arch/arm/mach-at91rm9200/at91sam926x_time.c

   1 /*
   2  * linux/arch/arm/mach-at91rm9200/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  *  'tick' is usecs per jiffy (linux/timex.h).
  34  */
  35 static unsigned long at91sam926x_gettimeoffset(void)
  36 {
  37         unsigned long elapsed;
  38         unsigned long t = at91_sys_read(AT91_PIT_PIIR);
  39
  40         elapsed = (PIT_PICNT(t) * LATCH) + PIT_CPIV(t);         /* hardware clock cycles */
  41
  42         return (unsigned long)(elapsed * 1000000) / LATCH;
  43 }
  44
  45 /*
  46  * IRQ handler for the timer.
  47  */
  48 static irqreturn_t at91sam926x_timer_interrupt(int irq, void *dev_id)
  49 {
  50         volatile long nr_ticks;
  51
  52         if (at91_sys_read(AT91_PIT_SR) & AT91_PIT_PITS) {       /* This is a shared interrupt */
  53                 write_seqlock(&xtime_lock);
  54
  55                 /* Get number to ticks performed before interrupt and clear PIT interrupt */
  56                 nr_ticks = PIT_PICNT(at91_sys_read(AT91_PIT_PIVR));
  57                 do {
  58                         timer_tick();
  59                         nr_ticks--;
  60                 } while (nr_ticks);
  61
  62                 write_sequnlock(&xtime_lock);
  63                 return IRQ_HANDLED;
  64         } else
  65                 return IRQ_NONE;                /* not handled */
  66 }
  67
  68 static struct irqaction at91sam926x_timer_irq = {
  69         .name           = "at91_tick",
  70         .flags          = IRQF_SHARED | IRQF_DISABLED | IRQF_TIMER,
  71         .handler        = at91sam926x_timer_interrupt
  72 };
  73
  74 void at91sam926x_timer_reset(void)
  75 {
  76         /* Disable timer */
  77         at91_sys_write(AT91_PIT_MR, 0);
  78
  79         /* Clear any pending interrupts */
  80         (void) at91_sys_read(AT91_PIT_PIVR);
  81
  82         /* Set Period Interval timer and enable its interrupt */
  83         at91_sys_write(AT91_PIT_MR, (LATCH & AT91_PIT_PIV) | AT91_PIT_PITIEN | AT91_PIT_PITEN);
  84 }
  85
  86 /*
  87  * Set up timer interrupt.
  88  */
  89 void __init at91sam926x_timer_init(void)
  90 {
  91         /* Initialize and enable the timer */
  92         at91sam926x_timer_reset();
  93
  94         /* Make IRQs happen for the system timer. */
  95         setup_irq(AT91_ID_SYS, &at91sam926x_timer_irq);
  96 }
  97
  98 #ifdef CONFIG_PM
  99 static void at91sam926x_timer_suspend(void)
 100 {
 101         /* Disable timer */
 102         at91_sys_write(AT91_PIT_MR, 0);
 103 }
 104 #else
 105 #define at91sam926x_timer_suspend       NULL
 106 #endif
 107
 108 struct sys_timer at91sam926x_timer = {
 109         .init           = at91sam926x_timer_init,
 110         .offset         = at91sam926x_gettimeoffset,
 111         .suspend        = at91sam926x_timer_suspend,
 112         .resume         = at91sam926x_timer_reset,
 113 };
 114