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
  32 imx_gettimeoffset(void)
  33 {
  34         unsigned long ticks;
  35
  36         /*
  37          * Get the current number of ticks.  Note that there is a race
  38          * condition between us reading the timer and checking for
  39          * an interrupt.  We get around this by ensuring that the
  40          * counter has not reloaded between our two reads.
  41          */
  42         ticks = IMX_TCN(TIMER_BASE);
  43
  44         /*
  45          * Interrupt pending?  If so, we've reloaded once already.
  46          */
  47         if (IMX_TSTAT(TIMER_BASE) & TSTAT_COMP)
  48                 ticks += LATCH;
  49
  50         /*
  51          * Convert the ticks to usecs
  52          */
  53         return (1000000 / CLK32) * ticks;
  54 }
  55
  56 /*
  57  * IRQ handler for the timer
  58  */
  59 static irqreturn_t
  60 imx_timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
  61 {
  62         /* clear the interrupt */
  63         if (IMX_TSTAT(TIMER_BASE))
  64                 IMX_TSTAT(TIMER_BASE) = 0;
  65
  66         timer_tick(regs);
  67         return IRQ_HANDLED;
  68 }
  69
  70 static struct irqaction imx_timer_irq = {
  71         .name           = "i.MX Timer Tick",
  72         .flags          = SA_INTERRUPT,
  73         .handler        = imx_timer_interrupt
  74 };
  75
  76 /*
  77  * Set up timer interrupt, and return the current time in seconds.
  78  */
  79 void __init
  80 imx_init_time(void)
  81 {
  82         /*
  83          * Initialise to a known state (all timers off, and timing reset)
  84          */
  85         IMX_TCTL(TIMER_BASE) = 0;
  86         IMX_TPRER(TIMER_BASE) = 0;
  87         IMX_TCMP(TIMER_BASE) = LATCH - 1;
  88         IMX_TCTL(TIMER_BASE) = TCTL_CLK_32 | TCTL_IRQEN | TCTL_TEN;
  89
  90         /*
  91          * Make irqs happen for the system timer
  92          */
  93         setup_irq(TIM1_INT, &imx_timer_irq);
  94         gettimeoffset = imx_gettimeoffset;
  95 }