When rate-control is performed in HW, we cannot calculate frame
duration as we do not have the skb transmission rate in SW.

ieee80211_tx_h_calculate_duration() should only be called when
ieee80211_tx_h_rate_ctrl() has been called before to initialize data
in skb->cb. This doesn't happen for drivers with HW rate-control.

Fixes the following warning when operating in AP-mode
in a driver with HW rate-control.

<4>[16747.586029] WARNING: at net/mac80211/tx.c:57 ieee80211_duration
+0x54/0x1d8 [mac80211]()
<4>[16747.594085] Modules linked in: wl12xx_sdio wl12xx firmware_class crc7
mac80211 cfg80211 [last unloaded: crc7]
<4>[16747.604095] [<c004707c>] (unwind_backtrace+0x0/0x124) from [<c006644c>]
(warn_slowpath_common+0x4c/0x64)
<4>[16747.613616] [<c006644c>] (warn_slowpath_common+0x4c/0x64) from
[<c006647c>] (warn_slowpath_null+0x18/0x1c)
<4>[16747.623382] [<c006647c>] (warn_slowpath_null+0x18/0x1c) from [<bf1aa8e8>]
(ieee80211_duration+0x54/0x1d8 [mac80211])
<4>[16747.634124] [<bf1aa8e8>] (ieee80211_duration+0x54/0x1d8 [mac80211]) from
[<bf1aacec>] (ieee80211_tx_h_calculate_duration+0x3c/0x5c [mac80211])
<4>[16747.647094] [<bf1aacec>] (ieee80211_tx_h_calculate_duration+0x3c/0x5c
[mac80211]) from [<bf1ab21c>] (invoke_tx_handlers+0xdc/0x118 [mac80211])
<4>[16747.660064] [<bf1ab21c>] (invoke_tx_handlers+0xdc/0x118 [mac80211])
from [<bf1ab2dc>] (ieee80211_tx+0x84/0x248 [mac80211])
<4>[16747.671295] [<bf1ab2dc>] (ieee80211_tx+0x84/0x248 [mac80211]) from
[<bf1abe3c>] (ieee80211_tx_pending+0x12c/0x278 [mac80211])
<4>[16747.682739] [<bf1abe3c>] (ieee80211_tx_pending+0x12c/0x278 [mac80211])
from [<c006b3bc>] (tasklet_action+0x68/0xc0)

Signed-off-by: Arik Nemtsov <redacted>
---
 net/mac80211/tx.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 5950e3a..e0d6d5c 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c

@@ -1394,7 +1394,8 @@ static int invoke_tx_handlers(struct ieee80211_tx_data *tx)
 	/* handlers after fragment must be aware of tx info fragmentation! */
 	CALL_TXH(ieee80211_tx_h_stats);
 	CALL_TXH(ieee80211_tx_h_encrypt);
-	CALL_TXH(ieee80211_tx_h_calculate_duration);
+	if (!(tx->local->hw.flags & IEEE80211_HW_HAS_RATE_CONTROL))
+		CALL_TXH(ieee80211_tx_h_calculate_duration);
 #undef CALL_TXH
 
  txh_done:

-- 
1.7.1