1/* SPDX-License-Identifier: GPL-2.0-only */
 2/*
 3 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
 4 *
 
 
 
 
 5 * Delay routines using pre computed loops_per_jiffy value.
 6 *
 7 * vineetg: Feb 2012
 8 *  -Rewrote in "C" to avoid dealing with availability of H/w MPY
 9 *  -Also reduced the num of MPY operations from 3 to 2
10 *
11 * Amit Bhor: Codito Technologies 2004
12 */
13
14#ifndef __ASM_ARC_UDELAY_H
15#define __ASM_ARC_UDELAY_H
16
17#include <asm-generic/types.h>
18#include <asm/param.h>		/* HZ */
19
20extern unsigned long loops_per_jiffy;
21
22static inline void __delay(unsigned long loops)
23{
24	__asm__ __volatile__(
25	"	mov lp_count, %0	\n"
26	"	lp  1f			\n"
27	"	nop			\n"
28	"1:				\n"
29	:
30        : "r"(loops)
31        : "lp_count");
32}
33
34extern void __bad_udelay(void);
35
36/*
37 * Normal Math for computing loops in "N" usecs
38 *  -we have precomputed @loops_per_jiffy
39 *  -1 sec has HZ jiffies
40 * loops per "N" usecs = ((loops_per_jiffy * HZ / 1000000) * N)
41 *
42 * Approximate Division by multiplication:
43 *  -Mathematically if we multiply and divide a number by same value the
44 *   result remains unchanged:  In this case, we use 2^32
45 *  -> (loops_per_N_usec * 2^32 ) / 2^32
46 *  -> (((loops_per_jiffy * HZ / 1000000) * N) * 2^32) / 2^32
47 *  -> (loops_per_jiffy * HZ * N * 4295) / 2^32
48 *
49 *  -Divide by 2^32 is very simply right shift by 32
50 *  -We simply need to ensure that the multiply per above eqn happens in
51 *   64-bit precision (if CPU doesn't support it - gcc can emaulate it)
52 */
53
54static inline void __udelay(unsigned long usecs)
55{
56	unsigned long loops;
57
58	/* (u64) cast ensures 64 bit MPY - real or emulated
59	 * HZ * 4295 is pre-evaluated by gcc - hence only 2 mpy ops
60	 */
61	loops = ((u64) usecs * 4295 * HZ * loops_per_jiffy) >> 32;
62
63	__delay(loops);
64}
65
66#define udelay(n) (__builtin_constant_p(n) ? ((n) > 20000 ? __bad_udelay() \
67				: __udelay(n)) : __udelay(n))
68
69#endif /* __ASM_ARC_UDELAY_H */

 
 1/*
 2 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
 3 *
 4 * This program is free software; you can redistribute it and/or modify
 5 * it under the terms of the GNU General Public License version 2 as
 6 * published by the Free Software Foundation.
 7 *
 8 * Delay routines using pre computed loops_per_jiffy value.
 9 *
10 * vineetg: Feb 2012
11 *  -Rewrote in "C" to avoid dealing with availability of H/w MPY
12 *  -Also reduced the num of MPY operations from 3 to 2
13 *
14 * Amit Bhor: Codito Technologies 2004
15 */
16
17#ifndef __ASM_ARC_UDELAY_H
18#define __ASM_ARC_UDELAY_H
19
 
20#include <asm/param.h>		/* HZ */
21
 
 
22static inline void __delay(unsigned long loops)
23{
24	__asm__ __volatile__(
25	"1:	sub.f %0, %0, 1	\n"
26	"	jpnz 1b		\n"
27	: "+r"(loops)
 
28	:
29	: "cc");
 
30}
31
32extern void __bad_udelay(void);
33
34/*
35 * Normal Math for computing loops in "N" usecs
36 *  -we have precomputed @loops_per_jiffy
37 *  -1 sec has HZ jiffies
38 * loops per "N" usecs = ((loops_per_jiffy * HZ / 1000000) * N)
39 *
40 * Approximate Division by multiplication:
41 *  -Mathematically if we multiply and divide a number by same value the
42 *   result remains unchanged:  In this case, we use 2^32
43 *  -> (loops_per_N_usec * 2^32 ) / 2^32
44 *  -> (((loops_per_jiffy * HZ / 1000000) * N) * 2^32) / 2^32
45 *  -> (loops_per_jiffy * HZ * N * 4295) / 2^32
46 *
47 *  -Divide by 2^32 is very simply right shift by 32
48 *  -We simply need to ensure that the multiply per above eqn happens in
49 *   64-bit precision (if CPU doesn't support it - gcc can emaulate it)
50 */
51
52static inline void __udelay(unsigned long usecs)
53{
54	unsigned long loops;
55
56	/* (u64) cast ensures 64 bit MPY - real or emulated
57	 * HZ * 4295 is pre-evaluated by gcc - hence only 2 mpy ops
58	 */
59	loops = ((u64) usecs * 4295 * HZ * loops_per_jiffy) >> 32;
60
61	__delay(loops);
62}
63
64#define udelay(n) (__builtin_constant_p(n) ? ((n) > 20000 ? __bad_udelay() \
65				: __udelay(n)) : __udelay(n))
66
67#endif /* __ASM_ARC_UDELAY_H */