[alsa-devel] [PATCH] ASoC: wm8804: Allow control of master clock divider in PLL generation

Charles Keepax ckeepax at opensource.wolfsonmicro.com
Mon Jan 13 12:14:31 CET 2014

On Sun, Jan 12, 2014 at 10:11:25PM +0100, Daniel Matuschek wrote:
> Signed-off-by: Daniel Matuschek <daniel at matuschek.net>
> After some discussions of the patch last week, here is a new version. 
> Simply reducing the post_table did not work, as for some frequencies
> both settings (MCLKDIV=0 and MCLKDIV=1) are needed (e.g. 96 and 192kHz)
>   WM8804 can run with PLL frequencies of 256xfs and 128xfs for
>   most sample rates. At 192kHz only 128xfs is supported. The
>   existing driver selects 128xfs automatically for some lower
>   samples rates. By using an additional mclk_div divider, is
>   is now possible to control the behaviour. This allows using
>   256xfs PLL frequency on all sample rates up to 96kHz. It
>   should allow lower jitter and better signal quality. The
>   behavior has to be controlled by the sound card driver,
>   because some sample frequency share the same setting. e.g.
>   192kHz and 96kHz use 24.576MHz master clock. The only
>   difference is the MCLK divider.

Commit message still needs fixed up, as per Mark's comments on
your last patch. Otherwise looks ok to me.


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