ath5k: fix short preamble rate duration value

Subtract the difference in preamble duration (in usec) from the value
returned by ieee80211_generic_frame_duration.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

3 files changed, 14 insertions, 21 deletions

diff --git a/drivers/net/wireless/ath/ath5k/ath5k.h b/drivers/net/wireless/ath/ath5k/ath5k.h
index 8a06dbd39629..996d8afafdb7 100644
--- a/drivers/net/wireless/ath/ath5k/ath5k.h
+++ b/drivers/net/wireless/ath/ath5k/ath5k.h
@@ -1233,7 +1233,7 @@ int ath5k_eeprom_read_mac(struct ath5k_hw *ah, u8 *mac);
 /* Protocol Control Unit Functions */
 /* Helpers */
 int ath5k_hw_get_frame_duration(struct ath5k_hw *ah,
-                int len, struct ieee80211_rate *rate);
+                int len, struct ieee80211_rate *rate, bool shortpre);
 unsigned int ath5k_hw_get_default_slottime(struct ath5k_hw *ah);
 unsigned int ath5k_hw_get_default_sifs(struct ath5k_hw *ah);
 extern int ath5k_hw_set_opmode(struct ath5k_hw *ah, enum nl80211_iftype opmode);
diff --git a/drivers/net/wireless/ath/ath5k/pcu.c b/drivers/net/wireless/ath/ath5k/pcu.c
index a702817daf72..e342e470fb05 100644
--- a/drivers/net/wireless/ath/ath5k/pcu.c
+++ b/drivers/net/wireless/ath/ath5k/pcu.c
@@ -75,7 +75,7 @@ static const unsigned int ack_rates_high[] =
  * bwmodes.
  */
 int ath5k_hw_get_frame_duration(struct ath5k_hw *ah,
-                int len, struct ieee80211_rate *rate)
+                int len, struct ieee80211_rate *rate, bool shortpre)
 {
         struct ath5k_softc *sc = ah->ah_sc;
         int sifs, preamble, plcp_bits, sym_time;
@@ -84,9 +84,15 @@ int ath5k_hw_get_frame_duration(struct ath5k_hw *ah,
 
         /* Fallback */
         if (!ah->ah_bwmode) {
-                dur = ieee80211_generic_frame_duration(sc->hw,
-                                                NULL, len, rate);
-                return le16_to_cpu(dur);
+                __le16 raw_dur = ieee80211_generic_frame_duration(sc->hw,
+                                        NULL, len, rate);
+
+                /* subtract difference between long and short preamble */
+                dur = le16_to_cpu(raw_dur);
+                if (shortpre)
+                        dur -= 96;
+
+                return dur;
         }
 
         bitrate = rate->bitrate;
@@ -263,27 +269,14 @@ static inline void ath5k_hw_write_rate_duration(struct ath5k_hw *ah)
                  * actual rate for this rate. See mac80211 tx.c
                  * ieee80211_duration() for a brief description of
                  * what rate we should choose to TX ACKs. */
-                tx_time = ath5k_hw_get_frame_duration(ah, 10, rate);
+                tx_time = ath5k_hw_get_frame_duration(ah, 10, rate, false);
 
                 ath5k_hw_reg_write(ah, tx_time, reg);
 
                 if (!(rate->flags & IEEE80211_RATE_SHORT_PREAMBLE))
                         continue;
 
-                /*
-                 * We're not distinguishing short preamble here,
-                 * This is true, all we'll get is a longer value here
-                 * which is not necessarilly bad. We could use
-                 * export ieee80211_frame_duration() but that needs to be
-                 * fixed first to be properly used by mac802111 drivers:
-                 *
-                 *  - remove erp stuff and let the routine figure ofdm
-                 *    erp rates
-                 *  - remove passing argument ieee80211_local as
-                 *    drivers don't have access to it
-                 *  - move drivers using ieee80211_generic_frame_duration()
-                 *    to this
-                 */
+                tx_time = ath5k_hw_get_frame_duration(ah, 10, rate, true);
                 ath5k_hw_reg_write(ah, tx_time,
                         reg + (AR5K_SET_SHORT_PREAMBLE << 2));
         }
diff --git a/drivers/net/wireless/ath/ath5k/qcu.c b/drivers/net/wireless/ath/ath5k/qcu.c
index 3343fb9e4940..93abcfacd990 100644
--- a/drivers/net/wireless/ath/ath5k/qcu.c
+++ b/drivers/net/wireless/ath/ath5k/qcu.c
@@ -550,7 +550,7 @@ int ath5k_hw_set_ifs_intervals(struct ath5k_hw *ah, unsigned int slot_time)
         else
                 rate = &sc->sbands[IEEE80211_BAND_2GHZ].bitrates[0];
 
-        ack_tx_time = ath5k_hw_get_frame_duration(ah, 10, rate);
+        ack_tx_time = ath5k_hw_get_frame_duration(ah, 10, rate, false);
 
         /* ack_tx_time includes an SIFS already */
         eifs = ack_tx_time + sifs + 2 * slot_time;