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[v6,4/7] math64: New DIV64_U64_ROUND_CLOSEST helper

Message ID 20190325163556.22025-5-horms+renesas@verge.net.au (mailing list archive)
State Accepted
Delegated to: Geert Uytterhoeven
Headers show
Series clk: renesas: r8a77990, r8a774c0: Add Z2 clock | expand

Commit Message

Simon Horman March 25, 2019, 4:35 p.m. UTC 
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>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
v6
- Updated changelog as per suggestions from
  Sergei Shtylyov and Geert Uytterhoeven
- Added Reviewed-by tag from Geert Uytterhoeven

v5
- New separate patch to add DIV64_U64_ROUND_CLOSEST
---
 include/linux/math64.h | 13 +++++++++++++
 1 file changed, 13 insertions(+)
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Patch

diff --git a/include/linux/math64.h b/include/linux/math64.h
index bb2c84afb80c..65bef21cdddb 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 */