USB: gadget: atmel_usba_udc: Start clocks on rising edge of the Vbus signal, stop clocks on falling edge of the Vbus signal

index ce88237..e207d75 100644
@@ -1791,6 +1791,8 @@ static int atmel_usba_start(struct usb_gadget *gadget,
 		toggle_bias(1);
 		usba_writel(udc, CTRL, USBA_ENABLE_MASK);
 		usba_writel(udc, INT_ENB, USBA_END_OF_RESET);
+
+		udc->vbus_prev = 1;
 	}
 	spin_unlock_irqrestore(&udc->lock, flags);
 

index e207d75..546da63 100644
@@ -1729,10 +1729,6 @@ static irqreturn_t usba_vbus_irq(int irq, void *devid)
 
 	spin_lock(&udc->lock);
 
-	/* May happen if Vbus pin toggles during probe() */
-	if (!udc->driver)
-		goto out;
-
 	vbus = vbus_is_present(udc);
 	if (vbus != udc->vbus_prev) {
 		if (vbus) {

@@ -1753,7 +1749,6 @@ static irqreturn_t usba_vbus_irq(int irq, void *devid)
 		udc->vbus_prev = vbus;
 	}
 
-out:
 	spin_unlock(&udc->lock);
 
 	return IRQ_HANDLED;

@@ -1767,23 +1762,27 @@ static int atmel_usba_start(struct usb_gadget *gadget,
 	unsigned long flags;
 
 	spin_lock_irqsave(&udc->lock, flags);
-
 	udc->devstatus = 1 << USB_DEVICE_SELF_POWERED;
 	udc->driver = driver;
 	spin_unlock_irqrestore(&udc->lock, flags);
 
 	ret = clk_prepare_enable(udc->pclk);
 	if (ret)
-		return ret;
+		goto err_pclk;
 	ret = clk_prepare_enable(udc->hclk);
-	if (ret) {
-		clk_disable_unprepare(udc->pclk);
-		return ret;
-	}
+	if (ret)
+		goto err_hclk;
 
 	udc->vbus_prev = 0;
-	if (gpio_is_valid(udc->vbus_pin))
-		enable_irq(gpio_to_irq(udc->vbus_pin));
+	if (gpio_is_valid(udc->vbus_pin)) {
+		ret = request_irq(gpio_to_irq(udc->vbus_pin),
+				usba_vbus_irq, 0,
+				"atmel_usba_udc", udc);
+		if (ret) {
+			udc->vbus_pin = -ENODEV;
+			goto err;
+		}
+	}
 
 	/* If Vbus is present, enable the controller and wait for reset */
 	spin_lock_irqsave(&udc->lock, flags);

@@ -1797,6 +1796,17 @@ static int atmel_usba_start(struct usb_gadget *gadget,
 	spin_unlock_irqrestore(&udc->lock, flags);
 
 	return 0;
+
+err:
+	clk_disable_unprepare(udc->hclk);
+err_hclk:
+	clk_disable_unprepare(udc->pclk);
+err_pclk:
+	spin_lock_irqsave(&udc->lock, flags);
+	udc->devstatus &= ~(1 << USB_DEVICE_SELF_POWERED);
+	udc->driver = NULL;
+	spin_unlock_irqrestore(&udc->lock, flags);
+	return ret;
 }
 
 static int atmel_usba_stop(struct usb_gadget *gadget)

@@ -1805,7 +1815,7 @@ static int atmel_usba_stop(struct usb_gadget *gadget)
 	unsigned long flags;
 
 	if (gpio_is_valid(udc->vbus_pin))
-		disable_irq(gpio_to_irq(udc->vbus_pin));
+		free_irq(gpio_to_irq(udc->vbus_pin), udc);
 
 	spin_lock_irqsave(&udc->lock, flags);
 	udc->gadget.speed = USB_SPEED_UNKNOWN;

@@ -2047,24 +2057,14 @@ static int usba_udc_probe(struct platform_device *pdev)
 	}
 	udc->irq = irq;
 
