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 #ifndef CONFIG_GENERIC_TIME
  97 /*
  98  * advance the kernel's time keeping clocks (xtime and jiffies)
  99  * - we use Timer 0 & 1 cascaded as a clock to nudge us the next time
 100  *   there's a need to update
 101  */
 102 static irqreturn_t timer_interrupt(int irq, void *dev_id)
 103 {
 104         unsigned tsc, elapse;
 105         irqreturn_t ret;
 106
 107         while (tsc = get_cycles(),
 108                elapse = tsc - mn10300_last_tsc, /* time elapsed since last
 109                                                  * tick */
 110                elapse > MN10300_TSC_PER_HZ
 111                ) {
 112                 mn10300_last_tsc += MN10300_TSC_PER_HZ;
 113
 114                 /* advance the kernel's time tracking system */
 115                 xtime_update(1);
 116         }
 117
 118         ret = local_timer_interrupt();
 119 #ifdef CONFIG_SMP
 120         send_IPI_allbutself(LOCAL_TIMER_IPI);
 121 #endif
 122         return ret;
 123 }
 124
 125 static struct irqaction timer_irq = {
 126         .handler        = timer_interrupt,
 127         .flags          = IRQF_DISABLED | IRQF_SHARED | IRQF_TIMER,
 128         .name           = "timer",
 129 };
 130 #endif /* CONFIG_GENERIC_TIME */
 131
 132 #ifdef CONFIG_CSRC_MN10300
 133 void __init clocksource_set_clock(struct clocksource *cs, unsigned int clock)
 134 {
 135         u64 temp;
 136         u32 shift;
 137
 138         /* Find a shift value */
 139         for (shift = 32; shift > 0; shift--) {
 140                 temp = (u64) NSEC_PER_SEC << shift;
 141                 do_div(temp, clock);
 142                 if ((temp >> 32) == 0)
 143                         break;
 144         }
 145         cs->shift = shift;
 146         cs->mult = (u32) temp;
 147 }
 148 #endif
 149
 150 #if CONFIG_CEVT_MN10300
 151 void __cpuinit clockevent_set_clock(struct clock_event_device *cd,
 152                                     unsigned int clock)
 153 {
 154         u64 temp;
 155         u32 shift;
 156
 157         /* Find a shift value */
 158         for (shift = 32; shift > 0; shift--) {
 159                 temp = (u64) clock << shift;
 160                 do_div(temp, NSEC_PER_SEC);
 161                 if ((temp >> 32) == 0)
 162                         break;
 163         }
 164         cd->shift = shift;
 165         cd->mult = (u32) temp;
 166 }
 167 #endif
 168
 169 /*
 170  * initialise the various timers used by the main part of the kernel
 171  */
 172 void __init time_init(void)
 173 {
 174         /* we need the prescalar running to be able to use IOCLK/8
 175          * - IOCLK runs at 1/4 (ST5 open) or 1/8 (ST5 closed) internal CPU clock
 176          * - IOCLK runs at Fosc rate (crystal speed)
 177          */
 178         TMPSCNT |= TMPSCNT_ENABLE;
 179
 180 #ifdef CONFIG_GENERIC_TIME
 181         init_clocksource();
 182 #else
 183         startup_timestamp_counter();
 184 #endif
 185
 186         printk(KERN_INFO
 187                "timestamp counter I/O clock running at %lu.%02lu"
 188                " (calibrated against RTC)\n",
 189                MN10300_TSCCLK / 1000000, (MN10300_TSCCLK / 10000) % 100);
 190
 191         mn10300_last_tsc = read_timestamp_counter();
 192
 193 #ifdef CONFIG_GENERIC_CLOCKEVENTS
 194         init_clockevents();
 195 #else
 196         reload_jiffies_counter(MN10300_JC_PER_HZ - 1);
 197         setup_jiffies_interrupt(TMJCIRQ, &timer_irq, CONFIG_TIMER_IRQ_LEVEL);
 198 #endif
 199
 200 #ifdef CONFIG_MN10300_WD_TIMER
 201         /* start the watchdog timer */
 202         watchdog_go();
 203 #endif
 204
 205         mn10300_sched_clock_init();
 206 }