[PATCH 6.1.y 1/2] wifi: rtw88: increase TX report timeout to fix race condition

[Sasha Levin <sashal@kernel.org>]

From: Luka Gejak <luka.gejak@linux.dev>

[ Upstream commit c80788f7c5aed8d420366b821f867a8a353d83a5 ]

The driver expects the firmware to report TX status within 500ms.
However, a timeout can be triggered when the hardware performs
background scans while under TX load. During these scans, the firmware
stays off-channel for periods exceeding 500ms, delaying the delivery of
TX reports back to the driver.

When this occurs, the purge timer fires prematurely and drops the
tracking skbs from the queue. This results in the host stack
interpreting the missing status as packet loss, leading to TCP window
collapse. In testing with iperf3, this causes throughput to drop from
~90 Mbps to near-zero for approximately 2 seconds until the connection
recovers.

Increase RTW_TX_PROBE_TIMEOUT to 2500ms for RTL8723DU. This duration is
sufficient to accommodate off-channel dwell time during full background
scans, ensuring the purge timer only trips during genuine firmware
lockups and preventing unnecessary TCP retransmission cycles.

Fixes: a82dfd33d123 ("wifi: rtw88: Add common USB chip support")
Cc: stable@vger.kernel.org
Acked-by: Ping-Ke Shih <pkshih@realtek.com>
Tested-by: Luka Gejak <luka.gejak@linux.dev>
Signed-off-by: Luka Gejak <luka.gejak@linux.dev>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/20260518142311.10328-1-luka.gejak@linux.dev
Stable-dep-of: 7cde94dab0e7 ("wifi: rtw88: TX report with long timeout for non-PCIE devices")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/net/wireless/realtek/rtw88/tx.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/net/wireless/realtek/rtw88/tx.c b/drivers/net/wireless/realtek/rtw88/tx.c
index 95ed32b83bd01..28edbec3d9fd3 100644
--- a/drivers/net/wireless/realtek/rtw88/tx.c
+++ b/drivers/net/wireless/realtek/rtw88/tx.c
@@ -176,6 +176,7 @@ void rtw_tx_report_purge_timer(struct timer_list *t)
 void rtw_tx_report_enqueue(struct rtw_dev *rtwdev, struct sk_buff *skb, u8 sn)
 {
 	struct rtw_tx_report *tx_report = &rtwdev->tx_report;
+	unsigned long timeout = RTW_TX_PROBE_TIMEOUT;
 	unsigned long flags;
 	u8 *drv_data;
 
@@ -187,7 +188,11 @@ void rtw_tx_report_enqueue(struct rtw_dev *rtwdev, struct sk_buff *skb, u8 sn)
 	__skb_queue_tail(&tx_report->queue, skb);
 	spin_unlock_irqrestore(&tx_report->q_lock, flags);
 
-	mod_timer(&tx_report->purge_timer, jiffies + RTW_TX_PROBE_TIMEOUT);
+	if (rtwdev->chip->id == RTW_CHIP_TYPE_8723D &&
+	    rtwdev->hci.type == RTW_HCI_TYPE_USB)
+		timeout = msecs_to_jiffies(2500);
+
+	mod_timer(&tx_report->purge_timer, jiffies + timeout);
 }
 EXPORT_SYMBOL(rtw_tx_report_enqueue);
 
-- 
2.53.0