[PATCH v2 4/4] wifi: ath12k: prevent CSA counter to reach 0 and hit WARN_ON_ONCE

[Aditya Kumar Singh <quic_adisi@quicinc.com>]

Currently, when the driver receives a channel switch count WMI event from
the firmware with a count greater than 1, it calls
ieee80211_beacon_update_cntdwn(). If the beacon transmission fails, the
event will be received again with the previous count value. In this
scenario, the host decrements the mac80211 counter again, causing it to
move ahead of the firmware counter. Ultimately, when the firmware count
reaches 1, the mac80211 counter will reach zero, triggering a
WARN_ON_ONCE(). Therefore, there is a need to check the count value in the
event.

Hence to fix this, maintain the current ongoing counter in arvif. If the
count in the event does not match the expected value, silently discard the
event.

Tested-on: QCN9274 hw2.0 PCI WLAN.WBE.1.3.1-00173-QCAHKSWPL_SILICONZ-1

Signed-off-by: Aditya Kumar Singh <quic_adisi@quicinc.com>
---
 drivers/net/wireless/ath/ath12k/core.h |  2 ++
 drivers/net/wireless/ath/ath12k/wmi.c  | 19 ++++++++++++++++---
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/drivers/net/wireless/ath/ath12k/core.h b/drivers/net/wireless/ath/ath12k/core.h
index 86a1eeec64a6e173048fd92a53df6b1d2df153f2..50acdb3fc8cba95542a1220486799cfc207b496b 100644
--- a/drivers/net/wireless/ath/ath12k/core.h
+++ b/drivers/net/wireless/ath/ath12k/core.h
@@ -299,6 +299,8 @@ struct ath12k_link_vif {
 	u8 link_id;
 	struct ath12k_vif *ahvif;
 	struct ath12k_rekey_data rekey_data;
+
+	u8 current_cntdown_counter;
 };
 
 struct ath12k_vif {
diff --git a/drivers/net/wireless/ath/ath12k/wmi.c b/drivers/net/wireless/ath/ath12k/wmi.c
index 35ebd54971a595ad5a07df09581f0ae9af38f27a..6406e6a19cb5bbb56f57fa4e87aa18e9c5f31732 100644
--- a/drivers/net/wireless/ath/ath12k/wmi.c
+++ b/drivers/net/wireless/ath/ath12k/wmi.c
@@ -1935,6 +1935,7 @@ int ath12k_wmi_bcn_tmpl(struct ath12k_link_vif *arvif,
 		cmd->ext_csa_switch_count_offset =
 				cpu_to_le32(offs->cntdwn_counter_offs[1]);
 		cmd->csa_event_bitmap = cpu_to_le32(0xFFFFFFFF);
+		arvif->current_cntdown_counter = bcn->data[offs->cntdwn_counter_offs[0]];
 	}
 
 	cmd->buf_len = cpu_to_le32(bcn->len);
@@ -6916,10 +6917,22 @@ ath12k_wmi_process_csa_switch_count_event(struct ath12k_base *ab,
 			continue;
 
 		/* Finish CSA when counter reaches zero */
-		if (!current_switch_count)
+		if (!current_switch_count) {
 			ieee80211_csa_finish(ahvif->vif, arvif->link_id);
-		else if (current_switch_count > 1)
-			ieee80211_beacon_update_cntdwn(ahvif->vif, arvif->link_id);
+			arvif->current_cntdown_counter = 0;
+		} else if (current_switch_count > 1) {
+			/* If the count in event is not what we expect, don't update the
+			 * mac80211 count. Since during beacon Tx failure, count in the
+			 * firmware will not decrement and this event will come with the
+			 * previous count value again
+			 */
+			if (current_switch_count != arvif->current_cntdown_counter)
+				continue;
+
+			arvif->current_cntdown_counter =
+				ieee80211_beacon_update_cntdwn(ahvif->vif,
+							       arvif->link_id);
+		}
 	}
 	rcu_read_unlock();
 }

-- 
2.34.1