xref: /openbmc/u-boot/lib/div64.c (revision cdb74977)
1 /*
2  * Copyright (C) 2003 Bernardo Innocenti <bernie@develer.com>
3  *
4  * Based on former do_div() implementation from asm-parisc/div64.h:
5  *	Copyright (C) 1999 Hewlett-Packard Co
6  *	Copyright (C) 1999 David Mosberger-Tang <davidm@hpl.hp.com>
7  *
8  *
9  * Generic C version of 64bit/32bit division and modulo, with
10  * 64bit result and 32bit remainder.
11  *
12  * The fast case for (n>>32 == 0) is handled inline by do_div().
13  *
14  * Code generated for this function might be very inefficient
15  * for some CPUs. __div64_32() can be overridden by linking arch-specific
16  * assembly versions such as arch/powerpc/lib/div64.S and arch/sh/lib/div64.S.
17  */
18 
19 #include <linux/types.h>
20 
21 uint32_t __div64_32(uint64_t *n, uint32_t base)
22 {
23 	uint64_t rem = *n;
24 	uint64_t b = base;
25 	uint64_t res, d = 1;
26 	uint32_t high = rem >> 32;
27 
28 	/* Reduce the thing a bit first */
29 	res = 0;
30 	if (high >= base) {
31 		high /= base;
32 		res = (uint64_t) high << 32;
33 		rem -= (uint64_t) (high*base) << 32;
34 	}
35 
36 	while ((int64_t)b > 0 && b < rem) {
37 		b = b+b;
38 		d = d+d;
39 	}
40 
41 	do {
42 		if (rem >= b) {
43 			rem -= b;
44 			res += d;
45 		}
46 		b >>= 1;
47 		d >>= 1;
48 	} while (d);
49 
50 	*n = res;
51 	return rem;
52 }
53