wifi: ath12k: avoid burning CPU while waiting for firmware stats

JIRA: https://issues.redhat.com/browse/RHEL-122256

commit 9a353a4
Author: Baochen Qiang <quic_bqiang@quicinc.com>
Date:   Thu Jun 12 09:31:50 2025 +0800

    wifi: ath12k: avoid burning CPU while waiting for firmware stats
    
    ath12k_mac_get_fw_stats() is busy polling fw_stats_done flag while waiting
    firmware finishing sending all events. This is not good as CPU is
    monopolized and kept burning during the wait.
    
    Change to the completion mechanism to fix it.
    
    Tested-on: WCN7850 hw2.0 PCI WLAN.HMT.1.1.c5-00284.1-QCAHMTSWPL_V1.0_V2.0_SILICONZ-3
    Tested-on: QCN9274 hw2.0 WLAN.WBE.1.5-01651-QCAHKSWPL_SILICONZ-1
    
    Fixes: e367c92 ("wifi: ath12k: Request vdev stats from firmware")
    Reported-by: Grégoire Stein <gregoire.s93@live.fr>
    Closes: https://lore.kernel.org/ath12k/AS8P190MB120575BBB25FCE697CD7D4988763A@AS8P190MB1205.EURP190.PROD.OUTLOOK.COM/
    Signed-off-by: Baochen Qiang <quic_bqiang@quicinc.com>
    Tested-by: Grégoire Stein <gregoire.s93@live.fr>
    Link: https://patch.msgid.link/20250612-ath12k-fw-fixes-v1-2-12f594f3b857@quicinc.com
    Signed-off-by: Jeff Johnson <jeff.johnson@oss.qualcomm.com>

Signed-off-by: Jose Ignacio Tornos Martinez <jtornosm@redhat.com>

Author: jtornosm

drivers/net/wireless/ath/ath12k/core.c

@@ -1216,6 +1216,7 @@ void ath12k_fw_stats_init(struct ath12k *ar)
 	INIT_LIST_HEAD(&ar->fw_stats.pdevs);
 	INIT_LIST_HEAD(&ar->fw_stats.bcn);
 	init_completion(&ar->fw_stats_complete);
+	init_completion(&ar->fw_stats_done);
 }
 
 void ath12k_fw_stats_free(struct ath12k_fw_stats *stats)
@@ -1228,7 +1229,6 @@ void ath12k_fw_stats_free(struct ath12k_fw_stats *stats)
 void ath12k_fw_stats_reset(struct ath12k *ar)
 {
 	spin_lock_bh(&ar->data_lock);
-	ar->fw_stats.fw_stats_done = false;
 	ath12k_fw_stats_free(&ar->fw_stats);
 	spin_unlock_bh(&ar->data_lock);
 }

drivers/net/wireless/ath/ath12k/core.h

@@ -632,7 +632,6 @@ struct ath12k_fw_stats {
 	struct list_head pdevs;
 	struct list_head vdevs;
 	struct list_head bcn;
-	bool fw_stats_done;
 };
 
 struct ath12k_dbg_htt_stats {
@@ -812,6 +811,7 @@ struct ath12k {
 	bool regdom_set_by_user;
 
 	struct completion fw_stats_complete;
+	struct completion fw_stats_done;
 
 	struct completion mlo_setup_done;
 	u32 mlo_setup_status;

drivers/net/wireless/ath/ath12k/mac.c

@@ -4360,27 +4360,21 @@ int ath12k_mac_get_fw_stats(struct ath12k *ar,
 {
 	struct ath12k_base *ab = ar->ab;
 	struct ath12k_hw *ah = ath12k_ar_to_ah(ar);
-	unsigned long timeout, time_left;
+	unsigned long time_left;
 	int ret;
 
 	guard(mutex)(&ah->hw_mutex);
 
 	if (ah->state != ATH12K_HW_STATE_ON)
 		return -ENETDOWN;
 
-	/* FW stats can get split when exceeding the stats data buffer limit.
-	 * In that case, since there is no end marking for the back-to-back
-	 * received 'update stats' event, we keep a 3 seconds timeout in case,
-	 * fw_stats_done is not marked yet
-	 */
-	timeout = jiffies + msecs_to_jiffies(3 * 1000);
 	ath12k_fw_stats_reset(ar);
 
 	reinit_completion(&ar->fw_stats_complete);
+	reinit_completion(&ar->fw_stats_done);
 
 	ret = ath12k_wmi_send_stats_request_cmd(ar, param->stats_id,
 						param->vdev_id, param->pdev_id);
-
 	if (ret) {
 		ath12k_warn(ab, "failed to request fw stats: %d\n", ret);
 		return ret;
@@ -4391,7 +4385,6 @@ int ath12k_mac_get_fw_stats(struct ath12k *ar,
 		   param->pdev_id, param->vdev_id, param->stats_id);
 
 	time_left = wait_for_completion_timeout(&ar->fw_stats_complete, 1 * HZ);
-
 	if (!time_left) {
 		ath12k_warn(ab, "time out while waiting for get fw stats\n");
 		return -ETIMEDOUT;
@@ -4400,19 +4393,15 @@ int ath12k_mac_get_fw_stats(struct ath12k *ar,
 	/* Firmware sends WMI_UPDATE_STATS_EVENTID back-to-back
 	 * when stats data buffer limit is reached. fw_stats_complete
 	 * is completed once host receives first event from firmware, but
-	 * still there could be more events following. Below loop is to wait
+	 * still there could be more events following. Below is to wait
 	 * until firmware completes sending all the events.
 	 */
-	for (;;) {
-		if (time_after(jiffies, timeout))
-			break;
-		spin_lock_bh(&ar->data_lock);
-		if (ar->fw_stats.fw_stats_done) {
-			spin_unlock_bh(&ar->data_lock);
-			break;
-		}
-		spin_unlock_bh(&ar->data_lock);
+	time_left = wait_for_completion_timeout(&ar->fw_stats_done, 3 * HZ);
+	if (!time_left) {
+		ath12k_warn(ab, "time out while waiting for fw stats done\n");
+		return -ETIMEDOUT;
 	}
+
 	return 0;
 }
 

drivers/net/wireless/ath/ath12k/wmi.c

@@ -8192,11 +8192,12 @@ static void ath12k_wmi_fw_stats_process(struct ath12k *ar,
 				      &ar->fw_stats.vdevs);
 
 		if (is_end) {
-			ar->fw_stats.fw_stats_done = true;
+			complete(&ar->fw_stats_done);
 			num_vdev = 0;
 		}
 		return;
 	}
+
 	if (stats->stats_id == WMI_REQUEST_BCN_STAT) {
 		if (list_empty(&stats->bcn)) {
 			ath12k_warn(ab, "empty beacon stats");
@@ -8211,7 +8212,7 @@ static void ath12k_wmi_fw_stats_process(struct ath12k *ar,
 				      &ar->fw_stats.bcn);
 
 		if (is_end) {
-			ar->fw_stats.fw_stats_done = true;
+			complete(&ar->fw_stats_done);
 			num_bcn = 0;
 		}
 	}
@@ -8249,7 +8250,7 @@ static void ath12k_update_stats_event(struct ath12k_base *ab, struct sk_buff *sk
 	/* Handle WMI_REQUEST_PDEV_STAT status update */
 	if (stats.stats_id == WMI_REQUEST_PDEV_STAT) {
 		list_splice_tail_init(&stats.pdevs, &ar->fw_stats.pdevs);
-		ar->fw_stats.fw_stats_done = true;
+		complete(&ar->fw_stats_done);
 		goto complete;
 	}