linux-kernel - Re: [PATCH v3 09/13] serial: sh-sci: Add support for RZ/G3E RSCI clks

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Message-ID: <CAMuHMdU_fUhM2-gxhYN3jpzj8F5FOHFYjYT+ahrVs=bsLVBZGw@mail.gmail.com>
Date: Fri, 21 Nov 2025 17:39:24 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Biju <biju.das.au@...il.com>
Cc: 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>, Biju Das <biju.das.jz@...renesas.com>, 
	Wolfram Sang <wsa+renesas@...g-engineering.com>, 
	Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>, linux-kernel@...r.kernel.org, 
	linux-serial@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-renesas-soc@...r.kernel.org
Subject: Re: [PATCH v3 09/13] serial: sh-sci: Add support for RZ/G3E RSCI clks

Hi Biju,

On Fri, 14 Nov 2025 at 11:52, Biju <biju.das.au@...il.com> wrote:
> From: Biju Das <biju.das.jz@...renesas.com>
>
> RZ/G3E RSCI has 6 clocks (5 module clocks + 1 external clock). Add
> support for the module clocks.
>
> Signed-off-by: Biju Das <biju.das.jz@...renesas.com>

Thanks for your patch!

> --- a/drivers/tty/serial/sh-sci-common.h
> +++ b/drivers/tty/serial/sh-sci-common.h
> @@ -17,6 +17,9 @@ enum SCI_CLKS {
>         SCI_SCK,                /* Optional External Clock */
>         SCI_BRG_INT,            /* Optional BRG Internal Clock Source */
>         SCI_SCIF_CLK,           /* Optional BRG External Clock Source */
> +       SCI_FCK_DIV64,          /* Optional Functional Clock frequency-divided by 64 */
> +       SCI_FCK_DIV16,          /* Optional Functional Clock frequency-divided by 16 */
> +       SCI_FCK_DIV4,           /* Optional Functional Clock frequency-divided by 4 */

Perhaps reverse the order?

>         SCI_NUM_CLKS
>  };
>
> diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
> index 2da36e8ce555..3b03d3d3f2c7 100644
> --- a/drivers/tty/serial/sh-sci.c
> +++ b/drivers/tty/serial/sh-sci.c
> @@ -3172,6 +3172,9 @@ static int sci_init_clocks(struct sci_port *sci_port, struct device *dev)
>                 [SCI_SCK] = "sck",
>                 [SCI_BRG_INT] = "brg_int",
>                 [SCI_SCIF_CLK] = "scif_clk",
> +               [SCI_FCK_DIV64] = "tclk_div64",
> +               [SCI_FCK_DIV16] = "tclk_div16",
> +               [SCI_FCK_DIV4] = "tclk_div4",

Likewise

>         };
>         struct clk *clk;
>         unsigned int i;
> @@ -3181,6 +3184,9 @@ static int sci_init_clocks(struct sci_port *sci_port, struct device *dev)
>         } else if (sci_port->type == SCI_PORT_RSCI) {
>                 clk_names[SCI_FCK] = "operation";
>                 clk_names[SCI_BRG_INT] = "bus";
> +       } else if (sci_port->type == RSCI_PORT_SCI || sci_port->type == RSCI_PORT_SCIF) {
> +               clk_names[SCI_FCK] = "tclk";
> +               clk_names[SCI_BRG_INT] = "bus";

pclk?

>         }
>
>         for (i = 0; i < SCI_NUM_CLKS; i++) {
> @@ -3194,6 +3200,12 @@ static int sci_init_clocks(struct sci_port *sci_port, struct device *dev)
>                     (i == SCI_FCK || i == SCI_BRG_INT))
>                         return dev_err_probe(dev, -ENODEV, "failed to get %s\n", name);
>
> +               if (!clk && (sci_port->type == RSCI_PORT_SCI ||
> +                            sci_port->type == RSCI_PORT_SCIF) &&
> +                   (i == SCI_FCK || i == SCI_BRG_INT || i == SCI_FCK_DIV64 ||
> +                    i == SCI_FCK_DIV16 || i == SCI_FCK_DIV4))
> +                       return dev_err_probe(dev, -ENODEV, "failed to get %s\n", name);
> +
>                 if (!clk && i == SCI_FCK) {
>                         /*
>                          * Not all SH platforms declare a clock lookup entry

This function is becoming a bit cumbersome.
Can it be simplified?
Can we avoid looking up clocks that are not relevant for the port?

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