linux/kernel/time/clockevents.c
Thomas Gleixner 80b816b736 clockevents: Provide interface to reconfigure an active clock event device
Some ARM SoCs have clock event devices which have their frequency
modified due to frequency scaling. Provide an interface which allows
to reconfigure an active device. After reconfiguration reprogram the
current pending event.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: LAK <linux-arm-kernel@lists.infradead.org>
Cc: John Stultz <john.stultz@linaro.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Ingo Molnar <mingo@elte.hu>
Link: http://lkml.kernel.org/r/%3C20110518210136.437459958%40linutronix.de%3E
2011-05-19 14:24:16 +02:00

339 lines
8.4 KiB
C

/*
* linux/kernel/time/clockevents.c
*
* This file contains functions which manage clock event devices.
*
* Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
* Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
* Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
*
* This code is licenced under the GPL version 2. For details see
* kernel-base/COPYING.
*/
#include <linux/clockchips.h>
#include <linux/hrtimer.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/notifier.h>
#include <linux/smp.h>
#include <linux/sysdev.h>
#include "tick-internal.h"
/* The registered clock event devices */
static LIST_HEAD(clockevent_devices);
static LIST_HEAD(clockevents_released);
/* Notification for clock events */
static RAW_NOTIFIER_HEAD(clockevents_chain);
/* Protection for the above */
static DEFINE_RAW_SPINLOCK(clockevents_lock);
/**
* clockevents_delta2ns - Convert a latch value (device ticks) to nanoseconds
* @latch: value to convert
* @evt: pointer to clock event device descriptor
*
* Math helper, returns latch value converted to nanoseconds (bound checked)
*/
u64 clockevent_delta2ns(unsigned long latch, struct clock_event_device *evt)
{
u64 clc = (u64) latch << evt->shift;
if (unlikely(!evt->mult)) {
evt->mult = 1;
WARN_ON(1);
}
do_div(clc, evt->mult);
if (clc < 1000)
clc = 1000;
if (clc > KTIME_MAX)
clc = KTIME_MAX;
return clc;
}
EXPORT_SYMBOL_GPL(clockevent_delta2ns);
/**
* clockevents_set_mode - set the operating mode of a clock event device
* @dev: device to modify
* @mode: new mode
*
* Must be called with interrupts disabled !
*/
void clockevents_set_mode(struct clock_event_device *dev,
enum clock_event_mode mode)
{
if (dev->mode != mode) {
dev->set_mode(mode, dev);
dev->mode = mode;
/*
* A nsec2cyc multiplicator of 0 is invalid and we'd crash
* on it, so fix it up and emit a warning:
*/
if (mode == CLOCK_EVT_MODE_ONESHOT) {
if (unlikely(!dev->mult)) {
dev->mult = 1;
WARN_ON(1);
}
}
}
}
/**
* clockevents_shutdown - shutdown the device and clear next_event
* @dev: device to shutdown
*/
void clockevents_shutdown(struct clock_event_device *dev)
{
clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
dev->next_event.tv64 = KTIME_MAX;
}
/**
* clockevents_program_event - Reprogram the clock event device.
* @expires: absolute expiry time (monotonic clock)
*
* Returns 0 on success, -ETIME when the event is in the past.
*/
int clockevents_program_event(struct clock_event_device *dev, ktime_t expires,
ktime_t now)
{
unsigned long long clc;
int64_t delta;
if (unlikely(expires.tv64 < 0)) {
WARN_ON_ONCE(1);
return -ETIME;
}
delta = ktime_to_ns(ktime_sub(expires, now));
if (delta <= 0)
return -ETIME;
dev->next_event = expires;
if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN)
return 0;
if (delta > dev->max_delta_ns)
delta = dev->max_delta_ns;
if (delta < dev->min_delta_ns)
delta = dev->min_delta_ns;
clc = delta * dev->mult;
clc >>= dev->shift;
return dev->set_next_event((unsigned long) clc, dev);
}
/**
* clockevents_register_notifier - register a clock events change listener
*/
int clockevents_register_notifier(struct notifier_block *nb)
{
unsigned long flags;
int ret;
raw_spin_lock_irqsave(&clockevents_lock, flags);
ret = raw_notifier_chain_register(&clockevents_chain, nb);
raw_spin_unlock_irqrestore(&clockevents_lock, flags);
return ret;
}
/*
* Notify about a clock event change. Called with clockevents_lock
* held.
*/
static void clockevents_do_notify(unsigned long reason, void *dev)
{
raw_notifier_call_chain(&clockevents_chain, reason, dev);
}
/*
* Called after a notify add to make devices available which were
* released from the notifier call.
