linux-kernel - Re: [PATCH v3 6/7] mfd: Add support for LAN966x PCI device

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Message-ID: <20240711184438.65446cc3@bootlin.com>
Date: Thu, 11 Jul 2024 18:44:38 +0200
From: Herve Codina <herve.codina@...tlin.com>
To: Lee Jones <lee@...nel.org>
Cc: Andy Shevchenko <andy.shevchenko@...il.com>, Simon Horman
 <horms@...nel.org>, Rob Herring <robh@...nel.org>, Krzysztof Kozlowski
 <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, Arnd Bergmann
 <arnd@...db.de>, UNGLinuxDriver@...rochip.com, Saravana Kannan
 <saravanak@...gle.com>, Bjorn Helgaas <bhelgaas@...gle.com>, Philipp Zabel
 <p.zabel@...gutronix.de>, Lars Povlsen <lars.povlsen@...rochip.com>, Steen
 Hegelund <Steen.Hegelund@...rochip.com>, Daniel Machon
 <daniel.machon@...rochip.com>, "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo
 Abeni <pabeni@...hat.com>, Horatiu Vultur <horatiu.vultur@...rochip.com>,
 Andrew Lunn <andrew@...n.ch>, linux-kernel@...r.kernel.org,
 devicetree@...r.kernel.org, netdev@...r.kernel.org,
 linux-pci@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, Allan
 Nielsen <allan.nielsen@...rochip.com>, Luca Ceresoli
 <luca.ceresoli@...tlin.com>, Thomas Petazzoni
 <thomas.petazzoni@...tlin.com>, Greg Kroah-Hartman
 <gregkh@...uxfoundation.org>
Subject: Re: [PATCH v3 6/7] mfd: Add support for LAN966x PCI device

Hi Lee,

On Thu, 11 Jul 2024 16:29:52 +0100
Lee Jones <lee@...nel.org> wrote:

> On Thu, 27 Jun 2024, Herve Codina wrote:
> 
> > Add a PCI driver that handles the LAN966x PCI device using a device-tree
> > overlay. This overlay is applied to the PCI device DT node and allows to
> > describe components that are present in the device.
> > 
> > The memory from the device-tree is remapped to the BAR memory thanks to
> > "ranges" properties computed at runtime by the PCI core during the PCI
> > enumeration.
> > 
> > The PCI device itself acts as an interrupt controller and is used as the
> > parent of the internal LAN966x interrupt controller to route the
> > interrupts to the assigned PCI INTx interrupt.  
> 
> Not entirely sure why this is in MFD.

This PCI driver purpose is to instanciate many other drivers using a DT
overlay. I think MFD is the right subsystem.

It acts as an interrupt controller because we need to have a bridge between the
device-tree interrupt world and the the PCI world.
This bridge is needed and specific to the driver in order to have resources
available from the device-tree world present in the applied overlay.

> 
> Also I'm unsure of his current views, but Greg has voiced pretty big
> feelings about representing PCI drivers as Platform ones in the past.

PCI drivers as Plaform ones ?
I probably missed something. Can you give me more details ?

Best regards,
Hervé