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

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Message-ID: <Z6PQEzvvCdDKQSnl@lore-desk>
Date: Wed, 5 Feb 2025 21:54:43 +0100
From: Lorenzo Bianconi <lorenzo.bianconi@...hat.com>
To: Conor Dooley <conor@...nel.org>
Cc: Lorenzo Bianconi <lorenzo@...nel.org>,
	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 08:01:26PM +0000, Conor Dooley wrote:
> > 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.
> 
> Also, where is the binding for this npu? It looks like a brand-new
> module that you're adding a driver for in this series and a phandle to
> the node for here but I see no binding for it.

The driver loads the NPU node just as syscon so I have not added the binding
for it to the series. I will add it in v2.

Regards,
Lorenzo

> 
> > 
> > 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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