usb: mtu3: implement udc_async_callbacks of gadget operation

Implement udc_async_callbacks hook function to avoid a race when unnbinding
gadget drivers, refer to:
7dc0c55e ('USB: UDC core: Add udc_async_callbacks gadget op')
Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Link: https://lore.kernel.org/r/20220609074233.15532-2-chunfeng.yun@mediatek.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/mtu3/mtu3.h

@@ -357,6 +357,7 @@ struct mtu3 {
 	unsigned delayed_status:1;
 	unsigned gen2cp:1;
 	unsigned connected:1;
+	unsigned async_callbacks:1;
 
 	u8 address;
 	u8 test_mode_nr;

drivers/usb/mtu3/mtu3_gadget.c

@@ -592,6 +592,18 @@ mtu3_gadget_set_speed(struct usb_gadget *g, enum usb_device_speed speed)
 	spin_unlock_irqrestore(&mtu->lock, flags);
 }
 
+static void mtu3_gadget_async_callbacks(struct usb_gadget *g, bool enable)
+{
+	struct mtu3 *mtu = gadget_to_mtu3(g);
+	unsigned long flags;
+
+	dev_dbg(mtu->dev, "%s %s\n", __func__, enable ? "en" : "dis");
+
+	spin_lock_irqsave(&mtu->lock, flags);
+	mtu->async_callbacks = enable;
+	spin_unlock_irqrestore(&mtu->lock, flags);
+}
+
 static const struct usb_gadget_ops mtu3_gadget_ops = {
 	.get_frame = mtu3_gadget_get_frame,
 	.wakeup = mtu3_gadget_wakeup,
@@ -600,6 +612,7 @@ static const struct usb_gadget_ops mtu3_gadget_ops = {
 	.udc_start = mtu3_gadget_start,
 	.udc_stop = mtu3_gadget_stop,
 	.udc_set_speed = mtu3_gadget_set_speed,
+	.udc_async_callbacks = mtu3_gadget_async_callbacks,
 };
 
 static void mtu3_state_reset(struct mtu3 *mtu)
@@ -697,7 +710,7 @@ void mtu3_gadget_cleanup(struct mtu3 *mtu)
 void mtu3_gadget_resume(struct mtu3 *mtu)
 {
 	dev_dbg(mtu->dev, "gadget RESUME\n");
-	if (mtu->gadget_driver && mtu->gadget_driver->resume) {
+	if (mtu->async_callbacks && mtu->gadget_driver && mtu->gadget_driver->resume) {
 		spin_unlock(&mtu->lock);
 		mtu->gadget_driver->resume(&mtu->g);
 		spin_lock(&mtu->lock);
@@ -708,7 +721,7 @@ void mtu3_gadget_resume(struct mtu3 *mtu)
 void mtu3_gadget_suspend(struct mtu3 *mtu)
 {
 	dev_dbg(mtu->dev, "gadget SUSPEND\n");
-	if (mtu->gadget_driver && mtu->gadget_driver->suspend) {
+	if (mtu->async_callbacks && mtu->gadget_driver && mtu->gadget_driver->suspend) {
 		spin_unlock(&mtu->lock);
 		mtu->gadget_driver->suspend(&mtu->g);
 		spin_lock(&mtu->lock);
@@ -719,7 +732,7 @@ void mtu3_gadget_suspend(struct mtu3 *mtu)
 void mtu3_gadget_disconnect(struct mtu3 *mtu)
 {
 	dev_dbg(mtu->dev, "gadget DISCONNECT\n");
-	if (mtu->gadget_driver && mtu->gadget_driver->disconnect) {
+	if (mtu->async_callbacks && mtu->gadget_driver && mtu->gadget_driver->disconnect) {
 		spin_unlock(&mtu->lock);
 		mtu->gadget_driver->disconnect(&mtu->g);
 		spin_lock(&mtu->lock);

drivers/usb/mtu3/mtu3_gadget_ep0.c

@@ -66,7 +66,7 @@ __acquires(mtu->lock)
 {
 	int ret;
 
-	if (!mtu->gadget_driver)
+	if (!mtu->gadget_driver || !mtu->async_callbacks)
 		return -EOPNOTSUPP;
 
 	spin_unlock(&mtu->lock);