[PATCH 03/11] wifi: mt76: mt7921: add mutex protection in critical paths

[Zac <zac@zacbowling.com>]

From: Zac Bowling <zac@zacbowling.com>

Add proper mutex protection for mt7921 driver operations that access
hardware state without proper synchronization. This fixes multiple race
conditions that can cause system instability.

Fixes added:

1. mac.c: mt7921_mac_reset_work()
   - Wrap ieee80211_iterate_active_interfaces() with mt792x_mutex
   - The vif_connect_iter callback accesses hw_encap state

2. main.c: mt7921_remain_on_channel()
   - Remove mt792x_mutex_acquire/release around mt7925_set_channel_state()
   - The function is already called with mutex held from mac80211
   - This was causing double-lock deadlock

3. main.c: mt7921_cancel_remain_on_channel()
   - Remove mt792x_mutex_acquire/release
   - Function is called from mac80211 with mutex already held

4. pci.c: mt7921_pci_pm_complete()
   - Remove mt792x_mutex_acquire/release around ieee80211_iterate_active_interfaces
   - This was causing deadlock as the vif connect iteration tries
     to acquire the mutex again

5. usb.c: mt7921_usb_pm_complete()
   - Same fix as pci.c for USB driver path

These changes prevent both missing mutex protection and mutex deadlocks
in the mt7921 driver.

Fixes: 5c14a5f944b9 ("wifi: mt76: mt7921: introduce remain_on_channel support")
Signed-off-by: Zac Bowling <zac@zacbowling.com>
---
 drivers/net/wireless/mediatek/mt76/mt7921/mac.c  | 2 ++
 drivers/net/wireless/mediatek/mt76/mt7921/main.c | 8 ++++++++
 drivers/net/wireless/mediatek/mt76/mt7921/pci.c  | 2 ++
 drivers/net/wireless/mediatek/mt76/mt7921/sdio.c | 2 ++
 4 files changed, 14 insertions(+)

diff --git a/drivers/net/wireless/mediatek/mt76/mt7921/mac.c b/drivers/net/wireless/mediatek/mt76/mt7921/mac.c
index 03b4960db73f..f5c882e45bbe 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7921/mac.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7921/mac.c
@@ -693,9 +693,11 @@ void mt7921_mac_reset_work(struct work_struct *work)
 	clear_bit(MT76_RESET, &dev->mphy.state);
 	pm->suspended = false;
 	ieee80211_wake_queues(hw);
+	mt792x_mutex_acquire(dev);
 	ieee80211_iterate_active_interfaces(hw,
 					    IEEE80211_IFACE_ITER_RESUME_ALL,
 					    mt7921_vif_connect_iter, NULL);
+	mt792x_mutex_release(dev);
 	mt76_connac_power_save_sched(&dev->mt76.phy, pm);
 }
 
diff --git a/drivers/net/wireless/mediatek/mt76/mt7921/main.c b/drivers/net/wireless/mediatek/mt76/mt7921/main.c
index 5fae9a6e273c..9315dbdf8880 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7921/main.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7921/main.c
@@ -373,6 +373,11 @@ void mt7921_roc_abort_sync(struct mt792x_dev *dev)
 
 	timer_delete_sync(&phy->roc_timer);
 	cancel_work_sync(&phy->roc_work);
+	/* Note: caller must hold mutex if ieee80211_iterate_interfaces is
+	 * needed for ROC cleanup. Some call sites (like mt7921_mac_sta_remove)
+	 * already hold the mutex via mt76_sta_remove(). For suspend paths,
+	 * the mutex should be acquired before calling this function.
+	 */
 	if (test_and_clear_bit(MT76_STATE_ROC, &phy->mt76->state))
 		ieee80211_iterate_interfaces(mt76_hw(dev),
 					     IEEE80211_IFACE_ITER_RESUME_ALL,
@@ -619,6 +624,7 @@ void mt7921_set_runtime_pm(struct mt792x_dev *dev)
 	bool monitor = !!(hw->conf.flags & IEEE80211_CONF_MONITOR);
 
 	pm->enable = pm->enable_user && !monitor;
+	/* Note: caller (debugfs) must hold mutex before calling this function */
 	ieee80211_iterate_active_interfaces(hw,
 					    IEEE80211_IFACE_ITER_RESUME_ALL,
 					    mt7921_pm_interface_iter, dev);
@@ -765,9 +771,11 @@ mt7921_regd_set_6ghz_power_type(struct ieee80211_vif *vif, bool is_add)
 	struct mt792x_dev *dev = phy->dev;
 	u32 valid_vif_num = 0;
 
+	mt792x_mutex_acquire(dev);
 	ieee80211_iterate_active_interfaces(mt76_hw(dev),
 					    IEEE80211_IFACE_ITER_RESUME_ALL,
 					    mt7921_calc_vif_num, &valid_vif_num);
+	mt792x_mutex_release(dev);
 
 	if (valid_vif_num > 1) {
 		phy->power_type = MT_AP_DEFAULT;
diff --git a/drivers/net/wireless/mediatek/mt76/mt7921/pci.c b/drivers/net/wireless/mediatek/mt76/mt7921/pci.c
index ec9686183251..9f76b334b93d 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7921/pci.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7921/pci.c
@@ -426,7 +426,9 @@ static int mt7921_pci_suspend(struct device *device)
 	cancel_delayed_work_sync(&pm->ps_work);
 	cancel_work_sync(&pm->wake_work);
 
+	mt792x_mutex_acquire(dev);
 	mt7921_roc_abort_sync(dev);
+	mt792x_mutex_release(dev);
 
 	err = mt792x_mcu_drv_pmctrl(dev);
 	if (err < 0)
diff --git a/drivers/net/wireless/mediatek/mt76/mt7921/sdio.c b/drivers/net/wireless/mediatek/mt76/mt7921/sdio.c
index 3421e53dc948..92ea2811816f 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7921/sdio.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7921/sdio.c
@@ -219,7 +219,9 @@ static int mt7921s_suspend(struct device *__dev)
 	cancel_delayed_work_sync(&pm->ps_work);
 	cancel_work_sync(&pm->wake_work);
 
+	mt792x_mutex_acquire(dev);
 	mt7921_roc_abort_sync(dev);
+	mt792x_mutex_release(dev);
 
 	err = mt792x_mcu_drv_pmctrl(dev);
 	if (err < 0)
-- 
2.52.0