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math64: New DIV64_U64_ROUND_CLOSEST helper

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Provide DIV64_U64_ROUND_CLOSEST helper which performs division rounded to
the closest integer using an unsigned 64bit dividend and divisor.

This will be used in a follow-up patch to allow calculation of clock
divisors with high frequency parents in the R-Car Gen3 CPG MSSR driver
where overflow occurs if either the dividend or divisor is 32bit.

Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
This commit is contained in:
Simon Horman 2019-03-25 17:35:53 +01:00 committed by Geert Uytterhoeven
parent e0836e3638
commit cb8be119d2
1 changed files with 13 additions and 0 deletions
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13
include/linux/math64.h
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@ -284,4 +284,17 @@ static inline u64 mul_u64_u32_div(u64 a, u32 mul, u32 divisor)
#define DIV64_U64_ROUND_UP(ll, d) \
({ u64 _tmp = (d); div64_u64((ll) + _tmp - 1, _tmp); })
/**
* DIV64_U64_ROUND_CLOSEST - unsigned 64bit divide with 64bit divisor rounded to nearest integer
* @dividend: unsigned 64bit dividend
* @divisor: unsigned 64bit divisor
*
* Divide unsigned 64bit dividend by unsigned 64bit divisor
* and round to closest integer.
*
* Return: dividend / divisor rounded to nearest integer
*/
#define DIV64_U64_ROUND_CLOSEST(dividend, divisor) \
({ u64 _tmp = (divisor); div64_u64((dividend) + _tmp / 2, _tmp); })
#endif /* _LINUX_MATH64_H */