host/trxcon/scheduler: add initial TCH/F channel support

This change implements basic TCH/F lchan handlers for both data
reception and transmission. Only FACCH (signaling), FR and EFR
payloads are supported at the moment.

Change-Id: If6b0eaede2b484484d2a824e7219ff04483266a1

5 files changed, 386 insertions, 2 deletions

diff --git a/src/host/trxcon/Makefile.am b/src/host/trxcon/Makefile.am
index 90c7a3c1..88ff2bee 100644
--- a/src/host/trxcon/Makefile.am
+++ b/src/host/trxcon/Makefile.am
@@ -34,6 +34,7 @@ trxcon_SOURCES += \
 	sched_lchan_common.c \
 	sched_lchan_desc.c \
 	sched_lchan_xcch.c \
+	sched_lchan_tchf.c \
 	sched_lchan_rach.c \
 	sched_lchan_sch.c \
 	sched_mframe.c \
diff --git a/src/host/trxcon/sched_lchan_common.c b/src/host/trxcon/sched_lchan_common.c
index 925a4415..6d75533d 100644
--- a/src/host/trxcon/sched_lchan_common.c
+++ b/src/host/trxcon/sched_lchan_common.c
@@ -33,6 +33,7 @@
 #include <osmocom/core/bits.h>
 
 #include <osmocom/gsm/protocol/gsm_04_08.h>
+#include <osmocom/gsm/protocol/gsm_08_58.h>
 
 #include "l1ctl_proto.h"
 #include "scheduler.h"
@@ -145,3 +146,82 @@ int sched_send_data_conf(struct trx_instance *trx, struct trx_ts *ts,
 
 	return 0;
 }
+
+/**
+ * Composes a bad frame indication message
+ * according to the current tch_mode.
+ *
+ * @param  l2       Pointer to allocated byte array
+ * @param  tch_mode Current TCH mode
+ * @return          How much bytes were written
+ */
+size_t sched_bad_frame_ind(uint8_t *l2, uint8_t rsl_cmode, uint8_t tch_mode)
+{
+	/* BFI is only required for speech */
+	if (rsl_cmode != RSL_CMOD_SPD_SPEECH)
+		return 0;
+
+	switch (tch_mode) {
+	case GSM48_CMODE_SIGN:
+	case GSM48_CMODE_SPEECH_V1: /* Full Rate */
+		memset(l2, 0x00, GSM_FR_BYTES);
+		l2[0] = 0xd0;
+		return GSM_FR_BYTES;
+	case GSM48_CMODE_SPEECH_EFR: /* Enhanced Full Rate */
+		memset(l2, 0x00, GSM_EFR_BYTES);
+		l2[0] = 0xc0;
+		return GSM_EFR_BYTES;
+	case GSM48_CMODE_SPEECH_AMR: /* Adaptive Multi Rate */
+		/* FIXME: AMR is not implemented yet */
+		return 0;
+	default:
+		LOGP(DSCH, LOGL_ERROR, "Invalid TCH mode: %u\n", tch_mode);
+		return 0;
+	}
+}
+
+#define PRIM_IS_FACCH(prim) \
+	prim->payload_len == GSM_MACBLOCK_LEN
+
+#define PRIM_IS_TCH(prim) \
+	prim->payload_len != GSM_MACBLOCK_LEN
+
+struct trx_ts_prim *sched_dequeue_tch_prim(struct llist_head *queue)
+{
+	struct trx_ts_prim *a, *b;
+
+	/* Obtain the first prim from TX queue */
+	a = llist_entry(queue->next, struct trx_ts_prim, list);
+
+	/* If this is the only one => do nothing... */
+	if (queue->next->next == queue)
+		return a;
+
+	/* Obtain the second prim from TX queue */
+	b = llist_entry(queue->next->next, struct trx_ts_prim, list);
+
+	/* Find and prioritize FACCH  */
+	if (PRIM_IS_FACCH(a) && PRIM_IS_TCH(b)) {
+		/**
+		 * Case 1: first is FACCH, second is TCH:
+		 * Prioritize FACCH, dropping TCH
+		 */
+		llist_del(&b->list);
+		talloc_free(b);
+		return a;
+	} else if (PRIM_IS_TCH(a) && PRIM_IS_FACCH(b)) {
+		/**
+		 * Case 2: first is TCH, second is FACCH:
+		 * Prioritize FACCH, dropping TCH
+		 */
+		llist_del(&a->list);
+		talloc_free(a);
+		return b;
+	} else {
+		/**
+		 * Otherwise: both are TCH or FACCH frames:
+		 * Nothing to prioritize, return the first one
+		 */
+		return a;
+	}
+}
diff --git a/src/host/trxcon/sched_lchan_desc.c b/src/host/trxcon/sched_lchan_desc.c
index c483db8b..390b1ef1 100644
--- a/src/host/trxcon/sched_lchan_desc.c
+++ b/src/host/trxcon/sched_lchan_desc.c
@@ -30,11 +30,9 @@
 
