linux/arch/alpha/kernel/time.c

387 lines
10 KiB
C
Raw Normal View History

/*
* linux/arch/alpha/kernel/time.c
*
* Copyright (C) 1991, 1992, 1995, 1999, 2000 Linus Torvalds
*
* This file contains the clocksource time handling.
* 1997-09-10 Updated NTP code according to technical memorandum Jan '96
* "A Kernel Model for Precision Timekeeping" by Dave Mills
* 1997-01-09 Adrian Sun
* use interval timer if CONFIG_RTC=y
* 1997-10-29 John Bowman (bowman@math.ualberta.ca)
* fixed tick loss calculation in timer_interrupt
* (round system clock to nearest tick instead of truncating)
* fixed algorithm in time_init for getting time from CMOS clock
* 1999-04-16 Thorsten Kranzkowski (dl8bcu@gmx.net)
* fixed algorithm in do_gettimeofday() for calculating the precise time
* from processor cycle counter (now taking lost_ticks into account)
* 2003-06-03 R. Scott Bailey <scott.bailey@eds.com>
* Tighten sanity in time_init from 1% (10,000 PPM) to 250 PPM
*/
#include <linux/errno.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/param.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/delay.h>
#include <linux/ioport.h>
#include <linux/irq.h>
#include <linux/interrupt.h>
#include <linux/init.h>
#include <linux/bcd.h>
#include <linux/profile.h>
#include <linux/irq_work.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#include <asm/hwrpb.h>
#include <linux/mc146818rtc.h>
#include <linux/time.h>
#include <linux/timex.h>
#include <linux/clocksource.h>
#include "proto.h"
#include "irq_impl.h"
DEFINE_SPINLOCK(rtc_lock);
EXPORT_SYMBOL(rtc_lock);
#define TICK_SIZE (tick_nsec / 1000)
/*
* Shift amount by which scaled_ticks_per_cycle is scaled. Shifting
* by 48 gives us 16 bits for HZ while keeping the accuracy good even
* for large CPU clock rates.
*/
#define FIX_SHIFT 48
/* lump static variables together for more efficient access: */
static struct {
/* cycle counter last time it got invoked */
__u32 last_time;
/* ticks/cycle * 2^48 */
unsigned long scaled_ticks_per_cycle;
/* partial unused tick */
unsigned long partial_tick;
} state;
unsigned long est_cycle_freq;
#ifdef CONFIG_IRQ_WORK
DEFINE_PER_CPU(u8, irq_work_pending);
#define set_irq_work_pending_flag() __get_cpu_var(irq_work_pending) = 1
#define test_irq_work_pending() __get_cpu_var(irq_work_pending)
#define clear_irq_work_pending() __get_cpu_var(irq_work_pending) = 0
void arch_irq_work_raise(void)
{
set_irq_work_pending_flag();
}
#else /* CONFIG_IRQ_WORK */
#define test_irq_work_pending() 0
#define clear_irq_work_pending()
#endif /* CONFIG_IRQ_WORK */
static inline __u32 rpcc(void)
{
return __builtin_alpha_rpcc();
}
/*
* timer_interrupt() needs to keep up the real-time clock,
* as well as call the "xtime_update()" routine every clocktick
*/
irqreturn_t timer_interrupt(int irq, void *dev)
{
unsigned long delta;
__u32 now;
long nticks;
#ifndef CONFIG_SMP
/* Not SMP, do kernel PC profiling here. */
profile_tick(CPU_PROFILING);
#endif
/*
* Calculate how many ticks have passed since the last update,
* including any previous partial leftover. Save any resulting
* fraction for the next pass.
