LXR uboot/arch/arm/cpu/arm926ejs/at91/timer.c

   1/*
   2 * (C) Copyright 2007-2008
   3 * Stelian Pop <stelian@popies.net>
   4 * Lead Tech Design <www.leadtechdesign.com>
   5 *
   6 * See file CREDITS for list of people who contributed to this
   7 * project.
   8 *
   9 * This program is free software; you can redistribute it and/or
  10 * modify it under the terms of the GNU General Public License as
  11 * published by the Free Software Foundation; either version 2 of
  12 * the License, or (at your option) any later version.
  13 *
  14 * This program is distributed in the hope that it will be useful,
  15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  17 * GNU General Public License for more details.
  18 *
  19 * You should have received a copy of the GNU General Public License
  20 * along with this program; if not, write to the Free Software
  21 * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
  22 * MA 02111-1307 USA
  23 */
  24
  25#include <common.h>
  26#include <asm/io.h>
  27#include <asm/arch/hardware.h>
  28#include <asm/arch/at91_pit.h>
  29#include <asm/arch/at91_pmc.h>
  30#include <asm/arch/clk.h>
  31#include <div64.h>
  32
  33#if !defined(CONFIG_AT91FAMILY)
  34# error You need to define CONFIG_AT91FAMILY in your board config!
  35#endif
  36
  37DECLARE_GLOBAL_DATA_PTR;
  38
  39/*
  40 * We're using the AT91CAP9/SAM9 PITC in 32 bit mode, by
  41 * setting the 20 bit counter period to its maximum (0xfffff).
  42 * (See the relevant data sheets to understand that this really works)
  43 *
  44 * We do also mimic the typical powerpc way of incrementing
  45 * two 32 bit registers called tbl and tbu.
  46 *
  47 * Those registers increment at 1/16 the main clock rate.
  48 */
  49
  50#define TIMER_LOAD_VAL  0xfffff
  51
  52static inline unsigned long long tick_to_time(unsigned long long tick)
  53{
  54        tick *= CONFIG_SYS_HZ;
  55        do_div(tick, gd->timer_rate_hz);
  56
  57        return tick;
  58}
  59
  60static inline unsigned long long usec_to_tick(unsigned long long usec)
  61{
  62        usec *= gd->timer_rate_hz;
  63        do_div(usec, 1000000);
  64
  65        return usec;
  66}
  67
  68/*
  69 * Use the PITC in full 32 bit incrementing mode
  70 */
  71int timer_init(void)
  72{
  73        at91_pmc_t *pmc = (at91_pmc_t *) ATMEL_BASE_PMC;
  74        at91_pit_t *pit = (at91_pit_t *) ATMEL_BASE_PIT;
  75
  76        /* Enable PITC Clock */
  77        writel(1 << ATMEL_ID_SYS, &pmc->pcer);
  78
  79        /* Enable PITC */
  80        writel(TIMER_LOAD_VAL | AT91_PIT_MR_EN , &pit->mr);
  81
  82        gd->timer_rate_hz = gd->mck_rate_hz / 16;
  83        gd->tbu = gd->tbl = 0;
  84
  85        return 0;
  86}
  87
  88/*
  89 * Get the current 64 bit timer tick count
  90 */
  91unsigned long long get_ticks(void)
  92{
  93        at91_pit_t *pit = (at91_pit_t *) ATMEL_BASE_PIT;
  94
  95        ulong now = readl(&pit->piir);
  96
  97        /* increment tbu if tbl has rolled over */
  98        if (now < gd->tbl)
  99                gd->tbu++;
 100        gd->tbl = now;
 101        return (((unsigned long long)gd->tbu) << 32) | gd->tbl;
 102}
 103
 104void __udelay(unsigned long usec)
 105{
 106        unsigned long long start;
 107        ulong tmo;
 108
 109        start = get_ticks();            /* get current timestamp */
 110        tmo = usec_to_tick(usec);       /* convert usecs to ticks */
 111        while ((get_ticks() - start) < tmo)
 112                ;                       /* loop till time has passed */
 113}
 114
 115/*
 116 * get_timer(base) can be used to check for timeouts or
 117 * to measure elasped time relative to an event:
 118 *
 119 * ulong start_time = get_timer(0) sets start_time to the current
 120 * time value.
 121 * get_timer(start_time) returns the time elapsed since then.
 122 *
 123 * The time is used in CONFIG_SYS_HZ units!
 124 */
 125ulong get_timer(ulong base)
 126{
 127        return tick_to_time(get_ticks()) - base;
 128}
 129
 130/*
 131 * Return the number of timer ticks per second.
 132 */
 133ulong get_tbclk(void)
 134{
 135        return gd->timer_rate_hz;
 136}
 137