usb: bdc: Adb shows offline after resuming from S2

On Android systems, After temporarily putting device to S2 by
short pressing the power button on the remote, the display turns
off. Then press the power button to turn the display back up. Adb
devices would show the devices is offline. It needs a physical
disconnect of the usb cable or power cycle to bring the device
back online. The device is operational otherwise.

The problem is that during S2 resume, the ADB gadget driver could
not link back with the BDC driver because the endpoint flags were
cleared. The fix is to clear the endpoint flags for the disconnect
case only and not for S2 exit.
Signed-off-by: Al Cooper <alcooperx@gmail.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>

drivers/usb/gadget/udc/bdc/bdc_core.c

@@ -288,9 +288,13 @@ static void bdc_mem_init(struct bdc *bdc, bool reinit)
 		/* Initialize SRR to 0 */
 		memset(bdc->srr.sr_bds, 0,
 					NUM_SR_ENTRIES * sizeof(struct bdc_bd));
-		/* clear ep flags to avoid post disconnect stops/deconfigs */
-		for (i = 1; i < bdc->num_eps; ++i)
-			bdc->bdc_ep_array[i]->flags = 0;
+		/*
+		 * clear ep flags to avoid post disconnect stops/deconfigs but
+		 * not during S2 exit
+		 */
+		if (!bdc->gadget.speed)
+			for (i = 1; i < bdc->num_eps; ++i)
+				bdc->bdc_ep_array[i]->flags = 0;
 	} else {
 		/* One time initiaization only */
 		/* Enable status report function pointers */