linux-kernel - Re: [PATCH v2 1/2] clk: renesas: rzv2h-cpg: Add support for dynamic switching divider clocks

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Message-ID: <CAMuHMdVHuej==aKo+6CTeo00cJLb59wDGu3Rq-ECRq7=cU2wdQ@mail.gmail.com>
Date: Mon, 26 Aug 2024 15:34:13 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Prabhakar <prabhakar.csengg@...il.com>
Cc: Michael Turquette <mturquette@...libre.com>, Stephen Boyd <sboyd@...nel.org>, 
	linux-renesas-soc@...r.kernel.org, linux-clk@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Biju Das <biju.das.jz@...renesas.com>, 
	Fabrizio Castro <fabrizio.castro.jz@...esas.com>, 
	Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: Re: [PATCH v2 1/2] clk: renesas: rzv2h-cpg: Add support for dynamic
 switching divider clocks

Hi Prabhakar,

On Thu, Aug 22, 2024 at 1:16 PM Prabhakar <prabhakar.csengg@...il.com> wrote:
> From: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
>
> Add support for dynamic switching divider clocks.
>
> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> ---
> v1->v2
> - Dropped DDIV_DIVCTL_WIDTH
> - width is now extracted from conf
> - Updated DDIV_GET_* macros
> - Now doing rmw as some of the DIVCTLx require it

Thanks for the update!

> --- a/drivers/clk/renesas/rzv2h-cpg.c
> +++ b/drivers/clk/renesas/rzv2h-cpg.c
> @@ -45,14 +45,23 @@
>  #define PDIV(val)              FIELD_GET(GENMASK(5, 0), (val))
>  #define SDIV(val)              FIELD_GET(GENMASK(2, 0), (val))
>
> +#define DDIV_DIVCTL_WEN(shift)         (1 << ((shift) + 16))

BIT((shift) + 16)

> +#define DDIV_GET_WIDTH(val)            FIELD_GET(GENMASK(3, 0), (val))
> +#define DDIV_GET_SHIFT(val)            FIELD_GET(GENMASK(7, 4), (val))
> +#define DDIV_GET_REG_OFFSET(val)       FIELD_GET(GENMASK(18, 8), (val))
> +#define DDIV_GET_MON(val)              FIELD_GET(GENMASK(23, 19), (val))

These are not register fields, so you might as well just use C bitfields
accesses instead:

    struct ddiv {
            unsigned int width:4;
            unsigned int shift:4;
            unsigned int offset:11;
            unsigned int monbit:5;
    };

    if ((shift + core->ddiv.width > 16)
            return ERR_PTR(-EINVAL);

(you can put cpg_core_clk.conf and cpg_core_clk.ddiv in a union to save space)

The rest LGTM.

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