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 */
sched_clock(void)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 */
mn10300_sched_clock_init(void)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 */
local_timer_interrupt(void)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 */
time_init(void)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 }
125