[PATCH v4 12/13] usb: gadget: udc: adapt to OTG core

[Roger Quadros <rogerq@ti.com>]

The OTG state machine needs a mechanism to start and
stop the gadget controller. Add usb_gadget_start()
and usb_gadget_stop().

Register with OTG core when gadget function driver
is available and unregister when function driver is unbound.

We need to unlock the usb_lock mutexbefore calling
usb_otg_register_gadget() in udc_bind_to_driver() and
usb_gadget_remove_driver() else it will cause a circular
locking dependency.

Ignore softconnect sysfs control when we're in OTG
mode as OTG FSM takes care of gadget softconnect using
the b_bus_req mechanism.

Signed-off-by: Roger Quadros <rogerq@ti.com>
---
 drivers/usb/gadget/udc/udc-core.c | 124 +++++++++++++++++++++++++++++++++++---
 1 file changed, 114 insertions(+), 10 deletions(-)

diff --git a/drivers/usb/gadget/udc/udc-core.c b/drivers/usb/gadget/udc/udc-core.c
index f660afb..e961668 100644
--- a/drivers/usb/gadget/udc/udc-core.c
+++ b/drivers/usb/gadget/udc/udc-core.c
@@ -28,6 +28,7 @@
 #include <linux/usb/ch9.h>
 #include <linux/usb/gadget.h>
 #include <linux/usb.h>
+#include <linux/usb/otg.h>
 
 /**
  * struct usb_udc - describes one usb device controller
@@ -37,6 +38,7 @@
  * @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
+ * @is_otg - we're registered with OTG core and it takes care of UDC start/stop
  *
  * This represents the internal data structure which is used by the UDC-class
  * to hold information about udc driver and gadget together.
@@ -47,6 +49,7 @@ struct usb_udc {
 	struct device			dev;
 	struct list_head		list;
 	bool				vbus;
+	bool				is_otg;
 };
 
 static struct class *udc_class;
@@ -300,6 +303,7 @@ EXPORT_SYMBOL_GPL(usb_gadget_udc_reset);
  */
 static inline int usb_gadget_udc_start(struct usb_udc *udc)
 {
+	dev_dbg(&udc->dev, "%s\n", __func__);
 	return udc->gadget->ops->udc_start(udc->gadget, udc->driver);
 }
 
@@ -317,10 +321,81 @@ static inline int usb_gadget_udc_start(struct usb_udc *udc)
  */
 static inline void usb_gadget_udc_stop(struct usb_udc *udc)
 {
+	dev_dbg(&udc->dev, "%s\n", __func__);
 	udc->gadget->ops->udc_stop(udc->gadget);
 }
 
 /**
+ * usb_gadget_start - start the usb gadget controller and connect to bus
+ * @gadget: the gadget device to start
+ *
+ * This is external API for use by OTG core.
+ *
+ * Start the usb device controller and connect to bus (enable pull).
+ */
+static int usb_gadget_start(struct usb_gadget *gadget)
+{
+	int ret;
+	struct usb_udc *udc = NULL;
+
+	dev_dbg(&gadget->dev, "%s\n", __func__);
+	mutex_lock(&udc_lock);
+	list_for_each_entry(udc, &udc_list, list)
+		if (udc->gadget == gadget)
+			goto found;
+
+	dev_err(gadget->dev.parent, "%s: gadget not registered.\n",
+		__func__);
+	mutex_unlock(&udc_lock);
+	return -EINVAL;
+
+found:
+	ret = usb_gadget_udc_start(udc);
+	if (ret)
+		dev_err(&udc->dev, "USB Device Controller didn't start: %d\n",
+			ret);
+	else
+		usb_udc_connect_control(udc);
+
+	mutex_unlock(&udc_lock);
+
+	return ret;
+}
+
+/**
+ * usb_gadget_stop - disconnect from bus and stop the usb gadget
+ * @gadget: The gadget device we want to stop
+ *
+ * This is external API for use by OTG core.
+ *
+ * Disconnect from the bus (disable pull) and stop the
+ * gadget controller.
+ */
+static int usb_gadget_stop(struct usb_gadget *gadget)
+{
+	struct usb_udc *udc = NULL;
+
+	dev_dbg(&gadget->dev, "%s\n", __func__);
+	mutex_lock(&udc_lock);
+	list_for_each_entry(udc, &udc_list, list)
+		if (udc->gadget == gadget)
+			goto found;
+
+	dev_err(gadget->dev.parent, "%s: gadget not registered.\n",
+		__func__);
+	mutex_unlock(&udc_lock);
+	return -EINVAL;
+
+found:
+	usb_gadget_disconnect(udc->gadget);
+	udc->driver->disconnect(udc->gadget);
+	usb_gadget_udc_stop(udc);
+	mutex_unlock(&udc_lock);
+
+	return 0;
+}
+
+/**
  * usb_udc_release - release the usb_udc struct
  * @dev: the dev member within usb_udc
  *
@@ -438,6 +513,7 @@ int usb_add_gadget_udc(struct device *parent, struct usb_gadget *gadget)
 }
 EXPORT_SYMBOL_GPL(usb_add_gadget_udc);
 
