On Thu, Dec 8, 2022 at 2:07 PM Geert Uytterhoeven
<geert+renesas@xxxxxxxxx> wrote:
> R-Car Gen4 PLLs support fractional multiplication, which can improve
> accuracy when configuring a specific frequency.
>
> Add support for fractional multiplication to the custom clock driver
> for PLLs, which is currently used only for PLL2 on R-Car V4H.
>
> Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
> ---
> I am not so sure it is worth supporting this.
> On R-Car V4H, the following clock rates are seen for PLL2 and the
> Cortex-A76 CPU core clock, when using the Normal vs. the
> High-Performance mode:
>
> Multiplication Mode
> Integer Frational
> ---------- ----------
> Normal (1.7 GHz): PLL2 3399999864 3399999997
> Z0 1699999932 1699999999
> High-Performance (1.8 GHz): PLL2 3599999856 3599999997
> Z0 1799999928 1799999999
>
> The improvement is of a similar order of magnitude as the accuracy of
> the external crystal, hence insignificant...
Hence I'm ignoring this, unless someone has a good reason to push
through...
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
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
