ath5k: fix slot time handling

Set the slot time based on the mac80211 short slot vs long slot setting
instead of just forcing long slot for all CCK-enabled channels.
This slightly improves 802.11g mode performance in in my tests.
Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath5k/ath5k.h

@@ -1057,6 +1057,7 @@ struct ath5k_hw {
 	u8			ah_coverage_class;
 	bool			ah_ack_bitrate_high;
 	u8			ah_bwmode;
+	bool			ah_short_slot;
 
 	/* Antenna Control */
 	u32			ah_ant_ctl[AR5K_EEPROM_N_MODES][AR5K_ANT_MAX];

drivers/net/wireless/ath/ath5k/mac80211-ops.c

@@ -282,6 +282,15 @@ ath5k_bss_info_changed(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
 	if (changes & BSS_CHANGED_BEACON_INT)
 		sc->bintval = bss_conf->beacon_int;
 
+	if (changes & BSS_CHANGED_ERP_SLOT) {
+		int slot_time;
+
+		ah->ah_short_slot = bss_conf->use_short_slot;
+		slot_time = ath5k_hw_get_default_slottime(ah) +
+			    3 * ah->ah_coverage_class;
+		ath5k_hw_set_ifs_intervals(ah, slot_time);
+	}
+
 	if (changes & BSS_CHANGED_ASSOC) {
 		avf->assoc = bss_conf->assoc;
 		if (bss_conf->assoc)

drivers/net/wireless/ath/ath5k/pcu.c

@@ -151,9 +151,9 @@ unsigned int ath5k_hw_get_default_slottime(struct ath5k_hw *ah)
 		slot_time = AR5K_INIT_SLOT_TIME_QUARTER_RATE;
 		break;
 	case AR5K_BWMODE_DEFAULT:
-		slot_time = AR5K_INIT_SLOT_TIME_DEFAULT;
 	default:
-		if (channel->hw_value & CHANNEL_CCK)
+		slot_time = AR5K_INIT_SLOT_TIME_DEFAULT;
+		if ((channel->hw_value & CHANNEL_CCK) && !ah->ah_short_slot)
 			slot_time = AR5K_INIT_SLOT_TIME_B;
 		break;
 	}