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 <asm/irq.h>
  21 #include <asm/div64.h>
  22 #include <asm/processor.h>
  23 #include <asm/intctl-regs.h>
  24 #include <asm/rtc.h>
  25 #include "internal.h"
  26
  27 static unsigned long mn10300_last_tsc;  /* time-stamp counter at last time
  28                                          * interrupt occurred */
  29
  30 static irqreturn_t timer_interrupt(int irq, void *dev_id);
  31
  32 static struct irqaction timer_irq = {
  33         .handler        = timer_interrupt,
  34         .flags          = IRQF_DISABLED | IRQF_SHARED | IRQF_TIMER,
  35         .name           = "timer",
  36 };
  37
  38 static unsigned long sched_clock_multiplier;
  39
  40 /*
  41  * scheduler clock - returns current time in nanosec units.
  42  */
  43 unsigned long long sched_clock(void)
  44 {
  45         union {
  46                 unsigned long long ll;
  47                 unsigned l[2];
  48         } tsc64, result;
  49         unsigned long tsc, tmp;
  50         unsigned product[3]; /* 96-bit intermediate value */
  51
  52         /* cnt32_to_63() is not safe with preemption */
  53         preempt_disable();
  54
  55         /* read the TSC value
  56          */
  57         tsc = 0 - get_cycles(); /* get_cycles() counts down */
  58
  59         /* expand to 64-bits.
  60          * - sched_clock() must be called once a minute or better or the
  61          *   following will go horribly wrong - see cnt32_to_63()
  62          */
  63         tsc64.ll = cnt32_to_63(tsc) & 0x7fffffffffffffffULL;
  64
  65         preempt_enable();
  66
  67         /* scale the 64-bit TSC value to a nanosecond value via a 96-bit
  68          * intermediate
  69          */
  70         asm("mulu       %2,%0,%3,%0     \n"     /* LSW * mult ->  0:%3:%0 */
  71             "mulu       %2,%1,%2,%1     \n"     /* MSW * mult -> %2:%1:0 */
  72             "add        %3,%1           \n"
  73             "addc       0,%2            \n"     /* result in %2:%1:%0 */
  74             : "=r"(product[0]), "=r"(product[1]), "=r"(product[2]), "=r"(tmp)
  75             :  "0"(tsc64.l[0]),  "1"(tsc64.l[1]),  "2"(sched_clock_multiplier)
  76             : "cc");
  77
  78         result.l[0] = product[1] << 16 | product[0] >> 16;
  79         result.l[1] = product[2] << 16 | product[1] >> 16;
  80
  81         return result.ll;
  82 }
  83
  84 /*
  85  * initialise the scheduler clock
  86  */
  87 static void __init mn10300_sched_clock_init(void)
  88 {
  89         sched_clock_multiplier =
  90                 __muldiv64u(NSEC_PER_SEC, 1 << 16, MN10300_TSCCLK);
  91 }
  92
  93 /**
  94  * local_timer_interrupt - Local timer interrupt handler
  95  *
  96  * Handle local timer interrupts for this CPU.  They may have been propagated
  97  * to this CPU from the CPU that actually gets them by way of an IPI.
  98  */
  99 irqreturn_t local_timer_interrupt(void)
 100 {
 101         profile_tick(CPU_PROFILING);
 102         update_process_times(user_mode(get_irq_regs()));
 103         return IRQ_HANDLED;
 104 }
 105
 106 /*
 107  * advance the kernel's time keeping clocks (xtime and jiffies)
 108  * - we use Timer 0 & 1 cascaded as a clock to nudge us the next time
 109  *   there's a need to update
 110  */
 111 static irqreturn_t timer_interrupt(int irq, void *dev_id)
 112 {
 113         unsigned tsc, elapse;
 114         irqreturn_t ret;
 115
 116         write_seqlock(&xtime_lock);
 117
 118         while (tsc = get_cycles(),
 119                elapse = mn10300_last_tsc - tsc, /* time elapsed since last
 120                                                  * tick */
 121                elapse > MN10300_TSC_PER_HZ
 122                ) {
 123                 mn10300_last_tsc -= MN10300_TSC_PER_HZ;
 124
 125                 /* advance the kernel's time tracking system */
 126                 do_timer(1);
 127         }
 128
 129         write_sequnlock(&xtime_lock);
 130
 131         ret = local_timer_interrupt();
 132 #ifdef CONFIG_SMP
 133         send_IPI_allbutself(LOCAL_TIMER_IPI);
 134 #endif
 135         return ret;
 136 }
 137
 138 /*
 139  * initialise the various timers used by the main part of the kernel
 140  */
 141 void __init time_init(void)
 142 {
 143         /* we need the prescalar running to be able to use IOCLK/8
 144          * - IOCLK runs at 1/4 (ST5 open) or 1/8 (ST5 closed) internal CPU clock
 145          * - IOCLK runs at Fosc rate (crystal speed)
 146          */
 147         TMPSCNT |= TMPSCNT_ENABLE;
 148
 149         startup_timestamp_counter();
 150
 151         printk(KERN_INFO
 152                "timestamp counter I/O clock running at %lu.%02lu"
 153                " (calibrated against RTC)\n",
 154                MN10300_TSCCLK / 1000000, (MN10300_TSCCLK / 10000) % 100);
 155
 156         mn10300_last_tsc = TMTSCBC;
 157
 158         /* use timer 0 & 1 cascaded to tick at as close to HZ as possible */
 159         setup_irq(TMJCIRQ, &timer_irq);
 160
 161         set_intr_level(TMJCIRQ, NUM2GxICR_LEVEL(CONFIG_TIMER_IRQ_LEVEL));
 162
 163         startup_jiffies_counter();
 164
 165 #ifdef CONFIG_MN10300_WD_TIMER
 166         /* start the watchdog timer */
 167         watchdog_go();
 168 #endif
 169
 170         mn10300_sched_clock_init();
 171 }