linux-kernel - Re: [PATCH v4 10/13] serial: sh-sci: Add support for RZ/T2H SCI

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Message-ID: <CAMuHMdU8VSD1Z4ing_NLXyo4x4ErzqkqzeM_n4nXX3h_GYCLnA@mail.gmail.com>
Date: Tue, 25 Mar 2025 17:24:41 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Thierry Bultel <thierry.bultel.yh@...renesas.com>
Cc: Wolfram Sang <wsa+renesas@...g-engineering.com>, Biju Das <biju.das.jz@...renesas.com>, 
	"thierry.bultel@...atsea.fr" <thierry.bultel@...atsea.fr>, 
	"linux-renesas-soc@...r.kernel.org" <linux-renesas-soc@...r.kernel.org>, 
	Paul Barker <paul.barker.ct@...renesas.com>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, 
	"linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>
Subject: Re: [PATCH v4 10/13] serial: sh-sci: Add support for RZ/T2H SCI

Hi Thierry,

On Tue, 25 Mar 2025 at 11:49, Thierry Bultel
<thierry.bultel.yh@...renesas.com> wrote:
> > From: Wolfram Sang <wsa+renesas@...g-engineering.com>
> > > > > > > +config SERIAL_RZ_SCI
> > > > > >
> > > > > > I think this name is too generic. Most RZ-variants so far do not
> > > > > > have this SoC. Would 'RZT2H' work or is it too narrow then?
> > > > >
> > > > > This is too narrow, because for instance the RZ/N2H , which is
> > > > > very similar, has the same SCI
> > > >
> > > > You know the differences better, what could be a suitable name?
> > >
> > > Please consider RZ/G3E and RZ/V2H SCI as well as it is almost similar
> > IP.
> >
> > So, I am thinking to not use a name based on SoC but based on feature like
> > SERIAL_SCI_32BIT or something. But I don't know the HW details enough to
> > make the best possible name or maybe this is a bogus idea.
>
> This seems a little bit confusing, and like said in former discussions,
> the 32 bits registers are not the main difference.
>
> Here are the known SoCs that have this IP, up to now:
>
> RZ/T2H
> RZ/N2H
> RZ/G3E
> RZ/V2H

+ RZ/V2N

> So that seems reasonable to keep RZ in the name, even there are other RZ SoCs that
> do not have it.
>
> The HW documentation does not mention a better name, or revision,

While the RZ/T2H and RZ/N2H documentation just call it "SCI" ("SCIE"
for a reduced-functionality variant), the RZ/G3E, RZV2H, and RZ/V2N
documentation calls it "RSCI". More below...

> so, the suggestion is to arbitrarily consider it as a new 'T2' type.
>
> Would SERIAL_RZ_SCI_T2 (and rz-sci-t2 for the driver) be specific enough ?

Please don't put the "SCI" in the middle of the part name
=> SERIAL_RZT2_SCI.

"RSCI" does not seem to be present on any Linux-capable Renesas SH,
ARM or RISC-V SoC I have documentation for.  However it seems to
originate from the RX series of microcontrollers:
  - RX Family Application Note: Comparison of the Differences Between
    the RSCI Module and the SCI Module[1],
  - The RX26T documentation[2] shows RSCI on RX26T is very similar
    to RSCI on the five RZ SoCs listed above, but not identical.
    The RZ variant seems to be a reduced version with 16 instead of 32
    FIFO entries, and less "special" (non-UART) modes.

So I'm in favor of calling it "RSCI" (CONFIG_SERIAL_RSCI).

[1] https://www.renesas.com/en/document/apn/comparison-differences-between-rsci-module-and-sci-module-rev100
[2] https://www.renesas.com/en/products/microcontrollers-microprocessors/rx-32-bit-performance-efficiency-mcus/rx26t-32-bit-microcontroller-optimized-dual-motor-and-pfc-control

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