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From:   Elson Roy Serrao <quic_eserrao@quicinc.com>
To:     gregkh@linuxfoundation.org, Thinh.Nguyen@synopsys.com,
        rogerq@kernel.org, robh+dt@kernel.org,
        krzysztof.kozlowski+dt@linaro.org, conor+dt@kernel.org,
        devicetree@vger.kernel.org
Cc:     linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org,
        Elson Roy Serrao <quic_eserrao@quicinc.com>
Subject: [PATCH v4 1/3] usb: function: u_ether: Handle rx requests during suspend/resume
Date:   Mon, 14 Aug 2023 11:50:41 -0700
Message-Id: <20230814185043.9252-2-quic_eserrao@quicinc.com>
In-Reply-To: <20230814185043.9252-1-quic_eserrao@quicinc.com>
References: <20230814185043.9252-1-quic_eserrao@quicinc.com>
Precedence: bulk

Some UDCs might have a vote against runtime suspend if there is any
request queued by the function driver. This would block the UDC driver
to enter runtime suspend state when the host sends bus suspend
notification. While tx requests get dequeued after completion, rx
requests always remain queued for the next OUT data to be handled. Since
during bus suspend scenario there are no active OUT transfers we can
dequeue these requests when the function driver suspend callback gets
called and queue them back during resume callback. Implement this
mechanism by adding a new list for queued requests.

Also move the gether_wakeup_host API to work queue context to better
align with the remote wakeup op's synchronous operation.

Signed-off-by: Elson Roy Serrao <quic_eserrao@quicinc.com>
---
 drivers/usb/gadget/function/u_ether.c | 47 ++++++++++++++++++++++-----
 1 file changed, 38 insertions(+), 9 deletions(-)

diff --git a/drivers/usb/gadget/function/u_ether.c b/drivers/usb/gadget/function/u_ether.c
index a366abb45623..107677b7656f 100644
--- a/drivers/usb/gadget/function/u_ether.c
+++ b/drivers/usb/gadget/function/u_ether.c
@@ -62,7 +62,7 @@ struct eth_dev {
 	struct usb_gadget	*gadget;
 
 	spinlock_t		req_lock;	/* guard {rx,tx}_reqs */
-	struct list_head	tx_reqs, rx_reqs;
+	struct list_head	tx_reqs, rx_reqs, rx_queued_reqs;
 	atomic_t		tx_qlen;
 
 	struct sk_buff_head	rx_frames;
@@ -75,7 +75,7 @@ struct eth_dev {
 						struct sk_buff *skb,
 						struct sk_buff_head *list);
 
-	struct work_struct	work;
+	struct work_struct	work, wakeup_work;
 
 	unsigned long		todo;
 #define	WORK_RX_MEMORY		0
@@ -213,7 +213,7 @@ rx_submit(struct eth_dev *dev, struct usb_request *req, gfp_t gfp_flags)
 		if (skb)
 			dev_kfree_skb_any(skb);
 		spin_lock_irqsave(&dev->req_lock, flags);
-		list_add(&req->list, &dev->rx_reqs);
+		list_move_tail(&req->list, &dev->rx_reqs);
 		spin_unlock_irqrestore(&dev->req_lock, flags);
 	}
 	return retval;
@@ -303,7 +303,7 @@ static void rx_complete(struct usb_ep *ep, struct usb_request *req)
 	if (!netif_running(dev->net)) {
 clean:
 		spin_lock(&dev->req_lock);
-		list_add(&req->list, &dev->rx_reqs);
+		list_move_tail(&req->list, &dev->rx_reqs);
 		spin_unlock(&dev->req_lock);
 		req = NULL;
 	}
@@ -378,7 +378,7 @@ static void rx_fill(struct eth_dev *dev, gfp_t gfp_flags)
 	spin_lock_irqsave(&dev->req_lock, flags);
 	while (!list_empty(&dev->rx_reqs)) {
 		req = list_first_entry(&dev->rx_reqs, struct usb_request, list);
-		list_del_init(&req->list);
+		list_move_tail(&req->list, &dev->rx_queued_reqs);
 		spin_unlock_irqrestore(&dev->req_lock, flags);
 
 		if (rx_submit(dev, req, gfp_flags) < 0) {
@@ -438,9 +438,11 @@ static inline int is_promisc(u16 cdc_filter)
 	return cdc_filter & USB_CDC_PACKET_TYPE_PROMISCUOUS;
 }
 
