sysmobts: Don't start with 0dBm TRX output power before ramping

In case a system has a high-gain external PA (like a 40dB PA) connected
externally, we cannot simply switch the transceiver to 0 dBm in
trx_init() only to then start the ramping at much lower levels once the
PHJ completes in trx_init_compl_cb().  The result would be a short
0 + 40 dBm spike followed by later ramping.  We want to avoid that
spike, particularly its associated inrush current, so let's bring up the
board with smething very conservative like -50 dBm, and then ramp from
there.

Change-Id: I0ad91fce64f65e0213c9fcfde3390ace519055db
Fixes: SYS#3259

5 files changed, 30 insertions, 3 deletions

diff --git a/include/osmo-bts/tx_power.h b/include/osmo-bts/tx_power.h
index 8d099bca..21887c7c 100644
--- a/include/osmo-bts/tx_power.h
+++ b/include/osmo-bts/tx_power.h
@@ -74,3 +74,5 @@ int get_p_trxout_actual_mdBm_lchan(struct gsm_lchan *lchan);
 int power_ramp_start(struct gsm_bts_trx *trx, int p_total_tgt_mdBm, int bypass);
 
 void power_trx_change_compl(struct gsm_bts_trx *trx, int p_trxout_cur_mdBm);
+
+int power_ramp_initial_power_mdBm(struct gsm_bts_trx *trx);
diff --git a/src/common/bts.c b/src/common/bts.c
index 9915e1ca..540caaa1 100644
--- a/src/common/bts.c
+++ b/src/common/bts.c
@@ -153,7 +153,7 @@ int bts_init(struct gsm_bts *bts)
 			}
 		}
 		/* Default values for the power adjustments */
-		tpp->ramp.max_initial_pout_mdBm = to_mdB(23);
+		tpp->ramp.max_initial_pout_mdBm = to_mdB(0);
 		tpp->ramp.step_size_mdB = to_mdB(2);
 		tpp->ramp.step_interval_sec = 1;
 	}
diff --git a/src/common/tx_power.c b/src/common/tx_power.c
index c5179181..3dfe1f7e 100644
--- a/src/common/tx_power.c
+++ b/src/common/tx_power.c
@@ -289,3 +289,18 @@ int power_ramp_start(struct gsm_bts_trx *trx, int p_total_tgt_mdBm, int bypass)
 
 	return 0;
 }
+
+/* determine the initial transceiver output power at start-up time */
+int power_ramp_initial_power_mdBm(struct gsm_bts_trx *trx)
+{
+	struct trx_power_params *tpp = &trx->power_params;
+	int pout_mdBm;
+
+	/* this is the maximum initial output on the antenna connector
+	 * towards the antenna */
+	pout_mdBm = tpp->ramp.max_initial_pout_mdBm;
+
+	/* use this as input to compute transceiver board power
+	 * (reflecting gains in internal/external amplifiers */
+	return get_p_trxout_eff_mdBm(trx, pout_mdBm);
+}
diff --git a/src/osmo-bts-sysmo/oml.c b/src/osmo-bts-sysmo/oml.c
index 01752d18..776a50c4 100644
--- a/src/osmo-bts-sysmo/oml.c
+++ b/src/osmo-bts-sysmo/oml.c
@@ -389,6 +389,7 @@ static int trx_init(struct gsm_bts_trx *trx)
 	GsmL1_MphInitReq_t *mi_req;
 	GsmL1_DeviceParam_t *dev_par;
 	int femto_band;
+	int initial_mdBm = power_ramp_initial_power_mdBm(trx);
 
 	if (!gsm_abis_mo_check_attr(&trx->mo, trx_rqd_attr,
 				    ARRAY_SIZE(trx_rqd_attr))) {
@@ -416,11 +417,12 @@ static int trx_init(struct gsm_bts_trx *trx)
 	dev_par->fRxPowerLevel = trx_ms_pwr_ctrl_is_osmo(trx)
 					? 0.0 : btsb->ul_power_target;
 
