usb: gadget: udc: core: Offload usb_udc_vbus_handler processing

usb_udc_vbus_handler() can be invoked from interrupt context by irq
handlers of the gadget drivers, however, usb_udc_connect_control() has
to run in non-atomic context due to the following:
a. Some of the gadget driver implementations expect the ->pullup
   callback to be invoked in non-atomic context.
b. usb_gadget_disconnect() acquires udc_lock which is a mutex.

Hence offload invocation of usb_udc_connect_control()
to workqueue.

UDC should not be pulled up unless gadget driver is bound. The new flag
"allow_connect" is now set by gadget_bind_driver() and cleared by
gadget_unbind_driver(). This prevents work item to pull up the gadget
even if queued when the gadget driver is already unbound.

Cc: stable@vger.kernel.org
Fixes: 1016fc0c096c ("USB: gadget: Fix obscure lockdep violation for udc_mutex")
Signed-off-by: Badhri Jagan Sridharan <badhri@google.com>
Reviewed-by: Alan Stern <stern@rowland.harvard.edu>
Message-ID: <20230609010227.978661-1-badhri@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.c
index 52e6d2e84e35283be4aa3f28c6cb6106c55008da..d2e4f78c53e396fdd256335df3eceaa19a817415 100644 (file)
--- a/drivers/usb/gadget/udc/core.c
+++ b/drivers/usb/gadget/udc/core.c
@@ -37,6 +37,9 @@ static const struct bus_type gadget_bus_type;
  * @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.
+ * @allow_connect: Indicates whether UDC is allowed to be pulled up.
+ * Set/cleared by gadget_(un)bind_driver() after gadget driver is bound or
+ * unbound.
  *
  * This represents the internal data structure which is used by the UDC-class
  * to hold information about udc driver and gadget together.
@@ -48,6 +51,8 @@ struct usb_udc {
        struct list_head                list;
        bool                            vbus;
        bool                            started;
+       bool                            allow_connect;
+       struct work_struct              vbus_work;
 };
 
 static struct class *udc_class;
@@ -706,7 +711,7 @@ int usb_gadget_connect(struct usb_gadget *gadget)
                goto out;
        }
 
-       if (gadget->deactivated) {
+       if (gadget->deactivated || !gadget->udc->allow_connect) {
                /*
                 * If gadget is deactivated we only save new state.
                 * Gadget will be connected automatically after activation.
@@ -1086,6 +1091,13 @@ static void usb_udc_connect_control(struct usb_udc *udc)
                usb_gadget_disconnect(udc->gadget);
 }
 
+static void vbus_event_work(struct work_struct *work)
+{
+       struct usb_udc *udc = container_of(work, struct usb_udc, vbus_work);
+
+       usb_udc_connect_control(udc);
+}
+
 /**
  * usb_udc_vbus_handler - updates the udc core vbus status, and try to
  * connect or disconnect gadget
@@ -1094,6 +1106,14 @@ static void usb_udc_connect_control(struct usb_udc *udc)
  *
  * The udc driver calls it when it wants to connect or disconnect gadget
  * according to vbus status.
+ *
+ * This function can be invoked from interrupt context by irq handlers of
+ * the gadget drivers, however, usb_udc_connect_control() has to run in
+ * non-atomic context due to the following:
+ * a. Some of the gadget driver implementations expect the ->pullup
+ * callback to be invoked in non-atomic context.
+ * b. usb_gadget_disconnect() acquires udc_lock which is a mutex.
+ * Hence offload invocation of usb_udc_connect_control() to workqueue.
  */
 void usb_udc_vbus_handler(struct usb_gadget *gadget, bool status)
 {
@@ -1101,7 +1121,7 @@ void usb_udc_vbus_handler(struct usb_gadget *gadget, bool status)
 
        if (udc) {
                udc->vbus = status;
-               usb_udc_connect_control(udc);
+               schedule_work(&udc->vbus_work);
        }
 }
 EXPORT_SYMBOL_GPL(usb_udc_vbus_handler);
@@ -1328,6 +1348,7 @@ int usb_add_gadget(struct usb_gadget *gadget)
        mutex_lock(&udc_lock);
        list_add_tail(&udc->list, &udc_list);
        mutex_unlock(&udc_lock);
+       INIT_WORK(&udc->vbus_work, vbus_event_work);
 
        ret = device_add(&udc->dev);
        if (ret)
@@ -1459,6 +1480,7 @@ void usb_del_gadget(struct usb_gadget *gadget)
        flush_work(&gadget->work);
        device_del(&gadget->dev);
        ida_free(&gadget_id_numbers, gadget->id_number);
+       cancel_work_sync(&udc->vbus_work);
        device_unregister(&udc->dev);
 }
 EXPORT_SYMBOL_GPL(usb_del_gadget);
@@ -1527,6 +1549,7 @@ static int gadget_bind_driver(struct device *dev)
        if (ret)
                goto err_start;
        usb_gadget_enable_async_callbacks(udc);
+       udc->allow_connect = true;
        usb_udc_connect_control(udc);
 
        kobject_uevent(&udc->dev.kobj, KOBJ_CHANGE);
@@ -1558,6 +1581,8 @@ static void gadget_unbind_driver(struct device *dev)
 
        kobject_uevent(&udc->dev.kobj, KOBJ_CHANGE);
 
+       udc->allow_connect = false;
+       cancel_work_sync(&udc->vbus_work);
        usb_gadget_disconnect(gadget);
        usb_gadget_disable_async_callbacks(udc);
        if (gadget->irq)