[alsa-devel] [PATCH v2 2/2] dt: binding: sound cs42l52 driver

[Tomasz Figa]

Hi Brian,

On Wednesday 13 of November 2013 09:44:34 Brian Austin wrote:
> Add Device Tree Binding for the CS42L52 Codec
> 
> v2 Adds clearer explaination of mic configs and select.
> Renames bindings to '-' instead of '_'.
> Definition of GPIO for reset pin.
> 
> Signed-off-by: Brian Austin <brian.austin at cirrus.com>
> ---
>  .../devicetree/bindings/sound/cs42l52.txt          | 48 ++++++++++++++++++++++
>  1 file changed, 48 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/sound/cs42l52.txt
> 
> diff --git a/Documentation/devicetree/bindings/sound/cs42l52.txt b/Documentation/devicetree/bindings/sound/cs42l52.txt
> new file mode 100644
> index 0000000..bd91ecf
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/sound/cs42l52.txt
> @@ -0,0 +1,48 @@
> +CS42L52 audio CODEC
> +
> +Required properties:
> +
> +  - compatible : "cirrus,cs42l52"
> +
> +  - reg : the I2C address of the device for I2C
> +
> +Optional properties:
> +
> +  - reset-gpio : GPIO controller's phandle and the number
> +		 of the GPIO used to reset the codec.

As Kumar has already mentioned, all device-specific properties should be
prefixed with vendor prefix, "cirrus," in this case.

> +  - chgfreq    : Charge Pump Frequency values. Allowable values of
> +		 0x00 through 0x0F.
> +		 Frequency = (64xFs)/(N+2)

I suppose N means the value of chgfreq property here, but this should be
clearly stated. Same for Fs - I suppose it is sampling frequency, but
is it default, minimum, maximum or maybe something else?

Personally I don't like this kind of raw values being passed using Device
Tree, but this one can't be really represented reasonably in a generic
way (such as in Hz units) without too much effort to calculate original
value in the driver, then it's fine.

> +  - mica-cfg   : MIC A single-ended or differential select.
> +		 0x00 = Single-Ended
> +		 0x01 = Differential

I'd rather make it boolean and call it cirrus,mic-a-differential.

> +  - micb-cfg   : MIC B single-ended or differential select.
> +		 0x00 = Single-Ended
> +		 0x01 = Differential

Ditto.

> +  - mica-sel   : MIC A single ended input select.  For Single-Ended
> +		 configuration, select which MIC to use.
> +		 0x00 = MIC1
> +		 0x01 = MIC2
> +  - micb-sel   : MIC B single ended input select.  For Single-Ended
> +		 configuration, select which MIC to use.
> +		 0x00 = MIC1
> +		 0x01 = MIC2

Could you explain what are MIC A, MIC B, MIC1 and MIC2?

> +  - micbias-lvl: Set the output voltage level on the MICBIAS Pin
> +		 0x00 = 0.5 x VA
> +		 0x01 = 0.6 x VA
> +		 0x02 = 0.7 x VA
> +		 0x03 = 0.8 x VA
> +		 0x04 = 0.83 x VA
> +		 0x05 = 0.91 x VA

For such small range of values, decimal representation is preferred from
readability reasons.

> +
> +Example:
> +
> +codec: cs42l52 at 4a {

coding style: Node name should be generic, i.e. codec at 4a.

Best regards,
Tomasz