-	dev_par->fTxPowerLevel = 0.0;
+	dev_par->fTxPowerLevel = ((float) initial_mdBm) / 1000;
 	LOGP(DL1C, LOGL_NOTICE, "Init TRX (ARFCN %u, TSC %u, RxPower % 2f dBm, "
 		"TxPower % 2.2f dBm\n", dev_par->u16Arfcn, dev_par->u8NbTsc,
 		dev_par->fRxPowerLevel, dev_par->fTxPowerLevel);
-	
+	trx->power_params.p_total_cur_mdBm = trx->power_params.ramp.max_initial_pout_mdBm;
+
 	/* send MPH-INIT-REQ, wait for MPH-INIT-CNF */
 	return l1if_gsm_req_compl(fl1h, msg, trx_init_compl_cb, NULL);
 }
diff --git a/tests/tx_power/tx_power_test.c b/tests/tx_power/tx_power_test.c
index d6573620..fb234095 100644
--- a/tests/tx_power/tx_power_test.c
+++ b/tests/tx_power/tx_power_test.c
@@ -44,6 +44,7 @@ static const struct trx_power_params tpp_1002 = {
 		.nominal_gain_mdB = 0,
 	},
 	.ramp = {
+		.max_initial_pout_mdBm = to_mdB(23),
 		.step_size_mdB = to_mdB(2),
 		.step_interval_sec = 1,
 	},
@@ -62,6 +63,7 @@ static const struct trx_power_params tpp_1020 = {
 		.nominal_gain_mdB = 0,
 	},
 	.ramp = {
+		.max_initial_pout_mdBm = to_mdB(0),
 		.step_size_mdB = to_mdB(2),
 		.step_interval_sec = 1,
 	},
@@ -80,6 +82,7 @@ static const struct trx_power_params tpp_1100 = {
 		.nominal_gain_mdB = 0,
 	},
 	.ramp = {
+		.max_initial_pout_mdBm = to_mdB(0),
 		.step_size_mdB = to_mdB(2),
 		.step_interval_sec = 1,
 	},
@@ -98,6 +101,7 @@ static const struct trx_power_params tpp_2050 = {
 		.nominal_gain_mdB = 0,
 	},
 	.ramp = {
+		.max_initial_pout_mdBm = to_mdB(0),
 		.step_size_mdB = to_mdB(2),
 		.step_interval_sec = 1,
 	},
@@ -108,6 +112,7 @@ static void test_sbts1002(struct gsm_bts_trx *trx)
 	printf("Testing tx_power calculation for sysmoBTS 1002\n");
 	trx->power_params = tpp_1002;
 	trx->max_power_red = 0;
+	OSMO_ASSERT(power_ramp_initial_power_mdBm(trx) == to_mdB(23));
 	OSMO_ASSERT(get_p_max_out_mdBm(trx) == to_mdB(23));
 	/* at max_power_red = 0, we expect full 23dBm */
 	OSMO_ASSERT(get_p_nominal_mdBm(trx) == to_mdB(23));
@@ -125,6 +130,7 @@ static void test_sbts1020(struct gsm_bts_trx *trx)
 	printf("Testing tx_power calculation for sysmoBTS 1020\n");
 	trx->power_params = tpp_1020;
 	trx->max_power_red = 0;
+	OSMO_ASSERT(power_ramp_initial_power_mdBm(trx) == to_mdB(-10));
 	OSMO_ASSERT(get_p_max_out_mdBm(trx) == to_mdB(33));
 	/* at max_power_red = 0, we expect full 33dBm */
 	OSMO_ASSERT(get_p_nominal_mdBm(trx) == to_mdB(33));
@@ -143,6 +149,7 @@ static void test_sbts1100(struct gsm_bts_trx *trx)
 	printf("Testing tx_power calculation for sysmoBTS 1100\n");
 	trx->power_params = tpp_1100;
 	trx->max_power_red = 0;
+	OSMO_ASSERT(power_ramp_initial_power_mdBm(trx) == to_mdB(-17));
 	OSMO_ASSERT(get_p_max_out_mdBm(trx) == to_mdB(40));
 	/* at max_power_red = 0, we expect full 33dBm */
 	OSMO_ASSERT(get_p_nominal_mdBm(trx) == to_mdB(40));
@@ -160,6 +167,7 @@ static void test_sbts2050(struct gsm_bts_trx *trx)
 	printf("Testing tx_power calculation for sysmoBTS 2050\n");
 	trx->power_params = tpp_2050;
 	trx->max_power_red = 0;
+	OSMO_ASSERT(power_ramp_initial_power_mdBm(trx) == to_mdB(0));
 	OSMO_ASSERT(get_p_max_out_mdBm(trx) == to_mdB(37));
 	/* at max_power_red = 0, we expect full 37dBm */
 	OSMO_ASSERT(get_p_nominal_mdBm(trx) == to_mdB(37));