trxcon/l1sched: rework burst buffer shifting for TCH/[FH]

This is how the buffer shifting is implemented in osmo-bts-trx.  Keep
trxcon's l1sched implementation as close to osmo-bts-trx as possible
in order to simplify the integration of CSD support.

Change-Id: Idb6e415f37f41b8ab92a3864962dac0a40c2fbaa
Related: OS#4396

2 files changed, 31 insertions, 40 deletions

diff --git a/src/host/trxcon/src/sched_lchan_tchf.c b/src/host/trxcon/src/sched_lchan_tchf.c
index 691ad5a5..a4aa80cb 100644
--- a/src/host/trxcon/src/sched_lchan_tchf.c
+++ b/src/host/trxcon/src/sched_lchan_tchf.c
@@ -75,9 +75,16 @@ int rx_tchf_fn(struct l1sched_lchan_state *lchan,
 	LOGP_LCHAND(lchan, LOGL_DEBUG,
 		    "Traffic received: fn=%u bid=%u\n", bi->fn, bi->bid);
 
-	/* Align to the first burst of a block */
-	if (*mask == 0x00 && bi->bid != 0)
-		return 0;
+	if (bi->bid == 0) {
+		/* Shift the burst buffer by 4 bursts leftwards */
+		memcpy(&bursts_p[0], &bursts_p[464], 464);
+		memset(&bursts_p[464], 0, 464);
+		*mask = *mask << 4;
+	} else {
+		/* Align to the first burst of a block */
+		if (*mask == 0x00)
+			return 0;
+	}
 
 	/* Update mask */
 	*mask |= (1 << bi->bid);
@@ -108,9 +115,6 @@ int rx_tchf_fn(struct l1sched_lchan_state *lchan,
 
 	}
 
-	/* Keep the mask updated */
-	*mask = *mask << 4;
-
 	switch (lchan->tch_mode) {
 	case GSM48_CMODE_SIGN:
 	case GSM48_CMODE_SPEECH_V1: /* FR */
@@ -157,9 +161,6 @@ int rx_tchf_fn(struct l1sched_lchan_state *lchan,
 		return -EINVAL;
 	}
 
-	/* Shift buffer by 4 bursts for interleaving */
-	memcpy(bursts_p, bursts_p + 464, 464);
-
 	/* Check decoding result */
 	if (rc < 4) {
 		LOGP_LCHAND(lchan, LOGL_ERROR,
@@ -227,8 +228,10 @@ int tx_tchf_fn(struct l1sched_lchan_state *lchan,
 	if (br->bid > 0)
 		goto send_burst;
 
-	/* Shift buffer by 4 bursts back for interleaving */
-	memcpy(bursts_p, bursts_p + 464, 464);
+	/* Shift the burst buffer by 4 bursts leftwards for interleaving */
+	memcpy(&bursts_p[0], &bursts_p[464], 464);
+	memset(&bursts_p[464], 0, 464);
+	*mask = *mask << 4;
 
 	/* populate the buffer with bursts */
 	switch (lchan->tch_mode) {
@@ -332,12 +335,9 @@ send_burst:
 	LOGP_LCHAND(lchan, LOGL_DEBUG, "Scheduled fn=%u burst=%u\n", br->fn, br->bid);
 
 	/* If we have sent the last (4/4) burst */
-	if (*mask == 0x0f) {
+	if ((*mask & 0x0f) == 0x0f) {
 		/* Confirm data / traffic sending (pass ownership of the prim) */
 		l1sched_lchan_emit_data_cnf(lchan, br->fn);
-
-		/* Reset mask */
-		*mask = 0x00;
 	}
 
 	return 0;
diff --git a/src/host/trxcon/src/sched_lchan_tchh.c b/src/host/trxcon/src/sched_lchan_tchh.c
index bff9b1b0..30d623b5 100644
--- a/src/host/trxcon/src/sched_lchan_tchh.c
+++ b/src/host/trxcon/src/sched_lchan_tchh.c
@@ -252,6 +252,14 @@ int rx_tchh_fn(struct l1sched_lchan_state *lchan,
 	LOGP_LCHAND(lchan, LOGL_DEBUG,
 		    "Traffic received: fn=%u bid=%u\n", bi->fn, bi->bid);
 
