linux-kernel - Re: [PATCH v10 01/10] dt-bindings: serial: Added secondary clock for RZ/T2H RSCI

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Message-ID: <CAMuHMdUThuWxxznhjvcn5cOFCWOkb5u-fRYwTOoenDRY=4H6FA@mail.gmail.com>
Date: Thu, 5 Jun 2025 20:47:10 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Rob Herring <robh@...nel.org>
Cc: Thierry Bultel <thierry.bultel.yh@...renesas.com>, thierry.bultel@...atsea.fr, 
	linux-renesas-soc@...r.kernel.org, paul.barker.ct@...renesas.com, 
	Geert Uytterhoeven <geert+renesas@...der.be>, linux-kernel@...r.kernel.org, 
	linux-serial@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v10 01/10] dt-bindings: serial: Added secondary clock for
 RZ/T2H RSCI

Hi Rob,

On Thu, 5 Jun 2025 at 16:39, Rob Herring <robh@...nel.org> wrote:
> On Fri, May 23, 2025 at 04:24:05PM +0200, Thierry Bultel wrote:
> > At boot, the default clock is the PCLKM core clock (synchronous
> > clock, which is enabled by the bootloader).
> > For different baudrates, the asynchronous clock input must be used.
> > Clock selection is made by an internal register of RCSI.
> >
> > Add the optional "sck", external clock input.
> >
> > Also remove the unneeded serial0 alias from the dts example.
> >
> > Signed-off-by: Thierry Bultel <thierry.bultel.yh@...renesas.com>
> > ---
> > Changes v9->v10:
> >  - mention sck in description
> >  - no maxItems on clock-names
> >  - fixed the #include dependency in dts example
> > Changes v8->v9:
> >  - typo in description
> >  - named clocks 'operational' and 'bus', and added optional 'sck' clock
> >  - uses value of 2nd core clock in example to break the dependency on cpg patch
> > ---
> >  .../bindings/serial/renesas,rsci.yaml           | 17 +++++++++--------
> >  1 file changed, 9 insertions(+), 8 deletions(-)
> >
> > diff --git a/Documentation/devicetree/bindings/serial/renesas,rsci.yaml b/Documentation/devicetree/bindings/serial/renesas,rsci.yaml
> > index ea879db5f485..1bf255407df0 100644
> > --- a/Documentation/devicetree/bindings/serial/renesas,rsci.yaml
> > +++ b/Documentation/devicetree/bindings/serial/renesas,rsci.yaml
> > @@ -35,10 +35,15 @@ properties:
> >        - const: tei
> >
> >    clocks:
> > -    maxItems: 1
> > +    minItems: 2
> > +    maxItems: 3
> >
> >    clock-names:
> > -    const: fck # UART functional clock
> > +    minItems: 2
> > +    items:
> > +      - const: operation
> > +      - const: bus
> > +      - const: sck # optional external clock input
>
> You can't just change the clock names. What happens to users of 'fck'?
>
> And you can't make additional entries required. What happens to users
> with only 1 clock defined?

There are no users of the bindings yet, and the RSCI driver updates haven't
reached linux-next yet.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds