include/asm-nios2nommu/delay.h

   1 #ifndef _NIOS_DELAY_H
   2 #define _NIOS_DELAY_H
   3
   4 /*--------------------------------------------------------------------
   5  *
   6  * include/asm-nios2nommu/delay.h
   7  *
   8  * Derived from various works, Alpha, ix86, M68K, Sparc, ...et al
   9  *
  10  * Copyright (C) 2004   Microtronix Datacom Ltd
  11  *
  12  * This program is free software; you can redistribute it and/or modify
  13  * it under the terms of the GNU General Public License as published by
  14  * the Free Software Foundation; either version 2 of the License, or
  15  * (at your option) any later version.
  16  *
  17  * This program is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  * GNU General Public License for more details.
  21  *
  22  *
  23  * Jan/20/2004      dgt     NiosII
  24  *
  25  ---------------------------------------------------------------------*/
  26
  27
  28 #include <asm/param.h>
  29
  30 extern __inline__ void __delay(unsigned long loops)
  31 {
  32         int dummy;
  33
  34         __asm__ __volatile__(
  35         "1:  \n\t"
  36         "    beq    %0,zero,2f\n\t"
  37         "    addi   %0, %0, -1\n\t"
  38         "    br     1b\n\t"
  39         "2:  \n\t"
  40
  41         :  "=r" (dummy)                     /* Need output for optimizer */
  42
  43         :  "0" (loops)                      /* %0  Input                */
  44         );
  45 }
  46
  47 /*
  48  * Note that 19 * 226 == 4294 ==~ 2^32 / 10^6, so
  49  * loops = (4294 * usecs * loops_per_jiffy * HZ) / 2^32.
  50  *
  51  * The mul instruction gives us loops = (a * b) / 2^32.
  52  * We choose a = usecs * 19 * HZ and b = loops_per_jiffy * 226
  53  * because this lets us support a wide range of HZ and
  54  * loops_per_jiffy values without either a or b overflowing 2^32.
  55  * Thus we need usecs * HZ <= (2^32 - 1) / 19 = 226050910 and
  56  * loops_per_jiffy <= (2^32 - 1) / 226 = 19004280
  57  * (which corresponds to ~3800 bogomips at HZ = 100).
  58  *  -- paulus
  59  */
  60 #define __MAX_UDELAY    (226050910UL/HZ)        /* maximum udelay argument */
  61 #define __MAX_NDELAY    (4294967295UL/HZ)       /* maximum ndelay argument */
  62
  63 extern unsigned long loops_per_jiffy;
  64
  65 extern __inline__ void __udelay(unsigned int x)
  66 {
  67         unsigned int loops;
  68
  69         __asm__("mulxuu %0,%1,%2" : "=r" (loops) :
  70                 "r" (x), "r" (loops_per_jiffy * 226));
  71         __delay(loops);
  72 }
  73
  74 extern __inline__ void __ndelay(unsigned int x)
  75 {
  76         unsigned int loops;
  77
  78         __asm__("mulxuu %0,%1,%2" : "=r" (loops) :
  79                 "r" (x), "r" (loops_per_jiffy * 5));
  80         __delay(loops);
  81 }
  82
  83 extern void __bad_udelay(void);         /* deliberately undefined */
  84 extern void __bad_ndelay(void);         /* deliberately undefined */
  85
  86 #define udelay(n) (__builtin_constant_p(n)? \
  87         ((n) > __MAX_UDELAY? __bad_udelay(): __udelay((n) * (19 * HZ))) : \
  88         __udelay((n) * (19 * HZ)))
  89
  90 #define ndelay(n) (__builtin_constant_p(n)? \
  91         ((n) > __MAX_NDELAY? __bad_ndelay(): __ndelay((n) * HZ)) : \
  92         __ndelay((n) * HZ))
  93
  94 #define muldiv(a, b, c)    (((a)*(b))/(c))
  95
  96 #endif /* defined(_NIOS_DELAY_H) */