arch/mn10300/kernel/time.c

   1 /* MN10300 Low level time management
   2  *
   3  * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  * - Derived from arch/i386/kernel/time.c
   6  *
   7  * This program is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public Licence
   9  * as published by the Free Software Foundation; either version
  10  * 2 of the Licence, or (at your option) any later version.
  11  */
  12 #include <linux/sched.h>
  13 #include <linux/kernel.h>
  14 #include <linux/interrupt.h>
  15 #include <linux/time.h>
  16 #include <linux/init.h>
  17 #include <linux/smp.h>
  18 #include <linux/profile.h>
  19 #include <asm/irq.h>
  20 #include <asm/div64.h>
  21 #include <asm/processor.h>
  22 #include <asm/intctl-regs.h>
  23 #include <asm/rtc.h>
  24
  25 #ifdef CONFIG_MN10300_RTC
  26 unsigned long mn10300_ioclk;            /* system I/O clock frequency */
  27 unsigned long mn10300_iobclk;           /* system I/O clock frequency */
  28 unsigned long mn10300_tsc_per_HZ;       /* number of ioclks per jiffy */
  29 #endif /* CONFIG_MN10300_RTC */
  30
  31 static unsigned long mn10300_last_tsc;  /* time-stamp counter at last time
  32                                          * interrupt occurred */
  33
  34 static irqreturn_t timer_interrupt(int irq, void *dev_id);
  35
  36 static struct irqaction timer_irq = {
  37         .handler        = timer_interrupt,
  38         .flags          = IRQF_DISABLED | IRQF_SHARED | IRQF_TIMER,
  39         .mask           = CPU_MASK_NONE,
  40         .name           = "timer",
  41 };
  42
  43 /*
  44  * scheduler clock - returns current time in nanosec units.
  45  */
  46 unsigned long long sched_clock(void)
  47 {
  48         union {
  49                 unsigned long long l;
  50                 u32 w[2];
  51         } quot;
  52
  53         quot.w[0] = mn10300_last_tsc - get_cycles();
  54         quot.w[1] = 1000000000;
  55
  56         asm("mulu %2,%3,%0,%1"
  57             : "=r"(quot.w[1]), "=r"(quot.w[0])
  58             : "0"(quot.w[1]), "1"(quot.w[0])
  59             : "cc");
  60
  61         do_div(quot.l, MN10300_TSCCLK);
  62
  63         return quot.l;
  64 }
  65
  66 /*
  67  * advance the kernel's time keeping clocks (xtime and jiffies)
  68  * - we use Timer 0 & 1 cascaded as a clock to nudge us the next time
  69  *   there's a need to update
  70  */
  71 static irqreturn_t timer_interrupt(int irq, void *dev_id)
  72 {
  73         unsigned tsc, elapse;
  74
  75         write_seqlock(&xtime_lock);
  76
  77         while (tsc = get_cycles(),
  78                elapse = mn10300_last_tsc - tsc, /* time elapsed since last
  79                                                  * tick */
  80                elapse > MN10300_TSC_PER_HZ
  81                ) {
  82                 mn10300_last_tsc -= MN10300_TSC_PER_HZ;
  83
  84                 /* advance the kernel's time tracking system */
  85                 profile_tick(CPU_PROFILING);
  86                 do_timer(1);
  87                 update_process_times(user_mode(get_irq_regs()));
  88                 check_rtc_time();
  89         }
  90
  91         write_sequnlock(&xtime_lock);
  92         return IRQ_HANDLED;
  93 }
  94
  95 /*
  96  * initialise the various timers used by the main part of the kernel
  97  */
  98 void __init time_init(void)
  99 {
 100         /* we need the prescalar running to be able to use IOCLK/8
 101          * - IOCLK runs at 1/4 (ST5 open) or 1/8 (ST5 closed) internal CPU clock
 102          * - IOCLK runs at Fosc rate (crystal speed)
 103          */
 104         TMPSCNT |= TMPSCNT_ENABLE;
 105
 106         startup_timestamp_counter();
 107
 108         printk(KERN_INFO
 109                "timestamp counter I/O clock running at %lu.%02lu"
 110                " (calibrated against RTC)\n",
 111                MN10300_TSCCLK / 1000000, (MN10300_TSCCLK / 10000) % 100);
 112
 113         xtime.tv_sec = get_initial_rtc_time();
 114         xtime.tv_nsec = 0;
 115
 116         mn10300_last_tsc = TMTSCBC;
 117
 118         /* use timer 0 & 1 cascaded to tick at as close to HZ as possible */
 119         setup_irq(TMJCIRQ, &timer_irq);
 120
 121         set_intr_level(TMJCIRQ, TMJCICR_LEVEL);
 122
 123         startup_jiffies_counter();
 124
 125 #ifdef CONFIG_MN10300_WD_TIMER
 126         /* start the watchdog timer */
 127         watchdog_go();
 128 #endif
 129 }