LXR linux/arch/arm/mach-at91/at91sam926x

   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 */
  34static 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 */
  47static 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                write_seqlock(&xtime_lock);
  53
  54                /* Get number to ticks performed before interrupt and clear PIT interrupt */
  55                nr_ticks = PIT_PICNT(at91_sys_read(AT91_PIT_PIVR));
  56                do {
  57                        timer_tick();
  58                        nr_ticks--;
  59                } while (nr_ticks);
  60
  61                write_sequnlock(&xtime_lock);
  62                return IRQ_HANDLED;
  63        } else
  64                return IRQ_NONE;                /* not handled */
  65}
  66
  67static struct irqaction at91sam926x_timer_irq = {
  68        .name           = "at91_tick",
  69        .flags          = IRQF_SHARED | IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL,
  70        .handler        = at91sam926x_timer_interrupt
  71};
  72
  73void at91sam926x_timer_reset(void)
  74{
  75        /* Disable timer */
  76        at91_sys_write(AT91_PIT_MR, 0);
  77
  78        /* Clear any pending interrupts */
  79        (void) at91_sys_read(AT91_PIT_PIVR);
  80
  81        /* Set Period Interval timer and enable its interrupt */
  82        at91_sys_write(AT91_PIT_MR, (LATCH & AT91_PIT_PIV) | AT91_PIT_PITIEN | AT91_PIT_PITEN);
  83}
  84
  85/*
  86 * Set up timer interrupt.
  87 */
  88void __init at91sam926x_timer_init(void)
  89{
  90        /* Initialize and enable the timer */
  91        at91sam926x_timer_reset();
  92
  93        /* Make IRQs happen for the system timer. */
  94        setup_irq(AT91_ID_SYS, &at91sam926x_timer_irq);
  95}
  96
  97#ifdef CONFIG_PM
  98static void at91sam926x_timer_suspend(void)
  99{
 100        /* Disable timer */
 101        at91_sys_write(AT91_PIT_MR, 0);
 102}
 103#else
 104#define at91sam926x_timer_suspend       NULL
 105#endif
 106
 107struct sys_timer at91sam926x_timer = {
 108        .init           = at91sam926x_timer_init,
 109        .offset         = at91sam926x_gettimeoffset,
 110        .suspend        = at91sam926x_timer_suspend,
 111        .resume         = at91sam926x_timer_reset,
 112};
 113
 114