-static int ether_wakeup_host(struct gether *port)
+static void ether_wakeup_work(struct work_struct *w)
 {
 	int			ret;
+	struct eth_dev		*dev = container_of(w, struct eth_dev, wakeup_work);
+	struct gether		*port = dev->port_usb;
 	struct usb_function	*func = &port->func;
 	struct usb_gadget	*gadget = func->config->cdev->gadget;
 
@@ -449,7 +451,8 @@ static int ether_wakeup_host(struct gether *port)
 	else
 		ret = usb_gadget_wakeup(gadget);
 
-	return ret;
+	if (ret)
+		DBG(dev, "failed to trigger wakeup:%d\n", ret);
 }
 
 static netdev_tx_t eth_start_xmit(struct sk_buff *skb,
@@ -476,7 +479,7 @@ static netdev_tx_t eth_start_xmit(struct sk_buff *skb,
 		DBG(dev, "Port suspended. Triggering wakeup\n");
 		netif_stop_queue(net);
 		spin_unlock_irqrestore(&dev->lock, flags);
-		ether_wakeup_host(dev->port_usb);
+		schedule_work(&dev->wakeup_work);
 		return NETDEV_TX_BUSY;
 	}
 
@@ -754,8 +757,10 @@ struct eth_dev *gether_setup_name(struct usb_gadget *g,
 	spin_lock_init(&dev->lock);
 	spin_lock_init(&dev->req_lock);
 	INIT_WORK(&dev->work, eth_work);
+	INIT_WORK(&dev->wakeup_work, ether_wakeup_work);
 	INIT_LIST_HEAD(&dev->tx_reqs);
 	INIT_LIST_HEAD(&dev->rx_reqs);
+	INIT_LIST_HEAD(&dev->rx_queued_reqs);
 
 	skb_queue_head_init(&dev->rx_frames);
 
@@ -825,8 +830,10 @@ struct net_device *gether_setup_name_default(const char *netname)
 	spin_lock_init(&dev->lock);
 	spin_lock_init(&dev->req_lock);
 	INIT_WORK(&dev->work, eth_work);
+	INIT_WORK(&dev->wakeup_work, ether_wakeup_work);
 	INIT_LIST_HEAD(&dev->tx_reqs);
 	INIT_LIST_HEAD(&dev->rx_reqs);
+	INIT_LIST_HEAD(&dev->rx_queued_reqs);
 
 	skb_queue_head_init(&dev->rx_frames);
 
@@ -1043,6 +1050,7 @@ EXPORT_SYMBOL_GPL(gether_set_ifname);
 void gether_suspend(struct gether *link)
 {
 	struct eth_dev *dev = link->ioport;
+	struct usb_request *req;
 	unsigned long flags;
 
 	if (!dev)
@@ -1053,9 +1061,20 @@ void gether_suspend(struct gether *link)
 		 * There is a transfer in progress. So we trigger a remote
 		 * wakeup to inform the host.
 		 */
-		ether_wakeup_host(dev->port_usb);
+		schedule_work(&dev->wakeup_work);
 		return;
 	}
+	/* Dequeue the submitted requests. */
+	spin_lock(&dev->req_lock);
+	while (!list_empty(&dev->rx_queued_reqs)) {
+		req = list_last_entry(&dev->rx_queued_reqs, struct usb_request, list);
+		list_move_tail(&req->list, &dev->rx_reqs);
+		spin_unlock(&dev->req_lock);
+		usb_ep_dequeue(dev->port_usb->out_ep, req);
+		spin_lock(&dev->req_lock);
+	}
+	spin_unlock(&dev->req_lock);
+
 	spin_lock_irqsave(&dev->lock, flags);
 	link->is_suspend = true;
 	spin_unlock_irqrestore(&dev->lock, flags);
@@ -1070,6 +1089,7 @@ void gether_resume(struct gether *link)
 	if (!dev)
 		return;
 
+	defer_kevent(dev, WORK_RX_MEMORY);
 	if (netif_queue_stopped(dev->net))
 		netif_start_queue(dev->net);
 
@@ -1231,6 +1251,15 @@ void gether_disconnect(struct gether *link)
 		usb_ep_free_request(link->out_ep, req);
 		spin_lock(&dev->req_lock);
 	}
+
+	while (!list_empty(&dev->rx_queued_reqs)) {
+		req = list_first_entry(&dev->rx_queued_reqs, struct usb_request, list);
+		list_del(&req->list);
+
+		spin_unlock(&dev->req_lock);
+		usb_ep_free_request(link->out_ep, req);
+		spin_lock(&dev->req_lock);
+	}
 	spin_unlock(&dev->req_lock);
 	link->out_ep->desc = NULL;
 
-- 
2.17.1