git: fcb5e8d0c19a - main - rtwn: don't do 64 bit TSF extension by default

The branch main has been updated by adrian:

URL: https://cgit.FreeBSD.org/src/commit/?id=fcb5e8d0c19ac21515ab3047d39a76b32d835cec

commit fcb5e8d0c19ac21515ab3047d39a76b32d835cec
Author:     Adrian Chadd <adrian@FreeBSD.org>
AuthorDate: 2024-12-02 05:22:45 +0000
Commit:     Adrian Chadd <adrian@FreeBSD.org>
CommitDate: 2024-12-05 07:27:46 +0000

    rtwn: don't do 64 bit TSF extension by default
    
    The TSF64 extension involves at least 3 reads from TSF registers
    (R92C_TSFTR(0), R92C_TSFTR(1), R92C_TSFTR(2)) which are 4 byte
    control transfers.  They take up valuable USB link time.
    
    It's likely much less expensive for PCIe adapters.  At some point
    it may be worthwhile enabling it by default just for those.
    
    With this disabled, the only USB traffic that I see during
    normal data operation are bulk TX/RX data transfers for 802.11
    packets, and on NICs w/ net80211 rate control, the control register
    space read/writes for TX completion.  (And that will also need
    addressing.)
    
    This is the difference between 15mbit TCP RX and 30mbit TCP RX
    on the 11n NICs, and around 40 to 50mbit TCP RX on the 11ac NICs
    in HT40 and VHT80.
    
    Locally tested:
    
    * RTL8188EU, STA mode
    * RTL8192CU, STA mode
    * RTL8192EU, STA mode
    * RTL8811AU, STA mode
    * RTL8821AU, STA mode
    
    Differential Revision:  https://reviews.freebsd.org/D47861
---
 sys/dev/rtwn/if_rtwn.c    |  5 +++++
 sys/dev/rtwn/if_rtwn_rx.c | 14 ++++++++++++--
 sys/dev/rtwn/if_rtwnvar.h |  1 +
 3 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/sys/dev/rtwn/if_rtwn.c b/sys/dev/rtwn/if_rtwn.c
index e452448976dd..3d0dce516f84 100644
--- a/sys/dev/rtwn/if_rtwn.c
+++ b/sys/dev/rtwn/if_rtwn.c
@@ -331,6 +331,11 @@ rtwn_sysctlattach(struct rtwn_softc *sc)
 	    "ht40", CTLFLAG_RDTUN, &sc->sc_ht40,
 	    sc->sc_ht40, "Enable 40 MHz mode support");
 
+	sc->sc_ena_tsf64 = 0;
+	SYSCTL_ADD_INT(ctx, SYSCTL_CHILDREN(tree), OID_AUTO,
+	    "ena_tsf64", CTLFLAG_RWTUN, &sc->sc_ena_tsf64,
+	    sc->sc_ena_tsf64, "Enable/disable per-packet TSF64 reporting");
+
 #ifdef RTWN_DEBUG
 	SYSCTL_ADD_U32(ctx, SYSCTL_CHILDREN(tree), OID_AUTO,
 	    "debug", CTLFLAG_RWTUN, &sc->sc_debug, sc->sc_debug,
diff --git a/sys/dev/rtwn/if_rtwn_rx.c b/sys/dev/rtwn/if_rtwn_rx.c
index ebfb8e67ec6d..58cd53b01e63 100644
--- a/sys/dev/rtwn/if_rtwn_rx.c
+++ b/sys/dev/rtwn/if_rtwn_rx.c
@@ -285,8 +285,18 @@ rtwn_rx_common(struct rtwn_softc *sc, struct mbuf *m, void *desc)
 		rxs.c_pktflags |= IEEE80211_RX_F_FAIL_FCSCRC;
 
 	rxs.r_flags |= IEEE80211_R_TSF_START;	/* XXX undocumented */
-	rxs.r_flags |= IEEE80211_R_TSF64;
-	rxs.c_rx_tsf = rtwn_extend_rx_tsf(sc, stat);
+
+	/*
+	 * Doing the TSF64 extension on USB is expensive, especially
+	 * if it's being done on every MPDU in an AMPDU burst.
+	 */
+	if (sc->sc_ena_tsf64) {
+		rxs.r_flags |= IEEE80211_R_TSF64;
+		rxs.c_rx_tsf = rtwn_extend_rx_tsf(sc, stat);
+	} else {
+		rxs.r_flags |= IEEE80211_R_TSF32;
+		rxs.c_rx_tsf = le32toh(stat->tsf_low);
+	}
 
 	/* Get RSSI from PHY status descriptor. */
 	is_cck = (rxs.c_pktflags & IEEE80211_RX_F_CCK) != 0;
diff --git a/sys/dev/rtwn/if_rtwnvar.h b/sys/dev/rtwn/if_rtwnvar.h
index 3d4db0a37a9e..d4458384dbd7 100644
--- a/sys/dev/rtwn/if_rtwnvar.h
+++ b/sys/dev/rtwn/if_rtwnvar.h
@@ -172,6 +172,7 @@ struct rtwn_softc {
 	device_t		sc_dev;
 
 	int			sc_ht40;
+	int			sc_ena_tsf64;
 	uint32_t		sc_debug;
 	int			sc_hwcrypto;
 	int			sc_ratectl_sysctl;