[PATCH 0/9] drm/msm: async commit support

Rob Clark robdclark at gmail.com
Tue Aug 27 21:33:30 UTC 2019

From: Rob Clark <robdclark at 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

Rob Clark (9):
  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

 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              | 210 +++++++++++++++---
 drivers/gpu/drm/msm/msm_drv.c                 |   1 +
 drivers/gpu/drm/msm/msm_drv.h                 |   4 +
 drivers/gpu/drm/msm/msm_kms.h                 | 108 ++++++++-
 12 files changed, 466 insertions(+), 199 deletions(-)


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