linux-kernel - Re: [PATCH 06/11] dt-bindings: dma: stm32-dma3: introduce st,axi-max-burst-len property

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Message-ID: <20394a61-72b8-4d92-ac35-201368035bde@foss.st.com>
Date: Fri, 11 Oct 2024 11:12:27 +0200
From: Amelie Delaunay <amelie.delaunay@...s.st.com>
To: Rob Herring <robh@...nel.org>
CC: Vinod Koul <vkoul@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Maxime Coquelin
	<mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        <dmaengine@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <devicetree@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 06/11] dt-bindings: dma: stm32-dma3: introduce
 st,axi-max-burst-len property



On 10/10/24 20:16, Rob Herring wrote:
> On Thu, Oct 10, 2024 at 04:27:56PM +0200, Amelie Delaunay wrote:
>> DMA3 maximum burst length (in unit of beat) may be restricted depending
>> on bus interconnect.
>>
>> As mentionned in STM32MP2 reference manual [1], "the maximum allowed AXI
>> burst length is 16. The user must set [S|D]BL_1 lower or equal to 15
>> if the Source/Destination allocated port is AXI (if [S|D]AP=0)".
> 
> This should be implied by the SoC specific compatible.
> 

I took an example from snps,dw-axi-dmac.yaml (snps,axi-max-burst-len). 
But I agree, it will be implied by st,stm32mp25-dma3 compatible in V2.
Patch 8/11 will then be dropped.

Regards,
Amelie

>>
>> Introduce st,axi-max-burst-len. If used, it will clamp the burst length
>> to that value if AXI port is used, if not, the maximum burst length value
>> supported by DMA3 is used.
>>
>> [1] https://www.st.com/resource/en/reference_manual/rm0457-stm32mp2325xx-advanced-armbased-3264bit-mpus-stmicroelectronics.pdf
>>
>> Signed-off-by: Amelie Delaunay <amelie.delaunay@...s.st.com>
>> ---
>>   .../devicetree/bindings/dma/stm32/st,stm32-dma3.yaml          | 11 +++++++++++
>>   1 file changed, 11 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/dma/stm32/st,stm32-dma3.yaml b/Documentation/devicetree/bindings/dma/stm32/st,stm32-dma3.yaml
>> index 38c30271f732e0c8da48199a224a88bb647eeca7..90ad70bb24eb790afe72bf2085478fa4cec60b94 100644
>> --- a/Documentation/devicetree/bindings/dma/stm32/st,stm32-dma3.yaml
>> +++ b/Documentation/devicetree/bindings/dma/stm32/st,stm32-dma3.yaml
>> @@ -51,6 +51,16 @@ properties:
>>     power-domains:
>>       maxItems: 1
>>   
>> +  st,axi-max-burst-len:
>> +    description: |
>> +      Restrict AXI burst length in unit of beat by value specified in this property.
>> +      The value specified in this property is clamped to the maximum burst length supported by DMA3.
>> +      If this property is missing, the maximum burst length supported by DMA3 is used.
>> +    $ref: /schemas/types.yaml#/definitions/uint32
>> +    minimum: 1
>> +    maximum: 256
>> +    default: 64
>> +
>>     "#dma-cells":
>>       const: 3
>>       description: |
>> @@ -137,5 +147,6 @@ examples:
>>                      <GIC_SPI 48 IRQ_TYPE_LEVEL_HIGH>;
>>         clocks = <&rcc CK_BUS_HPDMA1>;
>>         #dma-cells = <3>;
>> +      st,axi-max-burst-len = <16>;
>>       };
>>   ...
>>
>> -- 
>> 2.25.1
>>