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/*
* OsmocomBB <-> SDR connection bridge
* TDMA scheduler: clock synchronization
*
* (C) 2013 by Andreas Eversberg <jolly@eversberg.eu>
* (C) 2015 by Alexander Chemeris <Alexander.Chemeris@fairwaves.co>
* (C) 2015 by Harald Welte <laforge@gnumonks.org>
*
* All Rights Reserved
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation; either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <osmocom/core/talloc.h>
#include <osmocom/core/msgb.h>
#include <osmocom/core/bits.h>
#include <osmocom/core/fsm.h>
#include <osmocom/gsm/a5.h>
#include "scheduler.h"
#include "logging.h"
#include "trx_if.h"
#include "trxcon.h"
#define FRAME_DURATION_uS 4615
#define MAX_FN_SKEW 50
#define TRX_LOSS_FRAMES 400
static void sched_clck_tick(void *data)
{
struct trx_sched *sched = (struct trx_sched *) data;
struct timeval tv_now, *tv_clock;
int32_t elapsed;
/* Check if transceiver is still alive */
if (sched->fn_counter_lost++ == TRX_LOSS_FRAMES) {
LOGP(DSCH, LOGL_DEBUG, "No more clock from transceiver\n");
sched->state = SCH_CLCK_STATE_WAIT;
return;
}
/* Get actual / previous frame time */
gettimeofday(&tv_now, NULL);
tv_clock = &sched->clock;
elapsed = (tv_now.tv_sec - tv_clock->tv_sec) * 1000000
+ (tv_now.tv_usec - tv_clock->tv_usec);
/* If someone played with clock, or if the process stalled */
if (elapsed > FRAME_DURATION_uS * MAX_FN_SKEW || elapsed < 0) {
LOGP(DSCH, LOGL_NOTICE, "PC clock skew: "
"elapsed uS %d\n", elapsed);
sched->state = SCH_CLCK_STATE_WAIT;
return;
}
/* Schedule next FN clock */
while (elapsed > FRAME_DURATION_uS / 2) {
tv_clock->tv_usec += FRAME_DURATION_uS;
elapsed -= FRAME_DURATION_uS;
if (tv_clock->tv_usec >= 1000000) {
tv_clock->tv_sec++;
tv_clock->tv_usec -= 1000000;
}
sched->fn_counter_proc = (sched->fn_counter_proc + 1)
% GSM_HYPERFRAME;
/* Call frame callback */
if (sched->clock_cb)
sched->clock_cb(sched);
}
osmo_timer_schedule(&sched->clock_timer, 0,
FRAME_DURATION_uS - elapsed);
}
static void sched_clck_correct(struct trx_sched *sched,
struct timeval *tv_now, uint32_t fn)
{
sched->fn_counter_proc = fn;
/* Call frame callback */
if (sched->clock_cb)
sched->clock_cb(sched);
/* Schedule first FN clock */
memcpy(&sched->clock, tv_now, sizeof(struct timeval));
memset(&sched->clock_timer, 0, sizeof(sched->clock_timer));
sched->clock_timer.cb = sched_clck_tick;
sched->clock_timer.data = sched;
osmo_timer_schedule(&sched->clock_timer, 0, FRAME_DURATION_uS);
}
int sched_clck_handle(struct trx_sched *sched, uint32_t fn)
{
struct timeval tv_now, *tv_clock;
int32_t elapsed, elapsed_fn;
/* Reset lost counter */
sched->fn_counter_lost = 0;
/* Get actual / previous frame time */
gettimeofday(&tv_now, NULL);
tv_clock = &sched->clock;
/* If this is the first CLCK IND */
if (sched->state == SCH_CLCK_STATE_WAIT) {
sched_clck_correct(sched, &tv_now, fn);
LOGP(DSCH, LOGL_DEBUG, "Initial clock received: fn=%u\n", fn);
sched->state = SCH_CLCK_STATE_OK;
return 0;
}
LOGP(DSCH, LOGL_NOTICE, "Clock indication: fn=%u\n", fn);
osmo_timer_del(&sched->clock_timer);
/* Calculate elapsed time / frames since last processed fn */
elapsed = (tv_now.tv_sec - tv_clock->tv_sec) * 1000000
+ (tv_now.tv_usec - tv_clock->tv_usec);
elapsed_fn = (fn + GSM_HYPERFRAME - sched->fn_counter_proc)
% GSM_HYPERFRAME;
if (elapsed_fn >= 135774)
elapsed_fn -= GSM_HYPERFRAME;
/* Check for max clock skew */
if (elapsed_fn > MAX_FN_SKEW || elapsed_fn < -MAX_FN_SKEW) {
LOGP(DSCH, LOGL_NOTICE, "GSM clock skew: old fn=%u, "
"new fn=%u\n", sched->fn_counter_proc, fn);
sched_clck_correct(sched, &tv_now, fn);
return 0;
}
LOGP(DSCH, LOGL_INFO, "GSM clock jitter: %d\n",
elapsed_fn * FRAME_DURATION_uS - elapsed);
/* Too many frames have been processed already */
if (elapsed_fn < 0) {
/**
* Set clock to the time or last FN should
* have been transmitted
*/
tv_clock->tv_sec = tv_now.tv_sec;
tv_clock->tv_usec = tv_now.tv_usec +
(0 - elapsed_fn) * FRAME_DURATION_uS;
if (tv_clock->tv_usec >= 1000000) {
tv_clock->tv_sec++;
tv_clock->tv_usec -= 1000000;
}
/* Set time to the time our next FN has to be transmitted */
osmo_timer_schedule(&sched->clock_timer, 0,
FRAME_DURATION_uS * (1 - elapsed_fn));
return 0;
}
/* Transmit what we still need to transmit */
while (fn != sched->fn_counter_proc) {
sched->fn_counter_proc = (sched->fn_counter_proc + 1)
% GSM_HYPERFRAME;
/* Call frame callback */
if (sched->clock_cb)
sched->clock_cb(sched);
}
/* Schedule next FN to be transmitted */
memcpy(tv_clock, &tv_now, sizeof(struct timeval));
osmo_timer_schedule(&sched->clock_timer, 0, FRAME_DURATION_uS);
return 0;
}
void sched_clck_reset(struct trx_sched *sched)
{
/* Reset internal state */
sched->state = SCH_CLCK_STATE_WAIT;
/* Stop clock timer */
osmo_timer_del(&sched->clock_timer);
/* Flush counters */
sched->fn_counter_proc = 0;
sched->fn_counter_lost = 0;
}
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