207 lines
5.6 KiB
C
207 lines
5.6 KiB
C
/*
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* OsmocomBB <-> SDR connection bridge
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* TDMA scheduler: clock synchronization
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*
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* (C) 2013 by Andreas Eversberg <jolly@eversberg.eu>
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* (C) 2015 by Alexander Chemeris <Alexander.Chemeris@fairwaves.co>
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* (C) 2015 by Harald Welte <laforge@gnumonks.org>
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*
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* All Rights Reserved
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License as published by
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* the Free Software Foundation; either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU Affero General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*
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*/
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#include <stdio.h>
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#include <errno.h>
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#include <stdlib.h>
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#include <stdint.h>
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#include <inttypes.h>
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#include <string.h>
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#include <osmocom/core/talloc.h>
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#include <osmocom/core/msgb.h>
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#include <osmocom/core/bits.h>
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#include <osmocom/core/fsm.h>
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#include <osmocom/core/timer.h>
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#include <osmocom/core/timer_compat.h>
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#include <osmocom/gsm/a5.h>
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#include "scheduler.h"
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#include "logging.h"
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#include "trx_if.h"
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#define MAX_FN_SKEW 50
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#define TRX_LOSS_FRAMES 400
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static void sched_clck_tick(void *data)
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{
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struct trx_sched *sched = (struct trx_sched *) data;
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struct timespec tv_now, *tv_clock, elapsed;
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int64_t elapsed_us;
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const struct timespec frame_duration = { .tv_sec = 0, .tv_nsec = FRAME_DURATION_uS * 1000 };
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/* Check if transceiver is still alive */
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if (sched->fn_counter_lost++ == TRX_LOSS_FRAMES) {
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LOGP(DSCH, LOGL_DEBUG, "No more clock from transceiver\n");
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sched->state = SCH_CLCK_STATE_WAIT;
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return;
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}
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/* Get actual / previous frame time */
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osmo_clock_gettime(CLOCK_MONOTONIC, &tv_now);
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tv_clock = &sched->clock;
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timespecsub(&tv_now, tv_clock, &elapsed);
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elapsed_us = (elapsed.tv_sec * 1000000) + (elapsed.tv_nsec / 1000);
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/* If someone played with clock, or if the process stalled */
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if (elapsed_us > FRAME_DURATION_uS * MAX_FN_SKEW || elapsed_us < 0) {
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LOGP(DSCH, LOGL_NOTICE, "PC clock skew: "
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"elapsed uS %" PRId64 "\n", elapsed_us);
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sched->state = SCH_CLCK_STATE_WAIT;
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return;
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}
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/* Schedule next FN clock */
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while (elapsed_us > FRAME_DURATION_uS / 2) {
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timespecadd(tv_clock, &frame_duration, tv_clock);
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elapsed_us -= FRAME_DURATION_uS;
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sched->fn_counter_proc = TDMA_FN_INC(sched->fn_counter_proc);
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/* Call frame callback */
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if (sched->clock_cb)
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sched->clock_cb(sched);
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}
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osmo_timer_schedule(&sched->clock_timer, 0,
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FRAME_DURATION_uS - elapsed_us);
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}
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static void sched_clck_correct(struct trx_sched *sched,
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struct timespec *tv_now, uint32_t fn)
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{
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sched->fn_counter_proc = fn;
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/* Call frame callback */
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if (sched->clock_cb)
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sched->clock_cb(sched);
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/* Schedule first FN clock */
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sched->clock = *tv_now;
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memset(&sched->clock_timer, 0, sizeof(sched->clock_timer));
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sched->clock_timer.cb = sched_clck_tick;
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sched->clock_timer.data = sched;
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osmo_timer_schedule(&sched->clock_timer, 0, FRAME_DURATION_uS);
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}
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int sched_clck_handle(struct trx_sched *sched, uint32_t fn)
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{
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struct timespec tv_now, *tv_clock, elapsed;
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int64_t elapsed_us, elapsed_fn;
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/* Reset lost counter */
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sched->fn_counter_lost = 0;
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/* Get actual / previous frame time */
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osmo_clock_gettime(CLOCK_MONOTONIC, &tv_now);
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tv_clock = &sched->clock;
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/* If this is the first CLCK IND */
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if (sched->state == SCH_CLCK_STATE_WAIT) {
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sched_clck_correct(sched, &tv_now, fn);
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LOGP(DSCH, LOGL_DEBUG, "Initial clock received: fn=%u\n", fn);
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sched->state = SCH_CLCK_STATE_OK;
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return 0;
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}
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LOGP(DSCH, LOGL_NOTICE, "Clock indication: fn=%u\n", fn);
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osmo_timer_del(&sched->clock_timer);
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/* Calculate elapsed time / frames since last processed fn */
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timespecsub(&tv_now, tv_clock, &elapsed);
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elapsed_us = (elapsed.tv_sec * 1000000) + (elapsed.tv_nsec / 1000);
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elapsed_fn = TDMA_FN_SUB(fn, sched->fn_counter_proc);
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if (elapsed_fn >= 135774)
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elapsed_fn -= GSM_HYPERFRAME;
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/* Check for max clock skew */
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if (elapsed_fn > MAX_FN_SKEW || elapsed_fn < -MAX_FN_SKEW) {
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LOGP(DSCH, LOGL_NOTICE, "GSM clock skew: old fn=%u, "
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"new fn=%u\n", sched->fn_counter_proc, fn);
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sched_clck_correct(sched, &tv_now, fn);
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return 0;
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}
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LOGP(DSCH, LOGL_INFO, "GSM clock jitter: %" PRId64 "\n",
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elapsed_fn * FRAME_DURATION_uS - elapsed_us);
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/* Too many frames have been processed already */
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if (elapsed_fn < 0) {
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struct timespec duration;
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/**
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* Set clock to the time or last FN should
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* have been transmitted
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*/
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duration.tv_nsec = (0 - elapsed_fn) * FRAME_DURATION_uS * 1000;
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duration.tv_sec = duration.tv_nsec / 1000000000;
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duration.tv_nsec = duration.tv_nsec % 1000000000;
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timespecadd(&tv_now, &duration, tv_clock);
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/* Set time to the time our next FN has to be transmitted */
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osmo_timer_schedule(&sched->clock_timer, 0,
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FRAME_DURATION_uS * (1 - elapsed_fn));
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return 0;
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}
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/* Transmit what we still need to transmit */
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while (fn != sched->fn_counter_proc) {
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sched->fn_counter_proc = TDMA_FN_INC(sched->fn_counter_proc);
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/* Call frame callback */
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if (sched->clock_cb)
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sched->clock_cb(sched);
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}
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/* Schedule next FN to be transmitted */
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*tv_clock = tv_now;
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osmo_timer_schedule(&sched->clock_timer, 0, FRAME_DURATION_uS);
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return 0;
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}
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void sched_clck_reset(struct trx_sched *sched)
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{
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/* Reset internal state */
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sched->state = SCH_CLCK_STATE_WAIT;
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/* Stop clock timer */
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osmo_timer_del(&sched->clock_timer);
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/* Flush counters */
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sched->fn_counter_proc = 0;
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sched->fn_counter_lost = 0;
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}
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