sysmobts: Add a manual ms power level controlzecke/power-control

Currently the DSP is instructed to achieve a given uplink
power target but there are circumstances (e.g. EMV testing)
where we need more control over it. The "manual/software/osmo"
power control can only be implemented per TRX and not per
lchan. Add a very very basic control that checks the MS Power
used by the phone, the actual receive level and then adjust
the power.

The code doesn't take the history into account, if the phone
can not reach the requested power level the code will be stuck
(e.g. no timeout based on multiframes). It has a mode for a
fixed power control but no way to set it yet.

1 files changed, 80 insertions, 4 deletions

diff --git a/src/osmo-bts-sysmo/l1_if.c b/src/osmo-bts-sysmo/l1_if.c
index 4b9ab3e8..f791a25c 100644
--- a/src/osmo-bts-sysmo/l1_if.c
+++ b/src/osmo-bts-sysmo/l1_if.c
@@ -49,6 +49,7 @@
 #include <osmo-bts/measurement.h>
 #include <osmo-bts/pcu_if.h>
 #include <osmo-bts/handover.h>
+#include <osmo-bts/bts_model.h>
 
 #include <sysmocom/femtobts/superfemto.h>
 #include <sysmocom/femtobts/gsml1prim.h>
@@ -520,10 +521,11 @@ static int handle_ph_readytosend_ind(struct femtol1_hdl *fl1,
 		/* resolve the L2 entity using rts_ind->hLayer2 */
 		lchan = l1if_hLayer_to_lchan(trx, rts_ind->hLayer2);
 		le = &lchan->lapdm_ch.lapdm_acch;
-		/* if the DSP is taking care of power control
-		 * (ul_power_target==0), then this value will be
-		 * overridden. */
-		msu_param->u8Buffer[0] = lchan->ms_power;
+		/*
+		 * if the DSP is taking care of power control,
+		 * then this value will be overridden.
+		 */
+		msu_param->u8Buffer[0] = lchan->ms_power_ctrl.current;
 		msu_param->u8Buffer[1] = lchan->rqd_ta;
 		rc = lapdm_phsap_dequeue_prim(le, &pp);
 		if (rc < 0) {
@@ -768,6 +770,14 @@ static int handle_ph_data_ind(struct femtol1_hdl *fl1, GsmL1_PhDataInd_t *data_i
 				data_ind->msgUnitParam.u8Size);
 			break;
 		}
+
+		/*
+		 * Handle power control
+		 */
+		l1if_ms_pwr_ctrl(lchan, fl1->ul_power_target,
+				data_ind->msgUnitParam.u8Buffer[0] & 0x1f,
+				data_ind->measParam.fRssi);
+
 		/* Some brilliant engineer decided that the ordering of
 		 * fields on the Um interface is different from the
 		 * order of fields in RLS. See TS 04.04 (Chapter 7.2)
@@ -1681,3 +1691,69 @@ int l1if_rf_clock_info_correct(struct femtol1_hdl *fl1h)
 }
 
 #endif
+
+/*
+ * Check if manual power control is needed
+ * Check if fixed power was selected
+ * Check if the MS is already using our level if not
+ * the value is bogus..
+ * TODO: Add a timeout.. e.g. if the ms is not capable of reaching
+ * the value we have set.
+ */
+inline int l1if_ms_pwr_ctrl(struct gsm_lchan *lchan, const int ul_power_target,
+			const uint8_t ms_power, const float rxLevel)
+{
+	float rx;
+	int cur_dBm, new_dBm, new_pwr;
+	const enum gsm_band band = lchan->ts->trx->bts->band;
+
+	if (!trx_ms_pwr_ctrl_is_osmo(lchan->ts->trx))
+		return 0;
+	if (lchan->ms_power_ctrl.fixed)
+		return 0;
+
+	/* The phone hasn't reached the power level yet */
+	if (lchan->ms_power_ctrl.current != ms_power)
+		return 0;
+
+	/*
+	 * What is the difference between what we want and received?
+	 * Ignore a margin that is within the range of measurement
+	 * and MS output issues.
+	 */
+	rx = ul_power_target - rxLevel;
+	if (rx >= 0 && rx < 1.5f)
+		return 0;
+	if (rx < 0 && rx > -1.5f)
+		return 0;
+
+	/* We don't really care about the truncation of int + float */
+	cur_dBm = ms_pwr_dbm(band, ms_power);
+	new_dBm = cur_dBm + rx;
+
+	/* Clamp negative values and do it depending on the band */
+	if (new_dBm < 0)
+		new_dBm = 0;
+
+	switch (band) {
+	case GSM_BAND_1800:
+		/* If MS_TX_PWR_MAX_CCH is set the values 29,
+		 * 30, 31 are not used. Avoid specifying a dBm
+		 * that would lead to these power levels. The
+		 * phone might not be able to reach them. */
+		if (new_dBm > 30)
+			new_dBm = 30;
+		break;
+	default:
+		break;
+	}
+
+	new_pwr = ms_pwr_ctl_lvl(band, new_dBm);
+	if (lchan->ms_power_ctrl.current != new_pwr) {
+		lchan->ms_power_ctrl.current = new_pwr;
+		bts_model_adjst_ms_pwr(lchan);
+		return 1;
+	}
+
+	return 0;
+}