1// SPDX-License-Identifier: GPL-2.0-only
2/*
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 source
9 *	priority = value to priorize clock sources (0 = default)
10 *	ctl = callback function to enable/disable clock source
11 *	priv = private pointer of clock source
12 *	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, if
18 * enabled. If function call is delayed, tv must be set with the timestamp
19 * 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 value
24 * 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
44void
45mISDN_init_clock(u_int *dp)
46{
47	debug = dp;
48	iclock_timestamp = ktime_get();
49}
50
51static void
52select_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 mISDNclock
87*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
111void
112mISDN_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_DEBUG
123			       "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
133void
134mISDN_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 short
180mISDN_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