[PATCH v7 5/6] wifi: mt76: mt7925: add lockdep assertions for mutex verification

[Zac]

Add lockdep_assert_held() calls to critical MCU functions to help catch
mutex violations during development and debugging. This follows the
pattern used in other mt76 drivers (mt7996, mt7915, mt7615).

Functions with new assertions:
- mt7925_mcu_add_bss_info(): Core BSS configuration MCU command
- mt7925_mcu_sta_update(): Station record update MCU command
- mt7925_mcu_uni_bss_ps(): Power save state MCU command

These functions modify firmware state and must be called with the
device mutex held to prevent race conditions. The lockdep assertions
will trigger warnings at runtime if code paths exist that call these
functions without proper mutex protection.

Also fixes a potential NULL pointer issue in mt7925_mcu_sta_update()
by initializing mlink to NULL and checking it before use.

Signed-off-by: Zac Bowling <zac at zacbowling.com>
---
 drivers/net/wireless/mediatek/mt76/mt7925/mcu.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/mediatek/mt76/mt7925/mcu.c b/drivers/net/wireless/mediatek/mt76/mt7925/mcu.c
index 1379bf6a26b5..2ed4af282120 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7925/mcu.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7925/mcu.c
@@ -1532,6 +1532,8 @@ int mt7925_mcu_uni_bss_ps(struct mt792x_dev *dev,
 		},
 	};
 
+	lockdep_assert_held(&dev->mt76.mutex);
+
 	if (link_conf->vif->type != NL80211_IFTYPE_STATION)
 		return -EOPNOTSUPP;
 
@@ -2032,13 +2034,15 @@ int mt7925_mcu_sta_update(struct mt792x_dev *dev,
 		.rcpi = to_rcpi(rssi),
 	};
 	struct mt792x_sta *msta;
-	struct mt792x_link_sta *mlink;
+	struct mt792x_link_sta *mlink = NULL;
+
+	lockdep_assert_held(&dev->mt76.mutex);
 
 	if (link_sta) {
 		msta = (struct mt792x_sta *)link_sta->sta->drv_priv;
 		mlink = mt792x_sta_to_link(msta, link_sta->link_id);
 	}
-	info.wcid = link_sta ? &mlink->wcid : &mvif->sta.deflink.wcid;
+	info.wcid = (link_sta && mlink) ? &mlink->wcid : &mvif->sta.deflink.wcid;
 	info.newly = state != MT76_STA_INFO_STATE_ASSOC;
 
 	return mt7925_mcu_sta_cmd(&dev->mphy, &info);
@@ -2840,6 +2844,8 @@ int mt7925_mcu_add_bss_info(struct mt792x_phy *phy,
 	struct mt792x_link_sta *mlink_bc;
 	struct sk_buff *skb;
 
+	lockdep_assert_held(&dev->mt76.mutex);
+
 	skb = __mt7925_mcu_alloc_bss_req(&dev->mt76, &mconf->mt76,
 					 MT7925_BSS_UPDATE_MAX_SIZE);
 	if (IS_ERR(skb))
-- 
2.52.0