*/
now = rpcc();
delta = now - state.last_time;
state.last_time = now;
delta = delta * state.scaled_ticks_per_cycle + state.partial_tick;
state.partial_tick = delta & ((1UL << FIX_SHIFT) - 1);
nticks = delta >> FIX_SHIFT;
if (nticks)
xtime_update(nticks);
if (test_irq_work_pending()) {
clear_irq_work_pending();
irq_work_run();
}
#ifndef CONFIG_SMP
while (nticks--)
update_process_times(user_mode(get_irq_regs()));
#endif
return IRQ_HANDLED;
}
void __init
common_init_rtc(void)
{
unsigned char x, sel = 0;
/* Reset periodic interrupt frequency. */
#if CONFIG_HZ == 1024 || CONFIG_HZ == 1200
x = CMOS_READ(RTC_FREQ_SELECT) & 0x3f;
/* Test includes known working values on various platforms
where 0x26 is wrong; we refuse to change those. */
if (x != 0x26 && x != 0x25 && x != 0x19 && x != 0x06) {
sel = RTC_REF_CLCK_32KHZ + 6;
}
#elif CONFIG_HZ == 256 || CONFIG_HZ == 128 || CONFIG_HZ == 64 || CONFIG_HZ == 32
sel = RTC_REF_CLCK_32KHZ + __builtin_ffs(32768 / CONFIG_HZ);
#else
# error "Unknown HZ from arch/alpha/Kconfig"
#endif
if (sel) {
printk(KERN_INFO "Setting RTC_FREQ to %d Hz (%x)\n",
CONFIG_HZ, sel);
CMOS_WRITE(sel, RTC_FREQ_SELECT);
}
/* Turn on periodic interrupts. */
x = CMOS_READ(RTC_CONTROL);
if (!(x & RTC_PIE)) {
printk("Turning on RTC interrupts.\n");
x |= RTC_PIE;
x &= ~(RTC_AIE | RTC_UIE);
CMOS_WRITE(x, RTC_CONTROL);
}
(void) CMOS_READ(RTC_INTR_FLAGS);
outb(0x36, 0x43); /* pit counter 0: system timer */
outb(0x00, 0x40);
outb(0x00, 0x40);
outb(0xb6, 0x43); /* pit counter 2: speaker */
outb(0x31, 0x42);
outb(0x13, 0x42);
init_rtc_irq();
}
/* Validate a computed cycle counter result against the known bounds for
the given processor core. There's too much brokenness in the way of
timing hardware for any one method to work everywhere. :-(
Return 0 if the result cannot be trusted, otherwise return the argument. */
static unsigned long __init
validate_cc_value(unsigned long cc)
{
static struct bounds {
unsigned int min, max;
} cpu_hz[] __initdata = {
[EV3_CPU] = { 50000000, 200000000 }, /* guess */
[EV4_CPU] = { 100000000, 300000000 },
[LCA4_CPU] = { 100000000, 300000000 }, /* guess */
[EV45_CPU] = { 200000000, 300000000 },
[EV5_CPU] = { 250000000, 433000000 },
[EV56_CPU] = { 333000000, 667000000 },
[PCA56_CPU] = { 400000000, 600000000 }, /* guess */
[PCA57_CPU] = { 500000000, 600000000 }, /* guess */
[EV6_CPU] = { 466000000, 600000000 },
[EV67_CPU] = { 600000000, 750000000 },
[EV68AL_CPU] = { 750000000, 940000000 },
[EV68CB_CPU] = { 1000000000, 1333333333 },
/* None of the following are shipping as of 2001-11-01. */
[EV68CX_CPU] = { 1000000000, 1700000000 }, /* guess */
[EV69_CPU] = { 1000000000, 1700000000 }, /* guess */
[EV7_CPU] = { 800000000, 1400000000 }, /* guess */
[EV79_CPU] = { 1000000000, 2000000000 }, /* guess */
};
/* Allow for some drift in the crystal. 10MHz is more than enough. */
const unsigned int deviation = 10000000;
struct percpu_struct *cpu;
unsigned int index;
cpu = (struct percpu_struct *)((char*)hwrpb + hwrpb->processor_offset);
index = cpu->type & 0xffffffff;
/* If index out of bounds, no way to validate. */
if (index >= ARRAY_SIZE(cpu_hz))
return cc;
/* If index contains no data, no way to validate. */
if (cpu_hz[index].max == 0)
return cc;
if (cc < cpu_hz[index].min - deviation
|| cc > cpu_hz[index].max + deviation)
return 0;
return cc;
}
/*
* Calibrate CPU clock using legacy 8254 timer/counter. Stolen from
* arch/i386/time.c.
