linux-kernel - Re: [PATCH net-next V4 1/3] dt-bindings: net: xlnx,axi-ethernet: Introduce DMA support

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Message-ID: <20230630164659.GA1877117-robh@kernel.org>
Date:   Fri, 30 Jun 2023 10:46:59 -0600
From:   Rob Herring <robh@...nel.org>
To:     Sarath Babu Naidu Gaddam <sarath.babu.naidu.gaddam@....com>
Cc:     davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, krzysztof.kozlowski+dt@...aro.org,
        sbhatta@...vell.com, linux@...linux.org.uk, michal.simek@....com,
        radhey.shyam.pandey@....com, netdev@...r.kernel.org,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, anirudha.sarangi@....com,
        harini.katakam@....com, git@....com
Subject: Re: [PATCH net-next V4 1/3] dt-bindings: net: xlnx,axi-ethernet:
 Introduce DMA support

On Fri, Jun 30, 2023 at 11:08:42AM +0530, Sarath Babu Naidu Gaddam wrote:
> From: Radhey Shyam Pandey <radhey.shyam.pandey@...inx.com>
> 
> The axiethernet will use dmaengine framework to communicate
> with dma controller IP instead of built-in dma programming sequence.

What's dmaengine framework? This is a binding patch about the h/w.

> 
> To request dma transmit and receive channels the axiethernet uses
> generic dmas, dma-names properties.
> 
> Axiethernet may use AXI DMA or MCDMA. DMA has only two channels
> where as MCDMA has 16 Tx, 16 Rx channels. To uniquely identify each
> channel, we are using 'chan' suffix. Depending on the usecase AXI
> ethernet driver can request any combination of multichannel DMA
> channels.

The DMA provider is outside the scope of the binding. Instead, describe 
how Axiethernet can use 2 or 32 channels.

> 
> Example:
> dma-names = tx_chan0, rx_chan0, tx_chan1, rx_chan1;
> 
> Also to support the backward compatibility, use "dmas" property to
> identify as it should use dmaengine framework or legacy
> driver(built-in dma programming).
> 
> At this point it is recommended to use dmaengine framework but it's
> optional. Once the solution is stable will make dmas as
> required properties.
> 
> Signed-off-by: Radhey Shyam Pandey <radhey.shyam.pandey@...inx.com>
> Signed-off-by: Sarath Babu Naidu Gaddam <sarath.babu.naidu.gaddam@....com>
> 
> ---
> Changes in V4:
> 1) Updated commit description about tx/rx channels name.
> 2) Removed "dt-bindings" and "dmaengine" strings in subject.
> 3) Extended dmas and dma-names to support MCDMA channel names.
> 1) Remove "driver" from commit message.
> 2) Use pattern/regex for dma-names property.
> 
> Changes in V3:
> 1) Reverted reg and interrupts property to  support backward compatibility.
> 2) Moved dmas and dma-names properties from Required properties.
> 
> Changes in V2:
> - None.
> ---
>  .../bindings/net/xlnx,axi-ethernet.yaml          | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/net/xlnx,axi-ethernet.yaml b/Documentation/devicetree/bindings/net/xlnx,axi-ethernet.yaml
> index 1d33d80af11c..ea203504b8d4 100644
> --- a/Documentation/devicetree/bindings/net/xlnx,axi-ethernet.yaml
> +++ b/Documentation/devicetree/bindings/net/xlnx,axi-ethernet.yaml
> @@ -122,6 +122,20 @@ properties:
>        and "phy-handle" should point to an external PHY if exists.
>      maxItems: 1
>  
> +  dmas:
> +    minItems: 2
> +    maxItems: 32
> +    description: DMA Channel phandle and DMA request line number

Drop this description. That's every 'dmas' property. Instead define what 
each entry is.

> +
> +  dma-names:
> +    items:
> +      pattern: "^[tr]x_chan[0-9]|1[0-5]$"

I think you need some parentheses. Does a channel 10 or higher name 
validate?

> +    description:
> +      Should be "tx_chan0", "tx_chan1" ... "tx_chan15" for DMA Tx channel
> +      Should be "rx_chan0", "rx_chan1" ... "rx_chan15" for DMA Rx channel
> +    minItems: 2
> +    maxItems: 32
> +
>  required:
>    - compatible
>    - interrupts
> @@ -143,6 +157,8 @@ examples:
>          clocks = <&axi_clk>, <&axi_clk>, <&pl_enet_ref_clk>, <&mgt_clk>;
>          phy-mode = "mii";
>          reg = <0x40c00000 0x40000>,<0x50c00000 0x40000>;
> +        dmas = <&xilinx_dma 0>, <&xilinx_dma 1>;
> +        dma-names = "tx_chan0", "rx_chan0";
>          xlnx,rxcsum = <0x2>;
>          xlnx,rxmem = <0x800>;
>          xlnx,txcsum = <0x2>;
> -- 
> 2.25.1
>