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Thu, 10 Sep 2026 01:17:20 -0700 (PDT) From: Mehmet Fide To: Ping-Ke Shih Cc: Bitterblue Smith , linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org, mehmet.fide@screeningeagle.com Subject: [PATCH rtw-next v3 1/3] wifi: rtw88: usb: bound what the driver feeds the after-DTIM queue Date: Thu, 10 Sep 2026 10:17:14 +0200 Message-ID: <20260910081716.769081-2-mehmet.fide@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260910081716.769081-1-mehmet.fide@gmail.com> References: <20260910081716.769081-1-mehmet.fide@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Mehmet Fide Frames routed to the high queue are transmitted right after DTIM beacons only, inside the ATIM window, while they wait in the shared TX page pool. The driver puts no limit on how many it hands over, so as long as one station dozes, any sustained broadcast or multicast traffic outruns the drain and empties the pool: measured on an RTL8822BU AP with a single client in power save and ~40 frames/s of mDNS chatter, the free page count at 0x240 goes from 1803 to 16 in about 100 seconds and stays there for as long as the traffic lasts. From that point every other transmit queues behind the backlog, authentication responses arrive too late for anyone to join, and the reserved page download fails ("error beacon valid"). The AP keeps beaconing and only a reboot recovers. Feed the high queue through a small budget that refills below the measured drain rate (about 3 frames per DTIM, ~15/s at dtim_period 2 on the default 2 TU ATIM window); whatever exceeds the budget leaves on its access category queue right away. The high queue backlog is now bounded by the burst size under any load, so the page pool cannot run dry, at the price that a dozing station may miss part of a broadcast storm. Signed-off-by: Mehmet Fide Acked-by: Ping-Ke Shih --- v3: - the refill macro comment says what one interval buys (Ping-Ke) - the bookkeeping comment is a single line, blank lines around the refill block (Ping-Ke) drivers/net/wireless/realtek/rtw88/usb.c | 41 ++++++++++++++++++++++-- drivers/net/wireless/realtek/rtw88/usb.h | 5 +++ 2 files changed, 43 insertions(+), 3 deletions(-) diff --git a/drivers/net/wireless/realtek/rtw88/usb.c b/drivers/net/wireless/realtek/rtw88/usb.c index c90802919473..a03896260f1a 100644 --- a/drivers/net/wireless/realtek/rtw88/usb.c +++ b/drivers/net/wireless/realtek/rtw88/usb.c @@ -562,7 +562,37 @@ static int rtw_usb_write_data_h2c(struct rtw_dev *rtwdev, u8 *buf, u32 size) return rtw_usb_write_data(rtwdev, &pkt_info, buf); } -static u8 rtw_usb_tx_queue_mapping_to_qsel(struct sk_buff *skb) +#define RTW_USB_HIQ_REFILL_INTERVAL (HZ / 10) /* one unit of budget per 100 ms */ +#define RTW_USB_HIQ_BUDGET_MAX 16 + +static bool rtw_usb_hiq_take_budget(struct rtw_usb *rtwusb) +{ + unsigned long flags, elapsed, add; + bool ok; + + spin_lock_irqsave(&rtwusb->hiq_lock, flags); + + elapsed = jiffies - rtwusb->hiq_refill; + add = elapsed / RTW_USB_HIQ_REFILL_INTERVAL; + if (add) { + rtwusb->hiq_budget = min_t(unsigned long, rtwusb->hiq_budget + add, + RTW_USB_HIQ_BUDGET_MAX); + + /* keep the unfinished part of the interval for the next unit */ + rtwusb->hiq_refill = jiffies - elapsed % RTW_USB_HIQ_REFILL_INTERVAL; + } + + ok = rtwusb->hiq_budget > 0; + if (ok) + rtwusb->hiq_budget--; + + spin_unlock_irqrestore(&rtwusb->hiq_lock, flags); + + return ok; +} + +static u8 rtw_usb_tx_queue_mapping_to_qsel(struct rtw_usb *rtwusb, + struct sk_buff *skb) { struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb); @@ -573,7 +603,8 @@ static u8 rtw_usb_tx_queue_mapping_to_qsel(struct sk_buff *skb) qsel = TX_DESC_QSEL_MGMT; else if (is_broadcast_ether_addr(hdr->addr1) || is_multicast_ether_addr(hdr->addr1)) - qsel = (info->flags & IEEE80211_TX_CTL_SEND_AFTER_DTIM) ? + qsel = (info->flags & IEEE80211_TX_CTL_SEND_AFTER_DTIM) && + rtw_usb_hiq_take_budget(rtwusb) ? TX_DESC_QSEL_HIGH : skb->priority; else if (skb_get_queue_mapping(skb) <= IEEE80211_AC_BK) qsel = skb->priority; @@ -593,7 +624,7 @@ static int rtw_usb_tx_write(struct rtw_dev *rtwdev, u8 *pkt_desc; int ep; - pkt_info->qsel = rtw_usb_tx_queue_mapping_to_qsel(skb); + pkt_info->qsel = rtw_usb_tx_queue_mapping_to_qsel(rtwusb, skb); pkt_desc = skb_push(skb, chip->tx_pkt_desc_sz); memset(pkt_desc, 0, chip->tx_pkt_desc_sz); ep = qsel_to_ep(rtwusb, pkt_info->qsel); @@ -1034,6 +1065,10 @@ static int rtw_usb_init_tx(struct rtw_dev *rtwdev) struct rtw_usb *rtwusb = rtw_get_usb_priv(rtwdev); int i; + spin_lock_init(&rtwusb->hiq_lock); + rtwusb->hiq_budget = RTW_USB_HIQ_BUDGET_MAX; + rtwusb->hiq_refill = jiffies; + rtwusb->txwq = create_singlethread_workqueue("rtw88_usb: tx wq"); if (!rtwusb->txwq) { rtw_err(rtwdev, "failed to create TX work queue\n"); diff --git a/drivers/net/wireless/realtek/rtw88/usb.h b/drivers/net/wireless/realtek/rtw88/usb.h index 9b695b688b24..94ff21dd0846 100644 --- a/drivers/net/wireless/realtek/rtw88/usb.h +++ b/drivers/net/wireless/realtek/rtw88/usb.h @@ -75,6 +75,11 @@ struct rtw_usb { u8 out_ep[RTW_USB_EP_MAX]; int qsel_to_ep[TX_DESC_QSEL_MAX]; + /* protects hiq_budget and hiq_refill */ + spinlock_t hiq_lock; + u32 hiq_budget; + unsigned long hiq_refill; + struct workqueue_struct *txwq, *rxwq; struct sk_buff_head tx_queue[RTW_USB_EP_MAX]; -- 2.55.0