*/
#define CALIBRATE_LATCH 0xffff
#define TIMEOUT_COUNT 0x100000
static unsigned long __init
calibrate_cc_with_pit(void)
{
int cc, count = 0;
/* Set the Gate high, disable speaker */
outb((inb(0x61) & ~0x02) | 0x01, 0x61);
/*
* Now let's take care of CTC channel 2
*
* Set the Gate high, program CTC channel 2 for mode 0,
* (interrupt on terminal count mode), binary count,
* load 5 * LATCH count, (LSB and MSB) to begin countdown.
*/
outb(0xb0, 0x43); /* binary, mode 0, LSB/MSB, Ch 2 */
outb(CALIBRATE_LATCH & 0xff, 0x42); /* LSB of count */
outb(CALIBRATE_LATCH >> 8, 0x42); /* MSB of count */
cc = rpcc();
do {
count++;
} while ((inb(0x61) & 0x20) == 0 && count < TIMEOUT_COUNT);
cc = rpcc() - cc;
/* Error: ECTCNEVERSET or ECPUTOOFAST. */
if (count <= 1 || count == TIMEOUT_COUNT)
return 0;
return ((long)cc * PIT_TICK_RATE) / (CALIBRATE_LATCH + 1);
}
/* The Linux interpretation of the CMOS clock register contents:
When the Update-In-Progress (UIP) flag goes from 1 to 0, the
RTC registers show the second which has precisely just started.
Let's hope other operating systems interpret the RTC the same way. */
static unsigned long __init
rpcc_after_update_in_progress(void)
{
do { } while (!(CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP));
do { } while (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP);
return rpcc();
}
#ifndef CONFIG_SMP
/* Until and unless we figure out how to get cpu cycle counters
in sync and keep them there, we can't use the rpcc. */
static cycle_t read_rpcc(struct clocksource *cs)
{
cycle_t ret = (cycle_t)rpcc();
return ret;
}
static struct clocksource clocksource_rpcc = {
.name = "rpcc",
.rating = 300,
.read = read_rpcc,
.mask = CLOCKSOURCE_MASK(32),
.flags = CLOCK_SOURCE_IS_CONTINUOUS
};
static inline void register_rpcc_clocksource(long cycle_freq)
{
clocksource_register_hz(&clocksource_rpcc, cycle_freq);
}
#else /* !CONFIG_SMP */
static inline void register_rpcc_clocksource(long cycle_freq)
{
}
#endif /* !CONFIG_SMP */
void __init
time_init(void)
{
unsigned int cc1, cc2;
unsigned long cycle_freq, tolerance;
long diff;
/* Calibrate CPU clock -- attempt #1. */
if (!est_cycle_freq)
est_cycle_freq = validate_cc_value(calibrate_cc_with_pit());
cc1 = rpcc();
/* Calibrate CPU clock -- attempt #2. */
if (!est_cycle_freq) {
cc1 = rpcc_after_update_in_progress();
cc2 = rpcc_after_update_in_progress();
est_cycle_freq = validate_cc_value(cc2 - cc1);
cc1 = cc2;
}
cycle_freq = hwrpb->cycle_freq;
if (est_cycle_freq) {
/* If the given value is within 250 PPM of what we calculated,
accept it. Otherwise, use what we found. */
tolerance = cycle_freq / 4000;
diff = cycle_freq - est_cycle_freq;
if (diff < 0)
diff = -diff;
if ((unsigned long)diff > tolerance) {
cycle_freq = est_cycle_freq;
printk("HWRPB cycle frequency bogus. "
"Estimated %lu Hz\n", cycle_freq);
} else {
est_cycle_freq = 0;
}
} else if (! validate_cc_value (cycle_freq)) {
printk("HWRPB cycle frequency bogus, "
"and unable to estimate a proper value!\n");
}
/* From John Bowman <bowman@math.ualberta.ca>: allow the values
to settle, as the Update-In-Progress bit going low isn't good
enough on some hardware. 2ms is our guess; we haven't found
bogomips yet, but this is close on a 500Mhz box. */
__delay(1000000);
if (HZ > (1<<16)) {
extern void __you_loose (void);
__you_loose();
}
register_rpcc_clocksource(cycle_freq);
state.last_time = cc1;
state.scaled_ticks_per_cycle
= ((unsigned long) HZ << FIX_SHIFT) / cycle_freq;
state.partial_tick = 0L;
/* Startup the timer source. */
alpha_mv.init_rtc();
}