 /* TODO: implement */
 #define tx_pdtch_fn	NULL
-#define tx_tchf_fn	NULL
 #define tx_tchh_fn	NULL
 
 #define rx_pdtch_fn	NULL
-#define rx_tchf_fn	NULL
 #define rx_tchh_fn	NULL
 
 /* Forward declaration of handlers */
@@ -52,6 +50,13 @@ int rx_sch_fn(struct trx_instance *trx, struct trx_ts *ts,
 int tx_rach_fn(struct trx_instance *trx, struct trx_ts *ts,
 	struct trx_lchan_state *lchan, uint32_t fn, uint8_t bid);
 
+int rx_tchf_fn(struct trx_instance *trx, struct trx_ts *ts,
+	struct trx_lchan_state *lchan, uint32_t fn, uint8_t bid,
+	sbit_t *bits, int8_t rssi, float toa);
+
+int tx_tchf_fn(struct trx_instance *trx, struct trx_ts *ts,
+	struct trx_lchan_state *lchan, uint32_t fn, uint8_t bid);
+
 const struct trx_lchan_desc trx_lchan_desc[_TRX_CHAN_MAX] = {
 	{
 		TRXC_IDLE,		"IDLE",
diff --git a/src/host/trxcon/sched_lchan_tchf.c b/src/host/trxcon/sched_lchan_tchf.c
new file mode 100644
index 00000000..237e5388
--- /dev/null
+++ b/src/host/trxcon/sched_lchan_tchf.c
@@ -0,0 +1,292 @@
+/*
+ * OsmocomBB <-> SDR connection bridge
+ * TDMA scheduler: handlers for DL / UL bursts on logical channels
+ *
+ * (C) 2017 by Vadim Yanitskiy <axilirator@gmail.com>
+ *
+ * All Rights Reserved
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 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 General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ */
+
+#include <errno.h>
+#include <string.h>
+#include <talloc.h>
+#include <stdint.h>
+
+#include <osmocom/core/linuxlist.h>
+#include <osmocom/core/logging.h>
+#include <osmocom/core/bits.h>
+
+#include <osmocom/gsm/protocol/gsm_04_08.h>
+#include <osmocom/gsm/protocol/gsm_08_58.h>
+#include <osmocom/gsm/gsm_utils.h>
+
+#include <osmocom/coding/gsm0503_coding.h>
+#include <osmocom/codec/codec.h>
+
+#include "l1ctl_proto.h"
+#include "scheduler.h"
+#include "sched_trx.h"
+#include "logging.h"
+#include "trx_if.h"
+#include "trxcon.h"
+#include "l1ctl.h"
+
+int rx_tchf_fn(struct trx_instance *trx, struct trx_ts *ts,
+	struct trx_lchan_state *lchan, uint32_t fn, uint8_t bid,
+	sbit_t *bits, int8_t rssi, float toa)
+{
+	const struct trx_lchan_desc *lchan_desc;
+	uint8_t rsl_cmode, tch_mode, mode;
+	int n_errors, n_bits_total, rc;
+	sbit_t *buffer, *offset;
+	uint8_t l2[128], *mask;
+	uint32_t *first_fn;
+	size_t l2_len;
+
+	/* Set up pointers */
+	lchan_desc = &trx_lchan_desc[lchan->type];
+	first_fn = &lchan->rx_first_fn;
+	mask = &lchan->rx_burst_mask;
+	buffer = lchan->rx_bursts;
+
+	LOGP(DSCHD, LOGL_DEBUG, "Traffic received on %s: fn=%u ts=%u bid=%u\n",
+		lchan_desc->name, fn, ts->index, bid);
+
+	/* Reset internal state */
+	if (bid == 0) {
+		/* Clean up old measurements */
+		memset(&lchan->meas, 0x00, sizeof(lchan->meas));
+
+		*first_fn = fn;
+		*mask = 0x00;
+	}
+
+	/* Update mask */
+	*mask |= (1 << bid);
+
+	/* Update mask and RSSI */
+	lchan->meas.rssi_sum += rssi;
+	lchan->meas.toa_sum += toa;
+	lchan->meas.rssi_num++;
+	lchan->meas.toa_num++;
+
+	/* Copy burst to end of buffer of 8 bursts */
+	offset = buffer + bid * 116 + 464;
+	memcpy(offset, bits + 3, 58);
+	memcpy(offset + 58, bits + 87, 58);
+
