linux-kernel - Re: [PATCH v1] dt-bindings: riscv: deprecate riscv,isa

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Date:   Thu, 8 Jun 2023 13:15:37 -0600
From:   Rob Herring <robh@...nel.org>
To:     Conor Dooley <conor.dooley@...rochip.com>
Cc:     Conor Dooley <conor@...nel.org>,
        Sean Anderson <sean.anderson@...o.com>,
        Anup Patel <anup@...infault.org>,
        Andrew Jones <ajones@...tanamicro.com>, palmer@...belt.com,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Alistair Francis <alistair.francis@....com>,
        Anup Patel <apatel@...tanamicro.com>,
        Atish Patra <atishp@...shpatra.org>,
        Jessica Clarke <jrtc27@...c27.com>,
        Rick Chen <rick@...estech.com>, Leo <ycliang@...estech.com>,
        linux-riscv@...ts.infradead.org, qemu-riscv@...gnu.org,
        u-boot@...ts.denx.de, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] dt-bindings: riscv: deprecate riscv,isa

On Tue, May 30, 2023 at 03:12:12PM +0100, Conor Dooley wrote:
> On Thu, May 18, 2023 at 10:42:34PM +0100, Conor Dooley wrote:
> > On Thu, May 18, 2023 at 02:30:53PM -0400, Sean Anderson wrote:
> 
> > > 
> > > Why not just have something like
> > > 
> > > mycpu {
> > > 	...
> > > 	riscv,isa {
> > > 		i;
> > > 		m;
> > > 		a;
> > > 		zicsr;
> > > 		...

I prefer property names be globally unique. The tools are geared towards 
that too. That's largely a symptom of having 0 type information in the 
DT.

For example if you had an extension called 'reg', it would be a problem.

> > > 	};
> > > };
> >
> > Naming of the node aside (perhaps that could be riscv,isa-extensions)
> > there's not something hitting me immediately as to why that is a no-no.
> > If the size is a concern, this would certainly be more efficient & not
> > like the probing would be anything other than trivial more difficult
> > what I have in my proposal.
> 
> Having started messing around with this, one of the main advantages, to
> me, of this approach is proper validation.
> cpus.yaml has additionalProperties: true in it, which would have had to
> be sorted out, or worked around, but creating a child-node with the
> properties in it allows setting additionalProperties: false.

That's an issue on my radar to fix. I started that for the Arm cpus.yaml 
a while back. Sadly it involves adding all the misc properties vendors 
added. It's not a lot, but still better to get in front of that for 
Risc-V.

> > Rob's AFK at the moment, and I was hoping that he would take a look at
> > the idea, so I won't respin til he is back, but I'll give this a go in
> > the interim.
> 
> Mechanically, the conversion of the patch isn't difficult, but I'll still
> wait for Rob to come back before sending a v2. But that v2 will more
> than likely implement your suggestion.

I haven't read the whole thread, but the initial proposal looks okay to 
me.

Another way you could do this is a list of strings:

riscv,isa-ext = "i", "m", "zicsr";

I think we have a helper to test is a string in the list.

Rob