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1// SPDX-License-Identifier: GPL-2.0-only2/*3 * Copyright 2008 by Andreas Eversberg <andreas@eversberg.eu>4 *5 * Quick API description:6 *7 * A clock source registers using mISDN_register_clock:8 * name = text string to name clock source9 * priority = value to priorize clock sources (0 = default)10 * ctl = callback function to enable/disable clock source11 * priv = private pointer of clock source12 * return = pointer to clock source structure;13 *14 * Note: Callback 'ctl' can be called before mISDN_register_clock returns!15 * Also it can be called during mISDN_unregister_clock.16 *17 * A clock source calls mISDN_clock_update with given samples elapsed, if18 * enabled. If function call is delayed, tv must be set with the timestamp19 * of the actual event.20 *21 * A clock source unregisters using mISDN_unregister_clock.22 *23 * To get current clock, call mISDN_clock_get. The signed short value24 * counts the number of samples since. Time since last clock event is added.25 */26 27#include <linux/slab.h>28#include <linux/types.h>29#include <linux/stddef.h>30#include <linux/spinlock.h>31#include <linux/ktime.h>32#include <linux/mISDNif.h>33#include <linux/export.h>34#include "core.h"35 36static u_int *debug;37static LIST_HEAD(iclock_list);38static DEFINE_RWLOCK(iclock_lock);39static u16 iclock_count; /* counter of last clock */40static ktime_t iclock_timestamp; /* time stamp of last clock */41static int iclock_timestamp_valid; /* already received one timestamp */42static struct mISDNclock *iclock_current;43 44void45mISDN_init_clock(u_int *dp)46{47 debug = dp;48 iclock_timestamp = ktime_get();49}50 51static void52select_iclock(void)53{54 struct mISDNclock *iclock, *bestclock = NULL, *lastclock = NULL;55 int pri = -128;56 57 list_for_each_entry(iclock, &iclock_list, list) {58 if (iclock->pri > pri) {59 pri = iclock->pri;60 bestclock = iclock;61 }62 if (iclock_current == iclock)63 lastclock = iclock;64 }65 if (lastclock && bestclock != lastclock) {66 /* last used clock source still exists but changes, disable */67 if (*debug & DEBUG_CLOCK)68 printk(KERN_DEBUG "Old clock source '%s' disable.\n",69 lastclock->name);70 lastclock->ctl(lastclock->priv, 0);71 }72 if (bestclock && bestclock != iclock_current) {73 /* new clock source selected, enable */74 if (*debug & DEBUG_CLOCK)75 printk(KERN_DEBUG "New clock source '%s' enable.\n",76 bestclock->name);77 bestclock->ctl(bestclock->priv, 1);78 }79 if (bestclock != iclock_current) {80 /* no clock received yet */81 iclock_timestamp_valid = 0;82 }83 iclock_current = bestclock;84}85 86struct mISDNclock87*mISDN_register_clock(char *name, int pri, clockctl_func_t *ctl, void *priv)88{89 u_long flags;90 struct mISDNclock *iclock;91 92 if (*debug & (DEBUG_CORE | DEBUG_CLOCK))93 printk(KERN_DEBUG "%s: %s %d\n", __func__, name, pri);94 iclock = kzalloc(sizeof(struct mISDNclock), GFP_ATOMIC);95 if (!iclock) {96 printk(KERN_ERR "%s: No memory for clock entry.\n", __func__);97 return NULL;98 }99 strscpy(iclock->name, name, sizeof(iclock->name));100 iclock->pri = pri;101 iclock->priv = priv;102 iclock->ctl = ctl;103 write_lock_irqsave(&iclock_lock, flags);104 list_add_tail(&iclock->list, &iclock_list);105 select_iclock();106 write_unlock_irqrestore(&iclock_lock, flags);107 return iclock;108}109EXPORT_SYMBOL(mISDN_register_clock);110 111void112mISDN_unregister_clock(struct mISDNclock *iclock)113{114 u_long flags;115 116 if (*debug & (DEBUG_CORE | DEBUG_CLOCK))117 printk(KERN_DEBUG "%s: %s %d\n", __func__, iclock->name,118 iclock->pri);119 write_lock_irqsave(&iclock_lock, flags);120 if (iclock_current == iclock) {121 if (*debug & DEBUG_CLOCK)122 printk(KERN_DEBUG123 "Current clock source '%s' unregisters.\n",124 iclock->name);125 iclock->ctl(iclock->priv, 0);126 }127 list_del(&iclock->list);128 select_iclock();129 write_unlock_irqrestore(&iclock_lock, flags);130}131EXPORT_SYMBOL(mISDN_unregister_clock);132 133void134mISDN_clock_update(struct mISDNclock *iclock, int samples, ktime_t *timestamp)135{136 u_long flags;137 ktime_t timestamp_now;138 u16 delta;139 140 write_lock_irqsave(&iclock_lock, flags);141 if (iclock_current != iclock) {142 printk(KERN_ERR "%s: '%s' sends us clock updates, but we do "143 "listen to '%s'. This is a bug!\n", __func__,144 iclock->name,145 iclock_current ? iclock_current->name : "nothing");146 iclock->ctl(iclock->priv, 0);147 write_unlock_irqrestore(&iclock_lock, flags);148 return;149 }150 if (iclock_timestamp_valid) {151 /* increment sample counter by given samples */152 iclock_count += samples;153 if (timestamp) { /* timestamp must be set, if function call is delayed */154 iclock_timestamp = *timestamp;155 } else {156 iclock_timestamp = ktime_get();157 }158 } else {159 /* calc elapsed time by system clock */160 if (timestamp) { /* timestamp must be set, if function call is delayed */161 timestamp_now = *timestamp;162 } else {163 timestamp_now = ktime_get();164 }165 delta = ktime_divns(ktime_sub(timestamp_now, iclock_timestamp),166 (NSEC_PER_SEC / 8000));167 /* add elapsed time to counter and set new timestamp */168 iclock_count += delta;169 iclock_timestamp = timestamp_now;170 iclock_timestamp_valid = 1;171 if (*debug & DEBUG_CLOCK)172 printk("Received first clock from source '%s'.\n",173 iclock_current ? iclock_current->name : "nothing");174 }175 write_unlock_irqrestore(&iclock_lock, flags);176}177EXPORT_SYMBOL(mISDN_clock_update);178 179unsigned short180mISDN_clock_get(void)181{182 u_long flags;183 ktime_t timestamp_now;184 u16 delta;185 u16 count;186 187 read_lock_irqsave(&iclock_lock, flags);188 /* calc elapsed time by system clock */189 timestamp_now = ktime_get();190 delta = ktime_divns(ktime_sub(timestamp_now, iclock_timestamp),191 (NSEC_PER_SEC / 8000));192 /* add elapsed time to counter */193 count = iclock_count + delta;194 read_unlock_irqrestore(&iclock_lock, flags);195 return count;196}197EXPORT_SYMBOL(mISDN_clock_get);198