[PATCH v3 3/3] wifi: rtw89: restore channel after monitor interface restart

[Enver]

After the last monitor interface is removed, the hardware is stopped.
When monitor_chanreq remains unchanged across the next stop/start cycle,
mac80211 does not issue IEEE80211_CONF_CHANGE_CHANNEL, so
rtw89_set_channel() is not called. Hardware initialization completes, but
monitor-specific channel and RF calibration state is not restored,
leaving monitor RX and injection unusable.

Restore the channel after successful monitor VIF creation, once
pure_monitor_mode_vif has been published, so RF calibration sees the
monitor role. If channel restoration fails, disconnect the firmware role,
clear the pointer and synchronize RCU before unwinding the link. Preserve
the original error while logging any disconnect failure separately.

Tested on RTL8852AE with 25 monitor delete/recreate cycles, both with and
without concurrent raw injection. Post-stress RX and injection succeed,
with no new kernel alerts. A forced -EINVAL test verified the rollback
sequence and disconnect before link cleanup.

Fixes: d9204e99b696 ("wifi: rtw89: do RF calibration once setting channel when running pure monitor mode")
Signed-off-by: Enver <owner@xxxxxxxxxxxxxx>
---
 drivers/net/wireless/realtek/rtw89/mac80211.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/drivers/net/wireless/realtek/rtw89/mac80211.c b/drivers/net/wireless/realtek/rtw89/mac80211.c
index 5404e03..caaf817 100644
--- a/drivers/net/wireless/realtek/rtw89/mac80211.c
+++ b/drivers/net/wireless/realtek/rtw89/mac80211.c
@@ -189,7 +189,7 @@ static int rtw89_ops_add_interface(struct ieee80211_hw *hw,
 	struct rtw89_vif *rtwvif = vif_to_rtwvif(vif);
 	struct rtw89_vif_link *rtwvif_link;
 	u8 mac_id, port;
-	int ret = 0;
+	int ret = 0, disconnect_ret;
 
 	lockdep_assert_wiphy(hw->wiphy);
 
@@ -245,6 +245,9 @@ static int rtw89_ops_add_interface(struct ieee80211_hw *hw,
 		if (ret)
 			goto remove_link;
 		rcu_assign_pointer(rtwdev->pure_monitor_mode_vif, rtwvif);
+		ret = rtw89_set_channel(rtwdev);
+		if (ret)
+			goto remove_monitor;
 	} else if (rcu_access_pointer(rtwdev->pure_monitor_mode_vif)) {
 		rcu_assign_pointer(rtwdev->pure_monitor_mode_vif, NULL);
 		synchronize_rcu();
@@ -252,6 +255,14 @@ static int rtw89_ops_add_interface(struct ieee80211_hw *hw,
 	rtw89_recalc_lps(rtwdev);
 	return 0;
 
+remove_monitor:
+	rcu_assign_pointer(rtwdev->pure_monitor_mode_vif, NULL);
+	synchronize_rcu();
+	disconnect_ret = rtw89_fw_h2c_join_info(rtwdev, rtwvif_link, NULL, true);
+	if (disconnect_ret)
+		rtw89_warn(rtwdev,
+			   "failed to disconnect monitor vif during rollback: %d\n",
+			   disconnect_ret);
 remove_link:
 	__rtw89_ops_remove_iface_link(rtwdev, rtwvif_link);
 unset_link: