linux-kernel - Re: [PATCH v2 09/12] dt-bindings: memory-controllers: Convert fsl,elbc to YAML

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Message-ID: <Z7ILej_AJYot_wKP@probook>
Date: Sun, 16 Feb 2025 15:59:54 +0000
From: J. Neuschäfer <j.ne@...teo.net>
To: Rob Herring <robh@...nel.org>
Cc: Crystal Wood <oss@...error.net>, j.ne@...teo.net,
	devicetree@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	Krzysztof Kozlowski <krzk@...nel.org>, imx@...ts.linux.dev,
	Madhavan Srinivasan <maddy@...ux.ibm.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Nicholas Piggin <npiggin@...il.com>,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	Naveen N Rao <naveen@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Damien Le Moal <dlemoal@...nel.org>,
	Niklas Cassel <cassel@...nel.org>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	"David S. Miller" <davem@...emloft.net>, Lee Jones <lee@...nel.org>,
	Vinod Koul <vkoul@...nel.org>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	J. Neuschäfer <j.neuschaefer@....net>,
	Wim Van Sebroeck <wim@...ux-watchdog.org>,
	Guenter Roeck <linux@...ck-us.net>, Mark Brown <broonie@...nel.org>,
	Miquel Raynal <miquel.raynal@...tlin.com>,
	Richard Weinberger <richard@....at>,
	Vignesh Raghavendra <vigneshr@...com>, linux-kernel@...r.kernel.org,
	linux-ide@...r.kernel.org, linux-crypto@...r.kernel.org,
	dmaengine@...r.kernel.org, linux-pci@...r.kernel.org,
	linux-watchdog@...r.kernel.org, linux-spi@...r.kernel.org,
	linux-mtd@...ts.infradead.org, Li Yang <leoyang.li@....com>,
	John Ogness <john.ogness@...utronix.de>
Subject: Re: [PATCH v2 09/12] dt-bindings: memory-controllers: Convert
 fsl,elbc to YAML

On Mon, Feb 10, 2025 at 03:53:24PM -0600, Rob Herring wrote:
> On Sun, Feb 09, 2025 at 02:31:34PM -0600, Crystal Wood wrote:
> > On Fri, Feb 07, 2025 at 10:30:26PM +0100, J. Neuschäfer via B4 Relay wrote:
> > > From: "J. Neuschäfer" <j.ne@...teo.net>
> > > 
> > > Convert the Freescale localbus controller bindings from text form to
> > > YAML. The updated list of compatible strings reflects current usage
> > > in arch/powerpc/boot/dts/, except that many existing device trees
> > > erroneously specify "simple-bus" in addition to fsl,*elbc.
> > > 
> > > Changes compared to the txt version:
> > >  - removed the board-control (fsl,mpc8272ads-bcsr) node because it only
> > >    appears in this example and nowhere else
> > >  - added a new example with NAND flash
> > >  - updated list of compatible strings
> > > 
> > > Signed-off-by: J. Neuschäfer <j.ne@...teo.net>
> > > ---
> > > 
> > > V2:
> > > - fix order of properties in examples, according to dts coding style
> > > - move to Documentation/devicetree/bindings/memory-controllers
> > > - clarify the commit message a tiny bit
> > > - remove unnecessary multiline markers (|)
> > > - define address format in patternProperties
> > > - trim subject line (remove "binding")
> > > - remove use of "simple-bus", because it's technically incorrect
> > 
> > While I admit I haven't been following recent developments in this area,
> > as someone who was involved when "simple-bus" was created (and was on the
> > ePAPR committee that standardized it) I'm surprised to hear simple-bus
> > being called "erroneous" or "technically incorrect" here.
> 
> Erroneous because the binding did not say "simple-bus" was used. Not 
> uncommon with the old .txt bindings.
> 
> Generally, if a bus has control registers or resources like clocks, then 
> we tend not to call them 'simple-bus'. And '"specific-bus", 
> "simple-bus"' gives some problems around what driver if any do you 
> bind to. 
[...]
> > You'd probably need something like commit 3e25f800afb82bd9e5f8 ("memory:
> > fsl_ifc: populate child devices without relying on simple-bus") and the 
> > subsequent fix in dd8adc713b1656 ("memory: fsl_ifc: populate child
> > nodes of buses and mfd devices")...
> > 
> > I'm curious what the reasoning was for removing simple-bus from IFC.  It
> > seems that the schema verification also played a role in that:
> > https://www.spinics.net/lists/devicetree/msg220418.html
> 
> If a kernel change is needed to support changed .dts files, then we 
> shouldn't be doing that here (being mature platforms). That would mean 
> new DTB will not work with existing kernels.

Alright, I'll keep simple-bus in the eLBC binding for historical
compatibility.


Thank you both for your discussion.


J. Neuschäfer