684 lines
18 KiB
C
684 lines
18 KiB
C
/*
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* linux/kernel/time/clocksource.c
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*
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* This file contains the functions which manage clocksource drivers.
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*
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* Copyright (C) 2004, 2005 IBM, John Stultz (johnstul@us.ibm.com)
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*
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* TODO WishList:
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* o Allow clocksource drivers to be unregistered
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*/
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#include <linux/clocksource.h>
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#include <linux/sysdev.h>
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/sched.h> /* for spin_unlock_irq() using preempt_count() m68k */
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#include <linux/tick.h>
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void timecounter_init(struct timecounter *tc,
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const struct cyclecounter *cc,
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u64 start_tstamp)
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{
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tc->cc = cc;
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tc->cycle_last = cc->read(cc);
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tc->nsec = start_tstamp;
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}
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EXPORT_SYMBOL(timecounter_init);
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/**
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* timecounter_read_delta - get nanoseconds since last call of this function
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* @tc: Pointer to time counter
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*
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* When the underlying cycle counter runs over, this will be handled
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* correctly as long as it does not run over more than once between
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* calls.
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*
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* The first call to this function for a new time counter initializes
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* the time tracking and returns an undefined result.
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*/
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static u64 timecounter_read_delta(struct timecounter *tc)
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{
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cycle_t cycle_now, cycle_delta;
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u64 ns_offset;
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/* read cycle counter: */
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cycle_now = tc->cc->read(tc->cc);
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/* calculate the delta since the last timecounter_read_delta(): */
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cycle_delta = (cycle_now - tc->cycle_last) & tc->cc->mask;
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/* convert to nanoseconds: */
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ns_offset = cyclecounter_cyc2ns(tc->cc, cycle_delta);
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/* update time stamp of timecounter_read_delta() call: */
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tc->cycle_last = cycle_now;
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return ns_offset;
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}
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u64 timecounter_read(struct timecounter *tc)
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{
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u64 nsec;
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/* increment time by nanoseconds since last call */
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nsec = timecounter_read_delta(tc);
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nsec += tc->nsec;
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tc->nsec = nsec;
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return nsec;
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}
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EXPORT_SYMBOL(timecounter_read);
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u64 timecounter_cyc2time(struct timecounter *tc,
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cycle_t cycle_tstamp)
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{
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u64 cycle_delta = (cycle_tstamp - tc->cycle_last) & tc->cc->mask;
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u64 nsec;
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/*
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* Instead of always treating cycle_tstamp as more recent
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* than tc->cycle_last, detect when it is too far in the
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* future and treat it as old time stamp instead.
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*/
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if (cycle_delta > tc->cc->mask / 2) {
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cycle_delta = (tc->cycle_last - cycle_tstamp) & tc->cc->mask;
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nsec = tc->nsec - cyclecounter_cyc2ns(tc->cc, cycle_delta);
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} else {
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nsec = cyclecounter_cyc2ns(tc->cc, cycle_delta) + tc->nsec;
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}
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return nsec;
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}
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EXPORT_SYMBOL(timecounter_cyc2time);
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/*[Clocksource internal variables]---------
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* curr_clocksource:
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* currently selected clocksource.
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* next_clocksource:
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* pending next selected clocksource.
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* clocksource_list:
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* linked list with the registered clocksources
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* clocksource_lock:
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* protects manipulations to curr_clocksource and next_clocksource
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* and the clocksource_list
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* override_name:
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* Name of the user-specified clocksource.
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*/
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static struct clocksource *curr_clocksource;
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static struct clocksource *next_clocksource;
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static LIST_HEAD(clocksource_list);
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static DEFINE_SPINLOCK(clocksource_lock);
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static char override_name[32];
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static int finished_booting;
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/* clocksource_done_booting - Called near the end of core bootup
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*
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* Hack to avoid lots of clocksource churn at boot time.
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* We use fs_initcall because we want this to start before
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* device_initcall but after subsys_initcall.
