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                 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
  67 static 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
  73 void 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  */
  88 void __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
  98 static 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
 107 struct 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