netdev - Re: [PATCH net-next v2 1/2] dt-bindings: net: airoha: npu: Add EN7581-7996 support

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Message-ID: <aWvMhXIy5Qpniv39@lore-desk>
Date: Sat, 17 Jan 2026 18:53:09 +0100
From: Lorenzo Bianconi <lorenzo@...nel.org>
To: Andrew Lunn <andrew@...n.ch>
Cc: Christian Marangi <ansuelsmth@...il.com>,
	Krzysztof Kozlowski <krzk@...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>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, netdev@...r.kernel.org,
	devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH net-next v2 1/2] dt-bindings: net: airoha: npu: Add
 EN7581-7996 support

> > On Wed, Jan 14, 2026 at 11:35:10PM +0100, Lorenzo Bianconi wrote:
> > > > > In the current codebase the NPU driver does not need to access the WiFi PCIe
> > > > > slot (or any other external device) since the offloading (wired and wireless)
> > > > > is fully managed by the NPU chip (hw + firmware binaries).
> > > > 
> > > > Are you saying the NPU itself enumerates the PCI busses and finds the
> > > > WiFi device?  If it can do that, why not ask it which PCI device it is
> > > > using?
> > > 
> > > nope, we do not need any PCI enumeration in the NPU driver at the moment
> > > (please see below).
> > > 
> > > > 
> > > > Or this the PCI slot to use somehow embedded within the firmware?
> > > 
> > > in the current implementation the NPU driver does not need any reference to
> > > WiFi or Ethernet devices. The NPU exports offloading APIs to consumer devices
> > > (e.g. WiFi or Ethernet devices). In particular,
> > > 1- during NPU module probe, the NPU driver configures NPU hw registers and
> > >    loads the NPU firmware binaries.
> > > 2- NPU consumers (ethernet and/or wifi devices) get a reference to the NPU
> > >    device via device-tree in order to consume NPU APIs for offloading.
> > > 3- netfilter flowtable offloads traffic to the selected ethernet and/or WiFi
> > >    device that runs the NPU APIs accessible via the NPU reference obtained via
> > >    dts.
> > > 
> > > The issue here is the NPU firmware binaries for EN7581, loaded by the NPU
> > > driver during NPU probe and used for offloading, depend on the WiFi chipset
> > > (e.g. MT7996 or MT7992) available on the EN7581 board (we have two different
> > > NPU binaries for MT7996 offloading and for MT7992 offloading).
> > 
> > Maybe i'm getting the NPU wrong, but i assumed it was directly talking
> > to the Ethernet and WiFi device on the PCIe bus, bypassing the host?
> 
> correct
> 
> > If so, it most somehow know what PCIe slots these devices use?
> 
> I have low visibility on the NPU hw internals but I do not think there are
> any registers in NPU mmio memory where we can read this info, but I will
> confirm it (please remember the fw binaries are not load yet).

Airoha folks reported the NPU hw can't provide the PCIe Vendor/Device ID info
of the connected WiFi chip.
I guess we have the following options here:
- Rely on the firmware-name property as proposed in v1
- Access the PCIe bus from the NPU driver during probe in order to enumerate
  the PCIe devices and verify WiFi chip PCIe Vendor/Device ID
- During mt76 probe trigger the NPU fw reload if required. This approach would
  require adding a new callback in airoha_npu ops struct (please note I have
  not tested this approach and I not sure this is really doable).

What do you think? Which one do you prefer?

Regards,
Lorenzo

> 
> Regards,
> Lorenzo
> 
> > 
> >    Andrew



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