linux-kernel - Re: [PATCH 08/11] misc: rp1: RaspberryPi RP1 misc driver

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Message-ID: <26efbff0-ba1a-4e9a-bc5e-4fd53ac0ed99@lunn.ch>
Date: Fri, 30 Aug 2024 16:21:56 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Andrea della Porta <andrea.porta@...e.com>
Cc: Krzysztof Kozlowski <krzk@...nel.org>,
	Michael Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...nel.org>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Florian Fainelli <florian.fainelli@...adcom.com>,
	Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>,
	Derek Kiernan <derek.kiernan@....com>,
	Dragan Cvetic <dragan.cvetic@....com>,
	Arnd Bergmann <arnd@...db.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Nicolas Ferre <nicolas.ferre@...rochip.com>,
	Claudiu Beznea <claudiu.beznea@...on.dev>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Saravana Kannan <saravanak@...gle.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>, linux-clk@...r.kernel.org,
	devicetree@...r.kernel.org, linux-rpi-kernel@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-gpio@...r.kernel.org, netdev@...r.kernel.org,
	linux-pci@...r.kernel.org, linux-arch@...r.kernel.org,
	Lee Jones <lee@...nel.org>, Stefan Wahren <wahrenst@....net>
Subject: Re: [PATCH 08/11] misc: rp1: RaspberryPi RP1 misc driver

On Fri, Aug 30, 2024 at 03:49:04PM +0200, Andrea della Porta wrote:
> Hi Krzysztof,
> 
> On 10:38 Wed 21 Aug     , Krzysztof Kozlowski wrote:
> > On Tue, Aug 20, 2024 at 04:36:10PM +0200, Andrea della Porta wrote:
> > > The RaspberryPi RP1 is ia PCI multi function device containing
> > > peripherals ranging from Ethernet to USB controller, I2C, SPI
> > > and others.
> > > Implement a bare minimum driver to operate the RP1, leveraging
> > > actual OF based driver implementations for the on-borad peripherals
> > > by loading a devicetree overlay during driver probe.
> > > The peripherals are accessed by mapping MMIO registers starting
> > > from PCI BAR1 region.
> > > As a minimum driver, the peripherals will not be added to the
> > > dtbo here, but in following patches.
> > > 
> > > Link: https://datasheets.raspberrypi.com/rp1/rp1-peripherals.pdf
> > > Signed-off-by: Andrea della Porta <andrea.porta@...e.com>
> > > ---
> > >  MAINTAINERS                           |   2 +
> > >  arch/arm64/boot/dts/broadcom/rp1.dtso | 152 ++++++++++++
> > 
> > Do not mix DTS with drivers.
> > 
> > These MUST be separate.
> 
> Separating the dtso from the driver in two different patches would mean
> that the dtso patch would be ordered before the driver one. This is because
> the driver embeds the dtbo binary blob inside itself, at build time. So
> in order to build the driver, the dtso needs to be there also. This is not
> the standard approach used with 'normal' dtb/dtbo, where the dtb patch is
> ordered last wrt the driver it refers to.
> Are you sure you want to proceed in this way?

It is more about they are logically separate things. The .dtb/dtbo
describes the hardware. It should be possible to review that as a
standalone thing. The code them implements the binding. It makes no
sense to review the code until the binding is correct, because changes
to the binding will need changes to the code. Hence, we want the
binding first, then the code which implements it.

	Andrew