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ebe02a5b9e
This patch supports some type of machine drivers that set 0 to mclk
when sound device goes to idle state. After applied this patch,
sysclk == 0 means there is no constraint of sound rate and other
values will set constraints which is derived by sysclk setting.
Original code refuses sysclk == 0 setting. But some boards and SoC
(such as RockPro64 and RockChip I2S) has connected SoC MCLK out to
ES8316 MCLK in. In this case, SoC side I2S will choose suitable
frequency of MCLK such as fs * mclk-fs when user starts playing or
capturing.
Bad scenario as follows (mclk-fs = 256):
- Initialize sysclk by correct value (Ex. 12.288MHz)
- ES8316 set constraints of PCM rate by sysclk
48kHz (1/256), 32kHz (1/384), 30.720kHz (1/400),
24kHz (1/512), 16kHz (1/768), 12kHz (1/1024)
- Play 48kHz sound, it's acceptable
- Sysclk is not changed
- Play 32kHz sound, it's acceptable
- Set sysclk by 8.192MHz (= fs * mclk-fs = 32k * 256)
- ES8316 set constraints of PCM rate by sysclk
32kHz (1/256), 21.33kHz (1/384), 20.48kHz (1/400),
16kHz (1/512), 10.66kHz (1/768), 8kHz (1/1024)
- Play 48kHz again, but it's NOT acceptable because constraints
list does not allow 48kHz
Signed-off-by: Katsuhiro Suzuki <katsuhiro@katsuster.net>
Link: https://lore.kernel.org/r/20190907163653.9382-2-katsuhiro@katsuster.net
Signed-off-by: Mark Brown <broonie@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.