Subject: [PATCH] clk: factor: calculate rate by do_div

From: [email-masked] (Mike Turquette)
Date: Fri, 11 Jan 2013 18:45:33 -0800

Quoting Haojian Zhuang (2012-12-15 22:27:58)
> On Sun, Dec 16, 2012 at 4:54 AM, Mike Turquette <[email-masked]> wrote:
> > On Sat, Dec 15, 2012 at 8:41 AM, Haojian Zhuang
> > <[email-masked]> wrote:
> >> On Tue, Dec 4, 2012 at 9:32 AM, Haojian Zhuang <[email-masked]> wrote:
> >>> On Mon, Dec 3, 2012 at 4:14 PM, Haojian Zhuang <[email-masked]> 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 <[email-masked]>
> >>>> ---
> >>>>  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.
> >>
> >> Any comments? Does it mean that nobody want to fix the bug?
> >
> > Thanks for the patch.  My apologies for letting this one slip through
> > the cracks but my normal email workflow was unavoidably disrupted and
> > I find myself playing catch-up with pending patches.
> >
> > The patch looks good to me but I'll change the $SUBJECT to "clk:
> > fixed-factor: round_rate should use do_div" and do some testing before
> > taking it in.
> >
> > Regards,
> > Mike
> 
> It's nice. Thank you.
> 

Pulled the fix into clk-next.

Thanks for the patch,
Mike

> Best Regards
> Haojian