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

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Message-ID: <b09fc5f6-4029-3408-a7c7-19ec08dc10ac@st.com>
Date:   Wed, 26 Apr 2017 08:58:43 +0000
From:   Pierre Yves MORDRET <pierre-yves.mordret@...com>
To:     Rob Herring <robh@...nel.org>,
        "M'boumba Cedric Madianga" <cedric.madianga@...il.com>
CC:     "mark.rutland@....com" <mark.rutland@....com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Alexandre TORGUE <alexandre.torgue@...com>,
        "vinod.koul@...el.com" <vinod.koul@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "mcoquelin.stm32@...il.com" <mcoquelin.stm32@...il.com>,
        "dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
        "dan.j.williams@...el.com" <dan.j.williams@...el.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 1/5] dt-bindings: Document the STM32 DMAMUX bindings

Hi Rob

On 03/20/2017 10:34 PM, Rob Herring wrote:
> 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@...il.com>
>> ---
>>  .../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@...26400 {
>> +	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@...20820 {
>> +	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.
>

Would you mind to detail a little bit more your thoughts please ?
Are dma-map & dma-map-mask part of an existing bindings ? or need to be 
developed ?
I'm a little bit confused where come from values you used.

>> +};
>> +
>> +/* DMA client */
>> +usart1: serial@...11000 {
>> +	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
>>
>
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>
>

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