The RCAR-DU utilises a running VSPD pipeline to perform processing for the display pipeline.
Changes to this pipeline are performed with an atomic flush operation which updates the state in the VSPD. Due to the way the running pipeline is operated, any flush operation has an implicit latency of one frame interval.
This comes about as the display list is committed, but not updated until the next VSP1 interrupt. At this point the frame is being processed, but is not complete until the following VSP1 frame end interrupt.
To prevent reporting page flips early, we must track this timing through the VSP1, and only allow the rcar-du object to report the page-flip completion event after the VSP1 has processed.
This series ensures that tearing and flicker is prevented, without introducing the performance impact mentioned in the previous series.
[PATCH 1/3] extends the VSP1 to allow a callback to be registered giving the VSP1 the ability to notify completion events [PATCH 2/3] checks for race conditions in the commits of the display list, and in such event postpones the sending of the completion event [PATCH 3/3] Utilises the callback extension to send page flips at the end of VSP processing.
These patches have been tested by introducing artificial delays in the commit code paths and verifying that no visual tearing or flickering occurs.
Manual start/stop testing has also been performed
Kieran Bingham (3): v4l: vsp1: extend VSP1 module API to allow DRM callbacks v4l: vsp1: Postpone page flip in event of display list race drm: rcar-du: Register a completion callback with VSP1
drivers/gpu/drm/rcar-du/rcar_du_crtc.c | 10 +++++++-- drivers/gpu/drm/rcar-du/rcar_du_crtc.h | 2 ++- drivers/gpu/drm/rcar-du/rcar_du_vsp.c | 29 ++++++++++++++++++++++++++- drivers/media/platform/vsp1/vsp1_dl.c | 9 ++++++-- drivers/media/platform/vsp1/vsp1_dl.h | 2 +- drivers/media/platform/vsp1/vsp1_drm.c | 22 ++++++++++++++++++++- drivers/media/platform/vsp1/vsp1_drm.h | 10 +++++++++- drivers/media/platform/vsp1/vsp1_pipe.c | 6 ++++- drivers/media/platform/vsp1/vsp1_pipe.h | 2 ++- include/media/vsp1.h | 3 +++- 10 files changed, 89 insertions(+), 6 deletions(-)
base-commit: 55e78dfc82988a79773ccca67e121f9a88df81c2