From: Leo Li <[email protected]> These patches aim to make the amdgpgu KMS driver play nicer with compositors when building multi-plane scanout configurations. They do so by:
1. Making cursor behavior more sensible. 2. Allowing placement of DRM OVERLAY planes underneath the PRIMARY plane for 'underlay' configurations (perhaps more of a RFC, see below). Please see the commit messages for details. For #2, the simplest way to accomplish this was to increase the value of the immutable zpos property for the PRIMARY plane. This allowed OVERLAY planes with a mutable zpos range of (0-254) to be positioned underneath the PRIMARY for an underlay scanout configuration. Technically speaking, DCN hardware does not have a concept of primary or overlay planes - there are simply 4 general purpose hardware pipes that can be maped in any configuration. So the immutable zpos restriction on the PRIMARY plane is kind of arbitrary; it can have a mutable range of (0-254) just like the OVERLAYs. The distinction between PRIMARY and OVERLAY planes is also somewhat arbitrary. We can interpret PRIMARY as the first plane that should be enabled on a CRTC, but beyond that, it doesn't mean much for amdgpu. Therefore, I'm curious about how compositors devs understand KMS planes and their zpos properties, and how we would like to use them. It isn't clear to me how compositors wish to interpret and use the DRM zpos property, or differentiate between OVERLAY and PRIMARY planes, when it comes to setting up multi-plane scanout. Ultimately, what I'd like to answer is "What can we do on the KMS driver and DRM plane API side, that can make building multi-plane scanout configurations easier for compositors?" I'm hoping we can converge on something, whether that be updating the existing documentation to better define the usage, or update the API to provide support for something that is lacking. Thanks, Leo Some links to provide context and details: * What is underlay?: https://gitlab.freedesktop.org/emersion/libliftoff/-/issues/76 * Discussion on how to implement underlay on Weston: https://gitlab.freedesktop.org/wayland/weston/-/merge_requests/1258#note_2325164 Cc: Joshua Ashton <[email protected]> Cc: Michel Dänzer <[email protected]> Cc: Chao Guo <[email protected]> Cc: Xaver Hugl <[email protected]> Cc: Vikas Korjani <[email protected]> Cc: Robert Mader <[email protected]> Cc: Pekka Paalanen <[email protected]> Cc: Sean Paul <[email protected]> Cc: Simon Ser <[email protected]> Cc: Shashank Sharma <[email protected]> Cc: Harry Wentland <[email protected]> Cc: Sebastian Wick <[email protected]> Leo Li (2): drm/amd/display: Introduce overlay cursor mode drm/amd/display: Move PRIMARY plane zpos higher .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 405 ++++++++++++++++-- .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h | 7 + .../amd/display/amdgpu_dm/amdgpu_dm_crtc.c | 1 + .../amd/display/amdgpu_dm/amdgpu_dm_plane.c | 28 +- 4 files changed, 391 insertions(+), 50 deletions(-) -- 2.44.0
