cpu/arm_cortexa8/omap3/timer.c

   1 /*
   2  * (C) Copyright 2008
   3  * Texas Instruments
   4  *
   5  * Richard Woodruff <r-woodruff2@ti.com>
   6  * Syed Moahmmed Khasim <khasim@ti.com>
   7  *
   8  * (C) Copyright 2002
   9  * Sysgo Real-Time Solutions, GmbH <www.elinos.com>
  10  * Marius Groeger <mgroeger@sysgo.de>
  11  * Alex Zuepke <azu@sysgo.de>
  12  *
  13  * (C) Copyright 2002
  14  * Gary Jennejohn, DENX Software Engineering, <garyj@denx.de>
  15  *
  16  * See file CREDITS for list of people who contributed to this
  17  * project.
  18  *
  19  * This program is free software; you can redistribute it and/or
  20  * modify it under the terms of the GNU General Public License as
  21  * published by the Free Software Foundation; either version 2 of
  22  * the License, or (at your option) any later version.
  23  *
  24  * This program is distributed in the hope that it will be useful,
  25  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  26  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  27  * GNU General Public License for more details.
  28  *
  29  * You should have received a copy of the GNU General Public License
  30  * along with this program; if not, write to the Free Software
  31  * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
  32  * MA 02111-1307 USA
  33  */
  34
  35 #include <common.h>
  36 #include <asm/io.h>
  37
  38 static ulong timestamp;
  39 static ulong lastinc;
  40 static struct gptimer *timer_base = (struct gptimer *)CONFIG_SYS_TIMERBASE;
  41
  42 /*
  43  * Nothing really to do with interrupts, just starts up a counter.
  44  * We run the counter with 13MHz, divided by 8, resulting in timer
  45  * frequency of 1.625MHz. With 32bit counter register, counter
  46  * overflows in ~44min
  47  */
  48
  49 /* 13MHz / 8 = 1.625MHz */
  50 #define TIMER_CLOCK     (V_SCLK / (2 << CONFIG_SYS_PTV))
  51 #define TIMER_LOAD_VAL  0xffffffff
  52
  53 int timer_init(void)
  54 {
  55         /* start the counter ticking up, reload value on overflow */
  56         writel(TIMER_LOAD_VAL, &timer_base->tldr);
  57         /* enable timer */
  58         writel((CONFIG_SYS_PTV << 2) | TCLR_PRE | TCLR_AR | TCLR_ST,
  59                 &timer_base->tclr);
  60
  61         reset_timer_masked();   /* init the timestamp and lastinc value */
  62
  63         return 0;
  64 }
  65
  66 /*
  67  * timer without interrupts
  68  */
  69 void reset_timer(void)
  70 {
  71         reset_timer_masked();
  72 }
  73
  74 ulong get_timer(ulong base)
  75 {
  76         return get_timer_masked() - base;
  77 }
  78
  79 void set_timer(ulong t)
  80 {
  81         timestamp = t;
  82 }
  83
  84 /* delay x useconds */
  85 void __udelay(unsigned long usec)
  86 {
  87         long tmo = usec * (TIMER_CLOCK / 1000) / 1000;
  88         unsigned long now, last = readl(&timer_base->tcrr);
  89
  90         while (tmo > 0) {
  91                 now = readl(&timer_base->tcrr);
  92                 if (last > now) /* count up timer overflow */
  93                         tmo -= TIMER_LOAD_VAL - last + now;
  94                 else
  95                         tmo -= now - last;
  96                 last = now;
  97         }
  98 }
  99
 100 void reset_timer_masked(void)
 101 {
 102         /* reset time, capture current incrementer value time */
 103         lastinc = readl(&timer_base->tcrr) / (TIMER_CLOCK / CONFIG_SYS_HZ);
 104         timestamp = 0;          /* start "advancing" time stamp from 0 */
 105 }
 106
 107 ulong get_timer_masked(void)
 108 {
 109         /* current tick value */
 110         ulong now = readl(&timer_base->tcrr) / (TIMER_CLOCK / CONFIG_SYS_HZ);
 111
 112         if (now >= lastinc)     /* normal mode (non roll) */
 113                 /* move stamp fordward with absoulte diff ticks */
 114                 timestamp += (now - lastinc);
 115         else    /* we have rollover of incrementer */
 116                 timestamp += ((TIMER_LOAD_VAL / (TIMER_CLOCK / CONFIG_SYS_HZ))
 117                                 - lastinc) + now;
 118         lastinc = now;
 119         return timestamp;
 120 }
 121
 122 /*
 123  * This function is derived from PowerPC code (read timebase as long long).
 124  * On ARM it just returns the timer value.
 125  */
 126 unsigned long long get_ticks(void)
 127 {
 128         return get_timer(0);
 129 }
 130
 131 /*
 132  * This function is derived from PowerPC code (timebase clock frequency).
 133  * On ARM it returns the number of timer ticks per second.
 134  */
 135 ulong get_tbclk(void)
 136 {
 137         return CONFIG_SYS_HZ;
 138 }