lapdm: Use new libosmocore API to ensure per-channel-type N200 values

By using new libosmocore LAPDm API we can specify the GSM channel type
and hence enable the LAPDm code to use a per-channel-type specific N200
value.

At the same time, this new API also allows us to specify T200 values
when initializing the LAPDm channel, so we don't have to fiddle with
low-level lapdm data structures in what used to be oml_set_lchan_t200().

Change-Id: I0e814fbae13e0feddd148c47255dcc38cb718f48
Depends: libosmocore I90fdc4dd4720d4e02213197c894eb0a55a39158c
Closes: OS#4037

1 files changed, 40 insertions, 2 deletions

diff --git a/src/common/bts.c b/src/common/bts.c
index c57d9f4a..b912f333 100644
--- a/src/common/bts.c
+++ b/src/common/bts.c
@@ -377,15 +377,53 @@ int trx_set_available(struct gsm_bts_trx *trx, int avail)
 	return 0;
 }
 
+/* prepare the per-SAPI T200 arrays for a given lchan */
+static int t200_by_lchan(int *t200_ms_dcch, int *t200_ms_acch, struct gsm_lchan *lchan)
+{
+	struct gsm_bts *bts = lchan->ts->trx->bts;
+
+	/* we have to compensate for the "RTS advance" due to the asynchronous interface between
+	 * the BTS (LAPDm) and the PHY/L1 (OsmoTRX or DSP in case of osmo-bts-{sysmo,lc15,oc2g,octphy} */
+	int32_t fn_advance = bts_get_avg_fn_advance(bts);
+	int32_t fn_advance_us = fn_advance * 4615;
+	int fn_advance_ms = fn_advance_us / 1000;
+
+	t200_ms_acch[DL_SAPI0] = bts->t200_ms[T200_SACCH_SDCCH] + fn_advance_ms;
+	t200_ms_acch[DL_SAPI3] = bts->t200_ms[T200_SACCH_SDCCH] + fn_advance_ms;
+
+	switch (lchan->type) {
+	case GSM_LCHAN_SDCCH:
+		t200_ms_dcch[DL_SAPI0] = bts->t200_ms[T200_SDCCH] + fn_advance_ms;
+		t200_ms_dcch[DL_SAPI3] = bts->t200_ms[T200_SDCCH_SAPI3] + fn_advance_ms;
+		break;
+	case GSM_LCHAN_TCH_F:
+		t200_ms_dcch[DL_SAPI0] = bts->t200_ms[T200_FACCH_F] + fn_advance_ms;
+		t200_ms_dcch[DL_SAPI3] = bts->t200_ms[T200_FACCH_F] + fn_advance_ms;
+		break;
+	case GSM_LCHAN_TCH_H:
+		t200_ms_dcch[DL_SAPI0] = bts->t200_ms[T200_FACCH_H] + fn_advance_ms;
+		t200_ms_dcch[DL_SAPI3] = bts->t200_ms[T200_FACCH_H] + fn_advance_ms;
+		break;
+	default:
+		return -1;
+	}
+	return 0;
+}
+
 int lchan_init_lapdm(struct gsm_lchan *lchan)
 {
 	struct lapdm_channel *lc = &lchan->lapdm_ch;
+	int t200_ms_dcch[_NR_DL_SAPI], t200_ms_acch[_NR_DL_SAPI];
+
+	t200_by_lchan(t200_ms_dcch, t200_ms_acch, lchan);
+
+	LOGPLCHAN(lchan, DLLAPD, LOGL_DEBUG, "Setting T200 D0=%u, D3=%u, S0=%u, S3=%u (all in ms)\n",
+		  t200_ms_dcch[DL_SAPI0], t200_ms_dcch[DL_SAPI3], t200_ms_acch[DL_SAPI0], t200_ms_acch[DL_SAPI3]);
 
-	lapdm_channel_init(lc, LAPDM_MODE_BTS);
+	lapdm_channel_init2(lc, LAPDM_MODE_BTS, t200_ms_dcch, t200_ms_acch, lchan->type);
 	lapdm_channel_set_flags(lc, LAPDM_ENT_F_POLLING_ONLY);
 	lapdm_channel_set_l1(lc, NULL, lchan);
 	lapdm_channel_set_l3(lc, lapdm_rll_tx_cb, lchan);
-	oml_set_lchan_t200(lchan);
 
 	return 0;
 }