[PATCH] usb: dwc3: usb/dwc3: fake dissconnect event when turn off pullup

[changbin.du@intel.com]

From: "Du, Changbin" <changbin.du@intel.com>

The dwc3 controller can't generate a disconnect event after it is
stopped. Thus gadget dissconnect callback is not invoked when do
soft dissconnect. Call dissconnect here to workaround this issue.

Note, most time we still see disconnect be called that because
it is invoked by dwc3_gadget_reset_interrupt(). But if we
disconnect cable once pullup disabled quickly, issue can be
observed.

Signed-off-by: Du, Changbin <changbin.du@intel.com>
---
 drivers/usb/dwc3/gadget.c | 33 ++++++++++++++++++++++++---------
 1 file changed, 24 insertions(+), 9 deletions(-)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 8e4a1b1..cd73187 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -1566,6 +1566,15 @@ static int dwc3_gadget_run_stop(struct dwc3 *dwc, int is_on, int suspend)
 	return 0;
 }
 
+static void dwc3_disconnect_gadget(struct dwc3 *dwc)
+{
+	if (dwc->gadget_driver && dwc->gadget_driver->disconnect) {
+		spin_unlock(&dwc->lock);
+		dwc->gadget_driver->disconnect(&dwc->gadget);
+		spin_lock(&dwc->lock);
+	}
+}
+
 static int dwc3_gadget_pullup(struct usb_gadget *g, int is_on)
 {
 	struct dwc3		*dwc = gadget_to_dwc(g);
@@ -1575,6 +1584,21 @@ static int dwc3_gadget_pullup(struct usb_gadget *g, int is_on)
 	is_on = !!is_on;
 
 	spin_lock_irqsave(&dwc->lock, flags);
+	/**
+	 * WORKAROUND: The dwc3 controller can't generate a disconnect
+	 * event after it is stopped. Thus gadget dissconnect callback
+	 * is not invoked when do soft dissconnect. Call dissconnect
+	 * here to workaround this issue.
+	 * Note, most time we still see disconnect be called that because
+	 * it is invoked by dwc3_gadget_reset_interrupt(). But if we
+	 * disconnect cable once pullup disabled quickly, issue can be
+	 * observed.
+	 */
+	if (!is_on && (dwc->gadget.speed != USB_SPEED_UNKNOWN)) {
+		dev_dbg(dwc->dev, "fake dissconnect event on pullup off\n");
+		dwc3_disconnect_gadget(dwc);
+		dwc->gadget.speed = USB_SPEED_UNKNOWN;
+	}
 	ret = dwc3_gadget_run_stop(dwc, is_on, false);
 	spin_unlock_irqrestore(&dwc->lock, flags);
 
@@ -2144,15 +2168,6 @@ static void dwc3_endpoint_interrupt(struct dwc3 *dwc,
 	}
 }
 
-static void dwc3_disconnect_gadget(struct dwc3 *dwc)
-{
-	if (dwc->gadget_driver && dwc->gadget_driver->disconnect) {
-		spin_unlock(&dwc->lock);
-		dwc->gadget_driver->disconnect(&dwc->gadget);
-		spin_lock(&dwc->lock);
-	}
-}
-
 static void dwc3_suspend_gadget(struct dwc3 *dwc)
 {
 	if (dwc->gadget_driver && dwc->gadget_driver->suspend) {
-- 
2.7.4