netdev - Re: [PATCH net-next 09/13] dt-bindings: net: airoha: Add airoha,npu phandle property

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Message-ID: <20250205-disagree-motive-517efca2b90c@spud>
Date: Wed, 5 Feb 2025 20:01:26 +0000
From: Conor Dooley <conor@...nel.org>
To: Lorenzo Bianconi <lorenzo@...nel.org>
Cc: Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Felix Fietkau <nbd@....name>, Sean Wang <sean.wang@...iatek.com>,
	Matthias Brugger <matthias.bgg@...il.com>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	Philipp Zabel <p.zabel@...gutronix.de>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, netdev@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org, devicetree@...r.kernel.org,
	upstream@...oha.com
Subject: Re: [PATCH net-next 09/13] dt-bindings: net: airoha: Add airoha,npu
 phandle property

On Wed, Feb 05, 2025 at 08:33:13PM +0100, Lorenzo Bianconi wrote:
> > On Wed, Feb 05, 2025 at 07:21:28PM +0100, Lorenzo Bianconi wrote:
> > > Introduce the airoha,npu property for the npu syscon node available on
> > > EN7581 SoC. The airoha Network Processor Unit (NPU) is used to offload
> > > network traffic forwarded between Packet Switch Engine (PSE) ports.
> > > 
> > > Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
> > > ---
> > >  Documentation/devicetree/bindings/net/airoha,en7581-eth.yaml | 8 ++++++++
> > >  1 file changed, 8 insertions(+)
> > > 
> > > diff --git a/Documentation/devicetree/bindings/net/airoha,en7581-eth.yaml b/Documentation/devicetree/bindings/net/airoha,en7581-eth.yaml
> > > index c578637c5826db4bf470a4d01ac6f3133976ae1a..6388afff64e990a20230b0c4e58534aa61f984da 100644
> > > --- a/Documentation/devicetree/bindings/net/airoha,en7581-eth.yaml
> > > +++ b/Documentation/devicetree/bindings/net/airoha,en7581-eth.yaml
> > > @@ -63,6 +63,12 @@ properties:
> > >    "#size-cells":
> > >      const: 0
> > >  
> > > +  airoha,npu:
> > > +    $ref: /schemas/types.yaml#/definitions/phandle
> > > +    description:
> > > +      Phandle to the syscon node used to configure the NPU module
> > > +      used for traffic offloading.
> > 
> > Why do you need a phandle for this, instead of a lookup by compatible?
> > Do you have multiple instances of this ethernet controller on the
> > device, that each need to look up a different npu?
> 
> actually not, but looking up via the compatible string has been naked by
> Krzysztof on a different series [0].

Hmm, I disagree with adding phandles that are not needed. I don't agree
that there's no reuse, if you can treat the phandle identically on a new
device, in all likelihood, that node should have a fallback to the
existing one.

That said, the bigger problem in what you link is the ABI break caused by
requiring the presence of a new node. I'd NAK that patch too.

> 
> Regards,
> Lorenzo
> 
> [0] https://patchwork.kernel.org/project/linux-pci/patch/20250115-en7581-pcie-pbus-csr-v1-2-40d8fcb9360f@kernel.org/
> 
> > 
> > > +
> > >  patternProperties:
> > >    "^ethernet@[1-4]$":
> > >      type: object
> > > @@ -132,6 +138,8 @@ examples:
> > >                       <GIC_SPI 49 IRQ_TYPE_LEVEL_HIGH>,
> > >                       <GIC_SPI 64 IRQ_TYPE_LEVEL_HIGH>;
> > >  
> > > +        airoha,npu = <&npu>;
> > > +
> > >          #address-cells = <1>;
> > >          #size-cells = <0>;
> > >  
> > > 
> > > -- 
> > > 2.48.1
> > > 
> 
> 



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