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
 29static unsigned long mn10300_last_tsc;	/* time-stamp counter at last time
 30					 * interrupt occurred */
 31
 32static unsigned long sched_clock_multiplier;
 33
 34/*
 35 * scheduler clock - returns current time in nanosec units.
 36 */
 37unsigned 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 */
 77static 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 */
 89irqreturn_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 */
 99void __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}