*/
static void clockevents_notify_released(void)
{
struct clock_event_device *dev;
while (!list_empty(&clockevents_released)) {
dev = list_entry(clockevents_released.next,
struct clock_event_device, list);
list_del(&dev->list);
list_add(&dev->list, &clockevent_devices);
clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev);
}
}
/**
* clockevents_register_device - register a clock event device
* @dev: device to register
*/
void clockevents_register_device(struct clock_event_device *dev)
{
unsigned long flags;
BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED);
BUG_ON(!dev->cpumask);
raw_spin_lock_irqsave(&clockevents_lock, flags);
list_add(&dev->list, &clockevent_devices);
clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev);
clockevents_notify_released();
raw_spin_unlock_irqrestore(&clockevents_lock, flags);
}
EXPORT_SYMBOL_GPL(clockevents_register_device);
static void clockevents_config(struct clock_event_device *dev,
u32 freq)
{
unsigned long sec;
if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
return;
/*
* Calculate the maximum number of seconds we can sleep. Limit
* to 10 minutes for hardware which can program more than
* 32bit ticks so we still get reasonable conversion values.
*/
sec = dev->max_delta_ticks;
do_div(sec, freq);
if (!sec)
sec = 1;
else if (sec > 600 && dev->max_delta_ticks > UINT_MAX)
sec = 600;
clockevents_calc_mult_shift(dev, freq, sec);
dev->min_delta_ns = clockevent_delta2ns(dev->min_delta_ticks, dev);
dev->max_delta_ns = clockevent_delta2ns(dev->max_delta_ticks, dev);
}
/**
* clockevents_config_and_register - Configure and register a clock event device
* @dev: device to register
* @freq: The clock frequency
* @min_delta: The minimum clock ticks to program in oneshot mode
* @max_delta: The maximum clock ticks to program in oneshot mode
*
* min/max_delta can be 0 for devices which do not support oneshot mode.
*/
void clockevents_config_and_register(struct clock_event_device *dev,
u32 freq, unsigned long min_delta,
unsigned long max_delta)
{
dev->min_delta_ticks = min_delta;
dev->max_delta_ticks = max_delta;
clockevents_config(dev, freq);
clockevents_register_device(dev);
}
/**
* clockevents_update_freq - Update frequency and reprogram a clock event device.
* @dev: device to modify
* @freq: new device frequency
*
* Reconfigure and reprogram a clock event device in oneshot
* mode. Must be called on the cpu for which the device delivers per
* cpu timer events with interrupts disabled! Returns 0 on success,
* -ETIME when the event is in the past.
*/
int clockevents_update_freq(struct clock_event_device *dev, u32 freq)
{
clockevents_config(dev, freq);
if (dev->mode != CLOCK_EVT_MODE_ONESHOT)
return 0;
return clockevents_program_event(dev, dev->next_event, ktime_get());
}
/*
* Noop handler when we shut down an event device
*/
void clockevents_handle_noop(struct clock_event_device *dev)
{
}
/**
* clockevents_exchange_device - release and request clock devices
* @old: device to release (can be NULL)
* @new: device to request (can be NULL)
*
* Called from the notifier chain. clockevents_lock is held already
*/
void clockevents_exchange_device(struct clock_event_device *old,
struct clock_event_device *new)
{
unsigned long flags;
local_irq_save(flags);
/*
* Caller releases a clock event device. We queue it into the
* released list and do a notify add later.
*/
if (old) {
clockevents_set_mode(old, CLOCK_EVT_MODE_UNUSED);
list_del(&old->list);
list_add(&old->list, &clockevents_released);
}
if (new) {
BUG_ON(new->mode != CLOCK_EVT_MODE_UNUSED);
clockevents_shutdown(new);
}
local_irq_restore(flags);
}
#ifdef CONFIG_GENERIC_CLOCKEVENTS
/**
* clockevents_notify - notification about relevant events
*/
void clockevents_notify(unsigned long reason, void *arg)
{
struct clock_event_device *dev, *tmp;
unsigned long flags;
int cpu;
raw_spin_lock_irqsave(&clockevents_lock, flags);
clockevents_do_notify(reason, arg);
switch (reason) {
case CLOCK_EVT_NOTIFY_CPU_DEAD:
/*
* Unregister the clock event devices which were
* released from the users in the notify chain.
*/
list_for_each_entry_safe(dev, tmp, &clockevents_released, list)
list_del(&dev->list);
/*
* Now check whether the CPU has left unused per cpu devices
*/
cpu = *((int *)arg);
list_for_each_entry_safe(dev, tmp, &clockevent_devices, list) {
if (cpumask_test_cpu(cpu, dev->cpumask) &&
cpumask_weight(dev->cpumask) == 1 &&
!tick_is_broadcast_device(dev)) {
BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED);
list_del(&dev->list);
}
}
break;
default:
break;
}
raw_spin_unlock_irqrestore(&clockevents_lock, flags);
}
EXPORT_SYMBOL_GPL(clockevents_notify);
#endif