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// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright 2008 by Andreas Eversberg <andreas@eversberg.eu>
*
* Quick API description:
*
* A clock source registers using mISDN_register_clock:
* name = text string to name clock source
* priority = value to priorize clock sources (0 = default)
* ctl = callback function to enable/disable clock source
* priv = private pointer of clock source
* return = pointer to clock source structure;
*
* Note: Callback 'ctl' can be called before mISDN_register_clock returns!
* Also it can be called during mISDN_unregister_clock.
*
* A clock source calls mISDN_clock_update with given samples elapsed, if
* enabled. If function call is delayed, tv must be set with the timestamp
* of the actual event.
*
* A clock source unregisters using mISDN_unregister_clock.
*
* To get current clock, call mISDN_clock_get. The signed short value
* counts the number of samples since. Time since last clock event is added.
*/
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/stddef.h>
#include <linux/spinlock.h>
#include <linux/ktime.h>
#include <linux/mISDNif.h>
#include <linux/export.h>
#include "core.h"
static u_int *debug;
static LIST_HEAD(iclock_list);
static DEFINE_RWLOCK(iclock_lock);
static u16 iclock_count; /* counter of last clock */
static ktime_t iclock_timestamp; /* time stamp of last clock */
static int iclock_timestamp_valid; /* already received one timestamp */
static struct mISDNclock *iclock_current;
void
mISDN_init_clock(u_int *dp)
{
debug = dp;
iclock_timestamp = ktime_get();
}
static void
select_iclock(void)
{
struct mISDNclock *iclock, *bestclock = NULL, *lastclock = NULL;
int pri = -128;
list_for_each_entry(iclock, &iclock_list, list) {
if (iclock->pri > pri) {
pri = iclock->pri;
bestclock = iclock;
}
if (iclock_current == iclock)
lastclock = iclock;
}
if (lastclock && bestclock != lastclock) {
/* last used clock source still exists but changes, disable */
if (*debug & DEBUG_CLOCK)
printk(KERN_DEBUG "Old clock source '%s' disable.\n",
lastclock->name);
lastclock->ctl(lastclock->priv, 0);
}
if (bestclock && bestclock != iclock_current) {
/* new clock source selected, enable */
if (*debug & DEBUG_CLOCK)
printk(KERN_DEBUG "New clock source '%s' enable.\n",
bestclock->name);
bestclock->ctl(bestclock->priv, 1);
}
if (bestclock != iclock_current) {
/* no clock received yet */
iclock_timestamp_valid = 0;
}
iclock_current = bestclock;
}
struct mISDNclock
*mISDN_register_clock(char *name, int pri, clockctl_func_t *ctl, void *priv)
{
u_long flags;
struct mISDNclock *iclock;
if (*debug & (DEBUG_CORE | DEBUG_CLOCK))
printk(KERN_DEBUG "%s: %s %d\n", __func__, name, pri);
iclock = kzalloc(sizeof(struct mISDNclock), GFP_ATOMIC);
if (!iclock) {
printk(KERN_ERR "%s: No memory for clock entry.\n", __func__);
return NULL;
}
strscpy(iclock->name, name, sizeof(iclock->name));
iclock->pri = pri;
iclock->priv = priv;
iclock->ctl = ctl;
write_lock_irqsave(&iclock_lock, flags);
list_add_tail(&iclock->list, &iclock_list);
select_iclock();
write_unlock_irqrestore(&iclock_lock, flags);
return iclock;
}
EXPORT_SYMBOL(mISDN_register_clock);
void
mISDN_unregister_clock(struct mISDNclock *iclock)
{
u_long flags;
if (*debug & (DEBUG_CORE | DEBUG_CLOCK))
printk(KERN_DEBUG "%s: %s %d\n", __func__, iclock->name,
iclock->pri);
write_lock_irqsave(&iclock_lock, flags);
if (iclock_current == iclock) {
if (*debug & DEBUG_CLOCK)
printk(KERN_DEBUG
"Current clock source '%s' unregisters.\n",
iclock->name);
iclock->ctl(iclock->priv, 0);
}
list_del(&iclock->list);
select_iclock();
write_unlock_irqrestore(&iclock_lock, flags);
}
EXPORT_SYMBOL(mISDN_unregister_clock);
void
mISDN_clock_update(struct mISDNclock *iclock, int samples, ktime_t *timestamp)
{
u_long flags;
ktime_t timestamp_now;
u16 delta;
write_lock_irqsave(&iclock_lock, flags);
if (iclock_current != iclock) {
printk(KERN_ERR "%s: '%s' sends us clock updates, but we do "
"listen to '%s'. This is a bug!\n", __func__,
iclock->name,
iclock_current ? iclock_current->name : "nothing");
iclock->ctl(iclock->priv, 0);
write_unlock_irqrestore(&iclock_lock, flags);
return;
}
if (iclock_timestamp_valid) {
/* increment sample counter by given samples */
iclock_count += samples;
if (timestamp) { /* timestamp must be set, if function call is delayed */
iclock_timestamp = *timestamp;
} else {
iclock_timestamp = ktime_get();
}
} else {
/* calc elapsed time by system clock */
if (timestamp) { /* timestamp must be set, if function call is delayed */
timestamp_now = *timestamp;
} else {
timestamp_now = ktime_get();
}
delta = ktime_divns(ktime_sub(timestamp_now, iclock_timestamp),
(NSEC_PER_SEC / 8000));
/* add elapsed time to counter and set new timestamp */
iclock_count += delta;
iclock_timestamp = timestamp_now;
iclock_timestamp_valid = 1;
if (*debug & DEBUG_CLOCK)
printk("Received first clock from source '%s'.\n",
iclock_current ? iclock_current->name : "nothing");
}
write_unlock_irqrestore(&iclock_lock, flags);
}
EXPORT_SYMBOL(mISDN_clock_update);
unsigned short
mISDN_clock_get(void)
{
u_long flags;
ktime_t timestamp_now;
u16 delta;
u16 count;
read_lock_irqsave(&iclock_lock, flags);
/* calc elapsed time by system clock */
timestamp_now = ktime_get();
delta = ktime_divns(ktime_sub(timestamp_now, iclock_timestamp),
(NSEC_PER_SEC / 8000));
/* add elapsed time to counter */
count = iclock_count + delta;
read_unlock_irqrestore(&iclock_lock, flags);
return count;
}
EXPORT_SYMBOL(mISDN_clock_get);
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