wifi: mt76: Move RCU section in mt7996_mcu_add_rate_ctrl()

Since mt76_mcu_skb_send_msg() routine can't be executed in atomic context,
move RCU section in mt7996_mcu_add_rate_ctrl() and execute
mt76_mcu_skb_send_msg() in non-atomic context. This is a preliminary
patch to fix a 'sleep while atomic' issue in mt7996_mac_sta_rc_work().

Fixes: 0762bdd ("wifi: mt76: mt7996: rework mt7996_mac_sta_rc_work to support MLO")
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Link: https://patch.msgid.link/20250605-mt7996-sleep-while-atomic-v1-4-d46d15f9203c@kernel.org
Signed-off-by: Felix Fietkau <nbd@nbd.name>

Author: LorenzoBianconi

drivers/net/wireless/mediatek/mt76/mt7996/mac.c

@@ -2356,7 +2356,6 @@ void mt7996_mac_sta_rc_work(struct work_struct *work)
 	struct ieee80211_bss_conf *link_conf;
 	struct ieee80211_link_sta *link_sta;
 	struct mt7996_sta_link *msta_link;
-	struct mt7996_vif_link *link;
 	struct mt76_vif_link *mlink;
 	struct ieee80211_sta *sta;
 	struct ieee80211_vif *vif;
@@ -2398,13 +2397,10 @@ void mt7996_mac_sta_rc_work(struct work_struct *work)
 
 		spin_unlock_bh(&dev->mt76.sta_poll_lock);
 
-		link = (struct mt7996_vif_link *)mlink;
-
 		if (changed & (IEEE80211_RC_SUPP_RATES_CHANGED |
 			       IEEE80211_RC_NSS_CHANGED |
 			       IEEE80211_RC_BW_CHANGED))
-			mt7996_mcu_add_rate_ctrl(dev, vif, link_conf,
-						 link_sta, link, msta_link,
+			mt7996_mcu_add_rate_ctrl(dev, msta_link->sta, vif,
 						 link_id, true);
 
 		if (changed & IEEE80211_RC_SMPS_CHANGED)

drivers/net/wireless/mediatek/mt76/mt7996/main.c

@@ -1112,10 +1112,8 @@ mt7996_mac_sta_event(struct mt7996_dev *dev, struct ieee80211_vif *vif,
 			if (err)
 				return err;
 
-			err = mt7996_mcu_add_rate_ctrl(dev, vif, link_conf,
-						       link_sta, link,
-						       msta_link, link_id,
-						       false);
+			err = mt7996_mcu_add_rate_ctrl(dev, msta_link->sta, vif,
+						       link_id, false);
 			if (err)
 				return err;
 

drivers/net/wireless/mediatek/mt76/mt7996/mcu.c

@@ -2201,23 +2201,44 @@ mt7996_mcu_sta_rate_ctrl_tlv(struct sk_buff *skb, struct mt7996_dev *dev,
 	memset(ra->rx_rcpi, INIT_RCPI, sizeof(ra->rx_rcpi));
 }
 
-int mt7996_mcu_add_rate_ctrl(struct mt7996_dev *dev,
-			     struct ieee80211_vif *vif,
-			     struct ieee80211_bss_conf *link_conf,
-			     struct ieee80211_link_sta *link_sta,
-			     struct mt7996_vif_link *link,
-			     struct mt7996_sta_link *msta_link,
-			     u8 link_id, bool changed)
+int mt7996_mcu_add_rate_ctrl(struct mt7996_dev *dev, struct mt7996_sta *msta,
+			     struct ieee80211_vif *vif, u8 link_id,
+			     bool changed)
 {
-	struct mt7996_sta *msta = msta_link->sta;
+	struct ieee80211_bss_conf *link_conf;
+	struct ieee80211_link_sta *link_sta;
+	struct mt7996_sta_link *msta_link;
+	struct mt7996_vif_link *link;
+	struct ieee80211_sta *sta;
 	struct sk_buff *skb;
-	int ret;
+	int ret = -ENODEV;
+
+	rcu_read_lock();
+
+	link = mt7996_vif_link(dev, vif, link_id);
+	if (!link)
+		goto error_unlock;
+
+	msta_link = rcu_dereference(msta->link[link_id]);
+	if (!msta_link)
+		goto error_unlock;
+
+	sta = wcid_to_sta(&msta_link->wcid);
+	link_sta = rcu_dereference(sta->link[link_id]);
+	if (!link_sta)
+		goto error_unlock;
+
+	link_conf = rcu_dereference(vif->link_conf[link_id]);
+	if (!link_conf)
+		goto error_unlock;
 
 	skb = __mt76_connac_mcu_alloc_sta_req(&dev->mt76, &link->mt76,
 					      &msta_link->wcid,
 					      MT7996_STA_UPDATE_MAX_SIZE);
-	if (IS_ERR(skb))
-		return PTR_ERR(skb);
+	if (IS_ERR(skb)) {
+		ret = PTR_ERR(skb);
+		goto error_unlock;
+	}
 
 	/* firmware rc algorithm refers to sta_rec_he for HE control.
 	 * once dev->rc_work changes the settings driver should also
@@ -2231,12 +2252,19 @@ int mt7996_mcu_add_rate_ctrl(struct mt7996_dev *dev,
 	 */
 	mt7996_mcu_sta_rate_ctrl_tlv(skb, dev, vif, link_conf, link_sta, link);
 
+	rcu_read_unlock();
+
 	ret = mt76_mcu_skb_send_msg(&dev->mt76, skb,
 				    MCU_WMWA_UNI_CMD(STA_REC_UPDATE), true);
 	if (ret)
 		return ret;
 
 	return mt7996_mcu_add_rate_ctrl_fixed(dev, msta, vif, link_id);
+
+error_unlock:
+	rcu_read_unlock();
+
+	return ret;
 }
 
 static int

drivers/net/wireless/mediatek/mt76/mt7996/mt7996.h

@@ -620,13 +620,9 @@ int mt7996_mcu_beacon_inband_discov(struct mt7996_dev *dev,
 int mt7996_mcu_add_obss_spr(struct mt7996_phy *phy,
 			    struct mt7996_vif_link *link,
 			    struct ieee80211_he_obss_pd *he_obss_pd);
-int mt7996_mcu_add_rate_ctrl(struct mt7996_dev *dev,
-			     struct ieee80211_vif *vif,
-			     struct ieee80211_bss_conf *link_conf,
-			     struct ieee80211_link_sta *link_sta,
-			     struct mt7996_vif_link *link,
-			     struct mt7996_sta_link *msta_link,
-			     u8 link_id, bool changed);
+int mt7996_mcu_add_rate_ctrl(struct mt7996_dev *dev, struct mt7996_sta *msta,
+			     struct ieee80211_vif *vif, u8 link_id,
+			     bool changed);
 int mt7996_set_channel(struct mt76_phy *mphy);
 int mt7996_mcu_set_chan_info(struct mt7996_phy *phy, u16 tag);
 int mt7996_mcu_set_tx(struct mt7996_dev *dev, struct ieee80211_vif *vif,