Linux 6.1 To Drop Radeon DRM Driver's Legacy & Broken DP MST Code

In addition to the drm-misc-next pull from earlier in the week, another set of Direct Rendering Manager updates for the core DRM code and smaller drivers has now been submitted for DRM-Next.

With this second drm-misc-next pull for the week is the removal of legacy DP MST support, affecting the Radeon DRM driver (as in the older "Radeon" driver and not the modern AMDGPU driver) but that functionality was already broken so users will likely not notice or be impacted.

These pulls going into DRM-Next are queuing ahead of the Linux 6.1 merge window opening in October. The latest batch of highlights for today include:

- Legacy DisplayPort Multi-Stream Transport (DP MST) support has been removed, leaving only the modern DP MST implementation. DisplayPort Multi-Stream Transport is the feature allowing multiple independent video signals to be sent over a single DP output for use when daisy changing displays or an MST hub. The old "Radeon" DRM driver (pre-AMDGPU / pre-GCN 1.2 by default) was the only user of the DP MST legacy code while all the other DRM drivers used the newer code path. The Radeon DRM driver's DP MST support was known to be broken but no interested parties stepped up to fix it for these old GPUs.

- With the legacy DP MST support removed, the modern DP MST code has seen improvements for its mode-set handling in AMDGPU / Nouveau / i915.

- The MediaTek DRM driver has added MT8195 DisplayPort support.

- The Sun4i TV support is now using the atomic mode-setting path.

- Refactored VC4/VEC TV mode-setting and fixed the timing-related code.

- Various improvements to the VKMS driver.

See this PR for all of the patches sent in as part of this latest pull.