Re: [PATCH v3 1/5] clk: renesas: rzv2h-cpg: Use per-SoC PLL reference frequency for calculations

[Geert Uytterhoeven]

Hi Prabhakar,

On Wed, 17 Jun 2026 at 22:17, Lad, Prabhakar <prabhakar.csengg@xxxxxxxxx> wrote:
> On Wed, Jun 17, 2026 at 10:48 AM Geert Uytterhoeven
> <geert@xxxxxxxxxxxxxx> wrote:
> > On Mon, 15 Jun 2026 at 12:48, Prabhakar <prabhakar.csengg@xxxxxxxxx> wrote:
> > > From: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
> > >
> > > Introduce a per-SoC PLL reference input frequency parameter to avoid
> > > relying on a hardcoded 24MHz constant during PLL configuration math.
> > >
> > > Add an input_fref member to struct rzv2h_pll_limits. In the core
> > > calculation helper rzv2h_get_pll_pars(), derive the base input clock
> > > rate from limits->input_fref, utilizing the conditional ternary operator
> > > to fall back to 24MHz if the struct field is left uninitialized (0), and
> > > drop the obsolete macro RZ_V2H_OSC_CLK_IN_MEGA.
> > >
> > > This abstraction permits the reuse of the common PLL divider logic on
> > > newer SoC platforms like the RZ/T2H, which feature a 48 MHz PLL reference
> > > clock input instead of the 24 MHz signal used by RZ/V2H(P), without
> > > disrupting existing platforms.
> > >
> > > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
> >
> > Thanks for your patch!
> >
> > > --- a/include/linux/clk/renesas.h
> > > +++ b/include/linux/clk/renesas.h
> > > @@ -53,6 +53,9 @@ static inline void rzg2l_cpg_dsi_div_set_divider(u8 divider, int target) { }
> > >   * various parameters used to configure a PLL. These limits ensure
> > >   * the PLL operates within valid and stable ranges.
> > >   *
> > > + * @input_fref: Reference input frequency to the PLL (in MHz). If set
> >
> > "in Hz", as pointed out by Sashiko.
> >
> Agreed.
>
> > > + * to 0, a default value of 24MHz is used.
> > > + *
> I'll also replace `24MHz` to `24000000 Hz`.

Personally, I find "24 MHz" easier to read.
Counting zeroes without thousands-grouping can be hard...
https://lore.kernel.org/CAMuHMdUp3fOkAttk2FKJTh5svaiMwgu4JZ8utPeHghU4TQLE-w@xxxxxxxxxxxxxx

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

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