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*/
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static int __init clocksource_done_booting(void)
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{
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finished_booting = 1;
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return 0;
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}
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fs_initcall(clocksource_done_booting);
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#ifdef CONFIG_CLOCKSOURCE_WATCHDOG
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static LIST_HEAD(watchdog_list);
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static struct clocksource *watchdog;
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static struct timer_list watchdog_timer;
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static struct work_struct watchdog_work;
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static DEFINE_SPINLOCK(watchdog_lock);
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static cycle_t watchdog_last;
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static int watchdog_running;
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static void clocksource_watchdog_work(struct work_struct *work);
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/*
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* Interval: 0.5sec Threshold: 0.0625s
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*/
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#define WATCHDOG_INTERVAL (HZ >> 1)
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#define WATCHDOG_THRESHOLD (NSEC_PER_SEC >> 4)
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static void clocksource_unstable(struct clocksource *cs, int64_t delta)
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{
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printk(KERN_WARNING "Clocksource %s unstable (delta = %Ld ns)\n",
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cs->name, delta);
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cs->flags &= ~(CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_WATCHDOG);
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cs->flags |= CLOCK_SOURCE_UNSTABLE;
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schedule_work(&watchdog_work);
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}
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static void clocksource_watchdog(unsigned long data)
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{
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struct clocksource *cs;
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cycle_t csnow, wdnow;
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int64_t wd_nsec, cs_nsec;
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int next_cpu;
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spin_lock(&watchdog_lock);
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if (!watchdog_running)
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goto out;
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wdnow = watchdog->read(watchdog);
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wd_nsec = clocksource_cyc2ns((wdnow - watchdog_last) & watchdog->mask,
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watchdog->mult, watchdog->shift);
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watchdog_last = wdnow;
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list_for_each_entry(cs, &watchdog_list, wd_list) {
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/* Clocksource already marked unstable? */
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if (cs->flags & CLOCK_SOURCE_UNSTABLE)
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continue;
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csnow = cs->read(cs);
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/* Clocksource initialized ? */
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if (!(cs->flags & CLOCK_SOURCE_WATCHDOG)) {
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cs->flags |= CLOCK_SOURCE_WATCHDOG;
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cs->wd_last = csnow;
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continue;
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}
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/* Check the deviation from the watchdog clocksource. */
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cs_nsec = clocksource_cyc2ns((csnow - cs->wd_last) &
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cs->mask, cs->mult, cs->shift);
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cs->wd_last = csnow;
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if (abs(cs_nsec - wd_nsec) > WATCHDOG_THRESHOLD) {
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clocksource_unstable(cs, cs_nsec - wd_nsec);
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continue;
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}
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if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) &&
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(cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) &&
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(watchdog->flags & CLOCK_SOURCE_IS_CONTINUOUS)) {
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cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
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/*
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* We just marked the clocksource as highres-capable,
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* notify the rest of the system as well so that we
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* transition into high-res mode:
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*/
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tick_clock_notify();
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}
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}
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/*
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* Cycle through CPUs to check if the CPUs stay synchronized
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* to each other.
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*/
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next_cpu = cpumask_next(raw_smp_processor_id(), cpu_online_mask);
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if (next_cpu >= nr_cpu_ids)
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next_cpu = cpumask_first(cpu_online_mask);
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watchdog_timer.expires += WATCHDOG_INTERVAL;
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add_timer_on(&watchdog_timer, next_cpu);
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out:
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spin_unlock(&watchdog_lock);
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}
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static inline void clocksource_start_watchdog(void)
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{
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if (watchdog_running || !watchdog || list_empty(&watchdog_list))
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return;
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INIT_WORK(&watchdog_work, clocksource_watchdog_work);
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init_timer(&watchdog_timer);
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watchdog_timer.function = clocksource_watchdog;
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watchdog_last = watchdog->read(watchdog);
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watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL;
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add_timer_on(&watchdog_timer, cpumask_first(cpu_online_mask));
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watchdog_running = 1;
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}
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static inline void clocksource_stop_watchdog(void)
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{
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if (!watchdog_running || (watchdog && !list_empty(&watchdog_list)))
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return;
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del_timer(&watchdog_timer);
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watchdog_running = 0;
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}
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static inline void clocksource_reset_watchdog(void)
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{
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struct clocksource *cs;
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list_for_each_entry(cs, &watchdog_list, wd_list)
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cs->flags &= ~CLOCK_SOURCE_WATCHDOG;
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}
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static void clocksource_resume_watchdog(void)
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{
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unsigned long flags;
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spin_lock_irqsave(&watchdog_lock, flags);
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clocksource_reset_watchdog();
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spin_unlock_irqrestore(&watchdog_lock, flags);
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}
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static void clocksource_enqueue_watchdog(struct clocksource *cs)
