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Date:      Tue, 19 Jul 2016 00:27:18 +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: r303015 - head/sys/dev/ath
Message-ID:  <201607190027.u6J0RInI001362@repo.freebsd.org>
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Author: adrian
Date: Tue Jul 19 00:27:17 2016
New Revision: 303015
URL: https://svnweb.freebsd.org/changeset/base/303015

Log:
  [ath] don't do LDPC, STBC or short-gi for locationing frames.
  
  The 11n duration calculation function in net80211 and the HAL round /up/
  the duration calculation for short-gi, so we can't use that.
  
  The 11n duration calculation doesn't know about the extra symbol time
  needed for STBC, nor the LDPC encoding duration, so we can't use
  that.
  
  This (along with other, local hacks) allow the locationing services to
  get down to around 200nS (yes, nanoseconds) of variance when speaking
  to a "good" AP.
  
  Tested:
  
  * AR9380, STA mode, local locationing frame hacks

Modified:
  head/sys/dev/ath/if_ath_tx_ht.c

Modified: head/sys/dev/ath/if_ath_tx_ht.c
==============================================================================
--- head/sys/dev/ath/if_ath_tx_ht.c	Tue Jul 19 00:25:27 2016	(r303014)
+++ head/sys/dev/ath/if_ath_tx_ht.c	Tue Jul 19 00:27:17 2016	(r303015)
@@ -242,6 +242,14 @@ ath_tx_rate_fill_rcflags(struct ath_soft
 	if ((ni->ni_vap->iv_htcaps & IEEE80211_HTCAP_LDPC) &&
 	    (ni->ni_htcap & IEEE80211_HTCAP_LDPC))
 		do_ldpc = 1;
+
+	/*
+	 * The 11n duration calculation doesn't know about LDPC,
+	 * so don't enable it for positioning.
+	 */
+	if (bf->bf_flags & ATH_BUF_TOA_PROBE)
+		do_ldpc = 0;
+
 	do_stbc = 0;
 
 	for (i = 0; i < ATH_RC_NUM; i++) {
@@ -279,29 +287,43 @@ ath_tx_rate_fill_rcflags(struct ath_soft
 			if (ni->ni_chw == 40)
 				rc[i].flags |= ATH_RC_CW40_FLAG;
 
+			/*
+			 * NOTE: Don't do short-gi for positioning frames.
+			 *
+			 * For now, the ath_hal and net80211 HT duration
+			 * calculation rounds up the 11n data txtime
+			 * to the nearest multiple of 3.6 microseconds
+			 * and doesn't return the fractional part, so
+			 * we are always "out" by some amount.
+			 */
 			if (ni->ni_chw == 40 &&
 			    ic->ic_htcaps & IEEE80211_HTCAP_SHORTGI40 &&
 			    ni->ni_htcap & IEEE80211_HTCAP_SHORTGI40 &&
-			    vap->iv_flags_ht & IEEE80211_FHT_SHORTGI40)
+			    vap->iv_flags_ht & IEEE80211_FHT_SHORTGI40 &&
+			    (bf->bf_flags & ATH_BUF_TOA_PROBE) == 0) {
 				rc[i].flags |= ATH_RC_SGI_FLAG;
+			}
 
 			if (ni->ni_chw == 20 &&
 			    ic->ic_htcaps & IEEE80211_HTCAP_SHORTGI20 &&
 			    ni->ni_htcap & IEEE80211_HTCAP_SHORTGI20 &&
-			    vap->iv_flags_ht & IEEE80211_FHT_SHORTGI20)
+			    vap->iv_flags_ht & IEEE80211_FHT_SHORTGI20 &&
+			    (bf->bf_flags & ATH_BUF_TOA_PROBE) == 0) {
 				rc[i].flags |= ATH_RC_SGI_FLAG;
+			}
 
 			/*
 			 * If we have STBC TX enabled and the receiver
 			 * can receive (at least) 1 stream STBC, AND it's
 			 * MCS 0-7, AND we have at least two chains enabled,
-			 * enable STBC.
+			 * and we're not doing positioning, enable STBC.
 			 */
 			if (ic->ic_htcaps & IEEE80211_HTCAP_TXSTBC &&
 			    ni->ni_vap->iv_flags_ht & IEEE80211_FHT_STBC_TX &&
 			    ni->ni_htcap & IEEE80211_HTCAP_RXSTBC_1STREAM &&
 			    (sc->sc_cur_txchainmask > 1) &&
-			    HT_RC_2_STREAMS(rate) == 1) {
+			    (HT_RC_2_STREAMS(rate) == 1) &&
+			    (bf->bf_flags & ATH_BUF_TOA_PROBE) == 0) {
 				rc[i].flags |= ATH_RC_STBC_FLAG;
 				do_stbc = 1;
 			}

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