trxcon/scheduler: refactor TDMA frame number calculation

Using TDMA frame number of a burst with bid=0 is fine for xCCH,
but not for TCH and FACCH, because they use the block-diagonel
interleaving. A single block on TCH may be interleaved over
8, 4 or even 6 consecutive bursts depending on its type.

Since we now have the measurement history, we can attach TDMA
frame number to each measurement set, and then look up N-th
one when averaging the measurements in sched_trx_meas_avg().

Change-Id: I9221957297a6154edc1767a0e3753f5ee383173f

src/host/trxcon/sched_lchan_common.c

@@ -137,9 +137,11 @@ int sched_send_dt_ind(struct trx_instance *trx, struct trx_ts *ts,
 	dl_hdr.chan_nr = lchan_desc->chan_nr | ts->index;
 	dl_hdr.link_id = lchan_desc->link_id;
 	dl_hdr.band_arfcn = htons(trx->band_arfcn);
-	dl_hdr.frame_nr = htonl(lchan->rx_first_fn);
 	dl_hdr.num_biterr = bit_error_count;
 
+	/* sched_trx_meas_avg() gives us TDMA frame number of the first burst */
+	dl_hdr.frame_nr = htonl(meas->fn);
+
 	/* RX level: 0 .. 63 in typical GSM notation (dBm + 110) */
 	dl_hdr.rx_level = dbm2rxlev(meas->rssi);
 
@@ -154,7 +156,7 @@ int sched_send_dt_ind(struct trx_instance *trx, struct trx_ts *ts,
 
 	/* Optional GSMTAP logging */
 	if (l2_len > 0 && (!traffic || lchan_desc->chan_nr == RSL_CHAN_OSMO_PDCH)) {
-		sched_gsmtap_send(lchan->type, lchan->rx_first_fn, ts->index,
+		sched_gsmtap_send(lchan->type, meas->fn, ts->index,
 				  trx->band_arfcn, meas->rssi, 0, l2, l2_len);
 	}
 

src/host/trxcon/sched_lchan_pdtch.c

@@ -48,12 +48,10 @@ int rx_pdtch_fn(struct trx_instance *trx, struct trx_ts *ts,
 	uint8_t l2[GPRS_L2_MAX_LEN], *mask;
 	int n_errors, n_bits_total, rc;
 	sbit_t *buffer, *offset;
-	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;
 
@@ -61,10 +59,8 @@ int rx_pdtch_fn(struct trx_instance *trx, struct trx_ts *ts,
 		"fn=%u ts=%u bid=%u\n", lchan_desc->name, fn, ts->index, bid);
 
 	/* Reset internal state */
-	if (bid == 0) {
-		*first_fn = fn;
+	if (bid == 0)
 		*mask = 0x0;
-	}
 
 	/* Update mask */
 	*mask |= (1 << bid);
@@ -88,8 +84,8 @@ int rx_pdtch_fn(struct trx_instance *trx, struct trx_ts *ts,
 	if ((*mask & 0xf) != 0xf) {
 		LOGP(DSCHD, LOGL_ERROR, "Received incomplete (%s) data frame at "
 			"fn=%u (%u/%u) for %s\n",
-			burst_mask2str(mask, 4), *first_fn,
-			(*first_fn) % ts->mf_layout->period,
+			burst_mask2str(mask, 4), lchan->meas_avg.fn,
+			lchan->meas_avg.fn % ts->mf_layout->period,
 			ts->mf_layout->period,
 			lchan_desc->name);
 
@@ -101,8 +97,8 @@ int rx_pdtch_fn(struct trx_instance *trx, struct trx_ts *ts,
 		NULL, &n_errors, &n_bits_total);
 	if (rc < 0) {
 		LOGP(DSCHD, LOGL_ERROR, "Received bad packet data frame "
-			"at fn=%u (%u/%u) for %s\n", *first_fn,
-			(*first_fn) % ts->mf_layout->period,
+			"at fn=%u (%u/%u) for %s\n", lchan->meas_avg.fn,
+			lchan->meas_avg.fn % ts->mf_layout->period,
 			ts->mf_layout->period,
 			lchan_desc->name);
 	}

src/host/trxcon/sched_lchan_tchf.c

@@ -50,12 +50,10 @@ int rx_tchf_fn(struct trx_instance *trx, struct trx_ts *ts,
 	int n_errors = -1, 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;
 