+	if (bi->bid == 0) {
+		/* Shift the burst buffer by 2 bursts leftwards */
+		memcpy(&bursts_p[0], &bursts_p[232], 232);
+		memcpy(&bursts_p[232], &bursts_p[464], 232);
+		memset(&bursts_p[464], 0, 232);
+		*mask = *mask << 2;
+	}
+
 	if (*mask == 0x00) {
 		/* Align to the first burst */
 		if (bi->bid > 0)
@@ -286,17 +294,17 @@ int rx_tchh_fn(struct l1sched_lchan_state *lchan,
 	if (lchan->tch_mode == GSM48_CMODE_SIGN) {
 		/* FACCH/H is interleaved over 6 bursts */
 		if ((*mask & 0x3f) != 0x3f)
-			goto bfi_shift;
+			goto bfi;
 	} else {
 		/* Traffic is interleaved over 4 bursts */
 		if ((*mask & 0x0f) != 0x0f)
-			goto bfi_shift;
+			goto bfi;
 	}
 
 	/* Skip decoding attempt in case of FACCH/H */
 	if (lchan->dl_ongoing_facch) {
 		lchan->dl_ongoing_facch = false;
-		goto bfi_shift; /* 2/2 BFI */
+		goto bfi; /* 2/2 BFI */
 	}
 
 	switch (lchan->tch_mode) {
@@ -340,13 +348,6 @@ int rx_tchh_fn(struct l1sched_lchan_state *lchan,
 		return -EINVAL;
 	}
 
-	/* Shift buffer by 4 bursts for interleaving */
-	memcpy(bursts_p, bursts_p + 232, 232);
-	memcpy(bursts_p + 232, bursts_p + 464, 232);
-
-	/* Shift burst mask */
-	*mask = *mask << 2;
-
 	/* Check decoding result */
 	if (rc < 4) {
 		/* Calculate AVG of the measurements (assuming 4 bursts) */
@@ -384,14 +385,6 @@ int rx_tchh_fn(struct l1sched_lchan_state *lchan,
 	return l1sched_lchan_emit_data_ind(lchan, &tch_data[0], tch_data_len,
 					   n_errors, n_bits_total, true);
 
-bfi_shift:
-	/* Shift buffer */
-	memcpy(bursts_p, bursts_p + 232, 232);
-	memcpy(bursts_p + 232, bursts_p + 464, 232);
-
-	/* Shift burst mask */
-	*mask = *mask << 2;
-
 bfi:
 	/* Didn't try to decode, fake measurements */
 	if (n_errors < 0) {
@@ -441,17 +434,15 @@ int tx_tchh_fn(struct l1sched_lchan_state *lchan,
 				return 0;
 	}
 
-	/* Shift buffer by 2 bursts back for interleaving */
-	memcpy(bursts_p, bursts_p + 232, 232);
-
-	/* Also shift TX burst mask */
+	/* Shift the burst buffer by 2 bursts leftwards for interleaving */
+	memcpy(&bursts_p[0], &bursts_p[232], 232);
+	memcpy(&bursts_p[232], &bursts_p[464], 232);
+	memset(&bursts_p[464], 0, 232);
 	*mask = *mask << 2;
 
 	/* If FACCH/H blocks are still pending */
-	if (lchan->ul_facch_blocks > 2) {
-		memcpy(bursts_p + 232, bursts_p + 464, 232);
+	if (lchan->ul_facch_blocks > 2)
 		goto send_burst;
-	}
 
 	if (msgb_l2len(lchan->prim) == GSM_MACBLOCK_LEN)
 		lchan->ul_facch_blocks = 6;