[WIP] HO: Add SCH read of neighbor cells to TCH channels

The task will try to sync to neighbor cell during search (idle) frame.

Change-Id: I7f2c6b5438676a816c546cb9dce404762ee5d5b5

8 files changed, 185 insertions, 0 deletions

diff --git a/src/target/firmware/include/layer1/prim.h b/src/target/firmware/include/layer1/prim.h
index bff51deb..652a9147 100644
--- a/src/target/firmware/include/layer1/prim.h
+++ b/src/target/firmware/include/layer1/prim.h
@@ -31,5 +31,6 @@ extern const struct tdma_sched_item tch_a_sched_set[];
 extern const struct tdma_sched_item tch_d_sched_set[];
 extern const struct tdma_sched_item neigh_pm_idle_sched_set[];
 extern const struct tdma_sched_item neigh_pm_tch_sched_set[];
+extern const struct tdma_sched_item neigh_sync_sched_set[];
 
 #endif /* _L1_PRIM_H */
diff --git a/src/target/firmware/include/layer1/sync.h b/src/target/firmware/include/layer1/sync.h
index af743195..11faf81b 100644
--- a/src/target/firmware/include/layer1/sync.h
+++ b/src/target/firmware/include/layer1/sync.h
@@ -163,8 +163,20 @@ struct l1s_state {
 		uint16_t level_sum[64]; /* sum while processing rounds */
 		uint8_t level[64]; /* latest results */
 	} neigh_pm;
+
+	/* neighbor cell SCH sync process */
+	struct {
+		uint8_t flags_bsic[64]; /* flags + bsic */
+		int16_t toa[64]; /* time difference */
+		uint8_t count; /* counter for sync process */
+		uint8_t index; /* cell of current sync process (0..63) */
+		uint8_t running; /* DSP task running */
+	} neigh_sb;
 };
 
+#define NEIGH_PM_FLAG_SCANNED	0x80
+#define NEIGH_PM_FLAG_BSIC	0x40
+
 extern struct l1s_state l1s;
 
 struct l1s_meas_hdr {
diff --git a/src/target/firmware/include/layer1/tpu_window.h b/src/target/firmware/include/layer1/tpu_window.h
index 7b146f12..f460ef01 100644
--- a/src/target/firmware/include/layer1/tpu_window.h
+++ b/src/target/firmware/include/layer1/tpu_window.h
@@ -6,6 +6,7 @@ enum l1_rxwin_type {
 	L1_RXWIN_FB,	/* FCCH burst detection */
 	L1_RXWIN_SB,	/* SCH burst detection */
 	L1_RXWIN_NB,	/* Normal burst decoding */
+	L1_RXWIN_SB26,	/* SCH burst detection of neighbour cell */
 	_NUM_L1_RXWIN
 };
 
diff --git a/src/target/firmware/layer1/l23_api.c b/src/target/firmware/layer1/l23_api.c
index e487864e..7d126cf1 100644
--- a/src/target/firmware/layer1/l23_api.c
+++ b/src/target/firmware/layer1/l23_api.c
@@ -564,7 +564,9 @@ static void l1ctl_rx_neigh_pm_req(struct msgb *msg)
 		l1s.neigh_pm.band_arfcn[i] = ntohs(pm_req->band_arfcn[i]);
 		l1s.neigh_pm.tn[i] = pm_req->tn[i];
 		l1s.neigh_pm.level[i] = 0;
+		l1s.neigh_sb.flags_bsic[i] = 0;
 	}
+	l1s.neigh_sb.count = 0;
 	printf("L1CTL_NEIGH_PM_REQ new list with %u entries\n", pm_req->n);
 	l1s.neigh_pm.n = pm_req->n; /* atomic */
 
diff --git a/src/target/firmware/layer1/mframe_sched.c b/src/target/firmware/layer1/mframe_sched.c
index b242f990..a83da812 100644
--- a/src/target/firmware/layer1/mframe_sched.c
+++ b/src/target/firmware/layer1/mframe_sched.c
@@ -52,6 +52,7 @@ struct mframe_sched_item {
 #define NB_QUAD_FH_UL	NB_QUAD_UL
 #define NEIGH_PM_IDLE	neigh_pm_idle_sched_set
 #define NEIGH_PM_TCH	neigh_pm_tch_sched_set
+#define NEIGH_SYNC	neigh_sync_sched_set
 
