arch/arm/mach-imx/time.c

   1 /*
   2  *  linux/arch/arm/mach-imx/time.c
   3  *
   4  *  Copyright (C) 2000-2001 Deep Blue Solutions
   5  *  Copyright (C) 2002 Shane Nay (shane@minirl.com)
   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 #include <linux/config.h>
  12 #include <linux/kernel.h>
  13 #include <linux/sched.h>
  14 #include <linux/init.h>
  15 #include <linux/interrupt.h>
  16 #include <linux/time.h>
  17
  18 #include <asm/hardware.h>
  19 #include <asm/io.h>
  20 #include <asm/leds.h>
  21 #include <asm/irq.h>
  22 #include <asm/mach/time.h>
  23
  24 /* Use timer 1 as system timer */
  25 #define TIMER_BASE IMX_TIM1_BASE
  26
  27 /*
  28  * Returns number of us since last clock interrupt.  Note that interrupts
  29  * will have been disabled by do_gettimeoffset()
  30  */
  31 static unsigned long imx_gettimeoffset(void)
  32 {
  33         unsigned long ticks;
  34
  35         /*
  36          * Get the current number of ticks.  Note that there is a race
  37          * condition between us reading the timer and checking for
  38          * an interrupt.  We get around this by ensuring that the
  39          * counter has not reloaded between our two reads.
  40          */
  41         ticks = IMX_TCN(TIMER_BASE);
  42
  43         /*
  44          * Interrupt pending?  If so, we've reloaded once already.
  45          */
  46         if (IMX_TSTAT(TIMER_BASE) & TSTAT_COMP)
  47                 ticks += LATCH;
  48
  49         /*
  50          * Convert the ticks to usecs
  51          */
  52         return (1000000 / CLK32) * ticks;
  53 }
  54
  55 /*
  56  * IRQ handler for the timer
  57  */
  58 static irqreturn_t
  59 imx_timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
  60 {
  61         write_seqlock(&xtime_lock);
  62
  63         /* clear the interrupt */
  64         if (IMX_TSTAT(TIMER_BASE))
  65                 IMX_TSTAT(TIMER_BASE) = 0;
  66
  67         timer_tick(regs);
  68         write_sequnlock(&xtime_lock);
  69
  70         return IRQ_HANDLED;
  71 }
  72
  73 static struct irqaction imx_timer_irq = {
  74         .name           = "i.MX Timer Tick",
  75         .flags          = SA_INTERRUPT,
  76         .handler        = imx_timer_interrupt
  77 };
  78
  79 /*
  80  * Set up timer interrupt, and return the current time in seconds.
  81  */
  82 static void __init imx_timer_init(void)
  83 {
  84         /*
  85          * Initialise to a known state (all timers off, and timing reset)
  86          */
  87         IMX_TCTL(TIMER_BASE) = 0;
  88         IMX_TPRER(TIMER_BASE) = 0;
  89         IMX_TCMP(TIMER_BASE) = LATCH - 1;
  90         IMX_TCTL(TIMER_BASE) = TCTL_CLK_32 | TCTL_IRQEN | TCTL_TEN;
  91
  92         /*
  93          * Make irqs happen for the system timer
  94          */
  95         setup_irq(TIM1_INT, &imx_timer_irq);
  96 }
  97
  98 struct sys_timer imx_timer = {
  99         .init           = imx_timer_init,
 100         .offset         = imx_gettimeoffset,
 101 };