linux-kernel - RE: [PATCH 02/14] dt-bindings: serial: Document sci bindings for the Renesas RZ/T2H (a.k.a r9a09g077) SoC

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Message-ID:
 <TY3PR01MB11346287906F19FDFF7ACA52886F22@TY3PR01MB11346.jpnprd01.prod.outlook.com>
Date: Mon, 10 Feb 2025 14:46:14 +0000
From: Biju Das <biju.das.jz@...renesas.com>
To: Biju Das <biju.das.jz@...renesas.com>, Geert Uytterhoeven
	<geert@...ux-m68k.org>
CC: Thierry Bultel <thierry.bultel.yh@...renesas.com>, Greg Kroah-Hartman
	<gregkh@...uxfoundation.org>, Jiri Slaby <jirislaby@...nel.org>, Rob Herring
	<robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
	<conor+dt@...nel.org>, Magnus Damm <magnus.damm@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-renesas-soc@...r.kernel.org" <linux-renesas-soc@...r.kernel.org>
Subject: RE: [PATCH 02/14] dt-bindings: serial: Document sci bindings for the
 Renesas RZ/T2H (a.k.a r9a09g077) SoC

Hi Geert,


> -----Original Message-----
> From: Biju Das <biju.das.jz@...renesas.com>
> Sent: 10 February 2025 14:42
> To: Geert Uytterhoeven <geert@...ux-m68k.org>
> Subject: RE: [PATCH 02/14] dt-bindings: serial: Document sci bindings for the Renesas RZ/T2H (a.k.a
> r9a09g077) SoC
> 
> Hi Geert,
> 
> > -----Original Message-----
> > From: Geert Uytterhoeven <geert@...ux-m68k.org>
> > Sent: 10 February 2025 14:35
> > Subject: Re: [PATCH 02/14] dt-bindings: serial: Document sci bindings
> > for the Renesas RZ/T2H (a.k.a
> > r9a09g077) SoC
> >
> > Hi Biju,
> >
> > On Mon, 10 Feb 2025 at 15:26, Biju Das <biju.das.jz@...renesas.com> wrote:
> > > > -----Original Message-----
> > > > From: Geert Uytterhoeven <geert@...ux-m68k.org>
> > > > Sent: 10 February 2025 14:15
> > > > Subject: Re: [PATCH 02/14] dt-bindings: serial: Document sci
> > > > bindings for the Renesas RZ/T2H (a.k.a
> > > > r9a09g077) SoC
> > > >
> > > > On Mon, 10 Feb 2025 at 14:19, Biju Das <biju.das.jz@...renesas.com> wrote:
> > > > > > -----Original Message-----
> > > > > > From: Geert Uytterhoeven <geert@...ux-m68k.org>
> > > > > > Sent: 10 February 2025 13:15
> > > > > > Subject: Re: [PATCH 02/14] dt-bindings: serial: Document sci
> > > > > > bindings for the Renesas RZ/T2H (a.k.a
> > > > > > r9a09g077) SoC
> > > > > >
> > > > > > On Wed, 29 Jan 2025 at 17:52, Thierry Bultel <thierry.bultel.yh@...renesas.com> wrote:
> > > > > > > Document RZ/T2H (a.k.a r9a09g077) in SCI binding.
> > > > > > >
> > > > > > > Signed-off-by: Thierry Bultel
> > > > > > > <thierry.bultel.yh@...renesas.com>
> > > > > >
> > > > > > Thanks for your patch!
> > > > > >
> > > > > > > --- /dev/null
> > > > > > > +++ b/Documentation/devicetree/bindings/serial/renesas,rzsci
> > > > > > > +++ .y
> > > > > > > +++ aml
> > > > > > > @@ -0,0 +1,100 @@
> > > > > > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > > > > > > +%YAML
> > > > > > > +1.2
> > > > > > > +---
> > > > > > > +$id:
> > > > > > > +http://devicetree.org/schemas/serial/renesas,rzsci.yaml#
> > > > > >
> > > > > > "rzsci" is IMHO a bad name, as SCI on RZ/T2 differs from the
> > > > > > similar-named "SCI" (sometimes called "RSCI" or "SCIg") on
> > > > > > RZ/A1H, RZ/A2M, RZ/G2L, RZ/V2L, and
> > > > RZ/G3S (and most old SuperH SoCs).
> > > > > >
> > > > > > BTW, I believe the variant on RZ/T2 is also used on RZ/N2, RZ/V2H, and RZ/G3E?
> > > > > >
> > > > > > However, binding-wise, they all seem to be very similar.
> > > > > > So perhaps you can just add this to the existing
> > > > > > Documentation/devicetree/bindings/serial/renesas,sci.yaml?
> > > > >
> > > > > It is present in RZ/G3E as well.
> > > > > RSCI supports sci, scif, i2c and spi that is the reason renesas,rzsci.yaml introduced.
> > > >
> > > > If you plan to add support for I2C and SPI, you will need
> > > > different bindings under Documentation/devicetree/bindings/{i2c,spi}/.
> > >
> > > OK, I thought since it is a single IP, we need to use a single
> > > compatible and instantiate appropriate device based on the device
> > > property rather than separate SCI,
> > i2c and spi compatible.
> > >
> > > Yes, I agree having different device compatible for same IP make
> > > life easier, no need to add specific vendor property.
> >
> > I said "different bindings", not "different compatible values"!
> >
> > Cfr. "renesas,tpu" having bindings in both
> > Documentation/devicetree/bindings/timer/renesas,tpu.yaml
> > and Documentation/devicetree/bindings/pwm/renesas,tpu-pwm.yaml.
> 
> Thanks for clarification. This is simple solution.

But, here we need to decide, which channels to be used in SCI, I2C and SPI
in SoC dtsi

or

Maybe define all the channels as sci as default and override it in board dts for
I2c and spi based on customer use case??

Cheers,
Biju