diff options
Diffstat (limited to 'drivers/isdn/mISDN/clock.c')
| -rw-r--r-- | drivers/isdn/mISDN/clock.c | 197 |
1 files changed, 197 insertions, 0 deletions
diff --git a/drivers/isdn/mISDN/clock.c b/drivers/isdn/mISDN/clock.c new file mode 100644 index 000000000..01d878168 --- /dev/null +++ b/drivers/isdn/mISDN/clock.c @@ -0,0 +1,197 @@ +// 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; + } + strncpy(iclock->name, name, sizeof(iclock->name) - 1); + 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); |