[PATCH 4/5] usb: gadget: f_ecm: Add suspend/resume and remote wakeup support

[Elson Roy Serrao <quic_eserrao@quicinc.com>]

When the host sends a suspend notification to the device, handle
the suspend callbacks in the function driver. Depending on the
remote wakeup capability the device can either trigger a remote
wakeup or wait for the host initiated resume to start data
transfer again.

Signed-off-by: Elson Roy Serrao <quic_eserrao@quicinc.com>
---
 drivers/usb/gadget/function/f_ecm.c   | 22 +++++++++++
 drivers/usb/gadget/function/u_ether.c | 72 +++++++++++++++++++++++++++++++++++
 drivers/usb/gadget/function/u_ether.h |  4 ++
 3 files changed, 98 insertions(+)

diff --git a/drivers/usb/gadget/function/f_ecm.c b/drivers/usb/gadget/function/f_ecm.c
index ffe2486..fb1dec3 100644
--- a/drivers/usb/gadget/function/f_ecm.c
+++ b/drivers/usb/gadget/function/f_ecm.c
@@ -889,6 +889,26 @@ static struct usb_function_instance *ecm_alloc_inst(void)
 	return &opts->func_inst;
 }
 
+static void ecm_suspend(struct usb_function *f)
+{
+	struct f_ecm *ecm = func_to_ecm(f);
+	struct usb_composite_dev *cdev = ecm->port.func.config->cdev;
+
+	DBG(cdev, "ECM Suspend\n");
+
+	gether_suspend(&ecm->port);
+}
+
+static void ecm_resume(struct usb_function *f)
+{
+	struct f_ecm *ecm = func_to_ecm(f);
+	struct usb_composite_dev *cdev = ecm->port.func.config->cdev;
+
+	DBG(cdev, "ECM Resume\n");
+
+	gether_resume(&ecm->port);
+}
+
 static void ecm_free(struct usb_function *f)
 {
 	struct f_ecm *ecm;
@@ -956,6 +976,8 @@ static struct usb_function *ecm_alloc(struct usb_function_instance *fi)
 	ecm->port.func.setup = ecm_setup;
 	ecm->port.func.disable = ecm_disable;
 	ecm->port.func.free_func = ecm_free;
+	ecm->port.func.suspend = ecm_suspend;
+	ecm->port.func.resume = ecm_resume;
 
 	return &ecm->port.func;
 }
diff --git a/drivers/usb/gadget/function/u_ether.c b/drivers/usb/gadget/function/u_ether.c
index 7887def..78391de 100644
--- a/drivers/usb/gadget/function/u_ether.c
+++ b/drivers/usb/gadget/function/u_ether.c
@@ -471,6 +471,18 @@ static inline int is_promisc(u16 cdc_filter)
 	return cdc_filter & USB_CDC_PACKET_TYPE_PROMISCUOUS;
 }
 
+static int ether_wakeup_host(struct gether *port)
+{
+	int ret = -EOPNOTSUPP;
+	struct usb_function *func = &port->func;
+	struct usb_gadget *gadget = func->config->cdev->gadget;
+
+	if (gadget->speed < USB_SPEED_SUPER)
+		ret = usb_gadget_wakeup(gadget);
+
+	return ret;
+}
+
 static netdev_tx_t eth_start_xmit(struct sk_buff *skb,
 					struct net_device *net)
 {
@@ -490,6 +502,25 @@ static netdev_tx_t eth_start_xmit(struct sk_buff *skb,
 		in = NULL;
 		cdc_filter = 0;
 	}
+
+	if (dev->port_usb->is_suspend) {
+		DBG(dev, "Port suspended. Triggering wakeup\n");
+		retval = ether_wakeup_host(dev->port_usb);
+		if (retval) {
+			/*
+			 * Either the remote wakeup is not yet complete or
+			 * wakeup is not supported. In either case we cannot
+			 * send data and hence inform the upper layer to stop
+			 * sending data. The queue is re-started in resume
+			 * callback once the remote wakeup is successful or when
+			 * host initiated resume happens.
+			 */
+			netif_stop_queue(net);
+			spin_unlock_irqrestore(&dev->lock, flags);
+			return NETDEV_TX_BUSY;
+		}
+	}
+
 	spin_unlock_irqrestore(&dev->lock, flags);
 
 	if (!in) {
@@ -1050,6 +1081,46 @@ int gether_set_ifname(struct net_device *net, const char *name, int len)
 }
 EXPORT_SYMBOL_GPL(gether_set_ifname);
 
+void gether_suspend(struct gether *link)
+{
+	struct eth_dev *dev = link->ioport;
+	unsigned long flags;
+
+	if (!dev)
+		return;
+
+	if (atomic_read(&dev->tx_qlen)) {
+		/*
+		 * There is a transfer in progress. So we trigger a remote
+		 * wakeup to inform the host.
+		 */
+		ether_wakeup_host(dev->port_usb);
+		return;
+	}
+	spin_lock_irqsave(&dev->lock, flags);
+	link->is_suspend = true;
+	spin_unlock_irqrestore(&dev->lock, flags);
+}
+EXPORT_SYMBOL_GPL(gether_suspend);
+
+void gether_resume(struct gether *link)
+{
+	struct eth_dev *dev = link->ioport;
+	unsigned long flags;
+
+	if (!dev)
+		return;
+
+	spin_lock_irqsave(&dev->lock, flags);
+
+	if (netif_queue_stopped(dev->net))
+		netif_start_queue(dev->net);
+
+	link->is_suspend = false;
+	spin_unlock_irqrestore(&dev->lock, flags);
+}
+EXPORT_SYMBOL_GPL(gether_resume);
+
 /*
  * gether_cleanup - remove Ethernet-over-USB device
  * Context: may sleep
@@ -1212,6 +1283,7 @@ void gether_disconnect(struct gether *link)
 
 	spin_lock(&dev->lock);
 	dev->port_usb = NULL;
+	link->is_suspend = false;
 	spin_unlock(&dev->lock);
 }
 EXPORT_SYMBOL_GPL(gether_disconnect);
diff --git a/drivers/usb/gadget/function/u_ether.h b/drivers/usb/gadget/function/u_ether.h
index 4014454..851ee10 100644
--- a/drivers/usb/gadget/function/u_ether.h
+++ b/drivers/usb/gadget/function/u_ether.h
@@ -79,6 +79,7 @@ struct gether {
 	/* called on network open/close */
 	void				(*open)(struct gether *);
 	void				(*close)(struct gether *);
+	bool				is_suspend;
 };
 
 #define	DEFAULT_FILTER	(USB_CDC_PACKET_TYPE_BROADCAST \
@@ -258,6 +259,9 @@ int gether_set_ifname(struct net_device *net, const char *name, int len);
 
 void gether_cleanup(struct eth_dev *dev);
 
+void gether_suspend(struct gether *link);
+void gether_resume(struct gether *link);
+
 /* connect/disconnect is handled by individual functions */
 struct net_device *gether_connect(struct gether *);
 void gether_disconnect(struct gether *);
-- 
2.7.4