wifi: ath11k: avoid burning CPU in ath11k_debugfs_fw_stats_request()

We get report [1] that CPU is running a hot loop in
ath11k_debugfs_fw_stats_request():

94.60%     0.00%  i3status         [kernel.kallsyms]                 [k] do_syscall_64
        |
         --94.60%--do_syscall_64
                   |
                    --94.55%--__sys_sendmsg
                              ___sys_sendmsg
                              ____sys_sendmsg
                              netlink_sendmsg
                              netlink_unicast
                              genl_rcv
                              netlink_rcv_skb
                              genl_rcv_msg
                              |
                               --94.55%--genl_family_rcv_msg_dumpit
                                         __netlink_dump_start
                                         netlink_dump
                                         genl_dumpit
                                         nl80211_dump_station
                                         |
                                          --94.55%--ieee80211_dump_station
                                                    sta_set_sinfo
                                                    |
                                                     --94.55%--ath11k_mac_op_sta_statistics
                                                               ath11k_debugfs_get_fw_stats
                                                               |
                                                                --94.55%--ath11k_debugfs_fw_stats_request
                                                                          |
                                                                          |--41.73%--_raw_spin_lock_bh
                                                                          |
                                                                          |--22.74%--__local_bh_enable_ip
                                                                          |
                                                                          |--9.22%--_raw_spin_unlock_bh
                                                                          |
                                                                           --6.66%--srso_alias_safe_ret

This is because, if for whatever reason ar->fw_stats_done is not set by
ath11k_update_stats_event(), ath11k_debugfs_fw_stats_request() won't yield
CPU before an up to 3s timeout.

Change to completion mechanism to avoid CPU burning.

Tested-on: WCN6855 hw2.0 PCI WLAN.HSP.1.1-03125-QCAHSPSWPL_V1_V2_SILICONZ_LITE-3.6510.37

Fixes: d5c6515 ("ath11k: driver for Qualcomm IEEE 802.11ax devices")
Reported-by: Yury Vostrikov <[email protected]>
Closes: https://lore.kernel.org/all/[email protected]/ # [1]
Signed-off-by: Baochen Qiang <[email protected]>
Reviewed-by: Vasanthakumar Thiagarajan <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jeff Johnson <[email protected]>

Author: Baochen Qiang

drivers/net/wireless/ath/ath11k/core.c

@@ -990,6 +990,7 @@ void ath11k_fw_stats_init(struct ath11k *ar)
 	INIT_LIST_HEAD(&ar->fw_stats.bcn);
 
 	init_completion(&ar->fw_stats_complete);
+	init_completion(&ar->fw_stats_done);
 }
 
 void ath11k_fw_stats_free(struct ath11k_fw_stats *stats)

drivers/net/wireless/ath/ath11k/core.h

@@ -784,7 +784,7 @@ struct ath11k {
 	u8 alpha2[REG_ALPHA2_LEN + 1];
 	struct ath11k_fw_stats fw_stats;
 	struct completion fw_stats_complete;
-	bool fw_stats_done;
+	struct completion fw_stats_done;
 
 	/* protected by conf_mutex */
 	bool ps_state_enable;

drivers/net/wireless/ath/ath11k/debugfs.c

@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: BSD-3-Clause-Clear
 /*
  * Copyright (c) 2018-2020 The Linux Foundation. All rights reserved.
- * Copyright (c) 2021-2024 Qualcomm Innovation Center, Inc. All rights reserved.
+ * Copyright (c) 2021-2025 Qualcomm Innovation Center, Inc. All rights reserved.
  */
 
