arch/arm/mach-iop13xx/time.c

   1 /*
   2  * arch/arm/mach-iop13xx/time.c
   3  *
   4  * Timer code for IOP13xx (copied from IOP32x/IOP33x implementation)
   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 #include <asm/io.h>
  22 #include <asm/irq.h>
  23 #include <asm/uaccess.h>
  24 #include <asm/mach/irq.h>
  25 #include <asm/mach/time.h>
  26
  27 static unsigned long ticks_per_jiffy;
  28 static unsigned long ticks_per_usec;
  29 static unsigned long next_jiffy_time;
  30
  31 static inline u32 read_tcr1(void)
  32 {
  33         u32 val;
  34         asm volatile("mrc p6, 0, %0, c3, c9, 0" : "=r" (val));
  35         return val;
  36 }
  37
  38 unsigned long iop13xx_gettimeoffset(void)
  39 {
  40         unsigned long offset;
  41
  42         offset = next_jiffy_time - read_tcr1();
  43
  44         return offset / ticks_per_usec;
  45 }
  46
  47 static irqreturn_t
  48 iop13xx_timer_interrupt(int irq, void *dev_id)
  49 {
  50         write_seqlock(&xtime_lock);
  51
  52         asm volatile("mcr p6, 0, %0, c6, c9, 0" : : "r" (1));
  53
  54         while ((signed long)(next_jiffy_time - read_tcr1())
  55                                                         >= ticks_per_jiffy) {
  56                 timer_tick();
  57                 next_jiffy_time -= ticks_per_jiffy;
  58         }
  59
  60         write_sequnlock(&xtime_lock);
  61
  62         return IRQ_HANDLED;
  63 }
  64
  65 static struct irqaction iop13xx_timer_irq = {
  66         .name           = "IOP13XX Timer Tick",
  67         .handler        = iop13xx_timer_interrupt,
  68         .flags          = IRQF_DISABLED | IRQF_TIMER,
  69 };
  70
  71 void __init iop13xx_init_time(unsigned long tick_rate)
  72 {
  73         u32 timer_ctl;
  74
  75         ticks_per_jiffy = (tick_rate + HZ/2) / HZ;
  76         ticks_per_usec = tick_rate / 1000000;
  77         next_jiffy_time = 0xffffffff;
  78
  79         timer_ctl = IOP13XX_TMR_EN | IOP13XX_TMR_PRIVILEGED |
  80                         IOP13XX_TMR_RELOAD | IOP13XX_TMR_RATIO_1_1;
  81
  82         /*
  83          * We use timer 0 for our timer interrupt, and timer 1 as
  84          * monotonic counter for tracking missed jiffies.
  85          */
  86         asm volatile("mcr p6, 0, %0, c4, c9, 0" : : "r" (ticks_per_jiffy - 1));
  87         asm volatile("mcr p6, 0, %0, c0, c9, 0" : : "r" (timer_ctl));
  88         asm volatile("mcr p6, 0, %0, c5, c9, 0" : : "r" (0xffffffff));
  89         asm volatile("mcr p6, 0, %0, c1, c9, 0" : : "r" (timer_ctl));
  90
  91         setup_irq(IRQ_IOP13XX_TIMER0, &iop13xx_timer_irq);
  92 }