 /* BCCH Normal */
 static const struct mframe_sched_item mf_bcch_norm[] = {
@@ -314,6 +315,7 @@ static const struct mframe_sched_item mf_neigh_pm26_even[] = {
 	{ .sched_set = NEIGH_PM_TCH, .modulo = 13, .frame_nr = 6 },
 	{ .sched_set = NEIGH_PM_TCH, .modulo = 13, .frame_nr = 8 },
 	{ .sched_set = NEIGH_PM_TCH, .modulo = 13, .frame_nr = 10 },
+	{ .sched_set = NEIGH_SYNC,   .modulo = 26, .frame_nr = 24 },
 	{ .sched_set = NULL }
 };
 static const struct mframe_sched_item mf_neigh_pm26_odd[] = {
@@ -323,6 +325,7 @@ static const struct mframe_sched_item mf_neigh_pm26_odd[] = {
 	{ .sched_set = NEIGH_PM_TCH, .modulo = 13, .frame_nr = 6 },
 	{ .sched_set = NEIGH_PM_TCH, .modulo = 13, .frame_nr = 8 },
 	{ .sched_set = NEIGH_PM_TCH, .modulo = 13, .frame_nr = 10 },
+	{ .sched_set = NEIGH_SYNC,   .modulo = 26, .frame_nr = 11 },
 	{ .sched_set = NULL }
 };
 
diff --git a/src/target/firmware/layer1/prim_fbsb.c b/src/target/firmware/layer1/prim_fbsb.c
index 50acefcc..1682c509 100644
--- a/src/target/firmware/layer1/prim_fbsb.c
+++ b/src/target/firmware/layer1/prim_fbsb.c
@@ -571,6 +571,165 @@ void l1s_fbsb_req(uint8_t base_fn, struct l1ctl_fbsb_req *req)
 
