/* SPDX-License-Identifier: GPL-2.0 */#ifndef _LINUX_AVERAGE_H#define _LINUX_AVERAGE_H #include <linux/bug.h>#include <linux/compiler.h>#include <linux/log2.h> /* * Exponentially weighted moving average (EWMA) * * This implements a fixed-precision EWMA algorithm, with both the * precision and fall-off coefficient determined at compile-time * and built into the generated helper funtions. * * The first argument to the macro is the name that will be used * for the struct and helper functions. * * The second argument, the precision, expresses how many bits are * used for the fractional part of the fixed-precision values. * * The third argument, the weight reciprocal, determines how the * new values will be weighed vs. the old state, new values will * get weight 1/weight_rcp and old values 1-1/weight_rcp. Note * that this parameter must be a power of two for efficiency. */ #define DECLARE_EWMA(name, _precision, _weight_rcp)			\	struct ewma_##name {						\		unsigned long internal;					\	};								\	static inline void ewma_##name##_init(struct ewma_##name *e)	\	{								\		BUILD_BUG_ON(!__builtin_constant_p(_precision));	\		BUILD_BUG_ON(!__builtin_constant_p(_weight_rcp));	\		/*							\		 * Even if you want to feed it just 0/1 you should have	\		 * some bits for the non-fractional part...		\		 */							\		BUILD_BUG_ON((_precision) > 30);			\		BUILD_BUG_ON_NOT_POWER_OF_2(_weight_rcp);		\		e->internal = 0;					\	}								\	static inline unsigned long					\	ewma_##name##_read(struct ewma_##name *e)			\	{								\		BUILD_BUG_ON(!__builtin_constant_p(_precision));	\		BUILD_BUG_ON(!__builtin_constant_p(_weight_rcp));	\		BUILD_BUG_ON((_precision) > 30);			\		BUILD_BUG_ON_NOT_POWER_OF_2(_weight_rcp);		\		return e->internal >> (_precision);			\	}								\	static inline void ewma_##name##_add(struct ewma_##name *e,	\					     unsigned long val)		\	{								\		unsigned long internal = READ_ONCE(e->internal);	\		unsigned long weight_rcp = ilog2(_weight_rcp);		\		unsigned long precision = _precision;			\									\		BUILD_BUG_ON(!__builtin_constant_p(_precision));	\		BUILD_BUG_ON(!__builtin_constant_p(_weight_rcp));	\		BUILD_BUG_ON((_precision) > 30);			\		BUILD_BUG_ON_NOT_POWER_OF_2(_weight_rcp);		\									\		WRITE_ONCE(e->internal, internal ?			\			(((internal << weight_rcp) - internal) +	\				(val << precision)) >> weight_rcp :	\			(val << precision));				\	} #endif /* _LINUX_AVERAGE_H */