DTX DL: use FSM for AMR

Use dedicated FSM to handle all DTX DL related events:
- add explicit checks if DTX DL is enabled (fixes regression for non-DTX
setup introduced in 654175f33bd412671e3ef8cdd65c0689d10f278c)
- fix handling of AMR CMI for SPEECH frames
- add FSM for DTX DL
- sync with corresponding changes in OpenBSC's
- handle FACCH-related DTX ONSET events

This affects both lc15 and sysmobts and requires corresponding change in
OpenBSC (Change-Id: Idac8609faf9b5ced818fde899ccfc6ed0c42e8fd).

Change-Id: I74a0b42cb34d525b8a70d264135e82994ca70d31

3 files changed, 41 insertions, 6 deletions

diff --git a/include/osmo-bts/Makefile.am b/include/osmo-bts/Makefile.am
index d0b55ff9..ef4165f3 100644
--- a/include/osmo-bts/Makefile.am
+++ b/include/osmo-bts/Makefile.am
@@ -1,4 +1,5 @@
 noinst_HEADERS = abis.h bts.h bts_model.h gsm_data.h logging.h measurement.h \
 		 oml.h paging.h rsl.h signal.h vty.h amr.h pcu_if.h pcuif_proto.h \
 		 handover.h msg_utils.h tx_power.h control_if.h cbch.h l1sap.h \
-		 power_control.h scheduler.h scheduler_backend.h phy_link.h
+		 power_control.h scheduler.h scheduler_backend.h phy_link.h \
+		 dtx_dl_amr_fsm.h
diff --git a/include/osmo-bts/dtx_dl_amr_fsm.h b/include/osmo-bts/dtx_dl_amr_fsm.h
new file mode 100644
index 00000000..8b195953
--- /dev/null
+++ b/include/osmo-bts/dtx_dl_amr_fsm.h
@@ -0,0 +1,35 @@
+#pragma once
+
+#include <osmocom/core/fsm.h>
+#include <osmocom/core/utils.h>
+#include <osmocom/core/logging.h>
+
+/* DTX DL AMR FSM */
+
+#define X(s) (1 << (s))
+
+enum dtx_dl_amr_fsm_states {
+	ST_VOICE,
+	ST_SID_F1,
+	ST_SID_F2,
+	ST_F1_INH,
+	ST_U_INH,
+	ST_SID_U,
+	ST_ONSET_V,
+	ST_ONSET_F,
+	ST_FACCH_V,
+	ST_FACCH,
+};
+
+enum dtx_dl_amr_fsm_events {
+	E_VOICE,
+	E_ONSET,
+	E_FACCH,
+	E_COMPL,
+	E_INHIB,
+	E_SID_F,
+	E_SID_U,
+};
+
+extern const struct value_string dtx_dl_amr_fsm_event_names[];
+extern struct osmo_fsm dtx_dl_amr_fsm;
diff --git a/include/osmo-bts/msg_utils.h b/include/osmo-bts/msg_utils.h
index f99f3c40..31bd1725 100644
--- a/include/osmo-bts/msg_utils.h
+++ b/include/osmo-bts/msg_utils.h
@@ -26,12 +26,11 @@ enum {
 };
 
 void lchan_set_marker(bool t, struct gsm_lchan *lchan);
-void save_last_sid(struct gsm_lchan *lchan, const uint8_t *l1_payload,
-		   size_t length, uint32_t fn, int update, uint8_t cmr,
-		   int8_t cmi);
-int dtx_amr_check_onset(struct gsm_lchan *lchan, const uint8_t *rtp_pl,
+void dtx_cache_payload(struct gsm_lchan *lchan, const uint8_t *l1_payload,
+		       size_t length, uint32_t fn, int update);
+int dtx_dl_amr_fsm_step(struct gsm_lchan *lchan, const uint8_t *rtp_pl,
 			size_t rtp_pl_len, uint32_t fn, uint8_t *l1_payload,
-			uint8_t *ft_out);
+			bool marker, uint8_t *len, uint8_t *ft_out);
 uint8_t repeat_last_sid(struct gsm_lchan *lchan, uint8_t *dst, uint32_t fn);
 int msg_verify_ipa_structure(struct msgb *msg);
 int msg_verify_oml_structure(struct msgb *msg);