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         u32 cp_flags;
  42
  43         cp_flags = iop13xx_cp6_save();
  44         offset = next_jiffy_time - read_tcr1();
  45         iop13xx_cp6_restore(cp_flags);
  46
  47         return offset / ticks_per_usec;
  48 }
  49
  50 static irqreturn_t
  51 iop13xx_timer_interrupt(int irq, void *dev_id)
  52 {
  53         u32 cp_flags = iop13xx_cp6_save();
  54
  55         write_seqlock(&xtime_lock);
  56
  57         asm volatile("mcr p6, 0, %0, c6, c9, 0" : : "r" (1));
  58
  59         while ((signed long)(next_jiffy_time - read_tcr1())
  60                                                         >= ticks_per_jiffy) {
  61                 timer_tick();
  62                 next_jiffy_time -= ticks_per_jiffy;
  63         }
  64
  65         write_sequnlock(&xtime_lock);
  66
  67         iop13xx_cp6_restore(cp_flags);
  68
  69         return IRQ_HANDLED;
  70 }
  71
  72 static struct irqaction iop13xx_timer_irq = {
  73         .name           = "IOP13XX Timer Tick",
  74         .handler        = iop13xx_timer_interrupt,
  75         .flags          = IRQF_DISABLED | IRQF_TIMER,
  76 };
  77
  78 void __init iop13xx_init_time(unsigned long tick_rate)
  79 {
  80         u32 timer_ctl;
  81         u32 cp_flags;
  82
  83         ticks_per_jiffy = (tick_rate + HZ/2) / HZ;
  84         ticks_per_usec = tick_rate / 1000000;
  85         next_jiffy_time = 0xffffffff;
  86
  87         timer_ctl = IOP13XX_TMR_EN | IOP13XX_TMR_PRIVILEGED |
  88                         IOP13XX_TMR_RELOAD | IOP13XX_TMR_RATIO_1_1;
  89
  90         /*
  91          * We use timer 0 for our timer interrupt, and timer 1 as
  92          * monotonic counter for tracking missed jiffies.
  93          */
  94         cp_flags = iop13xx_cp6_save();
  95         asm volatile("mcr p6, 0, %0, c4, c9, 0" : : "r" (ticks_per_jiffy - 1));
  96         asm volatile("mcr p6, 0, %0, c0, c9, 0" : : "r" (timer_ctl));
  97         asm volatile("mcr p6, 0, %0, c5, c9, 0" : : "r" (0xffffffff));
  98         asm volatile("mcr p6, 0, %0, c1, c9, 0" : : "r" (timer_ctl));
  99         iop13xx_cp6_restore(cp_flags);
 100
 101         setup_irq(IRQ_IOP13XX_TIMER0, &iop13xx_timer_irq);
 102 }