/* * linux/kernel/time/clocksource.c * * This file contains the functions which manage clocksource drivers. * * Copyright (C) 2004, 2005 IBM, John Stultz (johnstul@us.ibm.com) * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. * * TODO WishList: * o Allow clocksource drivers to be unregistered * o get rid of clocksource_jiffies extern */ #include <linux/clocksource.h> #include <linux/sysdev.h> #include <linux/init.h> #include <linux/module.h> #include <linux/sched.h> /* for spin_unlock_irq() using preempt_count() m68k */ #include <linux/tick.h> /* XXX - Would like a better way for initializing curr_clocksource */ extern struct clocksource clocksource_jiffies; /*[Clocksource internal variables]--------- * curr_clocksource: * currently selected clocksource. Initialized to clocksource_jiffies. * next_clocksource: * pending next selected clocksource. * clocksource_list: * linked list with the registered clocksources * clocksource_lock: * protects manipulations to curr_clocksource and next_clocksource * and the clocksource_list * override_name: * Name of the user-specified clocksource. */ static struct clocksource *curr_clocksource = &clocksource_jiffies; static struct clocksource *next_clocksource; static struct clocksource *clocksource_override; static LIST_HEAD(clocksource_list); static DEFINE_SPINLOCK(clocksource_lock); static char override_name[32]; static int finished_booting; /* clocksource_done_booting - Called near the end of core bootup * * Hack to avoid lots of clocksource churn at boot time. * We use fs_initcall because we want this to start before * device_initcall but after subsys_initcall. */ static int __init clocksource_done_booting(void) { finished_booting = 1; return 0; } fs_initcall(clocksource_done_booting); #ifdef CONFIG_CLOCKSOURCE_WATCHDOG static LIST_HEAD(watchdog_list); static struct clocksource *watchdog; static struct timer_list watchdog_timer; static DEFINE_SPINLOCK(watchdog_lock); static cycle_t watchdog_last; static unsigned long watchdog_resumed; /* * Interval: 0.5sec Threshold: 0.0625s */ #define WATCHDOG_INTERVAL (HZ >> 1) #define WATCHDOG_THRESHOLD (NSEC_PER_SEC >> 4) static void clocksource_ratewd(struct clocksource *cs, int64_t delta) { if (delta > -WATCHDOG_THRESHOLD && delta < WATCHDOG_THRESHOLD) return; printk(KERN_WARNING "Clocksource %s unstable (delta = %Ld ns)\n", cs->name, delta); cs->flags &= ~(CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_WATCHDOG); clocksource_change_rating(cs, 0); list_del(&cs->wd_list); } static void clocksource_watchdog(unsigned long data) { struct clocksource *cs, *tmp; cycle_t csnow, wdnow; int64_t wd_nsec, cs_nsec; int resumed; spin_lock(&watchdog_lock); resumed = test_and_clear_bit(0, &watchdog_resumed); wdnow = watchdog->read(); wd_nsec = cyc2ns(watchdog, (wdnow - watchdog_last) & watchdog->mask); watchdog_last = wdnow; list_for_each_entry_safe(cs, tmp, &watchdog_list, wd_list) { csnow = cs->read(); if (unlikely(resumed)) { cs->wd_last = csnow; continue; } /* Initialized ? */ if (!(cs->flags & CLOCK_SOURCE_WATCHDOG)) { if ((cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) && (watchdog->flags & CLOCK_SOURCE_IS_CONTINUOUS)) { cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES; /* * We just marked the clocksource as * highres-capable, notify the rest of the * system as well so that we transition * into high-res mode: */ tick_clock_notify(); } cs->flags |= CLOCK_SOURCE_WATCHDOG; cs->wd_last = csnow; } else { cs_nsec = cyc2ns(cs, (csnow - cs->wd_last) & cs->mask); cs->wd_last = csnow; /* Check the delta. Might remove from the list ! */ clocksource_ratewd(cs, cs_nsec - wd_nsec); } } if (!list_empty(&watchdog_list)) { /* * Cycle through CPUs to check if the CPUs stay * synchronized to each other. */ int next_cpu = next_cpu(raw_smp_processor_id(), cpu_online_map); if (next_cpu >= NR_CPUS) next_cpu = first_cpu(cpu_online_map); watchdog_timer.expires += WATCHDOG_INTERVAL; add_timer_on(&watchdog_timer, next_cpu); } spin_unlock(&watchdog_lock); } static void clocksource_resume_watchdog(void) { set_bit(0, &watchdog_resumed); } static void clocksource_check_watchdog(struct clocksource *cs) { struct clocksource *cse; unsigned long flags; spin_lock_irqsave(&watchdog_lock, flags); if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) { int started = !list_empty(&watchdog_list); list_add(&cs->wd_list, &watchdog_list); if (!started && watchdog) { watchdog_last = watchdog->read(); watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL; add_timer_on(&watchdog_timer, first_cpu(cpu_online_map)); } } else { if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES; if (!watchdog || cs->rating > watchdog->rating) { if (watchdog) del_timer(&watchdog_timer); watchdog = cs; init_timer(&watchdog_timer); watchdog_timer.function = clocksource_watchdog; /* Reset watchdog cycles */ list_for_each_entry(cse, &watchdog_list, wd_list) cse->flags &= ~CLOCK_SOURCE_WATCHDOG; /* Start