[cip-dev] [PATCH 4.19.y-cip 14/23] math64: New DIV64_U64_ROUND_CLOSEST helper

Biju Das
2019-07-15T13:29:59Z

From: Simon Horman <horms+renesas@verge.net.au>

commit cb8be119d21d8a0affc3598a928dd0baf5da238f upstream.

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>
Signed-off-by: Biju Das <biju.das@bp.renesas.com>
---
include/linux/math64.h | 13 +++++++++++++
1 file changed, 13 insertions(+)

diff --git a/include/linux/math64.h b/include/linux/math64.h
index bb2c84a..65bef21 100644
--- a/include/linux/math64.h
+++ b/include/linux/math64.h
@@ -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 */
--
2.7.4