[U-Boot] Illegal use of FP ops in clock_ti814x.c

Wolfgang Denk
2013-10-28T23:56:19Z

Dear M?ns Rullg?rd,

In message <yw1xd2mp0yqu.fsf@unicorn.mansr.com> you wrote:
>
> Something like this should be equivalent. That said, it looks
> suspiciously like it's meant to simply do a division and round up. If
> that is the case, +225 should be +249. It probably makes no difference
> for the values actually encountered.

Umm... this is the part which I do not understand.

The original code adds 90%; you add 90%, too. However, to round up,
one usually adds only 50% ?

> diff --git a/arch/arm/cpu/armv7/am33xx/clock_ti814x.c b/arch/arm/cpu/armv7/am33xx/clock_ti814x.c
> index ef14f47..9b5a47b 100644
> --- a/arch/arm/cpu/armv7/am33xx/clock_ti814x.c
> +++ b/arch/arm/cpu/armv7/am33xx/clock_ti814x.c
> @@ -211,11 +211,8 @@ static u32 pll_dco_freq_sel(u32 clkout_dco)
> static u32 pll_sigma_delta_val(u32 clkout_dco)
> {
> u32 sig_val = 0;
> - float frac_div;
>
> - frac_div = (float) clkout_dco / 250;
> - frac_div = frac_div + 0.90;
> - sig_val = (int)frac_div;
> + sig_val = (clkout_dco + 225) / 250;
> sig_val = sig_val << 24;

Where are these 90% coming from? Are they in any way meaningful, or
even critical?

Best regards,

Wolfgang Denk

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