On Fri, 15 Mar 2024 13:09:57 -0400 <sunpeng.li@xxxxxxx> wrote: > From: Leo Li <sunpeng.li@xxxxxxx> > > [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. I can't comment on the code, but this explanation sounds like a really good move! Thanks, pq > [How] > > On each crtc, compute whether the cursor plane should be enabled in > overlay mode (which currently, is iff the immediate plane below has a > YUV format). If it is, mark the CRTC as requesting overlay cursor mode. > > 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. > > Signed-off-by: Leo Li <sunpeng.li@xxxxxxx> > --- > .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 309 +++++++++++++++--- > .../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 | 13 +- > 4 files changed, 288 insertions(+), 42 deletions(-)
Attachment:
pgpMDdsFgwhbs.pgp
Description: OpenPGP digital signature
