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 27unsigned long mn10300_ioclk; /* system I/O clock frequency */ 28unsigned long mn10300_iobclk; /* system I/O clock frequency */ 29unsigned long mn10300_tsc_per_HZ; /* number of ioclks per jiffy */ 30#endif /* CONFIG_MN10300_RTC */ 31 32static unsigned long mn10300_last_tsc; /* time-stamp counter at last time 33 * interrupt occurred */ 34 35static irqreturn_t timer_interrupt(int irq, void *dev_id); 36 37static struct irqaction timer_irq = { 38 .handler = timer_interrupt, 39 .flags = IRQF_DISABLED | IRQF_SHARED | IRQF_TIMER, 40 .name = "timer", 41}; 42 43static unsigned long sched_clock_multiplier; 44 45/* 46 * scheduler clock - returns current time in nanosec units. 47 */ 48unsigned 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 */ 87static 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 */ 98static 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 } 115 116 write_sequnlock(&xtime_lock); 117 118 update_process_times(user_mode(get_irq_regs())); 119 120 return IRQ_HANDLED; 121} 122 123/* 124 * initialise the various timers used by the main part of the kernel 125 */ 126void __init time_init(void) 127{ 128 /* we need the prescalar running to be able to use IOCLK/8 129 * - IOCLK runs at 1/4 (ST5 open) or 1/8 (ST5 closed) internal CPU clock 130 * - IOCLK runs at Fosc rate (crystal speed) 131 */ 132 TMPSCNT |= TMPSCNT_ENABLE; 133 134 startup_timestamp_counter(); 135 136 printk(KERN_INFO 137 "timestamp counter I/O clock running at %lu.%02lu" 138 " (calibrated against RTC)\n", 139 MN10300_TSCCLK / 1000000, (MN10300_TSCCLK / 10000) % 100); 140 141 mn10300_last_tsc = TMTSCBC; 142 143 /* use timer 0 & 1 cascaded to tick at as close to HZ as possible */ 144 setup_irq(TMJCIRQ, &timer_irq); 145 146 set_intr_level(TMJCIRQ, TMJCICR_LEVEL); 147 148 startup_jiffies_counter(); 149 150#ifdef CONFIG_MN10300_WD_TIMER 151 /* start the watchdog timer */ 152 watchdog_go(); 153#endif 154 155 mn10300_sched_clock_init(); 156} 157