arch/arm/mach-iop3xx/iop321-time.c

   1 /*
   2  * arch/arm/mach-iop3xx/iop321-time.c
   3  *
   4  * Timer code for IOP321 based systems
   5  *
   6  * Author: Deepak Saxena <dsaxena@mvista.com>
   7  *
   8  * Copyright 2002-2003 MontaVista Software Inc.
   9  *
  10  *  This program is free software; you can redistribute  it and/or modify it
  11  *  under  the terms of  the GNU General  Public License as published by the
  12  *  Free Software Foundation;  either version 2 of the  License, or (at your
  13  *  option) any later version.
  14  */
  15
  16 #include <linux/kernel.h>
  17 #include <linux/interrupt.h>
  18 #include <linux/time.h>
  19 #include <linux/init.h>
  20 #include <linux/timex.h>
  21
  22 #include <asm/hardware.h>
  23 #include <asm/io.h>
  24 #include <asm/irq.h>
  25 #include <asm/uaccess.h>
  26 #include <asm/mach/irq.h>
  27 #include <asm/mach/time.h>
  28
  29 #define IOP321_TIME_SYNC 0
  30
  31 static inline unsigned long get_elapsed(void)
  32 {
  33         return LATCH - *IOP321_TU_TCR0;
  34 }
  35
  36 static unsigned long iop321_gettimeoffset(void)
  37 {
  38         unsigned long elapsed, usec;
  39         u32 tisr1, tisr2;
  40
  41         /*
  42          * If an interrupt was pending before we read the timer,
  43          * we've already wrapped.  Factor this into the time.
  44          * If an interrupt was pending after we read the timer,
  45          * it may have wrapped between checking the interrupt
  46          * status and reading the timer.  Re-read the timer to
  47          * be sure its value is after the wrap.
  48          */
  49
  50         asm volatile("mrc p6, 0, %0, c6, c1, 0" : "=r" (tisr1));
  51         elapsed = get_elapsed();
  52         asm volatile("mrc p6, 0, %0, c6, c1, 0" : "=r" (tisr2));
  53
  54         if(tisr1 & 1)
  55                 elapsed += LATCH;
  56         else if (tisr2 & 1)
  57                 elapsed = LATCH + get_elapsed();
  58
  59         /*
  60          * Now convert them to usec.
  61          */
  62         usec = (unsigned long)(elapsed / (CLOCK_TICK_RATE/1000000));
  63
  64         return usec;
  65 }
  66
  67 static irqreturn_t
  68 iop321_timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
  69 {
  70         u32 tisr;
  71
  72         write_seqlock(&xtime_lock);
  73
  74         asm volatile("mrc p6, 0, %0, c6, c1, 0" : "=r" (tisr));
  75         tisr |= 1;
  76         asm volatile("mcr p6, 0, %0, c6, c1, 0" : : "r" (tisr));
  77
  78         timer_tick(regs);
  79
  80         write_sequnlock(&xtime_lock);
  81
  82         return IRQ_HANDLED;
  83 }
  84
  85 static struct irqaction iop321_timer_irq = {
  86         .name           = "IOP321 Timer Tick",
  87         .handler        = iop321_timer_interrupt,
  88         .flags          = SA_INTERRUPT | SA_TIMER,
  89 };
  90
  91 static void __init iop321_timer_init(void)
  92 {
  93         u32 timer_ctl;
  94
  95         setup_irq(IRQ_IOP321_TIMER0, &iop321_timer_irq);
  96
  97         timer_ctl = IOP321_TMR_EN | IOP321_TMR_PRIVILEGED | IOP321_TMR_RELOAD |
  98                         IOP321_TMR_RATIO_1_1;
  99
 100         asm volatile("mcr p6, 0, %0, c4, c1, 0" : : "r" (LATCH));
 101
 102         asm volatile("mcr p6, 0, %0, c0, c1, 0" : : "r" (timer_ctl));
 103 }
 104
 105 struct sys_timer iop321_timer = {
 106         .init           = &iop321_timer_init,
 107         .offset         = iop321_gettimeoffset,
 108 };