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[Why] DCN is the display hardware for amdgpu. DRM planes are backed by DCN hardware pipes, which carry pixel data from one end (memory), to the other (output encoder). Each DCN pipe has the ability to blend in a cursor early on in the pipeline. In other words, there are no dedicated cursor planes in DCN, which makes cursor behavior somewhat unintuitive for compositors. For example, if the cursor is in RGB format, but the top-most DRM plane is in YUV format, DCN will not be able to blend them. Because of this, amdgpu_dm rejects all configurations where a cursor needs to be enabled on top of a YUV formatted plane. From a compositor's perspective, when computing an allocation for hardware plane offloading, this cursor-on-yuv configuration result in an atomic test failure. Since the failure reason is not obvious at all, compositors will likely fall back to full rendering, which is not ideal. Instead, amdgpu_dm can try to accommodate the cursor-on-yuv configuration by opportunistically reserving a separate DCN pipe just for the cursor. We can refer to this as "overlay cursor mode". It is contrasted with "native cursor mode", where the native DCN per-pipe cursor is used. [How] On each crtc, compute whether the cursor plane should be enabled in overlay mode. If it is, mark the CRTC as requesting overlay cursor mode. Overlay cursor should be enabled whenever there exists a underlying plane that has YUV format, or is scaled differently than the cursor. It should also be enabled if there is no underlying plane, or if underlying planes do not cover the entire CRTC. During DC validation, attempt to enable a separate DCN pipe for the cursor if it's in overlay mode. If that fails, or if no overlay mode is requested, then fallback to native mode. v2: * Update commit message for when overlay cursor should be enabled * Also consider scale and no-underlying-plane case (cursor on crtc bg) * Consider all underlying planes when determinig overlay/native, not just the plane immediately beneath the cursor, as it may not cover the entire CRTC. * Fix typo s/decending/descending/ * Force native cursor on pre-DCN hardware Reviewed-by:
Harry Wentland <harry.wentland@amd.com> Acked-by:
Zaeem Mohamed <zaeem.mohamed@amd.com> Signed-off-by:
Leo Li <sunpeng.li@amd.com>
Acked-by: Pekka Paalanen <pekka.paalanen@collabora.com> Tested-by:
Daniel Wheeler <daniel.wheeler@amd.com>
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