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SubjectRe: [PATCH] clk: factor: calculate rate by do_div
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On Mon, Dec 3, 2012 at 4:14 PM, Haojian Zhuang <haojian.zhuang@gmail.com> wrote:
> clk->rate = parent->rate / div * mult
>
> The formula is OK. But it may overflow while we do operate with
> unsigned long. So use do_div instead.
>
> Signed-off-by: Haojian Zhuang <haojian.zhuang@gmail.com>
> ---
> drivers/clk/clk-fixed-factor.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/clk/clk-fixed-factor.c b/drivers/clk/clk-fixed-factor.c
> index a489985..1ef271e 100644
> --- a/drivers/clk/clk-fixed-factor.c
> +++ b/drivers/clk/clk-fixed-factor.c
> @@ -28,8 +28,11 @@ static unsigned long clk_factor_recalc_rate(struct clk_hw *hw,
> unsigned long parent_rate)
> {
> struct clk_fixed_factor *fix = to_clk_fixed_factor(hw);
> + unsigned long long int rate;
>
> - return parent_rate * fix->mult / fix->div;
> + rate = (unsigned long long int)parent_rate * fix->mult;
> + do_div(rate, fix->div);
> + return (unsigned long)rate;
> }
>
> static long clk_factor_round_rate(struct clk_hw *hw, unsigned long rate,
> --
> 1.7.10.4
>

Correct Mike's email address.


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