bts: st_op_enabled_on_enter(): resume C0 power reduction

If power saving is enabled for a BTS, it should remain enabled even
if the BTS is restarted for whatever reason.  This persistence can be
achieved by re-sending the configured power reduction value whenever
the BTS NM FSM enters the ENABLED state again (i.e. reconnects).

Separate gsm_bts_send_c0_power_red() from gsm_bts_set_c0_power_red()
and call the former from st_op_enabled_on_enter().  All we need to do
is to send the value that was configured before, per-timeslot power
reduction limits remain and need not to be updated.

Take a chance to move logging from BTS specific to the generic code.

Change-Id: Ic3f8a2ab0ffd049a8ed84361a3a588c1e1b23ac6
Related: SYS#6435

include/osmocom/bsc/bts.h

@@ -822,6 +822,7 @@ void gsm_bts_all_ts_dispatch(struct gsm_bts *bts, uint32_t ts_ev, void *data);
 
 int gsm_bts_set_system_infos(struct gsm_bts *bts);
 
+int gsm_bts_send_c0_power_red(const struct gsm_bts *bts, const uint8_t red);
 int gsm_bts_set_c0_power_red(struct gsm_bts *bts, const uint8_t red);
 
 void gsm_bts_stats_reset(struct gsm_bts *bts);

src/osmo-bsc/bts.c

@@ -978,21 +978,30 @@ int gsm_bts_set_system_infos(struct gsm_bts *bts)
 	return 0;
 }
 
+/* Send the given C0 power reduction value to the BTS */
+int gsm_bts_send_c0_power_red(const struct gsm_bts *bts, const uint8_t red)
+{
+	if (!osmo_bts_has_feature(&bts->features, BTS_FEAT_BCCH_POWER_RED))
+		return -ENOTSUP;
+	if (bts->model->power_ctrl_send_c0_power_red == NULL)
+		return -ENOTSUP;
+	return bts->model->power_ctrl_send_c0_power_red(bts, red);
+}
+
+/* Send the given C0 power reduction value to the BTS and update the internal state */
 int gsm_bts_set_c0_power_red(struct gsm_bts *bts, const uint8_t red)
 {
 	struct gsm_bts_trx *c0 = bts->c0;
 	unsigned int tn;
 	int rc;
 
-	if (!osmo_bts_has_feature(&bts->features, BTS_FEAT_BCCH_POWER_RED))
-		return -ENOTSUP;
-	if (bts->model->power_ctrl_send_c0_power_red == NULL)
-		return -ENOTSUP;
-
-	rc = bts->model->power_ctrl_send_c0_power_red(bts, red);
+	rc = gsm_bts_send_c0_power_red(bts, red);
 	if (rc != 0)
 		return rc;
 
+	LOG_BTS(bts, DRSL, LOGL_NOTICE, "%sabling BCCH carrier power reduction "
+		"operation mode (maximum %u dB)\n", red ? "En" : "Dis", red);
+
 	/* Timeslot 0 is always transmitting BCCH/CCCH */
 	c0->ts[0].c0_max_power_red_db = 0;
 

src/osmo-bsc/bts_osmobts.c

@@ -168,10 +168,6 @@ static int power_ctrl_send_c0_power_red(const struct gsm_bts *bts, const uint8_t
 	if (msg == NULL)
 		return -ENOMEM;
 
-	LOGP(DRSL, LOGL_NOTICE, "%sabling BCCH carrier power reduction "
-	     "operation mode for BTS%u (maximum %u dB)\n",
-	     red ? "En" : "Dis", bts->nr, red);
-
 	/* Abuse the standard BS POWER CONTROL message by specifying 'Common Channel'
 	 * in the Protocol Discriminator field and 'BCCH' in the Channel Number IE. */
 	dh = (struct abis_rsl_dchan_hdr *) msgb_put(msg, sizeof(*dh));

src/osmo-bsc/nm_bts_fsm.c

@@ -286,6 +286,13 @@ static void st_op_enabled_on_enter(struct osmo_fsm_inst *fi, uint32_t prev_state
 	bts->mo.get_attr_rep_received = false;
 	bts->mo.set_attr_sent = false;
 	bts->mo.set_attr_ack_received = false;
+
+	/* Resume power saving on the BCCH carrier, if was enabled */
+	if (bts->c0_max_power_red_db > 0) {
+		LOG_BTS(bts, DRSL, LOGL_NOTICE, "Resuming BCCH carrier power reduction "
+			"operation mode (maximum %u dB)\n", bts->c0_max_power_red_db);
+		gsm_bts_send_c0_power_red(bts, bts->c0_max_power_red_db);
+	}
 }
 
 static void st_op_enabled(struct osmo_fsm_inst *fi, uint32_t event, void *data)