[PATCH v2 2/2] wifi: ath12k: Fix firmware stats leak when pdev list is empty

[Saikiran <bjsaikiran@gmail.com>]

The commits bd6ec8111e65 and 2977567b244f changed firmware stats handling
to be caller-driven, requiring explicit ath12k_fw_stats_reset() calls
after using ath12k_mac_get_fw_stats().

In ath12k_mac_op_get_txpower(), when ath12k_mac_get_fw_stats() succeeds
but the pdev stats list is empty, the function exits without calling
ath12k_fw_stats_reset(). Even though the pdev list is empty, the firmware
may have populated other stats lists (vdevs, beacons, etc.) in the
ar->fw_stats structure.

Without resetting the stats buffer, this data accumulates across multiple
calls, eventually causing the stats buffer to overflow and leading to
firmware communication failures (error -71/EPROTO) during subsequent
operations.

The issue manifests during 5GHz scanning which triggers multiple TX power
queries. Symptoms include:
- "failed to pull fw stats: -71" errors in dmesg
- 5GHz networks not detected despite hardware support
- 2.4GHz networks work normally

Fix by calling ath12k_fw_stats_reset() when the pdev list is empty,
ensuring the stats buffer is properly cleaned up even when only partial
stats data is received from firmware.

Fixes: bd6ec8111e65 ("wifi: ath12k: Make firmware stats reset caller-driven")
Link: https://bugs.launchpad.net/ubuntu-concept/+bug/2138308
Tested-on: WCN7850 hw2.0 PCI WLAN.HMT.1.1.c5-00302 (Lenovo Yoga Slim 7x)
Signed-off-by: Saikiran <bjsaikiran@gmail.com>
---
 drivers/net/wireless/ath/ath12k/mac.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/net/wireless/ath/ath12k/mac.c b/drivers/net/wireless/ath/ath12k/mac.c
index e0e49f782bf8..6e35c3ee9864 100644
--- a/drivers/net/wireless/ath/ath12k/mac.c
+++ b/drivers/net/wireless/ath/ath12k/mac.c
@@ -5169,6 +5169,7 @@ static int ath12k_mac_op_get_txpower(struct ieee80211_hw *hw,
 					struct ath12k_fw_stats_pdev, list);
 	if (!pdev) {
 		spin_unlock_bh(&ar->data_lock);
+		ath12k_fw_stats_reset(ar);
 		goto err_fallback;
 	}
 
-- 
2.51.0