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
  16 extern 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
  42 extern unsigned long loops_per_jiffy;
  43
  44 extern 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
  59 extern void __bad_udelay(void);         /* deliberately undefined */
  60 extern 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 */