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{
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unsigned long flags;
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spin_lock_irqsave(&watchdog_lock, flags);
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if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) {
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/* cs is a clocksource to be watched. */
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list_add(&cs->wd_list, &watchdog_list);
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cs->flags &= ~CLOCK_SOURCE_WATCHDOG;
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} else {
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/* cs is a watchdog. */
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if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)
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cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
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/* Pick the best watchdog. */
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if (!watchdog || cs->rating > watchdog->rating) {
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watchdog = cs;
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/* Reset watchdog cycles */
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clocksource_reset_watchdog();
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}
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}
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/* Check if the watchdog timer needs to be started. */
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clocksource_start_watchdog();
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spin_unlock_irqrestore(&watchdog_lock, flags);
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}
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static void clocksource_dequeue_watchdog(struct clocksource *cs)
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{
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struct clocksource *tmp;
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unsigned long flags;
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spin_lock_irqsave(&watchdog_lock, flags);
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if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) {
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/* cs is a watched clocksource. */
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list_del_init(&cs->wd_list);
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} else if (cs == watchdog) {
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/* Reset watchdog cycles */
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clocksource_reset_watchdog();
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/* Current watchdog is removed. Find an alternative. */
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watchdog = NULL;
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list_for_each_entry(tmp, &clocksource_list, list) {
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if (tmp == cs || tmp->flags & CLOCK_SOURCE_MUST_VERIFY)
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continue;
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if (!watchdog || tmp->rating > watchdog->rating)
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watchdog = tmp;
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}
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}
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cs->flags &= ~CLOCK_SOURCE_WATCHDOG;
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/* Check if the watchdog timer needs to be stopped. */
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clocksource_stop_watchdog();
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spin_unlock_irqrestore(&watchdog_lock, flags);
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}
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static void clocksource_watchdog_work(struct work_struct *work)
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{
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struct clocksource *cs, *tmp;
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unsigned long flags;
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spin_lock_irqsave(&watchdog_lock, flags);
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list_for_each_entry_safe(cs, tmp, &watchdog_list, wd_list)
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if (cs->flags & CLOCK_SOURCE_UNSTABLE) {
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list_del_init(&cs->wd_list);
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clocksource_change_rating(cs, 0);
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}
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/* Check if the watchdog timer needs to be stopped. */
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clocksource_stop_watchdog();
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spin_unlock(&watchdog_lock);
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}
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#else /* CONFIG_CLOCKSOURCE_WATCHDOG */
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static void clocksource_enqueue_watchdog(struct clocksource *cs)
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{
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if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)
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cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
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}
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static inline void clocksource_dequeue_watchdog(struct clocksource *cs) { }
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static inline void clocksource_resume_watchdog(void) { }
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#endif /* CONFIG_CLOCKSOURCE_WATCHDOG */
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/**
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* clocksource_resume - resume the clocksource(s)
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*/
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void clocksource_resume(void)
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{
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struct clocksource *cs;
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unsigned long flags;
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spin_lock_irqsave(&clocksource_lock, flags);
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list_for_each_entry(cs, &clocksource_list, list) {
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if (cs->resume)
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cs->resume();
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}
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clocksource_resume_watchdog();
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spin_unlock_irqrestore(&clocksource_lock, flags);
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}
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/**
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* clocksource_touch_watchdog - Update watchdog
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*
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* Update the watchdog after exception contexts such as kgdb so as not
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* to incorrectly trip the watchdog.
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*
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*/
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void clocksource_touch_watchdog(void)
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{
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clocksource_resume_watchdog();
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}
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#ifdef CONFIG_GENERIC_TIME
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/**
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* clocksource_get_next - Returns the selected clocksource
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*
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*/
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struct clocksource *clocksource_get_next(void)
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{
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unsigned long flags;
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spin_lock_irqsave(&clocksource_lock, flags);
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if (next_clocksource && finished_booting) {
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curr_clocksource = next_clocksource;
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next_clocksource = NULL;
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}
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spin_unlock_irqrestore(&clocksource_lock, flags);
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return curr_clocksource;
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}
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/**
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* clocksource_select - Select the best clocksource available
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*
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* Private function. Must hold clocksource_lock when called.
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*
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* Select the clocksource with the best rating, or the clocksource,
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* which is selected by userspace override.