+	/* Wait until complete set of bursts */
+	if (bid != 3)
+		return 0;
+
+	/* Check for complete set of bursts */
+	if ((*mask & 0xf) != 0xf) {
+		LOGP(DSCHD, LOGL_DEBUG, "Received incomplete traffic frame at "
+			"fn=%u (%u/%u) for %s\n", *first_fn,
+			(*first_fn) % ts->mf_layout->period,
+			ts->mf_layout->period,
+			lchan_desc->name);
+		return -EINVAL;
+	}
+
+	/**
+	 * Get current RSL / TCH modes
+	 *
+	 * FIXME: we do support speech only, and
+	 * CSD support may be implemented latter.
+	 */
+	rsl_cmode = RSL_CMOD_SPD_SPEECH;
+	tch_mode = lchan->tch_mode;
+
+	mode = rsl_cmode != RSL_CMOD_SPD_SPEECH ?
+		GSM48_CMODE_SPEECH_V1 : tch_mode;
+
+	switch (mode) {
+	case GSM48_CMODE_SIGN:
+	case GSM48_CMODE_SPEECH_V1: /* FR */
+		rc = gsm0503_tch_fr_decode(l2, buffer,
+			1, 0, &n_errors, &n_bits_total);
+		break;
+	case GSM48_CMODE_SPEECH_EFR: /* EFR */
+		rc = gsm0503_tch_fr_decode(l2, buffer,
+			1, 1, &n_errors, &n_bits_total);
+		break;
+	case GSM48_CMODE_SPEECH_AMR: /* AMR */
+		/**
+		 * TODO: AMR requires a dedicated loop,
+		 * which will be implemented later...
+		 */
+		LOGP(DSCHD, LOGL_ERROR, "AMR isn't supported yet\n");
+		return -ENOTSUP;
+	default:
+		LOGP(DSCHD, LOGL_ERROR, "Invalid TCH mode: %u\n", tch_mode);
+		return -EINVAL;
+	}
+
+	/* Shift buffer by 4 bursts for interleaving */
+	memcpy(buffer, buffer + 464, 464);
+
+	/* Check decoding result */
+	if (rc < 4) {
+		LOGP(DSCHD, LOGL_DEBUG, "Received bad TCH frame ending at "
+			"fn=%u for %s\n", fn, lchan_desc->name);
+
+		l2_len = sched_bad_frame_ind(l2, rsl_cmode, tch_mode);
+	} else if (rc == GSM_MACBLOCK_LEN) {
+		/* FACCH received, forward it to the higher layers */
+		sched_send_data_ind(trx, ts, lchan, l2, GSM_MACBLOCK_LEN);
+		/* Send BFI instead of stolen TCH frame */
+		l2_len = sched_bad_frame_ind(l2, rsl_cmode, tch_mode);
+	} else {
+		/* A good TCH frame received */
+		l2_len = rc;
+	}
+
+	/* Send a traffic frame to the higher layers */
+	if (l2_len > 0)
+		sched_send_data_ind(trx, ts, lchan, l2, l2_len);
+
+	return 0;
+}
+
+int tx_tchf_fn(struct trx_instance *trx, struct trx_ts *ts,
+	struct trx_lchan_state *lchan, uint32_t fn, uint8_t bid)
+{
+	const struct trx_lchan_desc *lchan_desc;
+	struct trx_ts_prim *prim;
+	ubit_t burst[GSM_BURST_LEN];
+	ubit_t *buffer, *offset;
+	uint8_t *mask, *l2;
+	const uint8_t *tsc;
+	size_t l2_len;
+	int rc;
+
+	/* Set up pointers */
+	lchan_desc = &trx_lchan_desc[lchan->type];
+	mask = &lchan->tx_burst_mask;
+	buffer = lchan->tx_bursts;
+
+	/* If we have encoded bursts */
+	if (*mask)
+		goto send_burst;
+
+	/* Wait until a first burst in period */
+	if (bid > 0)
+		return 0;
+
+	/* Check the current TCH mode */
+	switch (lchan->tch_mode) {
+	case GSM48_CMODE_SIGN:
+	case GSM48_CMODE_SPEECH_V1: /* FR */
+		l2_len = GSM_FR_BYTES;
+		break;
+	case GSM48_CMODE_SPEECH_EFR: /* EFR */
+		l2_len = GSM_EFR_BYTES;
+		break;
+	case GSM48_CMODE_SPEECH_AMR: /* AMR */
+		/**
+		 * TODO: AMR requires a dedicated loop,
+		 * which will be implemented later...
+		 */
+		/* TODO: drop prim here */
+		LOGP(DSCHD, LOGL_ERROR, "AMR isn't supported yet\n");
+		return -ENOTSUP;
