Date: Fri, 23 Nov 2012 05:38:38 +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: r243426 - head/sys/dev/ath Message-ID: <201211230538.qAN5ccsl046682@svn.freebsd.org>
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Author: adrian Date: Fri Nov 23 05:38:38 2012 New Revision: 243426 URL: http://svnweb.freebsd.org/changeset/base/243426 Log: Fix up the nexttbtt -> TSF delta calculation to not wrap ridiculously on the 802.11n NICs. The 802.11n NICs return a TBTT value that continues far past the 16 bit HAL_BEACON_PERIOD time (in TU.) The code would constrain nextslot to HAL_BEACON_PERIOD, but it wasn't constraining nexttbtt - the pre-11n NICs would only return TU values from 0 -> HAL_BEACON_PERIOD. Thus, when nexttbtt exceeded 64 milliseconds, it would not wrap (but nextslot did) which lead to a huge tsfdelta. So until the slot calculation is converted to work in TSF rather than a mix of TSF and TU, "make" the nexttbtt values match the TU assumptions for pre-11n NICs. This fixes the crazy deltatsf calculations but it doesn't fix the non-convergent tsfdelta issue. That'll be fixed in a subsequent commit. Modified: head/sys/dev/ath/if_ath_tdma.c Modified: head/sys/dev/ath/if_ath_tdma.c ============================================================================== --- head/sys/dev/ath/if_ath_tdma.c Fri Nov 23 05:33:01 2012 (r243425) +++ head/sys/dev/ath/if_ath_tdma.c Fri Nov 23 05:38:38 2012 (r243426) @@ -336,7 +336,21 @@ ath_tdma_update(struct ieee80211_node *n * adjustments are done by pulling the TSF forward and possibly * rewriting the beacon timers. */ - nexttbtt = ath_hal_getnexttbtt(ah); + /* + * The logic here assumes the nexttbtt counter is in TSF + * but the prr-11n NICs are in TU. The HAL shifts them + * to TSF but there's two important differences: + * + * + The TU->TSF values have 0's for the low 9 bits, and + * + The counter wraps at TU_TO_TSF(HAL_BEACON_PERIOD + 1) for + * the pre-11n NICs, but not for the 11n NICs. + * + * So for now, just make sure the nexttbtt value we get + * matches the second issue or once nexttbtt exceeds this + * value, tsfdelta ends up becoming very negative and all + * of the adjustments get very messed up. + */ + nexttbtt = ath_hal_getnexttbtt(ah) % (TU_TO_TSF(HAL_BEACON_PERIOD + 1)); tsfdelta = (int32_t)((nextslot % TU_TO_TSF(HAL_BEACON_PERIOD + 1)) - nexttbtt); DPRINTF(sc, ATH_DEBUG_TDMA_TIMER,
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