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-types.h>
  27 #include <asm/mach/irq.h>
  28 #include <asm/mach/time.h>
  29
  30 #define IOP321_TIME_SYNC 0
  31
  32 static inline unsigned long get_elapsed(void)
  33 {
  34         return LATCH - *IOP321_TU_TCR0;
  35 }
  36
  37 static unsigned long iop321_gettimeoffset(void)
  38 {
  39         unsigned long elapsed, usec;
  40         u32 tisr1, tisr2;
  41
  42         /*
  43          * If an interrupt was pending before we read the timer,
  44          * we've already wrapped.  Factor this into the time.
  45          * If an interrupt was pending after we read the timer,
  46          * it may have wrapped between checking the interrupt
  47          * status and reading the timer.  Re-read the timer to
  48          * be sure its value is after the wrap.
  49          */
  50
  51         asm volatile("mrc p6, 0, %0, c6, c1, 0" : "=r" (tisr1));
  52         elapsed = get_elapsed();
  53         asm volatile("mrc p6, 0, %0, c6, c1, 0" : "=r" (tisr2));
  54
  55         if(tisr1 & 1)
  56                 elapsed += LATCH;
  57         else if (tisr2 & 1)
  58                 elapsed = LATCH + get_elapsed();
  59
  60         /*
  61          * Now convert them to usec.
  62          */
  63         usec = (unsigned long)(elapsed * (tick_nsec / 1000)) / LATCH;
  64
  65         return usec;
  66 }
  67
  68 static irqreturn_t
  69 iop321_timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
  70 {
  71         u32 tisr;
  72
  73         write_seqlock(&xtime_lock);
  74
  75         asm volatile("mrc p6, 0, %0, c6, c1, 0" : "=r" (tisr));
  76         tisr |= 1;
  77         asm volatile("mcr p6, 0, %0, c6, c1, 0" : : "r" (tisr));
  78
  79         timer_tick(regs);
  80
  81         write_sequnlock(&xtime_lock);
  82
  83         return IRQ_HANDLED;
  84 }
  85
  86 static struct irqaction iop321_timer_irq = {
  87         .name           = "IOP321 Timer Tick",
  88         .handler        = iop321_timer_interrupt,
  89         .flags          = SA_INTERRUPT
  90 };
  91
  92 static void __init iop321_timer_init(void)
  93 {
  94         u32 timer_ctl;
  95
  96         setup_irq(IRQ_IOP321_TIMER0, &iop321_timer_irq);
  97
  98         timer_ctl = IOP321_TMR_EN | IOP321_TMR_PRIVILEGED | IOP321_TMR_RELOAD |
  99                         IOP321_TMR_RATIO_1_1;
 100
 101         asm volatile("mcr p6, 0, %0, c4, c1, 0" : : "r" (LATCH));
 102
 103         asm volatile("mcr p6, 0, %0, c0, c1, 0" : : "r" (timer_ctl));
 104 }
 105
 106 struct sys_timer iop321_timer = {
 107         .init           = &iop321_timer_init,
 108         .offset         = iop321_gettimeoffset,
 109 };