[alsa-devel] [RFC PATCH] ASoC: pcm512x: enable set_sysclk callback

Mark Brown broonie at kernel.org
Mon Jun 4 12:40:29 CEST 2018


On Fri, Jun 01, 2018 at 04:26:43PM -0500, Pierre-Louis Bossart wrote:
> For codec master mode, the current pcm512x code relies on the clock API.

> Simple boards such as Hifiberry DAC+ PRO rely on 2 local oscillators
> to generate 44.1 or 48kHz multiples, with the clock selection being
> handled by the machine driver toggling GPIOS.

> The RaspberryPi kernel exposes a "hifiberry,dacpro-clk" clock driver
> which does nothing but tell the codec driver what rate is set by the
> machine driver [1][2]

> This patch suggests an alternate fallback solution to let the codec
> driver know what the sysclk is based on the existing .set_sysclk
> callback.

I'm not seeing a great advantage in this - we want to have more adoption
of standard APIs for clocking rather than less.  As that Pi board shows
it's easy to create static clocks in the clock API so why not just do
that?
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