in Errata E5 to DisplayPort_v2.0: https://vesa.org/join-vesamemberships/member-downloads/?action=stamp&fil... The details are mentioned in: VESA DP-to-HDMI PCON Specification Standalone Document https://groups.vesa.org/wg/DP/document/15651
This series starts with adding support for FRL (Fixed Rate Link) Training between the PCON and HDMI2.1 sink. As per HDMI2.1 specification, a new data-channel or lane is added in FRL mode, by repurposing the TMDS clock Channel. Through FRL, higher bit-rate can be supported, ie. up to 12 Gbps/lane (48 Gbps over 4 lanes).
With these patches, the HDMI2.1 PCON can be configured to achieve FRL training based on the maximum FRL rate supported by the panel, source and the PCON. The approach is to add the support for FRL training between PCON and HDMI2.1 sink and gradually add other blocks for supporting higher resolutions and other HDMI2.1 features, that can be supported by pcon for the sources that do not natively support HDMI2.1.
This is done before the DP Link training between the source and PCON is started. In case of FRL training is not achieved, the PCON will work in the regular TMDS mode, without HDMI2.1 feature support. Any interruption in FRL training between the PCON and HDMI2.1 sink is notified through IRQ_HPD. On receiving the IRQ_HPD the concerned DPCD registers are read and FRL training is re-attempted.
Currently, we have tested the FRL training and are able to enable 4K display with TGL Platform + Realtek PCON RTD2173 with HDMI2.1 supporting panel.
Per IRC chat with Maarten and Daniel, once all the reviews are in, I'll add a topic branch and apply the patches there, so we can merge the branch to both drm-misc-next and drm-intel-next.
BR, Jani.