tree fd30921df7e5882c38ee1a1c3907264a8aafe54b
parent c0ede398b52654edb8b2a90be69dec2fb966f483
author Takashi Sakamoto <o-takashi@sakamocchi.jp> 1570446328 +0900
committer Takashi Iwai <tiwai@suse.de> 1571306565 +0200

ALSA: dice: use the same size of period for PCM substream in AMDTP streams

In current implementation, when opening a PCM substream, it's needed to
check whether the opposite PCM substream runs. This is to assign
effectual constraints (e.g. sampling rate) to opened PCM substream.

The number of PCM substreams and MIDI substreams on AMDTP streams in
domain is recorded in own structure. Usage of this count is an
alternative of the above check. This is better because the count is
incremented in pcm.hw_params earlier than pcm.trigger.

This idea has one issue because it's incremented for MIDI substreams as
well. In current implementation, for a case that any MIDI substream run
and a PCM substream is going to start, PCM application to start the PCM
substream can decide hardware parameters by restart packet streaming.
Just checking the substream count can brings regression.

Now AMDTP domain structure has a member for the size of PCM period in
PCM substream which starts AMDTP streams in domain. When the value has
zero and the substream count is greater than 1, it means that any MIDI
substream starts AMDTP streams in domain. Usage of the value can resolve
the above issue.

This commit replaces the check with the substream count and the value for
the size of PCM period.

Dice hardware has a quirk called as 'Dual Wire'. For a case of higher
sampling transmission frequency, this commit performs calculations between
the number of PCM frames and the number of events in AMDTP stream.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20191007110532.30270-14-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Iwai <tiwai@suse.de>