if list is not empty */ if (!list_empty(&watchdog_list)) { watchdog_last = watchdog->read(); watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL; add_timer_on(&watchdog_timer, first_cpu(cpu_online_map)); } } } spin_unlock_irqrestore(&watchdog_lock, flags); } #else static void clocksource_check_watchdog(struct clocksource *cs) { if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES; } static inline void clocksource_resume_watchdog(void) { } #endif /** * clocksource_resume - resume the clocksource(s) */ void clocksource_resume(void) { struct clocksource *cs; unsigned long flags; spin_lock_irqsave(&clocksource_lock, flags); list_for_each_entry(cs, &clocksource_list, list) { if (cs->resume) cs->resume(); } clocksource_resume_watchdog(); spin_unlock_irqrestore(&clocksource_lock, flags); } /** * clocksource_touch_watchdog - Update watchdog * * Update the watchdog after exception contexts such as kgdb so as not * to incorrectly trip the watchdog. * */ void clocksource_touch_watchdog(void) { clocksource_resume_watchdog(); } /** * clocksource_get_next - Returns the selected clocksource * */ struct clocksource *clocksource_get_next(void) { unsigned long flags; spin_lock_irqsave(&clocksource_lock, flags); if (next_clocksource && finished_booting) { curr_clocksource = next_clocksource; next_clocksource = NULL; } spin_unlock_irqrestore(&clocksource_lock, flags); return curr_clocksource; } /** * select_clocksource - Selects the best registered clocksource. * * Private function. Must hold clocksource_lock when called. * * Select the clocksource with the best rating, or the clocksource, * which is selected by userspace override. */ static struct clocksource *select_clocksource(void) { struct clocksource *next; if (list_empty(&clocksource_list)) return NULL; if (clocksource_override) next = clocksource_override; else next = list_entry(clocksource_list.next, struct clocksource, list); if (next == curr_clocksource) return NULL; return next; } /* * Enqueue the clocksource sorted by rating */ static int clocksource_enqueue(struct clocksource *c) { struct list_head *tmp, *entry = &clocksource_list; list_for_each(tmp, &clocksource_list) { struct clocksource *cs; cs = list_entry(tmp, struct clocksource, list); if (cs == c) return -EBUSY; /* Keep track of the place, where to insert */ if (cs->rating >= c->rating) entry = tmp; } list_add(&c->list, entry); if (strlen(c->name) == strlen(override_name) && !strcmp(c->name, override_name)) clocksource_override = c; return 0; } /** * clocksource_register - Used to install new clocksources * @t: clocksource to be registered * * Returns -EBUSY if registration fails, zero otherwise. */ int clocksource_register(struct clocksource *c) { unsigned long flags; int ret; spin_lock_irqsave(&clocksource_lock, flags); ret = clocksource_enqueue(c); if (!ret) next_clocksource = select_clocksource(); spin_unlock_irqrestore(&clocksource_lock, flags); if (!ret) clocksource_check_watchdog(c); return ret; } EXPORT_SYMBOL(clocksource_register); /** * clocksource_change_rating - Change the rating of a registered clocksource * */ void clocksource_change_rating(struct clocksource *cs, int rating) { unsigned long flags; spin_lock_irqsave(&clocksource_lock, flags); list_del(&cs->list); cs->rating = rating; clocksource_enqueue(cs); next_clocksource = select_clocksource(); spin_unlock_irqrestore(&clocksource_lock, flags); } /** * clocksource_unregister - remove a registered clocksource */ void clocksource_unregister(struct clocksource *cs) { unsigned long flags; spin_lock_irqsave(&clocksource_lock, flags); list_del(&cs->list); if (clocksource_override == cs) clocksource_override = NULL; next_clocksource = select_clocksource(); spin_unlock_irqrestore(&clocksource_lock, flags); } #ifdef CONFIG_SYSFS /** * sysfs_show_current_clocksources - sysfs interface for current clocksource * @dev: unused * @buf: char buffer to be filled with clocksource list * * Provides sysfs interface for listing current clocksource. */ static ssize_t sysfs_show_current_clocksources(struct sys_device *dev, 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, const char *buf, size_t count) { struct clocksource *ovr = NULL; size_t ret = count; int len; /* 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; len = strlen(override_name); if (len) { struct clocksource *cs; ovr = clocksource_override; /* try to select it: */ list_for_each_entry(cs, &clocksource_list, list) { if (strlen(cs->name) == len && !strcmp(cs->name, override_name)) ovr = cs; } } /* Reselect, when the override name has changed */ if (ovr != clocksource_override) { clocksource_override = ovr; next_clocksource = select_clocksource(); } 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, char *buf) { struct clocksource *src; ssize_t count = 0; spin_lock_irq(&clocksource_lock); list_for_each_entry(src, &clocksource_list, list) { 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);