linux-kernel - Re: [PATCH 15/37] clk: renesas: rzg2l: add support for RZ/G3S PLL

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Message-ID: <CAMuHMdU5S6noFjkdYeyQjVSfa4oM780e0mMCAiScDoBjF=Rpqw@mail.gmail.com>
Date:   Thu, 14 Sep 2023 15:58:05 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Claudiu <claudiu.beznea@...on.dev>
Cc:     mturquette@...libre.com, sboyd@...nel.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
        ulf.hansson@...aro.org, linus.walleij@...aro.org,
        gregkh@...uxfoundation.org, jirislaby@...nel.org,
        magnus.damm@...il.com, catalin.marinas@....com, will@...nel.org,
        prabhakar.mahadev-lad.rj@...renesas.com,
        biju.das.jz@...renesas.com, quic_bjorande@...cinc.com,
        arnd@...db.de, konrad.dybcio@...aro.org, neil.armstrong@...aro.org,
        nfraprado@...labora.com, rafal@...ecki.pl,
        wsa+renesas@...g-engineering.com,
        linux-renesas-soc@...r.kernel.org, linux-clk@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mmc@...r.kernel.org, linux-gpio@...r.kernel.org,
        linux-serial@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
Subject: Re: [PATCH 15/37] clk: renesas: rzg2l: add support for RZ/G3S PLL

Hi Claudiu,

On Tue, Sep 12, 2023 at 6:52 AM Claudiu <claudiu.beznea@...on.dev> wrote:
> From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>
> Add support for reading the frequency of PLL1/4/6 available on RZ/G3S.
> The computation formula for PLL frequency is as follows:
> Fout = (nir + nfr / 4096) * Fin / (mr * pr)
>
> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>

Thanks for your patch!

> --- a/drivers/clk/renesas/rzg2l-cpg.c
> +++ b/drivers/clk/renesas/rzg2l-cpg.c
> @@ -718,11 +718,43 @@ static const struct clk_ops rzg2l_cpg_pll_ops = {
>         .recalc_rate = rzg2l_cpg_pll_clk_recalc_rate,
>  };
>
> +static unsigned long rzg3s_cpg_pll_clk_recalc_rate(struct clk_hw *hw,
> +                                                  unsigned long parent_rate)
> +{
> +       struct pll_clk *pll_clk = to_pll(hw);
> +       struct rzg2l_cpg_priv *priv = pll_clk->priv;
> +       u32 nir, nfr, mr, pr, val;
> +       u64 rate;
> +
> +       if (pll_clk->type != CLK_TYPE_G3S_SAM_PLL)
> +               return parent_rate;
> +
> +       val = readl(priv->base + GET_REG_SAMPLL_CLK1(pll_clk->conf));
> +
> +       pr = 1 << FIELD_GET(GENMASK(28, 26), val);

Please add defines for the various GENMASK(...) fields.

> +       /* Hardware interprets values higher than 8 as p = 16. */
> +       if (pr > 8)
> +               pr = 16;
> +
> +       mr  = FIELD_GET(GENMASK(25, 22), val) + 1;
> +       nir = FIELD_GET(GENMASK(21, 13), val) + 1;
> +       nfr = FIELD_GET(GENMASK(12, 1), val);
> +
> +       rate = DIV_ROUND_CLOSEST_ULL((u64)parent_rate * nfr, 4096);
> +       rate += (u64)parent_rate * nir;

When rewriting the formula as:

    Fout = (4096 * nir + nfr) * Fin / (4096 * mr * pr)

you can simplify to:

    rate = mul_u64_u32_shr(parent_rate, 4096 * nir + nfr, 12);

> +       return DIV_ROUND_CLOSEST_ULL(rate, (mr + pr));

mr * pr

> +}

> --- a/drivers/clk/renesas/rzg2l-cpg.h
> +++ b/drivers/clk/renesas/rzg2l-cpg.h
> @@ -102,6 +102,7 @@ enum clk_types {
>         CLK_TYPE_IN,            /* External Clock Input */
>         CLK_TYPE_FF,            /* Fixed Factor Clock */
>         CLK_TYPE_SAM_PLL,
> +       CLK_TYPE_G3S_SAM_PLL,

CLK_TYPE_G3S_PLL, as the documentation doesn't use SAM?

>
>         /* Clock with divider */
>         CLK_TYPE_DIV,
> @@ -129,6 +130,8 @@ enum clk_types {
>         DEF_TYPE(_name, _id, _type, .parent = _parent)
>  #define DEF_SAMPLL(_name, _id, _parent, _conf) \
>         DEF_TYPE(_name, _id, CLK_TYPE_SAM_PLL, .parent = _parent, .conf = _conf)
> +#define DEF_G3S_SAMPLL(_name, _id, _parent, _conf) \

DEF_G3S_PLL

> +       DEF_TYPE(_name, _id, CLK_TYPE_G3S_SAM_PLL, .parent = _parent, .conf = _conf)
>  #define DEF_INPUT(_name, _id) \
>         DEF_TYPE(_name, _id, CLK_TYPE_IN)
>  #define DEF_FIXED(_name, _id, _parent, _mult, _div) \

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