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

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Message-ID: <CANAwSgQqPREeFQisQZXqB52+w+j54Bwq4RMiHf3qUTXmnTxCAw@mail.gmail.com>
Date: Tue, 7 Jan 2025 16:43:38 +0530
From: Anand Moon <linux.amoon@...il.com>
To: Andrew Lunn <andrew@...n.ch>
Cc: Niklas Cassel <cassel@...nel.org>, 
	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

Hi Andrewm,

On Mon, 6 Jan 2025 at 19:14, Andrew Lunn <andrew@...n.ch> wrote:
>
> > 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
Ok Thanks for clarifying.

I was just trying to understand the call trace for mdio bus which got
me confused.

[0] https://lore.kernel.org/all/Z3fKkTSFFcU9gQLg@ryzen/

Thanks
-Anand