arch/arm/plat-iop/time.c

   1 /*
   2  * arch/arm/plat-iop/time.c
   3  *
   4  * Timer code for IOP32x and IOP33x 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 #include <linux/io.h>
  22 #include <mach/hardware.h>
  23 #include <asm/irq.h>
  24 #include <asm/uaccess.h>
  25 #include <asm/mach/irq.h>
  26 #include <asm/mach/time.h>
  27 #include <mach/time.h>
  28
  29 static unsigned long ticks_per_jiffy;
  30 static unsigned long ticks_per_usec;
  31 static unsigned long next_jiffy_time;
  32
  33 unsigned long iop_gettimeoffset(void)
  34 {
  35         unsigned long offset, temp;
  36
  37         /* enable cp6, if necessary, to avoid taking the overhead of an
  38          * undefined instruction trap
  39          */
  40         asm volatile (
  41         "mrc    p15, 0, %0, c15, c1, 0\n\t"
  42         "tst    %0, #(1 << 6)\n\t"
  43         "orreq  %0, %0, #(1 << 6)\n\t"
  44         "mcreq  p15, 0, %0, c15, c1, 0\n\t"
  45 #ifdef CONFIG_CPU_XSCALE
  46         "mrceq  p15, 0, %0, c15, c1, 0\n\t"
  47         "moveq  %0, %0\n\t"
  48         "subeq  pc, pc, #4\n\t"
  49 #endif
  50         : "=r"(temp) : : "cc");
  51
  52         offset = next_jiffy_time - read_tcr1();
  53
  54         return offset / ticks_per_usec;
  55 }
  56
  57 static irqreturn_t
  58 iop_timer_interrupt(int irq, void *dev_id)
  59 {
  60         write_tisr(1);
  61
  62         while ((signed long)(next_jiffy_time - read_tcr1())
  63                 >= ticks_per_jiffy) {
  64                 timer_tick();
  65                 next_jiffy_time -= ticks_per_jiffy;
  66         }
  67
  68         return IRQ_HANDLED;
  69 }
  70
  71 static struct irqaction iop_timer_irq = {
  72         .name           = "IOP Timer Tick",
  73         .handler        = iop_timer_interrupt,
  74         .flags          = IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL,
  75 };
  76
  77 static unsigned long iop_tick_rate;
  78 unsigned long get_iop_tick_rate(void)
  79 {
  80         return iop_tick_rate;
  81 }
  82 EXPORT_SYMBOL(get_iop_tick_rate);
  83
  84 void __init iop_init_time(unsigned long tick_rate)
  85 {
  86         u32 timer_ctl;
  87
  88         ticks_per_jiffy = DIV_ROUND_CLOSEST(tick_rate, HZ);
  89         ticks_per_usec = tick_rate / 1000000;
  90         next_jiffy_time = 0xffffffff;
  91         iop_tick_rate = tick_rate;
  92
  93         timer_ctl = IOP_TMR_EN | IOP_TMR_PRIVILEGED |
  94                         IOP_TMR_RELOAD | IOP_TMR_RATIO_1_1;
  95
  96         /*
  97          * We use timer 0 for our timer interrupt, and timer 1 as
  98          * monotonic counter for tracking missed jiffies.
  99          */
 100         write_trr0(ticks_per_jiffy - 1);
 101         write_tmr0(timer_ctl);
 102         write_trr1(0xffffffff);
 103         write_tmr1(timer_ctl);
 104
 105         setup_irq(IRQ_IOP_TIMER0, &iop_timer_irq);
 106 }