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
  26 #ifdef CONFIG_MN10300_RTC
  27 unsigned long mn10300_ioclk;            /* system I/O clock frequency */
  28 unsigned long mn10300_iobclk;           /* system I/O clock frequency */
  29 unsigned long mn10300_tsc_per_HZ;       /* number of ioclks per jiffy */
  30 #endif /* CONFIG_MN10300_RTC */
  31
  32 static unsigned long mn10300_last_tsc;  /* time-stamp counter at last time
  33                                          * interrupt occurred */
  34
  35 static irqreturn_t timer_interrupt(int irq, void *dev_id);
  36
  37 static struct irqaction timer_irq = {
  38         .handler        = timer_interrupt,
  39         .flags          = IRQF_DISABLED | IRQF_SHARED | IRQF_TIMER,
  40         .name           = "timer",
  41 };
  42
  43 static unsigned long sched_clock_multiplier;
  44
  45 /*
  46  * scheduler clock - returns current time in nanosec units.
  47  */
  48 unsigned long long sched_clock(void)
  49 {
  50         union {
  51                 unsigned long long ll;
  52                 unsigned l[2];
  53         } tsc64, result;
  54         unsigned long tsc, tmp;
  55         unsigned product[3]; /* 96-bit intermediate value */
  56
  57         /* read the TSC value
  58          */
  59         tsc = 0 - get_cycles(); /* get_cycles() counts down */
  60
  61         /* expand to 64-bits.
  62          * - sched_clock() must be called once a minute or better or the
  63          *   following will go horribly wrong - see cnt32_to_63()
  64          */
  65         tsc64.ll = cnt32_to_63(tsc) & 0x7fffffffffffffffULL;
  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  * advance the kernel's time keeping clocks (xtime and jiffies)
  95  * - we use Timer 0 & 1 cascaded as a clock to nudge us the next time
  96  *   there's a need to update
  97  */
  98 static irqreturn_t timer_interrupt(int irq, void *dev_id)
  99 {
 100         unsigned tsc, elapse;
 101
 102         write_seqlock(&xtime_lock);
 103
 104         while (tsc = get_cycles(),
 105                elapse = mn10300_last_tsc - tsc, /* time elapsed since last
 106                                                  * tick */
 107                elapse > MN10300_TSC_PER_HZ
 108                ) {
 109                 mn10300_last_tsc -= MN10300_TSC_PER_HZ;
 110
 111                 /* advance the kernel's time tracking system */
 112                 profile_tick(CPU_PROFILING);
 113                 do_timer(1);
 114                 check_rtc_time();
 115         }
 116
 117         write_sequnlock(&xtime_lock);
 118
 119         update_process_times(user_mode(get_irq_regs()));
 120
 121         return IRQ_HANDLED;
 122 }
 123
 124 /*
 125  * initialise the various timers used by the main part of the kernel
 126  */
 127 void __init time_init(void)
 128 {
 129         /* we need the prescalar running to be able to use IOCLK/8
 130          * - IOCLK runs at 1/4 (ST5 open) or 1/8 (ST5 closed) internal CPU clock
 131          * - IOCLK runs at Fosc rate (crystal speed)
 132          */
 133         TMPSCNT |= TMPSCNT_ENABLE;
 134
 135         startup_timestamp_counter();
 136
 137         printk(KERN_INFO
 138                "timestamp counter I/O clock running at %lu.%02lu"
 139                " (calibrated against RTC)\n",
 140                MN10300_TSCCLK / 1000000, (MN10300_TSCCLK / 10000) % 100);
 141
 142         xtime.tv_sec = get_initial_rtc_time();
 143         xtime.tv_nsec = 0;
 144
 145         mn10300_last_tsc = TMTSCBC;
 146
 147         /* use timer 0 & 1 cascaded to tick at as close to HZ as possible */
 148         setup_irq(TMJCIRQ, &timer_irq);
 149
 150         set_intr_level(TMJCIRQ, TMJCICR_LEVEL);
 151
 152         startup_jiffies_counter();
 153
 154 #ifdef CONFIG_MN10300_WD_TIMER
 155         /* start the watchdog timer */
 156         watchdog_go();
 157 #endif
 158
 159         mn10300_sched_clock_init();
 160 }