lkml.org 
[lkml]   [2015]   [Sep]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH v2] clk: add CS2000 Fractional-N driver
From
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


\
 
 \ /
  Last update: 2015-09-14 12:41    [W:0.042 / U:0.340 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site