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Date:      Sun, 18 Sep 2016 05:07:18 +0000 (UTC)
From:      Adrian Chadd <adrian@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r305917 - head/sys/dev/iwm
Message-ID:  <201609180507.u8I57Ivo039986@repo.freebsd.org>
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Author: adrian
Date: Sun Sep 18 05:07:18 2016
New Revision: 305917
URL: https://svnweb.freebsd.org/changeset/base/305917

Log:
  [iwm] fix up RSSI calculations for both scan results and normal RX operations.
  
  * hard code a noise floor of -96 for now. The noise floor update code returns
    some "interesting" values that I can't map to anything useful right now.
  * Ensure a default noise floor is set - otherwise the initial scan results
    have a noise floor of '0'.
  * Fix up the RSSI calculation to be correctly relative to the noise floor.
    The RSSI routines return an absolute value in dBm - so fix this up.
  * Cap RSSI values appropriately.
  * Ensure we pass in a 1/2 dB unit value in to net80211.
  
  Tested:
  
  * Intel 7260, STA mode
  
  iwm0: <Intel Dual Band Wireless AC 7260> mem 0xf1400000-0xf1401fff irq 17 at device 0.0 on pci2
  iwm0: hw rev 0x140, fw ver 16.242414.0, address xx:xx:xx:xx:xx:xx

Modified:
  head/sys/dev/iwm/if_iwm.c

Modified: head/sys/dev/iwm/if_iwm.c
==============================================================================
--- head/sys/dev/iwm/if_iwm.c	Sun Sep 18 05:06:15 2016	(r305916)
+++ head/sys/dev/iwm/if_iwm.c	Sun Sep 18 05:07:18 2016	(r305917)
@@ -312,7 +312,8 @@ static int	iwm_mvm_get_signal_strength(s
 static void	iwm_mvm_rx_rx_phy_cmd(struct iwm_softc *,
                                       struct iwm_rx_packet *,
                                       struct iwm_rx_data *);
-static int	iwm_get_noise(const struct iwm_mvm_statistics_rx_non_phy *);
+static int	iwm_get_noise(struct iwm_softc *sc,
+		    const struct iwm_mvm_statistics_rx_non_phy *);
 static void	iwm_mvm_rx_rx_mpdu(struct iwm_softc *, struct iwm_rx_packet *,
                                    struct iwm_rx_data *);
 static int	iwm_mvm_rx_tx_cmd_single(struct iwm_softc *,
@@ -2871,21 +2872,34 @@ iwm_mvm_rx_rx_phy_cmd(struct iwm_softc *
  * Retrieve the average noise (in dBm) among receivers.
  */
 static int
-iwm_get_noise(const struct iwm_mvm_statistics_rx_non_phy *stats)
+iwm_get_noise(struct iwm_softc *sc,
+    const struct iwm_mvm_statistics_rx_non_phy *stats)
 {
 	int i, total, nbant, noise;
 
 	total = nbant = noise = 0;
 	for (i = 0; i < 3; i++) {
 		noise = le32toh(stats->beacon_silence_rssi[i]) & 0xff;
+		IWM_DPRINTF(sc, IWM_DEBUG_RECV, "%s: i=%d, noise=%d\n",
+		    __func__,
+		    i,
+		    noise);
+
 		if (noise) {
 			total += noise;
 			nbant++;
 		}
 	}
 
+	IWM_DPRINTF(sc, IWM_DEBUG_RECV, "%s: nbant=%d, total=%d\n",
+	    __func__, nbant, total);
+#if 0
 	/* There should be at least one antenna but check anyway. */
 	return (nbant == 0) ? -127 : (total / nbant) - 107;
+#else
+	/* For now, just hard-code it to -96 to be safe */
+	return (-96);
+#endif
 }
 
 /*
@@ -2940,8 +2954,15 @@ iwm_mvm_rx_rx_mpdu(struct iwm_softc *sc,
 	} else {
 		rssi = iwm_mvm_calc_rssi(sc, phy_info);
 	}
-	rssi = (0 - IWM_MIN_DBM) + rssi;	/* normalize */
-	rssi = MIN(rssi, sc->sc_max_rssi);	/* clip to max. 100% */
+
+	/* Note: RSSI is absolute (ie a -ve value) */
+	if (rssi < IWM_MIN_DBM)
+		rssi = IWM_MIN_DBM;
+	else if (rssi > IWM_MAX_DBM)
+		rssi = IWM_MAX_DBM;
+
+	/* Map it to relative value */
+	rssi = rssi - sc->sc_noise;
 
 	/* replenish ring for the buffer we're going to feed to the sharks */
 	if (iwm_rx_addbuf(sc, IWM_RBUF_SIZE, sc->rxq.cur) != 0) {
@@ -2950,6 +2971,9 @@ iwm_mvm_rx_rx_mpdu(struct iwm_softc *sc,
 		return;
 	}
 
+	IWM_DPRINTF(sc, IWM_DEBUG_RECV,
+	    "%s: rssi=%d, noise=%d\n", __func__, rssi, sc->sc_noise);
+
 	ni = ieee80211_find_rxnode(ic, (struct ieee80211_frame_min *)wh);
 
 	IWM_DPRINTF(sc, IWM_DEBUG_RECV,
@@ -2970,7 +2994,9 @@ iwm_mvm_rx_rx_mpdu(struct iwm_softc *sc,
 	} else {
 		rxs.c_freq = ieee80211_ieee2mhz(rxs.c_ieee, IEEE80211_CHAN_5GHZ);
 	}
-	rxs.rssi = rssi - sc->sc_noise;
+
+	/* rssi is in 1/2db units */
+	rxs.rssi = rssi * 2;
 	rxs.nf = sc->sc_noise;
 
 	if (ieee80211_radiotap_active_vap(vap)) {
@@ -5172,7 +5198,7 @@ iwm_notif_intr(struct iwm_softc *sc)
 			struct iwm_notif_statistics *stats;
 			SYNC_RESP_STRUCT(stats, pkt);
 			memcpy(&sc->sc_stats, stats, sizeof(sc->sc_stats));
-			sc->sc_noise = iwm_get_noise(&stats->rx.general);
+			sc->sc_noise = iwm_get_noise(sc, &stats->rx.general);
 			break; }
 
 		case IWM_NVM_ACCESS_CMD:
@@ -5823,8 +5849,12 @@ iwm_attach(device_t dev)
 		sc->sc_phyctxt[i].channel = NULL;
 	}
 
+	/* Default noise floor */
+	sc->sc_noise = -96;
+
 	/* Max RSSI */
 	sc->sc_max_rssi = IWM_MAX_DBM - IWM_MIN_DBM;
+
 	sc->sc_preinit_hook.ich_func = iwm_preinit;
 	sc->sc_preinit_hook.ich_arg = sc;
 	if (config_intrhook_establish(&sc->sc_preinit_hook) != 0) {

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