+	default:
+		/* TODO: drop prim here */
+		LOGP(DSCHD, LOGL_ERROR, "Invalid TCH mode: %u\n",
+			lchan->tch_mode);
+		return -EINVAL;
+	}
+
+	/* Get a message from TX queue */
+	prim = sched_dequeue_tch_prim(&ts->tx_prims);
+	l2 = (uint8_t *) prim->payload;
+
+	/* Determine payload length */
+	if (prim->payload_len == GSM_MACBLOCK_LEN)
+		l2_len = GSM_MACBLOCK_LEN;
+
+	/* Shift buffer by 4 bursts back for interleaving */
+	memcpy(buffer, buffer + 464, 464);
+
+	/* Encode payload */
+	rc = gsm0503_tch_fr_encode(buffer, l2, l2_len, 1);
+	if (rc) {
+		LOGP(DSCHD, LOGL_ERROR, "Failed to encode L2 payload\n");
+
+		/* Remove primitive from queue and free memory */
+		llist_del(&prim->list);
+		talloc_free(prim);
+
+		return -EINVAL;
+	}
+
+send_burst:
+	/* Determine which burst should be sent */
+	offset = buffer + bid * 116;
+
+	/* Update mask */
+	*mask |= (1 << bid);
+
+	/* Choose proper TSC */
+	tsc = sched_nb_training_bits[trx->tsc];
+
+	/* Compose a new burst */
+	memset(burst, 0, 3); /* TB */
+	memcpy(burst + 3, offset, 58); /* Payload 1/2 */
+	memcpy(burst + 61, tsc, 26); /* TSC */
+	memcpy(burst + 87, offset + 58, 58); /* Payload 2/2 */
+	memset(burst + 145, 0, 3); /* TB */
+
+	LOGP(DSCHD, LOGL_DEBUG, "Transmitting %s fn=%u ts=%u burst=%u\n",
+		lchan_desc->name, fn, ts->index, bid);
+
+	/* Send burst to transceiver */
+	rc = trx_if_tx_burst(trx, ts->index, fn, trx->tx_power, burst);
+	if (rc) {
+		LOGP(DSCHD, LOGL_ERROR, "Could not send burst to transceiver\n");
+
+		/* Remove primitive from queue and free memory */
+		prim = llist_entry(ts->tx_prims.next, struct trx_ts_prim, list);
+		llist_del(&prim->list);
+		talloc_free(prim);
+
+		/* Reset mask */
+		*mask = 0x00;
+
+		return rc;
+	}
+
+	/* If we have sent the last (4/4) burst */
+	if (*mask == 0x0f) {
+		/* Get pointer to a prim which was sent */
+		prim = llist_entry(ts->tx_prims.next, struct trx_ts_prim, list);
+
+		/* Confirm data / traffic sending */
+		sched_send_data_conf(trx, ts, lchan, fn, prim->payload_len);
+
+		/* Remove primitive from queue and free memory */
+		llist_del(&prim->list);
+		talloc_free(prim);
+
+		/* Reset mask */
+		*mask = 0x00;
+	}
+
+	return 0;
+}
diff --git a/src/host/trxcon/sched_trx.h b/src/host/trxcon/sched_trx.h
index de7e0734..268c6b70 100644
--- a/src/host/trxcon/sched_trx.h
+++ b/src/host/trxcon/sched_trx.h
@@ -22,6 +22,11 @@
 
 #define MAX_A5_KEY_LEN		(128 / 8)
 
+/* TS 101318 Chapter 5.1: 260 bits + 4bit sig */
+#define GSM_FR_BYTES		33
+/* TS 101318 Chapter 5.3: 244 bits + 4bit sig */
+#define GSM_EFR_BYTES		31
+
 /* Forward declaration to avoid mutual include */
 struct trx_lchan_state;
 struct trx_instance;
@@ -262,6 +267,7 @@ int sched_trx_init_prim(struct trx_instance *trx, struct trx_ts_prim **prim,
 	size_t pl_len, uint8_t chan_nr, uint8_t link_id);
 int sched_trx_push_prim(struct trx_instance *trx,
 	struct trx_ts_prim *prim, uint8_t chan_nr);
+struct trx_ts_prim *sched_dequeue_tch_prim(struct llist_head *queue);
 
 int sched_trx_handle_rx_burst(struct trx_instance *trx, uint8_t tn,
 	uint32_t burst_fn, sbit_t *bits, uint16_t nbits, int8_t rssi, float toa);