/* SPDX-License-Identifier: GPL-2.0-only *//* * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com) * * Delay routines using pre computed loops_per_jiffy value. * * vineetg: Feb 2012 *  -Rewrote in "C" to avoid dealing with availability of H/w MPY *  -Also reduced the num of MPY operations from 3 to 2 * * Amit Bhor: Codito Technologies 2004 */ #ifndef __ASM_ARC_UDELAY_H#define __ASM_ARC_UDELAY_H #include <asm-generic/types.h>#include <asm/param.h>		/* HZ */ extern unsigned long loops_per_jiffy; static inline void __delay(unsigned long loops){	__asm__ __volatile__(	"	mov lp_count, %0	\n"	"	lp  1f			\n"	"	nop			\n"	"1:				\n"	:        : "r"(loops)        : "lp_count");} extern void __bad_udelay(void); /* * Normal Math for computing loops in "N" usecs *  -we have precomputed @loops_per_jiffy *  -1 sec has HZ jiffies * loops per "N" usecs = ((loops_per_jiffy * HZ / 1000000) * N) * * Approximate Division by multiplication: *  -Mathematically if we multiply and divide a number by same value the *   result remains unchanged:  In this case, we use 2^32 *  -> (loops_per_N_usec * 2^32 ) / 2^32 *  -> (((loops_per_jiffy * HZ / 1000000) * N) * 2^32) / 2^32 *  -> (loops_per_jiffy * HZ * N * 4295) / 2^32 * *  -Divide by 2^32 is very simply right shift by 32 *  -We simply need to ensure that the multiply per above eqn happens in *   64-bit precision (if CPU doesn't support it - gcc can emaulate it) */ static inline void __udelay(unsigned long usecs){	unsigned long loops; 	/* (u64) cast ensures 64 bit MPY - real or emulated	 * HZ * 4295 is pre-evaluated by gcc - hence only 2 mpy ops	 */	loops = ((u64) usecs * 4295 * HZ * loops_per_jiffy) >> 32; 	__delay(loops);} #define udelay(n) (__builtin_constant_p(n) ? ((n) > 20000 ? __bad_udelay() \				: __udelay(n)) : __udelay(n)) #endif /* __ASM_ARC_UDELAY_H */