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*/
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static void clocksource_select(void)
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{
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struct clocksource *best, *cs;
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if (list_empty(&clocksource_list))
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return;
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/* First clocksource on the list has the best rating. */
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best = list_first_entry(&clocksource_list, struct clocksource, list);
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/* Check for the override clocksource. */
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list_for_each_entry(cs, &clocksource_list, list) {
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if (strcmp(cs->name, override_name) != 0)
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continue;
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/*
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* Check to make sure we don't switch to a non-highres
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* capable clocksource if the tick code is in oneshot
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* mode (highres or nohz)
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*/
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if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) &&
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tick_oneshot_mode_active()) {
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/* Override clocksource cannot be used. */
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printk(KERN_WARNING "Override clocksource %s is not "
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"HRT compatible. Cannot switch while in "
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"HRT/NOHZ mode\n", cs->name);
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override_name[0] = 0;
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} else
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/* Override clocksource can be used. */
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best = cs;
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break;
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}
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if (curr_clocksource != best)
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next_clocksource = best;
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}
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#else /* CONFIG_GENERIC_TIME */
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static void clocksource_select(void) { }
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#endif
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/*
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* Enqueue the clocksource sorted by rating
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*/
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static void clocksource_enqueue(struct clocksource *cs)
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{
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struct list_head *entry = &clocksource_list;
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struct clocksource *tmp;
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list_for_each_entry(tmp, &clocksource_list, list)
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/* Keep track of the place, where to insert */
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if (tmp->rating >= cs->rating)
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entry = &tmp->list;
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list_add(&cs->list, entry);
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}
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/**
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* clocksource_register - Used to install new clocksources
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* @t: clocksource to be registered
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*
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* Returns -EBUSY if registration fails, zero otherwise.
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*/
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int clocksource_register(struct clocksource *cs)
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{
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unsigned long flags;
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spin_lock_irqsave(&clocksource_lock, flags);
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clocksource_enqueue(cs);
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clocksource_select();
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spin_unlock_irqrestore(&clocksource_lock, flags);
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clocksource_enqueue_watchdog(cs);
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return 0;
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}
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EXPORT_SYMBOL(clocksource_register);
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/**
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* clocksource_change_rating - Change the rating of a registered clocksource
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*/
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void clocksource_change_rating(struct clocksource *cs, int rating)
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{
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unsigned long flags;
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spin_lock_irqsave(&clocksource_lock, flags);
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list_del(&cs->list);
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cs->rating = rating;
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clocksource_enqueue(cs);
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clocksource_select();
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spin_unlock_irqrestore(&clocksource_lock, flags);
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}
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EXPORT_SYMBOL(clocksource_change_rating);
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/**
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* clocksource_unregister - remove a registered clocksource
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*/
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void clocksource_unregister(struct clocksource *cs)
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{
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unsigned long flags;
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clocksource_dequeue_watchdog(cs);
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spin_lock_irqsave(&clocksource_lock, flags);
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list_del(&cs->list);
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clocksource_select();
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spin_unlock_irqrestore(&clocksource_lock, flags);
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}
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EXPORT_SYMBOL(clocksource_unregister);
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#ifdef CONFIG_SYSFS
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/**
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* sysfs_show_current_clocksources - sysfs interface for current clocksource
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* @dev: unused
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* @buf: char buffer to be filled with clocksource list
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*
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* Provides sysfs interface for listing current clocksource.
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*/
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static ssize_t
|
|
sysfs_show_current_clocksources(struct sys_device *dev,
|
|
struct sysdev_attribute *attr, char *buf)
|
|
{
|
|
ssize_t count = 0;
|
|
|
|
spin_lock_irq(&clocksource_lock);
|
|
count = snprintf(buf, PAGE_SIZE, "%s\n", curr_clocksource->name);
|
|
spin_unlock_irq(&clocksource_lock);
|
|
|
|
return count;
|
|
}
|
|
|
|
/**
|
|
* sysfs_override_clocksource - interface for manually overriding clocksource
|
|
* @dev: unused
|
|
* @buf: name of override clocksource
|
|
* @count: length of buffer
|
|
*
|
|
* Takes input from sysfs interface for manually overriding the default
|
|
* clocksource selction.
