arch/arm/mach-iop3xx/iop331-time.c

   1 /*
   2  * arch/arm/mach-iop3xx/iop331-time.c
   3  *
   4  * Timer code for IOP331 based systems
   5  *
   6  * Author: Dave Jiang <dave.jiang@intel.com>
   7  *
   8  * Copyright 2003 Intel Corp.
   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 static inline unsigned long get_elapsed(void)
  30 {
  31         return LATCH - *IOP331_TU_TCR0;
  32 }
  33
  34 static unsigned long iop331_gettimeoffset(void)
  35 {
  36         unsigned long elapsed, usec;
  37         u32 tisr1, tisr2;
  38
  39         /*
  40          * If an interrupt was pending before we read the timer,
  41          * we've already wrapped.  Factor this into the time.
  42          * If an interrupt was pending after we read the timer,
  43          * it may have wrapped between checking the interrupt
  44          * status and reading the timer.  Re-read the timer to
  45          * be sure its value is after the wrap.
  46          */
  47
  48         asm volatile("mrc p6, 0, %0, c6, c1, 0" : "=r" (tisr1));
  49         elapsed = get_elapsed();
  50         asm volatile("mrc p6, 0, %0, c6, c1, 0" : "=r" (tisr2));
  51
  52         if(tisr1 & 1)
  53                 elapsed += LATCH;
  54         else if (tisr2 & 1)
  55                 elapsed = LATCH + get_elapsed();
  56
  57         /*
  58          * Now convert them to usec.
  59          */
  60         usec = (unsigned long)(elapsed / (CLOCK_TICK_RATE/1000000));
  61
  62         return usec;
  63 }
  64
  65 static irqreturn_t
  66 iop331_timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
  67 {
  68         u32 tisr;
  69
  70         write_seqlock(&xtime_lock);
  71
  72         asm volatile("mrc p6, 0, %0, c6, c1, 0" : "=r" (tisr));
  73         tisr |= 1;
  74         asm volatile("mcr p6, 0, %0, c6, c1, 0" : : "r" (tisr));
  75
  76         timer_tick(regs);
  77
  78         write_sequnlock(&xtime_lock);
  79         return IRQ_HANDLED;
  80 }
  81
  82 static struct irqaction iop331_timer_irq = {
  83         .name           = "IOP331 Timer Tick",
  84         .handler        = iop331_timer_interrupt,
  85         .flags          = IRQF_DISABLED | IRQF_TIMER,
  86 };
  87
  88 static void __init iop331_timer_init(void)
  89 {
  90         u32 timer_ctl;
  91
  92         setup_irq(IRQ_IOP331_TIMER0, &iop331_timer_irq);
  93
  94         timer_ctl = IOP331_TMR_EN | IOP331_TMR_PRIVILEGED | IOP331_TMR_RELOAD |
  95                         IOP331_TMR_RATIO_1_1;
  96
  97         asm volatile("mcr p6, 0, %0, c4, c1, 0" : : "r" (LATCH));
  98
  99         asm volatile("mcr p6, 0, %0, c0, c1, 0" : : "r" (timer_ctl));
 100
 101 }
 102
 103 struct sys_timer iop331_timer = {
 104         .init           = iop331_timer_init,
 105         .offset         = iop331_gettimeoffset,
 106 };