Re: [PATCH 1/5] dt-bindings: Document the STM32 DMAMUX bindings

[Rob Herring]

On Mon, Mar 13, 2017 at 03:15:57PM +0100, M'boumba Cedric Madianga wrote:
> This patch adds the documentation of device tree bindings for the STM32
> DMAMUX.
> 
> Signed-off-by: M'boumba Cedric Madianga <cedric.madianga@xxxxxxxxx>
> ---
>  .../devicetree/bindings/dma/stm32-dmamux.txt       | 57 ++++++++++++++++++++++
>  1 file changed, 57 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/dma/stm32-dmamux.txt
> 
> diff --git a/Documentation/devicetree/bindings/dma/stm32-dmamux.txt b/Documentation/devicetree/bindings/dma/stm32-dmamux.txt
> new file mode 100644
> index 0000000..1039420
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/dma/stm32-dmamux.txt
> @@ -0,0 +1,57 @@
> +STM32 DMA MUX (DMA request router)
> +
> +Required properties:
> +- compatible:	"st,stm32-dmamux"
> +- reg:		Memory map for accessing module
> +- #dma-cells:	Should be set to <4>.
> +		For more details about the four cells, please see stm32-dma.txt
> +		documentation binding file
> +- dma-masters:	Phandle pointing to the DMA controller
> +- clocks: Input clock of the DMAMUX instance.
> +
> +Optional properties:
> +- dma-channels : Number of DMA channels supported.
> +- dma-requests : Number of DMA requests supported.
> +- resets: Reference to a reset controller asserting the DMA controller
> +
> +Example:
> +
> +/* DMA controller */
> +dma2: dma-controller@40026400 {
> +	compatible = "st,stm32-dma";
> +	reg = <0x40026400 0x400>;
> +	interrupts = <56>,
> +		     <57>,
> +		     <58>,
> +		     <59>,
> +		     <60>,
> +		     <68>,
> +		     <69>,
> +		     <70>;
> +	clocks = <&clk_hclk>;
> +	#dma-cells = <4>;
> +	st,mem2mem;
> +	resets = <&rcc 150>;
> +	st,dmamux;
> +	dma-channels = <8>;
> +};
> +
> +/* DMA mux */
> +dmamux2: dma-router@40020820 {
> +	compatible = "st,stm32-dmamux";
> +	reg = <0x40020800 0x1c>;
> +	#dma-cells = <4>;
> +	dma-requests = <128>;
> +	dma-masters = <&dma2>;

I think this should be modeled after the interrupt-map property (or 
Stephen Boyd's gpio-map support which additionally allows pass thru of 
cell values). Something like this:

dma-map = <0 41 0 0 &dma2 0 <req> 0 0>,
	<1 42 0 0 &dma2 1 <req> 0 0>;
dma-map-mask = <0xffffffff 0xffffffff 0 0>;

<req> is the request number on dma2 controller.

This is more generic and would work if you have a single mux with 
multiple DMA controllers.

> +};
> +
> +/* DMA client */
> +usart1: serial@40011000 {
> +	compatible = "st,stm32-usart", "st,stm32-uart";
> +	reg = <0x40011000 0x400>;
> +	interrupts = <37>;
> +	clocks = <&clk_pclk2>;
> +	dmas = <&dmamux2 0 41 0x400 0x00>,
> +	       <&dmamux2 1 42 0x400 0x00>;
> +	dma-names = "rx", "tx";
> +};
> -- 
> 1.9.1
>