-	if (gpio_is_valid(udc->vbus_pin)) {
-		if (!devm_gpio_request(&pdev->dev, udc->vbus_pin, "atmel_usba_udc")) {
-			ret = devm_request_irq(&pdev->dev,
-					gpio_to_irq(udc->vbus_pin),
-					usba_vbus_irq, 0,
-					"atmel_usba_udc", udc);
-			if (ret) {
-				udc->vbus_pin = -ENODEV;
-				dev_warn(&udc->pdev->dev,
-					 "failed to request vbus irq; "
-					 "assuming always on\n");
-			} else {
-				disable_irq(gpio_to_irq(udc->vbus_pin));
-			}
-		} else {
-			/* gpio_request fail so use -EINVAL for gpio_is_valid */
-			udc->vbus_pin = -EINVAL;
-		}
+	if (gpio_is_valid(udc->vbus_pin)
+			&& devm_gpio_request(&pdev->dev, udc->vbus_pin,
+					"atmel_usba_udc")) {
+		/* gpio_request fail so use -EINVAL for gpio_is_valid */
+		udc->vbus_pin = -EINVAL;
+		dev_warn(&udc->pdev->dev,
+			"failed to request vbus gpio; "
+			"assuming always on\n");
 	}
 
 	ret = usb_add_gadget_udc(&pdev->dev, &udc->gadget);

index 546da63..e05b16c 100644
@@ -315,6 +315,37 @@ static inline void usba_cleanup_debugfs(struct usba_udc *udc)
 }
 #endif
 
+static int start_clock(struct usba_udc *udc)
+{
+	int ret;
+
+	if (udc->clocked)
+		return 0;
+
+	ret = clk_prepare_enable(udc->pclk);
+	if (ret)
+		return ret;
+	ret = clk_prepare_enable(udc->hclk);
+	if (ret) {
+		clk_disable_unprepare(udc->pclk);
+		return ret;
+	}
+
+	udc->clocked = true;
+	return 0;
+}
+
+static void stop_clock(struct usba_udc *udc)
+{
+	if (!udc->clocked)
+		return;
+
+	clk_disable_unprepare(udc->hclk);
+	clk_disable_unprepare(udc->pclk);
+
+	udc->clocked = false;
+}
+
 static int vbus_is_present(struct usba_udc *udc)
 {
 	if (gpio_is_valid(udc->vbus_pin))

@@ -1719,37 +1750,48 @@ static irqreturn_t usba_udc_irq(int irq, void *devid)
 	return IRQ_HANDLED;
 }
 
-static irqreturn_t usba_vbus_irq(int irq, void *devid)
+static irqreturn_t usba_vbus_irq_thread(int irq, void *devid)
 {
 	struct usba_udc *udc = devid;
 	int vbus;
+	int ret;
+	unsigned long flags;
 
 	/* debounce */
 	udelay(10);
 
-	spin_lock(&udc->lock);
+	mutex_lock(&udc->vbus_mutex);
 
 	vbus = vbus_is_present(udc);
 	if (vbus != udc->vbus_prev) {
 		if (vbus) {
+			ret = start_clock(udc);
+			if (ret)
+				goto out;
+
+			spin_lock_irqsave(&udc->lock, flags);
 			toggle_bias(1);
 			usba_writel(udc, CTRL, USBA_ENABLE_MASK);
 			usba_writel(udc, INT_ENB, USBA_END_OF_RESET);
+			spin_unlock_irqrestore(&udc->lock, flags);
 		} else {
+			spin_lock_irqsave(&udc->lock, flags);
 			udc->gadget.speed = USB_SPEED_UNKNOWN;
 			reset_all_endpoints(udc);
 			toggle_bias(0);
 			usba_writel(udc, CTRL, USBA_DISABLE_MASK);
-			if (udc->driver->disconnect) {
-				spin_unlock(&udc->lock);
+			spin_unlock_irqrestore(&udc->lock, flags);
+
+			stop_clock(udc);
+
+			if (udc->driver->disconnect)
 				udc->driver->disconnect(&udc->gadget);
-				spin_lock(&udc->lock);
-			}
 		}
 		udc->vbus_prev = vbus;
 	}
 