 }
 
+
+/* SB for Neighbours in dedicated mode
+ *
+ * Only when number of neighbor cells is > 0, perform synchronization.
+ *
+ * For each synchronization, l1s.neigh_pm.running is set. In case of an update
+ * of neighbor cell list, this state is cleared, so a pending sync result would
+ * be ignored.
+ *
+ * After a (new) list of neighbor cells are received, the measurements are not
+ * yet valid. A valid state flag is used to indicate valid measurements. Until
+ * there are no valid measurements, the synchronization is not performed.
+ *
+ * The task is to scan the 6 strongest neighbor cells by trying to synchronize
+ * to it. This is done by selecting the strongest unscanned neighbor cell.
+ * If 6 cells have been scanned or all cells (if less than 6) have been
+ * scanned, the process clears all 'scanned' flags and starts over with the
+ * strongest (now the strongest unscanned) cell.
+ *
+ * Each synchronization attempt is performed during the "search frame" (IDLE
+ * frame). The process attempts to sync 11 times to ensure that it hits the
+ * SCH of the neighbor's BCCH. (The alignment of BCCH shifts after every two
+ * 26-multiframe in a way that the "search frame" is aligned with the SCH, at
+ * least once for 11 successive "search frames".)
+ *
+ * If the synchronization attempt is successful, the BSIC and neighbor cell
+ * offset is stored. These are indicated to layer23 with the measurement
+ * results.
+ *
+ * When performing handover to a neighbor cell, the stored offset is used to
+ * calculate new GSM time and tpu_offset.
+ */
+
+static void select_neigh_cell(void)
+{
+	uint8_t strongest = 0, strongest_unscanned = 0;
+	int strongest_i = 0, strongest_unscanned_i = -1;
+	int num_scanned = 0;
+	int i;
+
+	/* find strongest cell and strongest unscanned cell and count */
+	for (i = 0; i < l1s.neigh_pm.n; i++) {
+		if (l1s.neigh_pm.level[i] > strongest) {
+			strongest = l1s.neigh_pm.level[i];
+			strongest_i = i;
+		}
+		if (!(l1s.neigh_sb.flags_bsic[i] & NEIGH_PM_FLAG_SCANNED)) {
+			if (l1s.neigh_pm.level[i] > strongest_unscanned) {
+				strongest_unscanned = l1s.neigh_pm.level[i];
+				strongest_unscanned_i = i;
+			}
+		} else
+			num_scanned++;
+	}
+
+	/* no unscanned cell or we have scanned enough */
+	if (strongest_unscanned_i < 0 || num_scanned >= 6) {
+		/* flag all cells unscanned */
+		for (i = 0; i < l1s.neigh_pm.n; i++)
+			l1s.neigh_sb.flags_bsic[i] &= ~NEIGH_PM_FLAG_SCANNED;
+		/* use strongest cell to begin scanning with */
+		l1s.neigh_sb.index = strongest_i;
+	} else {
+		/* use strongest unscanned cell to begin scanning with */
+		l1s.neigh_sb.index = strongest_unscanned_i;
+	}
+}
+
+static int l1s_neigh_sb_cmd(__unused uint8_t p1, __unused uint8_t p2,
+                            __unused uint16_t p3)
+{
+	int index = l1s.neigh_sb.index;
+	uint8_t last_gain;
+
+	if (l1s.neigh_pm.n == 0)
+		return 0;
+
+	/* if measurements are not yet valid, wait */
+	if (!l1s.neigh_pm.valid)
+		return 0;
+
+	/* check for cell to sync to */
+	if (l1s.neigh_sb.count == 0) {
+		/* there is no cell selected, search for cell */
+		select_neigh_cell();
+	}
+
+	printf("detect SB arfcn %d (#%d) %d dbm\n", l1s.neigh_pm.band_arfcn[index], l1s.neigh_sb.count, rxlev2dbm(l1s.neigh_pm.level[index]));
+
+	last_gain = rffe_get_gain();
+
+	/* Tell the RF frontend to set the gain appropriately */
