LXR linux/arch/microblaze/include/asm/delay.h

   1/*
   2 * include/asm-microblaze/delay.h
   3 *
   4 * This file is subject to the terms and conditions of the GNU General Public
   5 * License. See the file "COPYING" in the main directory of this archive
   6 * for more details.
   7 *
   8 * Copyright (C) 2008 Michal Simek
   9 * Copyright (C) 2007 John Williams
  10 * Copyright (C) 2006 Atmark Techno, Inc.
  11 */
  12
  13#ifndef _ASM_MICROBLAZE_DELAY_H
  14#define _ASM_MICROBLAZE_DELAY_H
  15
  16extern inline void __delay(unsigned long loops)
  17{
  18        asm volatile ("# __delay                \n\t"           \
  19                        "1: addi        %0, %0, -1\t\n"         \
  20                        "bneid  %0, 1b          \t\n"           \
  21                        "nop                    \t\n"
  22                        : "=r" (loops)
  23                        : "0" (loops));
  24}
  25
  26/*
  27 * Note that 19 * 226 == 4294 ==~ 2^32 / 10^6, so
  28 * loops = (4294 * usecs * loops_per_jiffy * HZ) / 2^32.
  29 *
  30 * The mul instruction gives us loops = (a * b) / 2^32.
  31 * We choose a = usecs * 19 * HZ and b = loops_per_jiffy * 226
  32 * because this lets us support a wide range of HZ and
  33 * loops_per_jiffy values without either a or b overflowing 2^32.
  34 * Thus we need usecs * HZ <= (2^32 - 1) / 19 = 226050910 and
  35 * loops_per_jiffy <= (2^32 - 1) / 226 = 19004280
  36 * (which corresponds to ~3800 bogomips at HZ = 100).
  37 * -- paulus
  38 */
  39#define __MAX_UDELAY    (226050910UL/HZ)        /* maximum udelay argument */
  40#define __MAX_NDELAY    (4294967295UL/HZ)       /* maximum ndelay argument */
  41
  42extern unsigned long loops_per_jiffy;
  43
  44extern inline void __udelay(unsigned int x)
  45{
  46
  47        unsigned long long tmp =
  48                (unsigned long long)x * (unsigned long long)loops_per_jiffy \
  49                        * 226LL;
  50        unsigned loops = tmp >> 32;
  51
  52/*
  53        __asm__("mulxuu %0,%1,%2" : "=r" (loops) :
  54                "r" (x), "r" (loops_per_jiffy * 226));
  55*/
  56        __delay(loops);
  57}
  58
  59extern void __bad_udelay(void);         /* deliberately undefined */
  60extern void __bad_ndelay(void);         /* deliberately undefined */
  61
  62#define udelay(n) (__builtin_constant_p(n) ? \
  63        ((n) > __MAX_UDELAY ? __bad_udelay() : __udelay((n) * (19 * HZ))) : \
  64        __udelay((n) * (19 * HZ)))
  65
  66#define ndelay(n) (__builtin_constant_p(n) ? \
  67        ((n) > __MAX_NDELAY ? __bad_ndelay() : __udelay((n) * HZ)) : \
  68        __udelay((n) * HZ))
  69
  70#define muldiv(a, b, c)         (((a)*(b))/(c))
  71
  72#endif /* _ASM_MICROBLAZE_DELAY_H */
  73