@@ -63,10 +61,8 @@ int rx_tchf_fn(struct trx_instance *trx, struct trx_ts *ts,
 		lchan_desc->name, fn, ts->index, bid);
 
 	/* Reset internal state */
-	if (bid == 0) {
-		*first_fn = fn;
+	if (bid == 0)
 		*mask = 0x00;
-	}
 
 	/* Update mask */
 	*mask |= (1 << bid);
@@ -90,8 +86,8 @@ int rx_tchf_fn(struct trx_instance *trx, struct trx_ts *ts,
 	if ((*mask & 0xf) != 0xf) {
 		LOGP(DSCHD, LOGL_ERROR, "Received incomplete (%s) traffic frame at "
 			"fn=%u (%u/%u) for %s\n",
-			burst_mask2str(mask, 8), *first_fn,
-			(*first_fn) % ts->mf_layout->period,
+			burst_mask2str(mask, 8), lchan->meas_avg.fn,
+			lchan->meas_avg.fn % ts->mf_layout->period,
 			ts->mf_layout->period,
 			lchan_desc->name);
 
@@ -152,6 +148,7 @@ bfi:
 	/* Didn't try to decode, fake measurements */
 	if (n_errors < 0) {
 		lchan->meas_avg = (struct trx_meas_set) {
+			.fn = lchan->meas_avg.fn,
 			.toa256 = 0,
 			.rssi = -110,
 		};

src/host/trxcon/sched_lchan_tchh.c

@@ -291,23 +291,19 @@ int rx_tchh_fn(struct trx_instance *trx, struct trx_ts *ts,
 
 	/* Check decoding result */
 	if (rc < 4) {
-		LOGP(DSCHD, LOGL_ERROR, "Received bad TCH frame (%s) ending at "
-			"fn=%u on %s (rc=%d)\n", burst_mask2str(mask, 6),
-			fn, lchan_desc->name, rc);
-
 		/* Calculate AVG of the measurements (assuming 4 bursts) */
 		sched_trx_meas_avg(lchan, 4);
 
+		LOGP(DSCHD, LOGL_ERROR, "Received bad TCH frame (%s) "
+			"at fn=%u on %s (rc=%d)\n", burst_mask2str(mask, 6),
+			lchan->meas_avg.fn, lchan_desc->name, rc);
+
 		/* Send BFI */
 		goto bfi;
 	} else if (rc == GSM_MACBLOCK_LEN) {
 		/* Skip decoding of the next 2 stolen bursts */
 		lchan->dl_ongoing_facch = true;
 
-		/* Calculate TDMA frame number of the first burst */
-		lchan->rx_first_fn = sched_tchh_block_dl_first_fn(lchan->type,
-			fn, true); /* FACCH/H */
-
 		/* Calculate AVG of the measurements (FACCH/H takes 6 bursts) */
 		sched_trx_meas_avg(lchan, 6);
 
@@ -326,10 +322,6 @@ int rx_tchh_fn(struct trx_instance *trx, struct trx_ts *ts,
 		sched_trx_meas_avg(lchan, 4);
 	}
 
-	/* Calculate TDMA frame number of the first burst */
-	lchan->rx_first_fn = sched_tchh_block_dl_first_fn(lchan->type,
-		fn, false); /* TCH/H */
-
 	/* Send a traffic frame to the higher layers */
 	return sched_send_dt_ind(trx, ts, lchan, l2, l2_len,
 		n_errors, false, true);
@@ -346,6 +338,7 @@ bfi:
 	/* Didn't try to decode, fake measurements */
 	if (n_errors < 0) {
 		lchan->meas_avg = (struct trx_meas_set) {
+			.fn = sched_tchh_block_dl_first_fn(lchan->type, fn, false),
 			.toa256 = 0,
 			.rssi = -110,
 		};
@@ -354,10 +347,6 @@ bfi:
 		n_errors = 0;
 	}
 
-	/* Calculate TDMA frame number of the first burst */
-	lchan->rx_first_fn = sched_tchh_block_dl_first_fn(lchan->type,
-		fn, false); /* TCH/H */
-
 	/* BFI is not applicable in signalling mode */
 	if (lchan->tch_mode == GSM48_CMODE_SIGN)
 		return sched_send_dt_ind(trx, ts, lchan, NULL, 0,

src/host/trxcon/sched_lchan_xcch.c

@@ -48,11 +48,9 @@ int rx_data_fn(struct trx_instance *trx, struct trx_ts *ts,
 	uint8_t l2[GSM_MACBLOCK_LEN], *mask;
 	int n_errors, n_bits_total, rc;
 	sbit_t *buffer, *offset;
-	uint32_t *first_fn;
 
