[PATCH 4.17 142/336] mt76x2: apply coverage class on slot time too

[Greg Kroah-Hartman]

4.17-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Lorenzo Bianconi <lorenzo.bianconi@xxxxxxxxxx>

[ Upstream commit 0d45d3fe42efc76b6c4f5a62f8d110c7a2e6f83f ]

According to 802.11-2007 17.3.8.6 (slot time), the slot time should
be increased by 3 us * coverage class. Taking into account coverage
class in slot time configuration allows to increase by an order of
magnitude the throughput on a 4Km link in a noisy environment

Tested-by: Luca Bisti <luca.bisti@xxxxxxxxx>
Tested-by: Gaetano Catalli <gaetano.catalli@xxxxxxxxx>
Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@xxxxxxxxxx>
Acked-by: Felix Fietkau <nbd@xxxxxxxx>
Signed-off-by: Kalle Valo <kvalo@xxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/net/wireless/mediatek/mt76/mt76x2_init.c |    3 +++
 drivers/net/wireless/mediatek/mt76/mt76x2_main.c |    3 +--
 2 files changed, 4 insertions(+), 2 deletions(-)

--- a/drivers/net/wireless/mediatek/mt76/mt76x2_init.c
+++ b/drivers/net/wireless/mediatek/mt76/mt76x2_init.c
@@ -482,7 +482,10 @@ void mt76x2_set_tx_ackto(struct mt76x2_d
 {
 	u8 ackto, sifs, slottime = dev->slottime;
 
+	/* As defined by IEEE 802.11-2007 17.3.8.6 */
 	slottime += 3 * dev->coverage_class;
+	mt76_rmw_field(dev, MT_BKOFF_SLOT_CFG,
+		       MT_BKOFF_SLOT_CFG_SLOTTIME, slottime);
 
 	sifs = mt76_get_field(dev, MT_XIFS_TIME_CFG,
 			      MT_XIFS_TIME_CFG_OFDM_SIFS);
--- a/drivers/net/wireless/mediatek/mt76/mt76x2_main.c
+++ b/drivers/net/wireless/mediatek/mt76/mt76x2_main.c
@@ -247,8 +247,7 @@ mt76x2_bss_info_changed(struct ieee80211
 		int slottime = info->use_short_slot ? 9 : 20;
 
 		dev->slottime = slottime;
-		mt76_rmw_field(dev, MT_BKOFF_SLOT_CFG,
-			       MT_BKOFF_SLOT_CFG_SLOTTIME, slottime);
+		mt76x2_set_tx_ackto(dev);
 	}
 
 	mutex_unlock(&dev->mutex);