AMDGPU Linux Driver's Latest Patches For HDMI Passive VRR Support

As part of AMD's ongoing effort for getting HDMI 2.1 support squared away in their upstream AMDGPU kernel graphics driver, sent out today were the latest patches around passive variable refresh rate "Passive VRR" for HDMI connections. Passive VRR is for avoiding screen blanking or a brightness flicker when a HDMI output is transitiong into VRR mode. This isn't an issue with DisplayPort or Embedded DisplayPort where seamless VRR transitions are mandated, but for HDMI the Passive VRR feature works by keeping an HDMI sink in its variable-refresh state during fixed-refresh desktop use. AMDGPU Passive VRR support for HDMI was previously carried as part of the HDMI 2.1 "gaming" patch series with VRR and ALLM but now has been split off into its own patch series. This patch series has that latest Passive VRR code for the AMDGPU driver where it's enabled by default but can be opted out should you prefer the blanking/flicker upon transitioning to the VRR mode. Hopefully these latest AMDGPU HDMI 2.1 additions all get reviewed and prepped in time for the Linux 7.4 merge window opening up in late October.