 #include <linux/vmalloc.h>
@@ -96,7 +96,6 @@ void ath11k_debugfs_add_dbring_entry(struct ath11k *ar,
 static void ath11k_debugfs_fw_stats_reset(struct ath11k *ar)
 {
 	spin_lock_bh(&ar->data_lock);
-	ar->fw_stats_done = false;
 	ath11k_fw_stats_pdevs_free(&ar->fw_stats.pdevs);
 	ath11k_fw_stats_vdevs_free(&ar->fw_stats.vdevs);
 	spin_unlock_bh(&ar->data_lock);
@@ -114,7 +113,7 @@ void ath11k_debugfs_fw_stats_process(struct ath11k *ar, struct ath11k_fw_stats *
 	/* WMI_REQUEST_PDEV_STAT request has been already processed */
 
 	if (stats->stats_id == WMI_REQUEST_RSSI_PER_CHAIN_STAT) {
-		ar->fw_stats_done = true;
+		complete(&ar->fw_stats_done);
 		return;
 	}
 
@@ -138,7 +137,7 @@ void ath11k_debugfs_fw_stats_process(struct ath11k *ar, struct ath11k_fw_stats *
 				      &ar->fw_stats.vdevs);
 
 		if (is_end) {
-			ar->fw_stats_done = true;
+			complete(&ar->fw_stats_done);
 			num_vdev = 0;
 		}
 		return;
@@ -158,7 +157,7 @@ void ath11k_debugfs_fw_stats_process(struct ath11k *ar, struct ath11k_fw_stats *
 				      &ar->fw_stats.bcn);
 
 		if (is_end) {
-			ar->fw_stats_done = true;
+			complete(&ar->fw_stats_done);
 			num_bcn = 0;
 		}
 	}
@@ -168,21 +167,15 @@ static int ath11k_debugfs_fw_stats_request(struct ath11k *ar,
 					   struct stats_request_params *req_param)
 {
 	struct ath11k_base *ab = ar->ab;
-	unsigned long timeout, time_left;
+	unsigned long time_left;
 	int ret;
 
 	lockdep_assert_held(&ar->conf_mutex);
 
-	/* 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 + secs_to_jiffies(3);
-
 	ath11k_debugfs_fw_stats_reset(ar);
 
 	reinit_completion(&ar->fw_stats_complete);
+	reinit_completion(&ar->fw_stats_done);
 
 	ret = ath11k_wmi_send_stats_request_cmd(ar, req_param);
 
@@ -193,21 +186,18 @@ static int ath11k_debugfs_fw_stats_request(struct ath11k *ar,
 	}
 
 	time_left = wait_for_completion_timeout(&ar->fw_stats_complete, 1 * HZ);
-
 	if (!time_left)
 		return -ETIMEDOUT;
 
-	for (;;) {
-		if (time_after(jiffies, timeout))
-			break;
+	/* 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
+	 */
+	time_left = wait_for_completion_timeout(&ar->fw_stats_done, 3 * HZ);
+	if (!time_left)
+		return -ETIMEDOUT;
 
-		spin_lock_bh(&ar->data_lock);
-		if (ar->fw_stats_done) {
-			spin_unlock_bh(&ar->data_lock);
-			break;
-		}
-		spin_unlock_bh(&ar->data_lock);
-	}
 	return 0;
 }
 

drivers/net/wireless/ath/ath11k/mac.c

@@ -9390,11 +9390,11 @@ static int ath11k_fw_stats_request(struct ath11k *ar,
 	lockdep_assert_held(&ar->conf_mutex);
 
 	spin_lock_bh(&ar->data_lock);
-	ar->fw_stats_done = false;
 	ath11k_fw_stats_pdevs_free(&ar->fw_stats.pdevs);
 	spin_unlock_bh(&ar->data_lock);
 
 	reinit_completion(&ar->fw_stats_complete);
+	reinit_completion(&ar->fw_stats_done);
 
 	ret = ath11k_wmi_send_stats_request_cmd(ar, req_param);
 	if (ret) {

drivers/net/wireless/ath/ath11k/wmi.c

@@ -8189,7 +8189,7 @@ static void ath11k_update_stats_event(struct ath11k_base *ab, struct sk_buff *sk
 	 */
 	if (stats.stats_id == WMI_REQUEST_PDEV_STAT) {
 		list_splice_tail_init(&stats.pdevs, &ar->fw_stats.pdevs);
-		ar->fw_stats_done = true;
+		complete(&ar->fw_stats_done);
 		goto complete;
 	}