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

J. Neuschäfer
2025-02-16T16:00:06Z

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@posteo.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@posteo.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