lib_ppc/time.c

   1 /*
   2  * (C) Copyright 2000, 2001
   3  * Wolfgang Denk, DENX Software Engineering, wd@denx.de.
   4  *
   5  * See file CREDITS for list of people who contributed to this
   6  * project.
   7  *
   8  * This program is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU General Public License as
  10  * published by the Free Software Foundation; either version 2 of
  11  * the License, or (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with this program; if not, write to the Free Software
  20  * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
  21  * MA 02111-1307 USA
  22  */
  23
  24 #include <common.h>
  25
  26 #ifndef CONFIG_WD_PERIOD
  27 # define CONFIG_WD_PERIOD       (10 * 1000 * 1000)      /* 10 seconds default*/
  28 #endif
  29
  30 /* ------------------------------------------------------------------------- */
  31
  32 /*
  33  * This function is intended for SHORT delays only.
  34  * It will overflow at around 10 seconds @ 400MHz,
  35  * or 20 seconds @ 200MHz.
  36  */
  37 unsigned long usec2ticks(unsigned long usec)
  38 {
  39         ulong ticks;
  40
  41         if (usec < 1000) {
  42                 ticks = ((usec * (get_tbclk()/1000)) + 500) / 1000;
  43         } else {
  44                 ticks = ((usec / 10) * (get_tbclk() / 100000));
  45         }
  46
  47         return (ticks);
  48 }
  49
  50 /* ------------------------------------------------------------------------- */
  51
  52 /*
  53  * We implement the delay by converting the delay (the number of
  54  * microseconds to wait) into a number of time base ticks; then we
  55  * watch the time base until it has incremented by that amount.
  56  */
  57 void udelay(unsigned long usec)
  58 {
  59         ulong ticks, kv;
  60
  61         do {
  62                 kv = usec > CONFIG_WD_PERIOD ? CONFIG_WD_PERIOD : usec;
  63                 ticks = usec2ticks (kv);
  64                 wait_ticks (ticks);
  65                 usec -= kv;
  66         } while(usec);
  67 }
  68
  69 /* ------------------------------------------------------------------------- */
  70
  71 unsigned long ticks2usec(unsigned long ticks)
  72 {
  73         ulong tbclk = get_tbclk();
  74
  75         /* usec = ticks * 1000000 / tbclk
  76          * Multiplication would overflow at ~4.2e3 ticks,
  77          * so we break it up into
  78          * usec = ( ( ticks * 1000) / tbclk ) * 1000;
  79          */
  80         ticks *= 1000L;
  81         ticks /= tbclk;
  82         ticks *= 1000L;
  83
  84         return ((ulong)ticks);
  85 }
  86
  87 /* ------------------------------------------------------------------------- */
  88
  89 int init_timebase (void)
  90 {
  91 #if defined(CONFIG_5xx) || defined(CONFIG_8xx)
  92         volatile immap_t *immap = (immap_t *) CFG_IMMR;
  93
  94         /* unlock */
  95         immap->im_sitk.sitk_tbk = KAPWR_KEY;
  96 #endif
  97
  98         /* reset */
  99         asm ("li 3,0 ; mttbu 3 ; mttbl 3 ;");
 100
 101 #if defined(CONFIG_5xx) || defined(CONFIG_8xx)
 102         /* enable */
 103         immap->im_sit.sit_tbscr |= TBSCR_TBE;
 104 #endif
 105         return (0);
 106 }
 107 /* ------------------------------------------------------------------------- */