[34-longterm 030/247] ath9k: Fix bug in delimiter padding computation

[Paul Gortmaker]

From: Vasanthakumar Thiagarajan <vasanth@xxxxxxxxxxx>

                   -------------------
    This is a commit scheduled for the next v2.6.34 longterm release.
    If you see a problem with using this for longterm, please comment.
                   -------------------

commit 39ec2997c374b528cdbf65099b6d6b8593a67f7f upstream.

There is a roundng error in delimiter padding computation
which causes severe throughput drop with some of AR9003.

signed-off-by: Felix Fietkau <nbd@xxxxxxxxxxx>
Signed-off-by: Vasanthakumar Thiagarajan <vasanth@xxxxxxxxxxx>
Signed-off-by: John W. Linville <linville@xxxxxxxxxxxxx>
Signed-off-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
---
 drivers/net/wireless/ath/ath9k/ath9k.h |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/ath/ath9k/ath9k.h b/drivers/net/wireless/ath/ath9k/ath9k.h
index 83c7ea4..7f36731 100644
--- a/drivers/net/wireless/ath/ath9k/ath9k.h
+++ b/drivers/net/wireless/ath/ath9k/ath9k.h
@@ -172,8 +172,8 @@ void ath_descdma_cleanup(struct ath_softc *sc, struct ath_descdma *dd,
 
 /* returns delimiter padding required given the packet length */
 #define ATH_AGGR_GET_NDELIM(_len)					\
-	(((((_len) + ATH_AGGR_DELIM_SZ) < ATH_AGGR_MINPLEN) ?           \
-	  (ATH_AGGR_MINPLEN - (_len) - ATH_AGGR_DELIM_SZ) : 0) >> 2)
+       (((_len) >= ATH_AGGR_MINPLEN) ? 0 :                             \
+        DIV_ROUND_UP(ATH_AGGR_MINPLEN - (_len), ATH_AGGR_DELIM_SZ))
 
 #define BAW_WITHIN(_start, _bawsz, _seqno) \
 	((((_seqno) - (_start)) & 4095) < (_bawsz))
-- 
1.7.4.4

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