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 36 static u_int *debug; 37 static LIST_HEAD(iclock_list); 38 static DEFINE_RWLOCK(iclock_lock); 39 static u16 iclock_count; /* counter of last clock */ 40 static ktime_t iclock_timestamp; /* time stamp of last clock */ 41 static int iclock_timestamp_valid; /* already received one timestamp */ 42 static struct mISDNclock *iclock_current; 43 44 void 45 mISDN_init_clock(u_int *dp) 46 { 47 debug = dp; 48 iclock_timestamp = ktime_get(); 49 } 50 51 static void 52 select_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 86 struct 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 } 109 EXPORT_SYMBOL(mISDN_register_clock); 110 111 void 112 mISDN_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 } 131 EXPORT_SYMBOL(mISDN_unregister_clock); 132 133 void 134 mISDN_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 } 177 EXPORT_SYMBOL(mISDN_clock_update); 178 179 unsigned short 180 mISDN_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 } 197 EXPORT_SYMBOL(mISDN_clock_get); 198