[alsa-devel] [PATCH] ASoC: fsl: imx-wm8962: Do FLL configuration in hw_params() and hw_free()

Mark Brown broonie at kernel.org
Wed Dec 4 20:02:11 CET 2013

On Thu, Dec 05, 2013 at 12:54:08AM +0800, Nicolin Chen wrote:

> Previously, we couldn't use hw_params() and hw_free() to open and close FLL
> becuase there might be race between two simmultaneous substreams and cause
> FLL configuration being changed and accordingly mulfunction. So we adopted
> DAPM to control it since there won't be any race in DAPM. However, if we
> want to playback a different sample rate file, we need to wait for DAPM to
> change its bias_level to reconfigure FLL.
> But after we introduced full symmetry protection in the soc-pcm, we don't
> need to worry about the race any more. And the instance by using hw_params()
> and hw_free() to control FLL would allow us to support flexible use cases,
> 'aplay -Dhw:0 44k16bit.wav 48k24bit.wav 32k32bit.wav' for example.
> Thus this patch mainly moves FLL configuration from set_bias_level() to
> hw_params() and hw_free() so as to enchance the sound card's capability.

That's not the only reason for using set_bias_level(), it's also used so
that bypass paths from the CODEC inputs to outputs get the FLL started
- all the outputs need the device to be clocked.
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