From a54be5d43aa2d6febc5a4f8dd3b87b9429b60437 Mon Sep 17 00:00:00 2001 From: Forrest Zhang Date: Wed, 13 May 2009 11:14:39 -0400 Subject: [PATCH] ath5k: fix exp off-by-one when computing OFDM delta slope Commit e8f055f0c3b ("ath5k: Update reset code") subtly changed the code that computes floating point values for the PHY3_TIMING register such that the exponent is off by a decimal point, which can cause problems with OFDM channel operation. get_bitmask_order() actually returns the highest bit set plus one, whereas the previous code wanted the highest bit set. Instead, use ilog2 which is what this code is really calculating. Also check coef_scaled to handle the (invalid) case where we need log2(0). Signed-off-by: Bob Copeland Signed-off-by: John W. Linville --- drivers/net/wireless/ath5k/reset.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/net/wireless/ath5k/reset.c b/drivers/net/wireless/ath5k/reset.c index faede82..5f72c11 100644 --- a/drivers/net/wireless/ath5k/reset.c +++ b/drivers/net/wireless/ath5k/reset.c @@ -26,7 +26,7 @@ \*****************************/ #include /* To determine if a card is pci-e */ -#include /* For get_bitmask_order */ +#include #include "ath5k.h" #include "reg.h" #include "base.h" @@ -69,10 +69,10 @@ static inline int ath5k_hw_write_ofdm_timings(struct ath5k_hw *ah, /* Get exponent * ALGO: coef_exp = 14 - highest set bit position */ - coef_exp = get_bitmask_order(coef_scaled); + coef_exp = ilog2(coef_scaled); /* Doesn't make sense if it's zero*/ - if (!coef_exp) + if (!coef_scaled || !coef_exp) return -EINVAL; /* Note: we've shifted coef_scaled by 24 */ -- 1.8.2.3