math64: New DIV_S64_ROUND_CLOSEST helper

Provide DIV_S64_ROUND_CLOSEST helper which uses div_s64 to perform
division rounded to the closest integer using signed 64bit
dividend and signed 32bit divisor.

Signed-off-by: Chunyan Zhang <[email protected]>
Signed-off-by: Sebastian Reichel <[email protected]>

Author: Chunyan Zhang

include/linux/math64.h

@@ -279,4 +279,23 @@ static inline u64 mul_u64_u32_div(u64 a, u32 mul, u32 divisor)
 #define DIV64_U64_ROUND_CLOSEST(dividend, divisor)	\
 	({ u64 _tmp = (divisor); div64_u64((dividend) + _tmp / 2, _tmp); })
 
+/*
+ * DIV_S64_ROUND_CLOSEST - signed 64bit divide with 32bit divisor rounded to nearest integer
+ * @dividend: signed 64bit dividend
+ * @divisor: signed 32bit divisor
+ *
+ * Divide signed 64bit dividend by signed 32bit divisor
+ * and round to closest integer.
+ *
+ * Return: dividend / divisor rounded to nearest integer
+ */
+#define DIV_S64_ROUND_CLOSEST(dividend, divisor)(	\
+{							\
+	s64 __x = (dividend);				\
+	s32 __d = (divisor);				\
+	((__x > 0) == (__d > 0)) ?			\
+		div_s64((__x + (__d / 2)), __d) :	\
+		div_s64((__x - (__d / 2)), __d);	\
+}							\
+)
 #endif /* _LINUX_MATH64_H */