> +/*
> + * macro to convert from milliseconds to hz without integer overflow
> + * Default version using only 32bits arithmetics.
> + * 64bit port can define 64bit version in their <machine/param.h>
> + * 100000 is safe for hz < 20000
> + */
> +#ifndef mstohz
> +#define mstohz(ms) \
> +	(__predict_false((ms) >= 100000)) ? \
> +	    (((ms) / 1000 + 1) * hz) : \
> +	    (((ms) * hz) / 1000)
> +#endif
> +#endif /* _KERNEL */

For systems with restricted constants, replacing 100000
with (say) 0x10000 is probably worthwhile.

Should the values be rounded up ever?

If the values can be rounded down, dividing by 1024 will
be a benefit on systems that don't have a fast divide.

Also any software divide will be faster if unsigned
arithmetic is used.  IIRC 1000u is enough to force this,
otherwise use ((ms) + 0u) * hz / 1000u

EEEK - you've added so many superfluous parentheses it is
impossibly to spot you've missed the most important set!

look what (fixed_delay + mstohz( ms )) evaluates to!
try:
#define mstohz(ms) \
	(__predict_false((ms) >= 0x10000u) ? \
	    ((ms) + 0u) / 1000u * hz : \
	    ((ms) + 0u) * hz / 1000u)

	David

-- 
David Laight: david@l8s.co.uk