-	spin_unlock(&udc->lock);
+out:
+	mutex_unlock(&udc->vbus_mutex);
 
 	return IRQ_HANDLED;
 }

@@ -1766,17 +1808,12 @@ static int atmel_usba_start(struct usb_gadget *gadget,
 	udc->driver = driver;
 	spin_unlock_irqrestore(&udc->lock, flags);
 
-	ret = clk_prepare_enable(udc->pclk);
-	if (ret)
-		goto err_pclk;
-	ret = clk_prepare_enable(udc->hclk);
-	if (ret)
-		goto err_hclk;
+	mutex_lock(&udc->vbus_mutex);
 
 	udc->vbus_prev = 0;
 	if (gpio_is_valid(udc->vbus_pin)) {
-		ret = request_irq(gpio_to_irq(udc->vbus_pin),
-				usba_vbus_irq, 0,
+		ret = request_threaded_irq(gpio_to_irq(udc->vbus_pin), NULL,
+				usba_vbus_irq_thread, IRQF_ONESHOT,
 				"atmel_usba_udc", udc);
 		if (ret) {
 			udc->vbus_pin = -ENODEV;

@@ -1785,23 +1822,24 @@ static int atmel_usba_start(struct usb_gadget *gadget,
 	}
 
 	/* If Vbus is present, enable the controller and wait for reset */
-	spin_lock_irqsave(&udc->lock, flags);
 	if (vbus_is_present(udc) && udc->vbus_prev == 0) {
+		ret = start_clock(udc);
+		if (ret)
+			goto err;
+
+		spin_lock_irqsave(&udc->lock, flags);
 		toggle_bias(1);
 		usba_writel(udc, CTRL, USBA_ENABLE_MASK);
 		usba_writel(udc, INT_ENB, USBA_END_OF_RESET);
+		spin_unlock_irqrestore(&udc->lock, flags);
 
 		udc->vbus_prev = 1;
 	}
-	spin_unlock_irqrestore(&udc->lock, flags);
 
+	mutex_unlock(&udc->vbus_mutex);
 	return 0;
-
 err:
-	clk_disable_unprepare(udc->hclk);
-err_hclk:
-	clk_disable_unprepare(udc->pclk);
-err_pclk:
+	mutex_unlock(&udc->vbus_mutex);
 	spin_lock_irqsave(&udc->lock, flags);
 	udc->devstatus &= ~(1 << USB_DEVICE_SELF_POWERED);
 	udc->driver = NULL;

@@ -1826,8 +1864,7 @@ static int atmel_usba_stop(struct usb_gadget *gadget)
 	toggle_bias(0);
 	usba_writel(udc, CTRL, USBA_DISABLE_MASK);
 
-	clk_disable_unprepare(udc->hclk);
-	clk_disable_unprepare(udc->pclk);
+	stop_clock(udc);
 
 	udc->driver = NULL;
 

@@ -2007,6 +2044,7 @@ static int usba_udc_probe(struct platform_device *pdev)
 		return PTR_ERR(hclk);
 
 	spin_lock_init(&udc->lock);
+	mutex_init(&udc->vbus_mutex);
 	udc->pdev = pdev;
 	udc->pclk = pclk;
 	udc->hclk = hclk;

index a70706e..3ceed76 100644
@@ -308,6 +308,9 @@ struct usba_udc {
 	/* Protect hw registers from concurrent modifications */
 	spinlock_t lock;
 
+	/* Mutex to prevent concurrent start or stop */
+	struct mutex vbus_mutex;
+
 	void __iomem *regs;
 	void __iomem *fifo;
 

@@ -321,6 +324,7 @@ struct usba_udc {
 	struct clk *pclk;
 	struct clk *hclk;
 	struct usba_ep *usba_ep;
+	bool clocked;
 
 	u16 devstatus;