|
|
*/
|
|
static ssize_t sysfs_override_clocksource(struct sys_device *dev,
|
|
struct sysdev_attribute *attr,
|
|
const char *buf, size_t count)
|
|
{
|
|
size_t ret = count;
|
|
|
|
/* strings from sysfs write are not 0 terminated! */
|
|
if (count >= sizeof(override_name))
|
|
return -EINVAL;
|
|
|
|
/* strip of \n: */
|
|
if (buf[count-1] == '\n')
|
|
count--;
|
|
|
|
spin_lock_irq(&clocksource_lock);
|
|
|
|
if (count > 0)
|
|
memcpy(override_name, buf, count);
|
|
override_name[count] = 0;
|
|
clocksource_select();
|
|
|
|
spin_unlock_irq(&clocksource_lock);
|
|
|
|
return ret;
|
|
}
|
|
|
|
/**
|
|
* sysfs_show_available_clocksources - sysfs interface for listing clocksource
|
|
* @dev: unused
|
|
* @buf: char buffer to be filled with clocksource list
|
|
*
|
|
* Provides sysfs interface for listing registered clocksources
|
|
*/
|
|
static ssize_t
|
|
sysfs_show_available_clocksources(struct sys_device *dev,
|
|
struct sysdev_attribute *attr,
|
|
char *buf)
|
|
{
|
|
struct clocksource *src;
|
|
ssize_t count = 0;
|
|
|
|
spin_lock_irq(&clocksource_lock);
|
|
list_for_each_entry(src, &clocksource_list, list) {
|
|
/*
|
|
* Don't show non-HRES clocksource if the tick code is
|
|
* in one shot mode (highres=on or nohz=on)
|
|
*/
|
|
if (!tick_oneshot_mode_active() ||
|
|
(src->flags & CLOCK_SOURCE_VALID_FOR_HRES))
|
|
count += snprintf(buf + count,
|
|
max((ssize_t)PAGE_SIZE - count, (ssize_t)0),
|
|
"%s ", src->name);
|
|
}
|
|
spin_unlock_irq(&clocksource_lock);
|
|
|
|
count += snprintf(buf + count,
|
|
max((ssize_t)PAGE_SIZE - count, (ssize_t)0), "\n");
|
|
|
|
return count;
|
|
}
|
|
|
|
/*
|
|
* Sysfs setup bits:
|
|
*/
|
|
static SYSDEV_ATTR(current_clocksource, 0644, sysfs_show_current_clocksources,
|
|
sysfs_override_clocksource);
|
|
|
|
static SYSDEV_ATTR(available_clocksource, 0444,
|
|
sysfs_show_available_clocksources, NULL);
|
|
|
|
static struct sysdev_class clocksource_sysclass = {
|
|
.name = "clocksource",
|
|
};
|
|
|
|
static struct sys_device device_clocksource = {
|
|
.id = 0,
|
|
.cls = &clocksource_sysclass,
|
|
};
|
|
|
|
static int __init init_clocksource_sysfs(void)
|
|
{
|
|
int error = sysdev_class_register(&clocksource_sysclass);
|
|
|
|
if (!error)
|
|
error = sysdev_register(&device_clocksource);
|
|
if (!error)
|
|
error = sysdev_create_file(
|
|
&device_clocksource,
|
|
&attr_current_clocksource);
|
|
if (!error)
|
|
error = sysdev_create_file(
|
|
&device_clocksource,
|
|
&attr_available_clocksource);
|
|
return error;
|
|
}
|
|
|
|
device_initcall(init_clocksource_sysfs);
|
|
#endif /* CONFIG_SYSFS */
|
|
|
|
/**
|
|
* boot_override_clocksource - boot clock override
|
|
* @str: override name
|
|
*
|
|
* Takes a clocksource= boot argument and uses it
|
|
* as the clocksource override name.
|
|
*/
|
|
static int __init boot_override_clocksource(char* str)
|
|
{
|
|
unsigned long flags;
|
|
spin_lock_irqsave(&clocksource_lock, flags);
|
|
if (str)
|
|
strlcpy(override_name, str, sizeof(override_name));
|
|
spin_unlock_irqrestore(&clocksource_lock, flags);
|
|
return 1;
|
|
}
|
|
|
|
__setup("clocksource=", boot_override_clocksource);
|
|
|
|
/**
|
|
* boot_override_clock - Compatibility layer for deprecated boot option
|
|
* @str: override name
|
|
*
|
|
* DEPRECATED! Takes a clock= boot argument and uses it
|
|
* as the clocksource override name
|
|
*/
|
|
static int __init boot_override_clock(char* str)
|
|
{
|
|
if (!strcmp(str, "pmtmr")) {
|
|
printk("Warning: clock=pmtmr is deprecated. "
|
|
"Use clocksource=acpi_pm.\n");
|
|
return boot_override_clocksource("acpi_pm");
|
|
}
|
|
printk("Warning! clock= boot option is deprecated. "
|
|
"Use clocksource=xyz\n");
|
|
return boot_override_clocksource(str);
|
|
}
|
|
|
|
__setup("clock=", boot_override_clock);
|