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 <div64.h> 20 #include <linux/types.h> 21 #include <linux/compiler.h> 22 23 uint32_t notrace __div64_32(uint64_t *n, uint32_t base) 24 { 25 uint64_t rem = *n; 26 uint64_t b = base; 27 uint64_t res, d = 1; 28 uint32_t high = rem >> 32; 29 30 /* Reduce the thing a bit first */ 31 res = 0; 32 if (high >= base) { 33 high /= base; 34 res = (uint64_t) high << 32; 35 rem -= (uint64_t) (high*base) << 32; 36 } 37 38 while ((int64_t)b > 0 && b < rem) { 39 b = b+b; 40 d = d+d; 41 } 42 43 do { 44 if (rem >= b) { 45 rem -= b; 46 res += d; 47 } 48 b >>= 1; 49 d >>= 1; 50 } while (d); 51 52 *n = res; 53 return rem; 54 } 55