usb: dwc3: gadget: Avoid runtime resume if disabling pullup

If the device is already in the runtime suspended state, any call to the pullup routine will issue a runtime resume on the DWC3 core device. If the USB gadget is disabling the pullup, then avoid having to issue a runtime resume, as DWC3 gadget has already been halted/stopped.

This fixes an issue where the following condition occurs:

usb_gadget_remove_driver()
-->usb_gadget_disconnect()
-->dwc3_gadget_pullup(0)
-->pm_runtime_get_sync() -> ret = 0
-->pm_runtime_put() [async]
-->usb_gadget_udc_stop()
-->dwc3_gadget_stop()
-->dwc->gadget_driver = NULL
...

dwc3_suspend_common()
-->dwc3_gadget_suspend()
-->DWC3 halt/stop routine skipped, driver_data == NULL

This leads to a situation where the DWC3 gadget is not properly stopped, as the runtime resume would have re-enabled EP0 and event interrupts, and since we avoided the DWC3 gadget suspend, these resources were never disabled.

---
Changes in v2:
- Added fixes tag with the problem commit.

 drivers/usb/dwc3/gadget.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

index a29a4ca..5d08454 100644
@@ -2435,6 +2435,17 @@ static int dwc3_gadget_pullup(struct usb_gadget *g, int is_on)
 	}
 
 	/*
+	 * Avoid issuing a runtime resume if the device is already in the
+	 * suspended state during gadget disconnect.  DWC3 gadget was already
+	 * halted/stopped during runtime suspend.
+	 */
+	if (!is_on) {
+		pm_runtime_barrier(dwc->dev);
+		if (pm_runtime_suspended(dwc->dev))
+			return 0;
+	}
+
+	/*
 	 * Check the return value for successful resume, or error.  For a
 	 * successful resume, the DWC3 runtime PM resume routine will handle
 	 * the run stop sequence, so avoid duplicate operations here.

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