usb: udc: core: Introduce started state

For some UDCs, the initialization sequence by udc_start() should not be
repeated until it is properly cleaned up with udc_stop() and vise versa.
We may run into some cleanup failure as seen with the DWC3 driver during
the irq cleanup. This issue can occur when the user triggers
soft-connect/soft-disconnect from the soft_connect sysfs. To avoid
adding checks to every UDC driver, at the UDC framework, introduce a
"started" state to track and prevent the UDC from repeating the
udc_start() and udc_stop() if it had already started/stopped.
Acked-by: Felipe Balbi <balbi@kernel.org>
Signed-off-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Link: https://lore.kernel.org/r/a7c4112fcd4dc2f0169af94a24f5685ca77f09fd.1610395599.git.Thinh.Nguyen@synopsys.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/gadget/udc/core.c

@@ -29,6 +29,7 @@
  * @list: for use by the udc class driver
  * @vbus: for udcs who care about vbus status, this value is real vbus status;
  * for udcs who do not care about vbus status, this value is always true
+ * @started: the UDC's started state. True if the UDC had started.
  *
  * This represents the internal data structure which is used by the UDC-class
  * to hold information about udc driver and gadget together.
@@ -39,6 +40,7 @@ struct usb_udc {
 	struct device			dev;
 	struct list_head		list;
 	bool				vbus;
+	bool				started;
 };
 
 static struct class *udc_class;
@@ -1082,7 +1084,18 @@ EXPORT_SYMBOL_GPL(usb_gadget_udc_reset);
  */
 static inline int usb_gadget_udc_start(struct usb_udc *udc)
 {
-	return udc->gadget->ops->udc_start(udc->gadget, udc->driver);
+	int ret;
+
+	if (udc->started) {
+		dev_err(&udc->dev, "UDC had already started\n");
+		return -EBUSY;
+	}
+
+	ret = udc->gadget->ops->udc_start(udc->gadget, udc->driver);
+	if (!ret)
+		udc->started = true;
+
+	return ret;
 }
 
 /**
@@ -1098,7 +1111,13 @@ static inline int usb_gadget_udc_start(struct usb_udc *udc)
  */
 static inline void usb_gadget_udc_stop(struct usb_udc *udc)
 {
+	if (!udc->started) {
+		dev_err(&udc->dev, "UDC had already stopped\n");
+		return;
+	}
+
 	udc->gadget->ops->udc_stop(udc->gadget);
+	udc->started = false;
 }
 
 /**
@@ -1222,6 +1241,8 @@ int usb_add_gadget(struct usb_gadget *gadget)
 	udc->gadget = gadget;
 	gadget->udc = udc;
 
+	udc->started = false;
+
 	mutex_lock(&udc_lock);
 	list_add_tail(&udc->list, &udc_list);