wifi: mt76: mt7915: introduce mt7915_get_power_bound()

Add a helper for common boundary check. This is a preliminary patch
to add per bandwidth power control.
Signed-off-by: Ryder Lee <ryder.lee@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/mt7915/mcu.c

@@ -3144,14 +3144,14 @@ int mt7915_mcu_set_txpower_frame(struct mt7915_phy *phy,
 		.txpower_max = DIV_ROUND_UP(mphy->txpower_cur, 2),
 		.wcid = cpu_to_le16(msta->wcid.idx),
 	};
-	int ret, n_chains = hweight8(mphy->antenna_mask);
+	int ret;
 	s8 txpower_sku[MT7915_SKU_RATE_NUM];
 
 	ret = mt7915_mcu_get_txpower_sku(phy, txpower_sku, sizeof(txpower_sku));
 	if (ret)
 		return ret;
 
-	txpower = txpower * 2 - mt76_tx_power_nss_delta(n_chains);
+	txpower = mt7915_get_power_bound(phy, txpower);
 	if (txpower > mphy->txpower_cur || txpower < 0)
 		return -EINVAL;
 
@@ -3203,12 +3203,10 @@ int mt7915_mcu_set_txpower_sku(struct mt7915_phy *phy)
 	};
 	struct mt76_power_limits limits_array;
 	s8 *la = (s8 *)&limits_array;
-	int i, idx, n_chains = hweight8(mphy->antenna_mask);
-	int tx_power = hw->conf.power_level * 2;
+	int i, idx;
+	int tx_power;
 
-	tx_power = mt76_get_sar_power(mphy, mphy->chandef.chan,
-				      tx_power);
-	tx_power -= mt76_tx_power_nss_delta(n_chains);
+	tx_power = mt7915_get_power_bound(phy, hw->conf.power_level);
 	tx_power = mt76_get_rate_power_limits(mphy, mphy->chandef.chan,
 					      &limits_array, tx_power);
 	mphy->txpower_cur = tx_power;

drivers/net/wireless/mediatek/mt76/mt7915/mcu.h

@@ -509,4 +509,16 @@ enum {
 					 sizeof(struct bss_info_bcn_cont) + \
 					 sizeof(struct bss_info_inband_discovery))
 
+static inline s8
+mt7915_get_power_bound(struct mt7915_phy *phy, s8 txpower)
+{
+	struct mt76_phy *mphy = phy->mt76;
+	int n_chains = hweight8(mphy->antenna_mask);
+
+	txpower = mt76_get_sar_power(mphy, mphy->chandef.chan, txpower * 2);
+	txpower -= mt76_tx_power_nss_delta(n_chains);
+
+	return txpower;
+}
+
 #endif