From 07a2fecf33ddaf1e497fa9118458f71230dc0032 Mon Sep 17 00:00:00 2001 From: IanR778 Date: Wed, 8 Oct 2014 21:00:37 +0100 Subject: [PATCH] FIX: support rstamps from the future too. * Extend a 32 bit TSF to nearest 64 bit TSF value. * When the adapter is a STATION, its local TSF is periodically modified by * the hardware to match the BSS TSF (as received in beacon packets), and * rstamp may appear to be from the future or from the past (with reference * to the current local TSF) because of jitter. This is mostly noticable in * highly congested channels. The code uses signed modulo arithmetic to * handle both past/future cases and signed-extension to avoid branches. * Test cases: * extend(0x0000001200000004, 0x00000006) == 0x0000001200000006 * extend(0x0000001200000004, 0x00000002) == 0x0000001200000002 * extend(0x0000001200000004, 0xfffffffe) == 0x00000011fffffffe ! tsfhigh-- * extend(0x00000012fffffffc, 0xfffffffe) == 0x00000012fffffffe * extend(0x00000012fffffffc, 0xfffffffa) == 0x00000012fffffffa * extend(0x00000012fffffffc, 0x00000002) == 0x0000001300000002 ! tsfhigh++ --- target_firmware/wlan/if_ath.c | 23 +++++++++++++++++++---- 1 file changed, 19 insertions(+), 4 deletions(-) diff --git a/target_firmware/wlan/if_ath.c b/target_firmware/wlan/if_ath.c index 206b5c0..78a02e1 100755 --- a/target_firmware/wlan/if_ath.c +++ b/target_firmware/wlan/if_ath.c @@ -82,19 +82,34 @@ void ath_tgt_tx_sched_normal(struct ath_softc_tgt *sc, struct ath_buf *bf); void ath_tgt_tx_sched_nonaggr(struct ath_softc_tgt *sc,struct ath_buf * bf_host); /* - * Extend a 32 bit TSF to 64 bit, taking wrapping into account. + * Extend a 32 bit TSF to nearest 64 bit TSF value. + * When the adapter is a STATION, its local TSF is periodically modified by + * the hardware to match the BSS TSF (as received in beacon packets), and + * rstamp may appear to be from the future or from the past (with reference + * to the current local TSF) because of jitter. This is mostly noticable in + * highly congested channels. The code uses signed modulo arithmetic to + * handle both past/future cases and signed-extension to avoid branches. + * Test cases: + * extend(0x0000001200000004, 0x00000006) == 0x0000001200000006 + * extend(0x0000001200000004, 0x00000002) == 0x0000001200000002 + * extend(0x0000001200000004, 0xfffffffe) == 0x00000011fffffffe ! tsfhigh-- + * extend(0x00000012fffffffc, 0xfffffffe) == 0x00000012fffffffe + * extend(0x00000012fffffffc, 0xfffffffa) == 0x00000012fffffffa + * extend(0x00000012fffffffc, 0x00000002) == 0x0000001300000002 ! tsfhigh++ */ static u_int64_t ath_extend_tsf(struct ath_softc_tgt *sc, u_int32_t rstamp) { struct ath_hal *ah = sc->sc_ah; u_int64_t tsf; + a_int32_t tsf_low; + a_int64_t tsf_delta; /* signed int64 */ tsf = ah->ah_getTsf64(ah); + tsf_low = tsf & 0xffffffff; - if (rstamp > (tsf & 0xffffffffULL)) - tsf -= 0x100000000ULL; + tsf_delta = (a_int32_t)rstamp - (a_int64_t)tsf_low; - return ((tsf & ~0xffffffffULL) | rstamp); + return (tsf + (u_int64_t)tsf_delta); } static a_int32_t ath_rate_setup(struct ath_softc_tgt *sc, a_uint32_t mode) -- 2.31.1