[v5,0/3] ALSA: compress: Document stream states and fix gapless SM

Message

Vinod Koul June 29, 2020, 1:47 p.m. UTC

Srini found issue with gapless implementation which prompted to look deeper
into SM for compressed stream.

So documenting SM was first step, so first two patches add that. Last patch
fixes the issue by keeping track on partial_drain and then moving state to
'running' in snd_compr_drain_notify() for partial_drain case on success.
While at it, noticed snd_compr_drain_notify() is lockless state change, so
fixed that as well.

I have tested this on Dragon board RB3, compressed audio works out of the
box on that platform and Srini will send driver and fcplay patches for
gapless soon.

Changes in v5:
 - Update SM diagram as suggested by Amadeusz

Changes in v4:
 - Add review tag by Charles
 - fix the lock deadlock pointed by Charles

Changes in v3:
 - Add pause->stop->free transition
 - Add setup->free transition
 - remove running->free as that goes thru stop

Changes in v2:
 - Added tested tag by Srini
 - Update compress SM with Free state and compr_stop() transitions

Vinod Koul (3):
  ALSA: compress: document the compress audio state machine
  ALSA: compress: document the compress gapless audio state machine
  ALSA: compress: fix partial_drain completion state

 .../sound/designs/compress-offload.rst        | 83 +++++++++++++++++++
 include/sound/compress_driver.h               | 10 ++-
 sound/core/compress_offload.c                 |  4 +
 3 files changed, 96 insertions(+), 1 deletion(-)