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.

Fixes: 77adb8bd ("usb: dwc3: gadget: Allow runtime suspend if UDC unbinded")
Cc: stable <stable@vger.kernel.org>
Acked-by: Felipe Balbi <balbi@kernel.org>
Signed-off-by: Wesley Cheng <wcheng@codeaurora.org>
Link: https://lore.kernel.org/r/1628058245-30692-1-git-send-email-wcheng@codeaurora.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/dwc3/gadget.c

@@ -2256,6 +2256,17 @@ 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