From: Rob Clark robdclark@chromium.org
Currently the dpu backend attempts to handle async commits. But it is racey and could result in flushing multiple times in a frame, or modifying hw state (such as scanout address or cursor position) after the previous flush, but before vblank, causing underflows (which manifest as brief black flashes).
This patchset removes the previous dpu async commit handling, and reworks the internal kms backend API to decouple flushing. And in the end introduces an hrtimer to flush async updates. The overall approach is:
1) Move flushing various hw state out of encoder/crtc atomic commit (which is anyways an improvement over the current state, where we either flush from crtc or encoder, depending on whether it is a full modeset)
2) Switch to crtc_mask for anything that completes after atomic _commit_tail(), so we do not need to keep the atomic state around. Ie. from drm core's perspective, an async commit completes immediately.
This avoids fighting with drm core about the lifecycle of an atomic state object.
3) Track a bitmask of crtcs w/ pending async flush, and setup an hrtimer with expiration 1ms before vblank, to trigger the flush. For async commits, we push the state down to the double buffered hw registers immediately, and only defer writing the flush registers.
Current patchset only includes the dpu backend support for async commits.. mdp4 and mdp5 should be relatively trivial (less layers of indirection involved). But I won't have access to any mdp4 hw for a few more weeks, so at least that part I might punt on for now.
v2: couple small cosmetic updates, re-work locking to avoid stalls, add some tracepoints
Rob Clark (10): drm/msm/dpu: unwind async commit handling drm/msm/dpu: add real wait_for_commit_done() drm/msm/dpu: handle_frame_done() from vblank irq drm/msm: add kms->wait_flush() drm/msm: convert kms->complete_commit() to crtc_mask drm/msm: add kms->flush_commit() drm/msm: split power control from prepare/complete_commit drm/msm: async commit support drm/msm/dpu: async commit support drm/msm: add atomic traces
drivers/gpu/drm/msm/Makefile | 1 + drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c | 48 +--- drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.h | 7 +- drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c | 46 ++-- drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h | 8 +- .../drm/msm/disp/dpu1/dpu_encoder_phys_vid.c | 39 +-- drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c | 99 +++++--- drivers/gpu/drm/msm/disp/mdp4/mdp4_kms.c | 48 ++-- drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c | 47 ++-- drivers/gpu/drm/msm/msm_atomic.c | 233 +++++++++++++++--- drivers/gpu/drm/msm/msm_atomic_trace.h | 110 +++++++++ drivers/gpu/drm/msm/msm_atomic_tracepoints.c | 3 + drivers/gpu/drm/msm/msm_drv.c | 1 + drivers/gpu/drm/msm/msm_drv.h | 4 + drivers/gpu/drm/msm/msm_gpu_trace.h | 2 +- drivers/gpu/drm/msm/msm_kms.h | 108 +++++++- 16 files changed, 603 insertions(+), 201 deletions(-) create mode 100644 drivers/gpu/drm/msm/msm_atomic_trace.h create mode 100644 drivers/gpu/drm/msm/msm_atomic_tracepoints.c