+	rffe_compute_gain(rxlev2dbm(l1s.neigh_pm.level[index]), CAL_DSP_TGT_BB_LVL);
+
+	/* Program DSP */
+	dsp_api.db_w->d_task_md = TCH_SB_DSP_TASK;  /* maybe with I/Q swap? */
+//	dsp_api.db_w->d_task_md = dsp_task_iq_swap(TCH_SB_DSP_TASK, l1s.neigh_pm.band_arfcn[index], 0);
+	dsp_api.ndb->d_fb_mode = 0;
+
+	/* Program TPU */
+	l1s_rx_win_ctrl(l1s.neigh_pm.band_arfcn[index], L1_RXWIN_SB26, 5);
+
+	/* restore last gain */
+	rffe_set_gain(last_gain);
+
+	l1s.neigh_sb.running = 1;
+
+	return 0;
+}
+
+static int l1s_neigh_sb_resp(__unused uint8_t p1, __unused uint8_t p2,
+                             __unused uint16_t p3)
+{
+	int index = l1s.neigh_sb.index;
+	uint32_t sb;
+
+	if (l1s.neigh_pm.n == 0 || !l1s.neigh_sb.running)
+		goto out;
+
+	/* check if sync was successful */
+	if (dsp_api.db_r->a_sch[0] & (1<<B_SCH_CRC)) {
+		printf("SB error arfcn %d\n", l1s.neigh_pm.band_arfcn[index]);
+
+		/* next sync */
+		if (++l1s.neigh_sb.count == 11) {
+			l1s.neigh_sb.count = 0;
+			l1s.neigh_sb.flags_bsic[index] |= NEIGH_PM_FLAG_SCANNED;
+		}
+	} else {
+		l1s.neigh_sb.count = 0;
+
+		read_sb_result(last_fb, 1);
+		sb = dsp_api.db_r->a_sch[3] | dsp_api.db_r->a_sch[4] << 16;
+		l1s.neigh_sb.flags_bsic[index] =
+			l1s_decode_sb(&fbs.mon.time, sb)
+				| NEIGH_PM_FLAG_BSIC | NEIGH_PM_FLAG_SCANNED;
+		printf("SB OK!!!!!! arfcn %d\n", l1s.neigh_pm.band_arfcn[index]);
+
+		/* store time offset */
+	}
+
+out:
+	l1s.neigh_sb.running = 0;
+
+	dsp_api.r_page_used = 1;
+
+	return 0;
+
+}
+
+/* NOTE: Prio 1 is below TCH's RX+TX prio 0 */
+const struct tdma_sched_item neigh_sync_sched_set[] = {
+	SCHED_ITEM_DT(l1s_neigh_sb_cmd, 1, 0, 1),	SCHED_END_FRAME(),
+							SCHED_END_FRAME(),
+	SCHED_ITEM(l1s_neigh_sb_resp, -4, 0, 1),	SCHED_END_FRAME(),
+	SCHED_END_SET()
+};
+
+
 static __attribute__ ((constructor)) void l1s_prim_fbsb_init(void)
 {
 	l1s.completion[L1_COMPL_FB] = &l1a_fb_compl;
diff --git a/src/target/firmware/layer1/prim_pm.c b/src/target/firmware/layer1/prim_pm.c
index a4b8e638..416dff39 100644
--- a/src/target/firmware/layer1/prim_pm.c
+++ b/src/target/firmware/layer1/prim_pm.c
@@ -183,6 +183,11 @@ static void neigh_pm_ind(void)
 			  / l1s.neigh_pm.rounds;
 		mi->pm[0] = l1s.neigh_pm.level[i];
 		l1s.neigh_pm.level_sum[i] = 0;
+		if ((l1s.neigh_sb.flags_bsic[i] & NEIGH_PM_FLAG_BSIC)) {
+			mi->bsic = l1s.neigh_sb.flags_bsic[i] & 0x3f;
+			mi->toa = l1s.neigh_sb.toa[i];
+		} else
+			mi->bsic = L1CTL_BSIC_INVAL;
 	}
 	l1_queue_for_l2(msg);
 }
diff --git a/src/target/firmware/layer1/tpu_window.c b/src/target/firmware/layer1/tpu_window.c
index abdad956..dbe64eee 100644
--- a/src/target/firmware/layer1/tpu_window.c
+++ b/src/target/firmware/layer1/tpu_window.c
@@ -48,6 +48,7 @@
 #define L1_SB_DURATION_Q	(L1_BURST_LENGTH_Q + 2 * L1_SB_MARGIN_Q - L1_TAIL_DURATION_Q)
 #define L1_FB_DURATION_Q	(11 * L1_TDMA_LENGTH_Q + 2057)	/* more than 11 full slots */
 #define L1_FB26_DURATION_Q	(L1_TDMA_LENGTH_Q + 798)
+#define L1_SB26_DURATION_Q	(L1_TDMA_LENGTH_Q + 984) // 984
 #define	L1_PW_DURATION_Q	289
 
 #define DSP_SETUP_TIME		66
@@ -57,6 +58,7 @@ static const uint16_t rx_burst_duration[_NUM_L1_RXWIN] = {
 	[L1_RXWIN_FB]	= L1_FB_DURATION_Q,
 	[L1_RXWIN_SB]	= L1_SB_DURATION_Q,
 	[L1_RXWIN_NB]	= L1_NB_DURATION_Q,
+	[L1_RXWIN_SB26]	= L1_SB26_DURATION_Q,
 };
 
 #define L1_TX_NB_DURATION_Q	626