Messages in this thread | | | Date | Mon, 14 Sep 2015 12:13:38 +0200 | Subject | Re: [PATCH v2] clk: add CS2000 Fractional-N driver | From | Geert Uytterhoeven <> |
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On Mon, Sep 14, 2015 at 11:47 AM, Kuninori Morimoto <kuninori.morimoto.gx@renesas.com> wrote: > +static int cs2000_ratio_set(struct i2c_client *client, > + int ch, u32 rate_in, u32 rate_out) > +{ > + u64 val; > + unsigned int i; > + int ret; > + > + if (CH_SIZE_ERR(ch)) > + return -EINVAL; > + > + /* > + * ratio = rate_out / rate_in * 2^20 > + * > + * To avoid over flow, rate_out is u64 > + * The result should be u32 > + */ > + > + val = rate_out; > + val *= (1 << 20);
val <<= 20
Or
val = (u64)rate_out << 20;
> + do_div(val, rate_in);
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-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
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