arch/arm/mach-at91/at91sam926x_time.c

   1 /*
   2  * linux/arch/arm/mach-at91/at91sam926x_time.c
   3  *
   4  * Copyright (C) 2005-2006 M. Amine SAYA, ATMEL Rousset, France
   5  * Revision      2005 M. Nicolas Diremdjian, ATMEL Rousset, France
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  */
  11
  12 #include <linux/init.h>
  13 #include <linux/interrupt.h>
  14 #include <linux/irq.h>
  15 #include <linux/kernel.h>
  16 #include <linux/sched.h>
  17 #include <linux/time.h>
  18
  19 #include <asm/hardware.h>
  20 #include <asm/io.h>
  21 #include <asm/mach/time.h>
  22
  23 #include <asm/arch/at91_pit.h>
  24
  25
  26 #define PIT_CPIV(x)     ((x) & AT91_PIT_CPIV)
  27 #define PIT_PICNT(x)    (((x) & AT91_PIT_PICNT) >> 20)
  28
  29 /*
  30  * Returns number of microseconds since last timer interrupt.  Note that interrupts
  31  * will have been disabled by do_gettimeofday()
  32  *  'LATCH' is hwclock ticks (see CLOCK_TICK_RATE in timex.h) per jiffy.
  33  */
  34 static unsigned long at91sam926x_gettimeoffset(void)
  35 {
  36         unsigned long elapsed;
  37         unsigned long t = at91_sys_read(AT91_PIT_PIIR);
  38
  39         elapsed = (PIT_PICNT(t) * LATCH) + PIT_CPIV(t);         /* hardware clock cycles */
  40
  41         return (unsigned long)(elapsed * jiffies_to_usecs(1)) / LATCH;
  42 }
  43
  44 /*
  45  * IRQ handler for the timer.
  46  */
  47 static irqreturn_t at91sam926x_timer_interrupt(int irq, void *dev_id)
  48 {
  49         volatile long nr_ticks;
  50
  51         if (at91_sys_read(AT91_PIT_SR) & AT91_PIT_PITS) {       /* This is a shared interrupt */
  52                 /* Get number to ticks performed before interrupt and clear PIT interrupt */
  53                 nr_ticks = PIT_PICNT(at91_sys_read(AT91_PIT_PIVR));
  54                 do {
  55                         timer_tick();
  56                         nr_ticks--;
  57                 } while (nr_ticks);
  58
  59                 return IRQ_HANDLED;
  60         } else
  61                 return IRQ_NONE;                /* not handled */
  62 }
  63
  64 static struct irqaction at91sam926x_timer_irq = {
  65         .name           = "at91_tick",
  66         .flags          = IRQF_SHARED | IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL,
  67         .handler        = at91sam926x_timer_interrupt
  68 };
  69
  70 void at91sam926x_timer_reset(void)
  71 {
  72         /* Disable timer */
  73         at91_sys_write(AT91_PIT_MR, 0);
  74
  75         /* Clear any pending interrupts */
  76         (void) at91_sys_read(AT91_PIT_PIVR);
  77
  78         /* Set Period Interval timer and enable its interrupt */
  79         at91_sys_write(AT91_PIT_MR, (LATCH & AT91_PIT_PIV) | AT91_PIT_PITIEN | AT91_PIT_PITEN);
  80 }
  81
  82 /*
  83  * Set up timer interrupt.
  84  */
  85 void __init at91sam926x_timer_init(void)
  86 {
  87         /* Initialize and enable the timer */
  88         at91sam926x_timer_reset();
  89
  90         /* Make IRQs happen for the system timer. */
  91         setup_irq(AT91_ID_SYS, &at91sam926x_timer_irq);
  92 }
  93
  94 #ifdef CONFIG_PM
  95 static void at91sam926x_timer_suspend(void)
  96 {
  97         /* Disable timer */
  98         at91_sys_write(AT91_PIT_MR, 0);
  99 }
 100 #else
 101 #define at91sam926x_timer_suspend       NULL
 102 #endif
 103
 104 struct sys_timer at91sam926x_timer = {
 105         .init           = at91sam926x_timer_init,
 106         .offset         = at91sam926x_gettimeoffset,
 107         .suspend        = at91sam926x_timer_suspend,
 108         .resume         = at91sam926x_timer_reset,
 109 };
 110