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 #include <linux/param.h>
  17
  18 static inline void __delay(unsigned long loops)
  19 {
  20         asm volatile ("# __delay                \n\t"           \
  21                         "1: addi        %0, %0, -1\t\n"         \
  22                         "bneid  %0, 1b          \t\n"           \
  23                         "nop                    \t\n"
  24                         : "=r" (loops)
  25                         : "0" (loops));
  26 }
  27
  28 /*
  29  * Note that 19 * 226 == 4294 ==~ 2^32 / 10^6, so
  30  * loops = (4294 * usecs * loops_per_jiffy * HZ) / 2^32.
  31  *
  32  * The mul instruction gives us loops = (a * b) / 2^32.
  33  * We choose a = usecs * 19 * HZ and b = loops_per_jiffy * 226
  34  * because this lets us support a wide range of HZ and
  35  * loops_per_jiffy values without either a or b overflowing 2^32.
  36  * Thus we need usecs * HZ <= (2^32 - 1) / 19 = 226050910 and
  37  * loops_per_jiffy <= (2^32 - 1) / 226 = 19004280
  38  * (which corresponds to ~3800 bogomips at HZ = 100).
  39  * -- paulus
  40  */
  41 #define __MAX_UDELAY    (226050910UL/HZ)        /* maximum udelay argument */
  42 #define __MAX_NDELAY    (4294967295UL/HZ)       /* maximum ndelay argument */
  43
  44 extern unsigned long loops_per_jiffy;
  45
  46 static inline void __udelay(unsigned int x)
  47 {
  48
  49         unsigned long long tmp =
  50                 (unsigned long long)x * (unsigned long long)loops_per_jiffy \
  51                         * 226LL;
  52         unsigned loops = tmp >> 32;
  53
  54 /*
  55         __asm__("mulxuu %0,%1,%2" : "=r" (loops) :
  56                 "r" (x), "r" (loops_per_jiffy * 226));
  57 */
  58         __delay(loops);
  59 }
  60
  61 extern void __bad_udelay(void);         /* deliberately undefined */
  62 extern void __bad_ndelay(void);         /* deliberately undefined */
  63
  64 #define udelay(n)                                               \
  65         ({                                                      \
  66                 if (__builtin_constant_p(n)) {                  \
  67                         if ((n) / __MAX_UDELAY >= 1)            \
  68                                 __bad_udelay();                 \
  69                         else                                    \
  70                                 __udelay((n) * (19 * HZ));      \
  71                 } else {                                        \
  72                         __udelay((n) * (19 * HZ));              \
  73                 }                                               \
  74         })
  75
  76 #define ndelay(n)                                               \
  77         ({                                                      \
  78                 if (__builtin_constant_p(n)) {                  \
  79                         if ((n) / __MAX_NDELAY >= 1)            \
  80                                 __bad_ndelay();                 \
  81                         else                                    \
  82                                 __udelay((n) * HZ);             \
  83                 } else {                                        \
  84                         __udelay((n) * HZ);                     \
  85                 }                                               \
  86         })
  87
  88 #define muldiv(a, b, c)         (((a)*(b))/(c))
  89
  90 #endif /* _ASM_MICROBLAZE_DELAY_H */