[PATCH v4] wifi: rtw88: increase TX report timeout to fix race condition

[PATCH v4] wifi: rtw88: increase TX report timeout to fix race condition

[luka.gejak]

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

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>
---
Changes in v4:
 - Picked up Acked-by tag.
Changes in v3:
 -Declared timeout with RTW_TX_PROBE_TIMEOUT as the default value and 
 removed the else branch.
 -Updated the Fixes tag to the commit that introduced USB support.
Changes in v2:
 -Isolated the change to RTL8723DU as requested by Ping-Ke

 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 3106edb84fb4..a6e43314a4e9 100644
--- a/drivers/net/wireless/realtek/rtw88/tx.c
+++ b/drivers/net/wireless/realtek/rtw88/tx.c
@@ -196,6 +196,7 @@ 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;
 
@@ -207,7 +208,11 @@ 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);
 
-- 
2.54.0

[PATCH v4] wifi: rtw88: usb: fix memory leaks on USB write failures

[luka.gejak]

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

When rtw_usb_write_port() fails to submit a USB Request Block (URB)
(e.g., due to device disconnect or ENOMEM), the completion callback is
never executed.

Currently, the driver ignores the return value of rtw_usb_write_port()
in rtw_usb_write_data() and rtw_usb_tx_agg_skb(). Because these
functions rely on the completion callback to free the socket buffers
(skbs) and the transaction control block (txcb), a submission failure
results in:
1. A memory leak of the allocated skb in rtw_usb_write_data().
2. A memory leak of the txcb structure and all aggregated skbs in
   rtw_usb_tx_agg_skb().

Fix this by checking the return value of rtw_usb_write_port(). If it
fails, explicitly free the skb in rtw_usb_write_data(), and properly
purge the tx_ack_queue and free the txcb in rtw_usb_tx_agg_skb().

The issue was discovered in practice during device disconnect/reconnect
scenarios and memory pressure conditions. Tested by verifying normal TX
operation continues after the fix without regressions.

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>
---
Changes in v4:
 - Fixed checkpatch issues and picked up Acked-by tag.
Changes in v3:
 - Updated the Fixes tag to the commit that introduced USB support.
Changes in v2:
 - Use ret = rtw_usb_write_port(...); style, and check by next line (in
   rtw_usb_tx_agg_skb)
 - Remove unnecessary comment
 - Use ieee80211_purge_tx_queue() instead of skb_queue_purge()
 - Add testing details to commit message

 drivers/net/wireless/realtek/rtw88/usb.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/realtek/rtw88/usb.c b/drivers/net/wireless/realtek/rtw88/usb.c
index 718940ebba31..1a0bdbf52cb0 100644
--- a/drivers/net/wireless/realtek/rtw88/usb.c
+++ b/drivers/net/wireless/realtek/rtw88/usb.c
@@ -399,6 +399,7 @@ static bool rtw_usb_tx_agg_skb(struct rtw_usb *rtwusb, struct sk_buff_head *list
 	int agg_num = 0;
 	unsigned int align_next = 0;
 	u8 qsel;
+	int ret;
 
 	if (skb_queue_empty(list))
 		return false;
@@ -456,7 +457,13 @@ static bool rtw_usb_tx_agg_skb(struct rtw_usb *rtwusb, struct sk_buff_head *list
 	tx_desc = (struct rtw_tx_desc *)skb_head->data;
 	qsel = le32_get_bits(tx_desc->w1, RTW_TX_DESC_W1_QSEL);
 
-	rtw_usb_write_port(rtwdev, qsel, skb_head, rtw_usb_write_port_tx_complete, txcb);
+	ret = rtw_usb_write_port(rtwdev, qsel, skb_head,
+				 rtw_usb_write_port_tx_complete, txcb);
+	if (ret) {
+		ieee80211_purge_tx_queue(rtwdev->hw, &txcb->tx_ack_queue);
+		kfree(txcb);
+		return false;
+	}
 
 	return true;
 }
@@ -518,8 +525,10 @@ static int rtw_usb_write_data(struct rtw_dev *rtwdev,
 
 	ret = rtw_usb_write_port(rtwdev, qsel, skb,
 				 rtw_usb_write_port_complete, skb);
-	if (unlikely(ret))
+	if (unlikely(ret)) {
 		rtw_err(rtwdev, "failed to do USB write, ret=%d\n", ret);
+		dev_kfree_skb_any(skb);
+	}
 
 	return ret;
 }
-- 
2.54.0