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When capture and playback substreams are both running at the same time, cs42l42_pcm_hw_params() would be called for each direction. The first call will configure the PLL. The second call must not write the PLL configuration registers again if the first substream is already running, as this could destabilize the PLL. The DAI is marked symmetric sample bits and sample rate, so the two directions will always have the same SCLK (I2S always has 2 channel slots so the DAI does not need to require symmetric channels to guarantee the same SCLK). However, since cs42l42_pll_config() is checking for an active stream it may as well test that the requested SCLK is the same as the currently active configuration. Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com> Link: https://lore.kernel.org/r/20211015133619.4698-2-rf@opensource.cirrus.com 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.