bsp/drv/lib/delay.c

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This source file includes following definitions.
delay_loop
delay_usec
calibrate_delay
   1 /*-
   2  * Copyright (c) 2005-2007, Kohsuke Ohtani
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. Neither the name of the author nor the names of any co-contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  */
  29 
  30 /*
  31  * delay.c - driver delay routine
  32  */
  33 
  34 #include <driver.h>
  35 
  36 #ifdef DEBUG
  37 #define DPRINTF(a) printf a
  38 #else
  39 #define DPRINTF(a)
  40 #endif
  41 
  42 static u_long delay_count;      /* Loop count for 1ms */
  43 
  44 static
  45 void delay_loop(u_long count)
  46 {
  47         volatile u_long i;
  48 
  49         for (i = 0; i < count; i++);
  50 }
  51 
  52 /*
  53  * Delay micro seconds (non-blocking)
  54  * timer_udelay() can be called from ISR at interrupt level.
  55  */
  56 void
  57 delay_usec(u_long usec)
  58 {
  59 
  60         delay_loop(delay_count * usec / 1000);
  61 }
  62 
  63 /*
  64  * Compute the loop count for 1ms.
  65  * Assumes clock interrupt is enabled.
  66  */
  67 void
  68 calibrate_delay(void)
  69 {
  70         u_long ticks, test_bit;
  71 
  72         DPRINTF(("Calibrating delay loop... "));
  73         delay_count = 1;
  74         for (;;) {
  75                 delay_count <<= 1;
  76 
  77                 ticks = timer_ticks();
  78                 while (ticks == timer_ticks());
  79 
  80                 ticks = timer_ticks();
  81                 delay_loop(delay_count);
  82                 if (ticks != timer_ticks())
  83                         break;
  84         }
  85         delay_count >>= 1;
  86         test_bit = delay_count;
  87 
  88         for (;;) {
  89                 test_bit >>= 1;
  90                 if (test_bit == 0)
  91                         break;
  92                 delay_count |= test_bit;
  93 
  94                 ticks = timer_ticks();
  95                 while (ticks == timer_ticks());
  96 
  97                 ticks = timer_ticks();
  98                 delay_loop(delay_count);
  99                 if (ticks != timer_ticks())
 100                         delay_count &= ~test_bit;
 101         }
 102         delay_count *= 1000;    /* count per 1sec */
 103         delay_count /= 1000;    /* count per 1ms */
 104         DPRINTF(("ok count=%ld\n", delay_count));
 105 }
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root/bsp/drv/lib/delay.c

DEFINITIONS
