[alsa-devel] [PATCH 1/4] dt-bindings: Document the dmas and dma-names properties for bcm2835-analog-audio

[Rob Herring]

On Sat, Mar 11, 2017 at 10:38:17PM -0800, Michael Zoran wrote:
> Add documentation for the DMA properties required when using the
> PWM controller of the bcm2835 for analog audio output.
> 
> Signed-off-by: Michael Zoran <mzoran at crowfest.net>
> ---
>  Documentation/devicetree/bindings/pwm/pwm-bcm2835.txt | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/devicetree/bindings/pwm/pwm-bcm2835.txt b/Documentation/devicetree/bindings/pwm/pwm-bcm2835.txt
> index cf573e85b11d..08fc06fc083a 100644
> --- a/Documentation/devicetree/bindings/pwm/pwm-bcm2835.txt
> +++ b/Documentation/devicetree/bindings/pwm/pwm-bcm2835.txt
> @@ -1,14 +1,21 @@
>  BCM2835 PWM controller (Raspberry Pi controller)
>  
>  Required properties:
> -- compatible: should be "brcm,bcm2835-pwm"
> +- compatible: should be "brcm,bcm2835-pwm" or "brcm,bcm2835-analog-audio"

Compatibles are not for selecting usage modes. You should describe the 
connection to the pwm that makes it an audio output rather than change 
the compatible.

>  - reg: physical base address and length of the controller's registers
>  - clocks: This clock defines the base clock frequency of the PWM hardware
>    system, the period and the duty_cycle of the PWM signal is a multiple of
>    the base period.
> +
> +Required properties(PWM Output):
>  - #pwm-cells: Should be 2. See pwm.txt in this directory for a description of
>    the cells format.
>  
> +Required properties(Audio Output):
> +- dmas: Should contain one entry pointing to the DMA channel used to
> +	transfer audio data
> +- dma-names:   Should contain "tx"
> +
>  Examples:
>  
>  pwm at 2020c000 {
> -- 
> 2.11.0
>