+/* udc_lock must be held */
 static void usb_gadget_remove_driver(struct usb_udc *udc)
 {
 	dev_dbg(&udc->dev, "unregistering UDC driver [%s]\n",
@@ -445,10 +521,18 @@ static void usb_gadget_remove_driver(struct usb_udc *udc)
 
 	kobject_uevent(&udc->dev.kobj, KOBJ_CHANGE);
 
-	usb_gadget_disconnect(udc->gadget);
-	udc->driver->disconnect(udc->gadget);
+	/* If OTG, the otg core ensures UDC is stopped on unregister */
+	if (udc->is_otg) {
+		mutex_unlock(&udc_lock);
+		usb_otg_unregister_gadget(udc->gadget);
+		mutex_lock(&udc_lock);
+	} else {
+		usb_gadget_disconnect(udc->gadget);
+		udc->driver->disconnect(udc->gadget);
+		usb_gadget_udc_stop(udc);
+	}
+
 	udc->driver->unbind(udc->gadget);
-	usb_gadget_udc_stop(udc);
 
 	udc->driver = NULL;
 	udc->dev.driver = NULL;
@@ -473,11 +557,12 @@ void usb_del_gadget_udc(struct usb_gadget *gadget)
 
 	mutex_lock(&udc_lock);
 	list_del(&udc->list);
-	mutex_unlock(&udc_lock);
 
 	if (udc->driver)
 		usb_gadget_remove_driver(udc);
 
+	mutex_unlock(&udc_lock);
+
 	kobject_uevent(&udc->dev.kobj, KOBJ_REMOVE);
 	flush_work(&gadget->work);
 	device_unregister(&udc->dev);
@@ -487,6 +572,12 @@ EXPORT_SYMBOL_GPL(usb_del_gadget_udc);
 
 /* ------------------------------------------------------------------------- */
 
+struct otg_gadget_ops otg_gadget_intf = {
+	.start = usb_gadget_start,
+	.stop = usb_gadget_stop,
+};
+
+/* udc_lock must be held */
 static int udc_bind_to_driver(struct usb_udc *udc, struct usb_gadget_driver *driver)
 {
 	int ret;
@@ -501,12 +592,19 @@ static int udc_bind_to_driver(struct usb_udc *udc, struct usb_gadget_driver *dri
 	ret = driver->bind(udc->gadget, driver);
 	if (ret)
 		goto err1;
-	ret = usb_gadget_udc_start(udc);
-	if (ret) {
-		driver->unbind(udc->gadget);
-		goto err1;
+
+	/* If OTG, the otg core starts the UDC when needed */
+	mutex_unlock(&udc_lock);
+	udc->is_otg = !usb_otg_register_gadget(udc->gadget, &otg_gadget_intf);
+	mutex_lock(&udc_lock);
+	if (!udc->is_otg) {
+		ret = usb_gadget_udc_start(udc);
+		if (ret) {
+			driver->unbind(udc->gadget);
+			goto err1;
+		}
+		usb_udc_connect_control(udc);
 	}
-	usb_udc_connect_control(udc);
 
 	kobject_uevent(&udc->dev.kobj, KOBJ_CHANGE);
 	return 0;
@@ -618,9 +716,15 @@ static ssize_t usb_udc_softconn_store(struct device *dev,
 		return -EOPNOTSUPP;
 	}
 
+	/* In OTG mode we don't support softconnect, but b_bus_req */
+	if (udc->is_otg) {
+		dev_err(dev, "soft-connect not supported in OTG mode\n");
+		return -EOPNOTSUPP;
+	}
+
 	if (sysfs_streq(buf, "connect")) {
 		usb_gadget_udc_start(udc);
-		usb_gadget_connect(udc->gadget);
+		usb_udc_connect_control(udc);
 	} else if (sysfs_streq(buf, "disconnect")) {
 		usb_gadget_disconnect(udc->gadget);
 		udc->driver->disconnect(udc->gadget);
-- 
2.1.4