USB: UDC: Implement udc_async_callbacks in net2272

This patch adds a udc_async_callbacks handler to the net2272 UDC
driver, which will prevent a theoretical race during gadget unbinding.

The net2272 driver is sufficiently complicated that I didn't want to
mess around with IRQ settings.  Instead, the patch simply adds a new
flag to control async callbacks, and checks the flag before issuing
any of them.

Acked-by: Felipe Balbi <balbi@kernel.org>
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Link: https://lore.kernel.org/r/20210520202206.GF1216852@rowland.harvard.edu
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/gadget/udc/net2272.c b/drivers/usb/gadget/udc/net2272.c
index 89f479b..7c38057 100644 (file)
--- a/drivers/usb/gadget/udc/net2272.c
+++ b/drivers/usb/gadget/udc/net2272.c
@@ -1150,6 +1150,7 @@ net2272_pullup(struct usb_gadget *_gadget, int is_on)
 static int net2272_start(struct usb_gadget *_gadget,
                struct usb_gadget_driver *driver);
 static int net2272_stop(struct usb_gadget *_gadget);
+static void net2272_async_callbacks(struct usb_gadget *_gadget, bool enable);
 
 static const struct usb_gadget_ops net2272_ops = {
        .get_frame      = net2272_get_frame,
@@ -1158,6 +1159,7 @@ static const struct usb_gadget_ops net2272_ops = {
        .pullup         = net2272_pullup,
        .udc_start      = net2272_start,
        .udc_stop       = net2272_stop,
+       .udc_async_callbacks = net2272_async_callbacks,
 };
 
 /*---------------------------------------------------------------------------*/
@@ -1476,7 +1478,7 @@ stop_activity(struct net2272 *dev, struct usb_gadget_driver *driver)
                net2272_dequeue_all(&dev->ep[i]);
 
        /* report disconnect; the driver is already quiesced */
-       if (driver) {
+       if (dev->async_callbacks && driver) {
                spin_unlock(&dev->lock);
                driver->disconnect(&dev->gadget);
                spin_lock(&dev->lock);
@@ -1501,6 +1503,15 @@ static int net2272_stop(struct usb_gadget *_gadget)
        return 0;
 }
 
+static void net2272_async_callbacks(struct usb_gadget *_gadget, bool enable)
+{
+       struct net2272  *dev = container_of(_gadget, struct net2272, gadget);
+
+       spin_lock_irq(&dev->lock);
+       dev->async_callbacks = enable;
+       spin_unlock_irq(&dev->lock);
+}
+
 /*---------------------------------------------------------------------------*/
 /* handle ep-a/ep-b dma completions */
 static void
@@ -1910,9 +1921,11 @@ net2272_handle_stat0_irqs(struct net2272 *dev, u8 stat)
                                u.r.bRequestType, u.r.bRequest,
                                u.r.wValue, u.r.wIndex,
                                net2272_ep_read(ep, EP_CFG));
-                       spin_unlock(&dev->lock);
-                       tmp = dev->driver->setup(&dev->gadget, &u.r);
-                       spin_lock(&dev->lock);
+                       if (dev->async_callbacks) {
+                               spin_unlock(&dev->lock);
+                               tmp = dev->driver->setup(&dev->gadget, &u.r);
+                               spin_lock(&dev->lock);
+                       }
                }
 
                /* stall ep0 on error */
@@ -1994,14 +2007,14 @@ net2272_handle_stat1_irqs(struct net2272 *dev, u8 stat)
                        if (disconnect || reset) {
                                stop_activity(dev, dev->driver);
                                net2272_ep0_start(dev);
-                               spin_unlock(&dev->lock);
-                               if (reset)
-                                       usb_gadget_udc_reset
-                                               (&dev->gadget, dev->driver);
-                               else
-                                       (dev->driver->disconnect)
-                                               (&dev->gadget);
-                               spin_lock(&dev->lock);
+                               if (dev->async_callbacks) {
+                                       spin_unlock(&dev->lock);
+                                       if (reset)
+                                               usb_gadget_udc_reset(&dev->gadget, dev->driver);
+                                       else
+                                               (dev->driver->disconnect)(&dev->gadget);
+                                       spin_lock(&dev->lock);
+                               }
                                return;
                        }
                }
@@ -2015,14 +2028,14 @@ net2272_handle_stat1_irqs(struct net2272 *dev, u8 stat)
        if (stat & tmp) {
                net2272_write(dev, IRQSTAT1, tmp);
                if (stat & (1 << SUSPEND_REQUEST_INTERRUPT)) {
-                       if (dev->driver->suspend)
+                       if (dev->async_callbacks && dev->driver->suspend)
                                dev->driver->suspend(&dev->gadget);
                        if (!enable_suspend) {
                                stat &= ~(1 << SUSPEND_REQUEST_INTERRUPT);
                                dev_dbg(dev->dev, "Suspend disabled, ignoring\n");
                        }
                } else {
-                       if (dev->driver->resume)
+                       if (dev->async_callbacks && dev->driver->resume)
                                dev->driver->resume(&dev->gadget);
                }
                stat &= ~tmp;

diff --git a/drivers/usb/gadget/udc/net2272.h b/drivers/usb/gadget/udc/net2272.h
index c669308..a9994f7 100644 (file)
--- a/drivers/usb/gadget/udc/net2272.h
+++ b/drivers/usb/gadget/udc/net2272.h
@@ -442,6 +442,7 @@ struct net2272 {
                 softconnect:1,
                 wakeup:1,
                 added:1,
+                async_callbacks:1,
                 dma_eot_polarity:1,
                 dma_dack_polarity:1,
                 dma_dreq_polarity:1,