Katsuhiro Suzuki 2458adb8f9

SoC: simple-card-utils: set 0Hz to sysclk when shutdown ...

This patch set 0Hz to sysclk when shutdown the card.

Some codecs set rate constraints that derives from sysclk. This
mechanism works correctly if machine drivers give fixed frequency.

But simple-audio and audio-graph card set variable clock rate if
'mclk-fs' property exists. In this case, rate constraints will go
bad scenario. For example a codec accepts three limited rates
(mclk / 256, mclk / 384, mclk / 512).

Bad scenario as follows (mclk-fs = 256):
   - Initialize sysclk by correct value (Ex. 12.288MHz)
     - Codec set constraints of PCM rate by sysclk
       48kHz (1/256), 32kHz (1/384), 24kHz (1/512)
   - Play 48kHz sound, it's acceptable
   - Sysclk is not changed

   - Play 32kHz sound, it's acceptable
   - Set sysclk to 8.192MHz (= fs * mclk-fs = 32k * 256)
     - Codec set constraints of PCM rate by sysclk
       32kHz (1/256), 21.33kHz (1/384), 16kHz (1/512)

   - Play 48kHz again, but it's NOT acceptable because constraints
     do not allow 48kHz

So codecs treat 0Hz sysclk as signal of applying no constraints to
avoid this problem.

Signed-off-by: Katsuhiro Suzuki <katsuhiro@katsuster.net>
Link: https://lore.kernel.org/r/20190907174501.19833-1-katsuhiro@katsuster.net
Signed-off-by: Mark Brown <broonie@kernel.org>

2019-09-09 10:51:21 +01:00

..

audio-graph-card.c

ASoC: audio-graph: indicate rebind issue

2019-09-03 12:36:24 +01:00

Kconfig

treewide: Add SPDX license identifier - Makefile/Kconfig

2019-05-21 10:50:46 +02:00

Makefile

ASoC: simple-scu-card: remove simple-scu-card

2019-01-03 16:34:19 +00:00

simple-card-utils.c

SoC: simple-card-utils: set 0Hz to sysclk when shutdown

2019-09-09 10:51:21 +01:00

simple-card.c

ASoC: simple-card: indicate rebind issue

2019-09-03 12:36:06 +01:00