linux-kernel - Re: [PATCH v2] PCI: dw-rockchip: Enable async probe by default

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Message-ID: <b49e6147-32c6-4239-bdba-72f25ef04a9f@lunn.ch>
Date: Mon, 6 Jan 2025 14:44:19 +0100
From: Andrew Lunn <andrew@...n.ch>
To: Niklas Cassel <cassel@...nel.org>
Cc: Anand Moon <linux.amoon@...il.com>,
	Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
	Heiko Stuebner <heiko@...ech.de>, linux-pci@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] PCI: dw-rockchip: Enable async probe by default

> As both me an Manivannan said earlier in this thread,
> PCIe endpoint devices should not be described in device tree
> (the exception is an FPGA, and when you need to describe devices
> within the FPGA).
> 
> So I think that adding a "ethernet-phy" device tree node in this case is
> wrong (as the Ethernet PHY in this case is integrated in the PCIe connected
> NIC, and not a discrete component on the SoC).

There are other cases when PCIe devices need a DT node. One is when
you have an onboard ethernet switch connected to the Ethernet
device. The switch has to be described in DT, and it needs a phandle
to the ethernet interface. Hence you need a DT node the phandle points
to.

You are also making the assumption that the PCIe ethernet interface
has firmware driving all its subsystems. Which results in every PCIe
ethernet device manufacture re-inventing what Linux can already do for
SoC style Ethernet interfaces which do not have firmware, linux drives
it all. I personally would prefer Linux to drive the hardware, via a
DT node, since i then don't have to deal with firmware bugs i cannot
fix, its just Linux all the way down.

	Andrew