[alsa-devel] DT soundcard driver with special clock routing

[Petr Kulhavy]

Hi,

I'm developing a DT-based driver for an ARM SoC device with the 
following special clock routing:

- WM8758 codec attached to the CPU DAI via I2S
- the codec is I2S clock master
- the CPU feeds the codec with 12MHz clock (outside of the I2S)
- the codec converts the 12MHz  internally to 48kHz*256 or 44.1kHz *256 
clock and provides it to I2S as MCLK

So the special set-up needed here is that the codec needs to be 
configured to:
a) generate the proper MCLK
b) enable the respective GPIO pin as clock output

What is the best way of representing this set-up using device tree?
I'm wondering if this can be done by adding a specific option in the 
codec DT binding for enabling the clock output and then use the simple 
audio card.
Or do I need to write a specific soundcard driver that sets up the codec 
registers? I would like to avoid that if possible and use existing code...

What would you recommend?

Thanks

-- 
Petr Kulhavy, MSc
System Architect

*BARIX*

petr at barix.com <mailto:petr at barix.com> | Skype: brain.barix

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