wifi: rtl8xxxu: Use a longer retry limit of 48

The Realtek rate control algorithm goes back and forth a lot between
the highest and the lowest rate it's allowed to use. This is due to
a lot of frames being dropped because the retry limits set by
IEEE80211_CONF_CHANGE_RETRY_LIMITS are too low. (Experimentally, they
are 4 for long frames and 7 for short frames.)

The vendor drivers hardcode the value 48 for both retry limits (for
station mode), which makes dropped frames very rare and thus the rate
control is more stable.

Because most Realtek chips handle the rate control in the firmware,
which can't be modified, ignore the limits set by
IEEE80211_CONF_CHANGE_RETRY_LIMITS and use the value 48 (set during
chip initialisation), same as the vendor drivers.

Cc: stable@vger.kernel.org
Signed-off-by: Bitterblue Smith <rtl8821cerfe2@gmail.com>
Reviewed-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/477d745b-6bac-111d-403c-487fc19aa30d@gmail.com

drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c

@@ -6180,7 +6180,6 @@ static int rtl8xxxu_config(struct ieee80211_hw *hw, u32 changed)
 {
 	struct rtl8xxxu_priv *priv = hw->priv;
 	struct device *dev = &priv->udev->dev;
-	u16 val16;
 	int ret = 0, channel;
 	bool ht40;
 
@@ -6190,14 +6189,6 @@ static int rtl8xxxu_config(struct ieee80211_hw *hw, u32 changed)
 			 __func__, hw->conf.chandef.chan->hw_value,
 			 changed, hw->conf.chandef.width);
 
-	if (changed & IEEE80211_CONF_CHANGE_RETRY_LIMITS) {
-		val16 = ((hw->conf.long_frame_max_tx_count <<
-			  RETRY_LIMIT_LONG_SHIFT) & RETRY_LIMIT_LONG_MASK) |
-			((hw->conf.short_frame_max_tx_count <<
-			  RETRY_LIMIT_SHORT_SHIFT) & RETRY_LIMIT_SHORT_MASK);
-		rtl8xxxu_write16(priv, REG_RETRY_LIMIT, val16);
-	}
-
 	if (changed & IEEE80211_CONF_CHANGE_CHANNEL) {
 		switch (hw->conf.chandef.width) {
 		case NL80211_CHAN_WIDTH_20_NOHT: