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

   1 /*
   2  * (C) Copyright 2007-2008
   3  * Stelian Pop <stelian.pop@leadtechdesign.com>
   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/arch/hardware.h>
  27 #include <asm/arch/at91_pit.h>
  28 #include <asm/arch/at91_pmc.h>
  29 #include <asm/arch/clk.h>
  30 #include <asm/arch/io.h>
  31 #include <div64.h>
  32
  33 /*
  34  * We're using the AT91CAP9/SAM9 PITC in 32 bit mode, by
  35  * setting the 20 bit counter period to its maximum (0xfffff).
  36  */
  37 #define TIMER_LOAD_VAL  0xfffff
  38
  39 static ulong timestamp;
  40 static ulong lastinc;
  41 static ulong timer_freq;
  42
  43 static inline unsigned long long tick_to_time(unsigned long long tick)
  44 {
  45         tick *= CONFIG_SYS_HZ;
  46         do_div(tick, timer_freq);
  47
  48         return tick;
  49 }
  50
  51 static inline unsigned long long usec_to_tick(unsigned long long usec)
  52 {
  53         usec *= timer_freq;
  54         do_div(usec, 1000000);
  55
  56         return usec;
  57 }
  58
  59 /* nothing really to do with interrupts, just starts up a counter. */
  60 int timer_init(void)
  61 {
  62         at91_pmc_t *pmc = (at91_pmc_t *) AT91_PMC_BASE;
  63         at91_pit_t *pit = (at91_pit_t *) AT91_PIT_BASE;
  64         /*
  65          * Enable PITC Clock
  66          * The clock is already enabled for system controller in boot
  67          */
  68         writel(1 << AT91_ID_SYS, &pmc->pcer);
  69
  70         /* Enable PITC */
  71         writel(TIMER_LOAD_VAL | AT91_PIT_MR_EN , &pit->mr);
  72
  73         reset_timer_masked();
  74
  75         timer_freq = get_mck_clk_rate() >> 4;
  76
  77         return 0;
  78 }
  79
  80 /*
  81  * timer without interrupts
  82  */
  83 unsigned long long get_ticks(void)
  84 {
  85         at91_pit_t *pit = (at91_pit_t *) AT91_PIT_BASE;
  86
  87         ulong now = readl(&pit->piir);
  88
  89         if (now >= lastinc)     /* normal mode (non roll) */
  90                 /* move stamp forward with absolut diff ticks */
  91                 timestamp += (now - lastinc);
  92         else                    /* we have rollover of incrementer */
  93                 timestamp += (0xFFFFFFFF - lastinc) + now;
  94         lastinc = now;
  95         return timestamp;
  96 }
  97
  98 void reset_timer_masked(void)
  99 {
 100         /* reset time */
 101         at91_pit_t *pit = (at91_pit_t *) AT91_PIT_BASE;
 102
 103         /* capture current incrementer value time */
 104         lastinc = readl(&pit->piir);
 105         timestamp = 0; /* start "advancing" time stamp from 0 */
 106 }
 107
 108 ulong get_timer_masked(void)
 109 {
 110         return tick_to_time(get_ticks());
 111 }
 112
 113 void __udelay(unsigned long usec)
 114 {
 115         unsigned long long tmp;
 116         ulong tmo;
 117
 118         tmo = usec_to_tick(usec);
 119         tmp = get_ticks() + tmo;        /* get current timestamp */
 120
 121         while (get_ticks() < tmp)       /* loop till event */
 122                  /*NOP*/;
 123 }
 124
 125 void reset_timer(void)
 126 {
 127         reset_timer_masked();
 128 }
 129
 130 ulong get_timer(ulong base)
 131 {
 132         return get_timer_masked () - base;
 133 }
 134
 135 /*
 136  * This function is derived from PowerPC code (timebase clock frequency).
 137  * On ARM it returns the number of timer ticks per second.
 138  */
 139 ulong get_tbclk(void)
 140 {
 141         ulong tbclk;
 142
 143         tbclk = CONFIG_SYS_HZ;
 144         return tbclk;
 145 }