AMD Enabling FreeSync Video Mode By Default With Linux 5.18, Merging AMDKFD CRIU

On Friday AMD submitted their first big batch of feature changes to their AMDGPU kernel graphics driver to DRM-Next for queuing ahead of the Linux 5.18 merge window. Most notable with this big batch of AMDGPU feature changes is the FreeSync video mode being enabled by default.

Back in 2020 AMD started working on a FreeSync video mode optimization. Enabling the option added additional mode-setting modes common to video frame rates and refresh rates adjusted for the VRR capability of the attached display. Ultimately the "freesync_video" mode adjusts the front porch timing to strive for a seamless mode change experience.

AMD got the feature all set last year. While this should lead to a better video playback experience for those with a FreeSync monitor, there is the possibility of higher power consumption when enabled. Originally this was intended to be a temporary solution until a long-term solution is sorted out for any user-space interface changes to imrove the Linux user experience around video playback on variable rate refresh displays.

Up to now enabling the feature required using the amdgpu.freesync_video=1 module parameter. With Linux 5.18 though that freesync_video option is being dropped with this FreeSync Video Mode now being used by default.

AMDGPU for Linux 5.18 also has clean-ups to its power management code, improved RAS code, SR-IOV fixes, improved vRAM access for debugging using SDMA, TLB flushing fixes for Arcturus / Vega20, DisplayPort tunneling fixes, support for enabling both SMU i2c buses where supported, suspend-to-idle (s2idle) improvements, and more.

Meanwhile the AMDKFD compute driver with this pull request is merging the CRIU checkpoint/restore capabilities that is improving for their ROCm stack and the big supercomputing / HPC customers.

The full list of initial AMDGPU/AMDKFD kernel driver feature changes building up for Linux 5.18 can be found via this pull request. Hopefully in the next month or two we begin seeing AMDGPU RDNA3 kernel patches if AMD is indeed planning for their next-generation cards in H2'2022 and wanting to have good out-of-the-box Linux support at launch given the alignment of kernel cycles and distributions.