arch/mn10300/kernel/time.c

   1 /* MN10300 Low level time management
   2  *
   3  * Copyright (C) 2007-2008 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 <linux/cnt32_to_63.h>
  20 #include <linux/clocksource.h>
  21 #include <linux/clockchips.h>
  22 #include <asm/irq.h>
  23 #include <asm/div64.h>
  24 #include <asm/processor.h>
  25 #include <asm/intctl-regs.h>
  26 #include <asm/rtc.h>
  27 #include "internal.h"
  28
  29 static unsigned long mn10300_last_tsc;  /* time-stamp counter at last time
  30                                          * interrupt occurred */
  31
  32 static unsigned long sched_clock_multiplier;
  33
  34 /*
  35  * scheduler clock - returns current time in nanosec units.
  36  */
  37 unsigned long long sched_clock(void)
  38 {
  39         union {
  40                 unsigned long long ll;
  41                 unsigned l[2];
  42         } tsc64, result;
  43         unsigned long tmp;
  44         unsigned product[3]; /* 96-bit intermediate value */
  45
  46         /* cnt32_to_63() is not safe with preemption */
  47         preempt_disable();
  48
  49         /* expand the tsc to 64-bits.
  50          * - sched_clock() must be called once a minute or better or the
  51          *   following will go horribly wrong - see cnt32_to_63()
  52          */
  53         tsc64.ll = cnt32_to_63(get_cycles()) & 0x7fffffffffffffffULL;
  54
  55         preempt_enable();
  56
  57         /* scale the 64-bit TSC value to a nanosecond value via a 96-bit
  58          * intermediate
  59          */
  60         asm("mulu       %2,%0,%3,%0     \n"     /* LSW * mult ->  0:%3:%0 */
  61             "mulu       %2,%1,%2,%1     \n"     /* MSW * mult -> %2:%1:0 */
  62             "add        %3,%1           \n"
  63             "addc       0,%2            \n"     /* result in %2:%1:%0 */
  64             : "=r"(product[0]), "=r"(product[1]), "=r"(product[2]), "=r"(tmp)
  65             :  "0"(tsc64.l[0]),  "1"(tsc64.l[1]),  "2"(sched_clock_multiplier)
  66             : "cc");
  67
  68         result.l[0] = product[1] << 16 | product[0] >> 16;
  69         result.l[1] = product[2] << 16 | product[1] >> 16;
  70
  71         return result.ll;
  72 }
  73
  74 /*
  75  * initialise the scheduler clock
  76  */
  77 static void __init mn10300_sched_clock_init(void)
  78 {
  79         sched_clock_multiplier =
  80                 __muldiv64u(NSEC_PER_SEC, 1 << 16, MN10300_TSCCLK);
  81 }
  82
  83 /**
  84  * local_timer_interrupt - Local timer interrupt handler
  85  *
  86  * Handle local timer interrupts for this CPU.  They may have been propagated
  87  * to this CPU from the CPU that actually gets them by way of an IPI.
  88  */
  89 irqreturn_t local_timer_interrupt(void)
  90 {
  91         profile_tick(CPU_PROFILING);
  92         update_process_times(user_mode(get_irq_regs()));
  93         return IRQ_HANDLED;
  94 }
  95
  96 /*
  97  * initialise the various timers used by the main part of the kernel
  98  */
  99 void __init time_init(void)
 100 {
 101         /* we need the prescalar running to be able to use IOCLK/8
 102          * - IOCLK runs at 1/4 (ST5 open) or 1/8 (ST5 closed) internal CPU clock
 103          * - IOCLK runs at Fosc rate (crystal speed)
 104          */
 105         TMPSCNT |= TMPSCNT_ENABLE;
 106
 107         init_clocksource();
 108
 109         printk(KERN_INFO
 110                "timestamp counter I/O clock running at %lu.%02lu"
 111                " (calibrated against RTC)\n",
 112                MN10300_TSCCLK / 1000000, (MN10300_TSCCLK / 10000) % 100);
 113
 114         mn10300_last_tsc = read_timestamp_counter();
 115
 116         init_clockevents();
 117
 118 #ifdef CONFIG_MN10300_WD_TIMER
 119         /* start the watchdog timer */
 120         watchdog_go();
 121 #endif
 122
 123         mn10300_sched_clock_init();
 124 }