 	/* 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;
 
@@ -60,10 +58,8 @@ int rx_data_fn(struct trx_instance *trx, struct trx_ts *ts,
 		lchan_desc->name, fn, ts->index, bid);
 
 	/* Reset internal state */
-	if (bid == 0) {
-		*first_fn = fn;
+	if (bid == 0)
 		*mask = 0x0;
-	}
 
 	/* Update mask */
 	*mask |= (1 << bid);
@@ -87,8 +83,8 @@ int rx_data_fn(struct trx_instance *trx, struct trx_ts *ts,
 	if ((*mask & 0xf) != 0xf) {
 		LOGP(DSCHD, LOGL_ERROR, "Received incomplete (%s) data frame at "
 			"fn=%u (%u/%u) for %s\n",
-			burst_mask2str(mask, 4), *first_fn,
-			(*first_fn) % ts->mf_layout->period,
+			burst_mask2str(mask, 4), lchan->meas_avg.fn,
+			lchan->meas_avg.fn % ts->mf_layout->period,
 			ts->mf_layout->period,
 			lchan_desc->name);
 		/* NOTE: xCCH has an insane amount of redundancy for error
@@ -101,8 +97,8 @@ int rx_data_fn(struct trx_instance *trx, struct trx_ts *ts,
 	rc = gsm0503_xcch_decode(l2, buffer, &n_errors, &n_bits_total);
 	if (rc) {
 		LOGP(DSCHD, LOGL_ERROR, "Received bad data frame at fn=%u "
-			"(%u/%u) for %s\n", *first_fn,
-			(*first_fn) % ts->mf_layout->period,
+			"(%u/%u) for %s\n", lchan->meas_avg.fn,
+			lchan->meas_avg.fn % ts->mf_layout->period,
 			ts->mf_layout->period,
 			lchan_desc->name);
 

src/host/trxcon/sched_trx.c

@@ -464,7 +464,6 @@ static void sched_trx_reset_lchan(struct trx_lchan_state *lchan)
 	/* Reset internal state variables */
 	lchan->rx_burst_mask = 0x00;
 	lchan->tx_burst_mask = 0x00;
-	lchan->rx_first_fn = 0;
 
 	/* Free burst memory */
 	talloc_free(lchan->rx_bursts);
@@ -747,6 +746,10 @@ void sched_trx_meas_avg(struct trx_lchan_state *lchan, unsigned int n)
 		toa256_sum += meas->toa256;
 		rssi_sum += meas->rssi;
 
+		/* Do not go below the first burst */
+		if (i + 1 == n)
+			break;
+
 		if (meas == MEAS_HIST_FIRST(hist))
 			meas = MEAS_HIST_LAST(hist);
 		else
@@ -756,4 +759,7 @@ void sched_trx_meas_avg(struct trx_lchan_state *lchan, unsigned int n)
 	/* Calculate the AVG */
 	lchan->meas_avg.toa256 = toa256_sum / n;
 	lchan->meas_avg.rssi = rssi_sum / n;
+
+	/* As a bonus, store TDMA frame number of the first burst */
+	lchan->meas_avg.fn = meas->fn;
 }

src/host/trxcon/sched_trx.h

@@ -159,6 +159,8 @@ struct trx_multiframe {
 };
 
 struct trx_meas_set {
+	/*! \brief TDMA frame number of the first burst this set belongs to */
+	uint32_t fn;
 	/*! \brief ToA256 (Timing of Arrival, 1/256 of a symbol) */
 	int16_t toa256;
 	/*! \brief RSSI (Received Signal Strength Indication) */
@@ -182,8 +184,6 @@ struct trx_lchan_state {
 
 	/*! \brief Burst type: GMSK or 8PSK */
 	enum trx_burst_type burst_type;
-	/*! \brief Frame number of first burst */
-	uint32_t rx_first_fn;
 	/*! \brief Mask of received bursts */
 	uint8_t rx_burst_mask;
 	/*! \brief Mask of transmitted bursts */

src/host/trxcon/trx_if.c

@@ -600,6 +600,7 @@ static int trx_data_rx_cb(struct osmo_fd *ofd, unsigned int what)
 	meas = (struct trx_meas_set) {
 		.toa256 = toa256,
 		.rssi = rssi,
+		.fn = fn,
 	};
 
 	/* Poke scheduler */