[PATCH] wifi: mt76: mt7921: refactor regd update to fix recursive mutex deadlock

[JB Tsai <jb.tsai@mediatek.com>]

From: Charlie-cy Wu <charlie-cy.wu@mediatek.corp-partner.google.com>

Split mt7921_mcu_regd_update() into two functions to prevent recursive
mutex acquisition. Introduce __mt7921_mcu_regd_update() as the internal
implementation that assumes the mutex is already held by the caller,
while mt7921_mcu_regd_update() remains as the external interface that
handles mutex acquisition and release.

This fixes a deadlock issue when mt7921_regd_set_6ghz_power_type() is
called with the device mutex already held. Without this change, calling
mt7921_mcu_regd_update() would attempt to acquire the same mutex again,
causing a recursive lock deadlock.

The __mt7921_mcu_regd_update() function can be safely called when the
caller has already acquired the device mutex, avoiding the deadlock
while maintaining proper synchronization for regulatory domain updates.

Fixes: dc2608cf5224 ("wifi: mt76: mt7921: refactor regulatory notifier flow")
Signed-off-by: Charlie-cy Wu <Charlie-cy.Wu@mediatek.com>
---
 .../net/wireless/mediatek/mt76/mt7921/main.c  |  2 +-
 .../net/wireless/mediatek/mt76/mt7921/regd.c  | 30 ++++++++++++-------
 .../net/wireless/mediatek/mt76/mt7921/regd.h  |  2 ++
 3 files changed, 22 insertions(+), 12 deletions(-)

diff --git a/drivers/net/wireless/mediatek/mt76/mt7921/main.c b/drivers/net/wireless/mediatek/mt76/mt7921/main.c
index af5d16055396..b3f29ebf4015 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7921/main.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7921/main.c
@@ -808,7 +808,7 @@ mt7921_regd_set_6ghz_power_type(struct ieee80211_vif *vif, bool is_add)
 
 out:
 	if (vif->bss_conf.chanreq.oper.chan->band == NL80211_BAND_6GHZ)
-		mt7921_mcu_regd_update(dev, dev->mt76.alpha2, dev->country_ie_env);
+		__mt7921_mcu_regd_update(dev, dev->mt76.alpha2, dev->country_ie_env);
 }
 
 int mt7921_mac_sta_add(struct mt76_dev *mdev, struct ieee80211_vif *vif,
diff --git a/drivers/net/wireless/mediatek/mt76/mt7921/regd.c b/drivers/net/wireless/mediatek/mt76/mt7921/regd.c
index f122e418d825..f923af1440d7 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7921/regd.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7921/regd.c
@@ -71,36 +71,44 @@ mt7921_regd_channel_update(struct wiphy *wiphy, struct mt792x_dev *dev)
 	}
 }
 
-int mt7921_mcu_regd_update(struct mt792x_dev *dev, u8 *alpha2,
-			   enum environment_cap country_ie_env)
+/* Internal version that assumes mutex is already held by caller */
+int __mt7921_mcu_regd_update(struct mt792x_dev *dev, u8 *alpha2,
+			     enum environment_cap country_ie_env)
 {
 	struct mt76_dev *mdev = &dev->mt76;
 	struct ieee80211_hw *hw = mdev->hw;
 	struct wiphy *wiphy = hw->wiphy;
 	int ret = 0;
 
-	dev->regd_in_progress = true;
-
-	mt792x_mutex_acquire(dev);
 	if (!dev->regd_change)
-		goto err;
+		return 0;
 
 	ret = mt7921_mcu_set_clc(dev, alpha2, country_ie_env);
 	if (ret < 0)
-		goto err;
+		return ret;
 
 	mt7921_regd_channel_update(wiphy, dev);
 
 	ret = mt76_connac_mcu_set_channel_domain(hw->priv);
 	if (ret < 0)
-		goto err;
+		return ret;
 
 	ret = mt7921_set_tx_sar_pwr(hw, NULL);
-	if (ret < 0)
-		goto err;
 
-err:
+	return ret;
+}
+
+int mt7921_mcu_regd_update(struct mt792x_dev *dev, u8 *alpha2,
+			   enum environment_cap country_ie_env)
+{
+	int ret = 0;
+
+	dev->regd_in_progress = true;
+
+	mt792x_mutex_acquire(dev);
+	ret = __mt7921_mcu_regd_update(dev, alpha2, country_ie_env);
 	mt792x_mutex_release(dev);
+
 	dev->regd_change = false;
 	dev->regd_in_progress = false;
 	wake_up(&dev->wait);
diff --git a/drivers/net/wireless/mediatek/mt76/mt7921/regd.h b/drivers/net/wireless/mediatek/mt76/mt7921/regd.h
index 571f31629e9e..5b24d0902c36 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7921/regd.h
+++ b/drivers/net/wireless/mediatek/mt76/mt7921/regd.h
@@ -10,6 +10,8 @@ struct regulatory_request;
 
 int mt7921_mcu_regd_update(struct mt792x_dev *dev, u8 *alpha2,
 			   enum environment_cap country_ie_env);
+int __mt7921_mcu_regd_update(struct mt792x_dev *dev, u8 *alpha2,
+			     enum environment_cap country_ie_env);
 void mt7921_regd_notifier(struct wiphy *wiphy,
 			  struct regulatory_request *request);
 bool mt7921_regd_clc_supported(struct mt792x_dev *dev);
-- 
2.45.2