AMDGPU Driver Seeing HDMI 2.2 FRL Fixes For Linux 7.4

With Linux 7.4 the AMDGPU driver enables HDMI 2.1 FRL functionality by default for driving higher refresh rate and higher resolution displays. That default enabling comes as HDMI FreeSync/VRR and ALLM features are also in place for Linux 7.4. Now coming by way of fixes for Linux 7.4 is also improving the Fixed Rate Link support with the newer HDMI 2.2 specification. Sent out today was a batch of AMDGPU driver fixes for Linux 7.4 with items like correcting defects in UALink, GPU reset, SR-IOV, DCN, FreeSync/VRR, and other random fixes throughout. Arguably most exciting with this AMDGPU fixes pull request is shipping fixes for HDMI 2.2 FRL. AMD engineer Fangzhi Zuo explained of the patches for supporting HDMI 2.2 FRL rates from the sink: "The HDMI 2.2 spec defines three new FRL rates - 16, 20 and 24 Gbps per lane over 4 lanes (Max_FRL_Rate values 7, 8 and 9 in the HF-SCDB). The current code stops at the HDMI 2.1 ceiling of 12 Gbps per lane, so a sink that advertises an HDMI 2.2 rate is treated as having no FRL support at all and the link ends up trained far below what the sink actually supports. Patch 1 teaches the DRM EDID parser to decode the three new rates. Patch 2 maps them back to the FRL rate index used by DC in amdgpu_dm and extends the KUnit coverage." This HDMI 2.2 FRL work is part of this pull request sent in to the DRM fixes area. If all goes well this week's DRM fixes pull will then be sent to Linus Torvalds in the next day or two and be incorporated for Sunday's Linux 7.4-rc2 release.