usb: dwc3: core: support optional PHYs

Since PHYs for dwc3 is optional (not all SoCs having PHYs for DWC3
should be programmed), do not return from probe if the USB PHY library
returns -ENODEV as that indicates the platform does not have a
programmable PHY.

While this can be considered as a temporary fix, a long term solution
would be to add 'nop' PHY for platforms that does not have programmable
PHY.
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Reviewed-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/dwc3/core.c

@@ -534,32 +534,26 @@ static int dwc3_probe(struct platform_device *pdev)
 
 	if (IS_ERR(dwc->usb2_phy)) {
 		ret = PTR_ERR(dwc->usb2_phy);
-
-		/*
-		 * if -ENXIO is returned, it means PHY layer wasn't
-		 * enabled, so it makes no sense to return -EPROBE_DEFER
-		 * in that case, since no PHY driver will ever probe.
-		 */
-		if (ret == -ENXIO)
+		if (ret == -ENXIO || ret == -ENODEV) {
+			dwc->usb2_phy = NULL;
+		} else if (ret == -EPROBE_DEFER) {
 			return ret;
-
+		} else {
 			dev_err(dev, "no usb2 phy configured\n");
-		return -EPROBE_DEFER;
+			return ret;
+		}
 	}
 
 	if (IS_ERR(dwc->usb3_phy)) {
 		ret = PTR_ERR(dwc->usb3_phy);
-
-		/*
-		 * if -ENXIO is returned, it means PHY layer wasn't
-		 * enabled, so it makes no sense to return -EPROBE_DEFER
-		 * in that case, since no PHY driver will ever probe.
-		 */
-		if (ret == -ENXIO)
+		if (ret == -ENXIO || ret == -ENODEV) {
+			dwc->usb3_phy = NULL;
+		} else if (ret == -EPROBE_DEFER) {
 			return ret;
-
+		} else {
 			dev_err(dev, "no usb3 phy configured\n");
-		return -EPROBE_DEFER;
+			return ret;
+		}
 	}
 
 	dwc->xhci_resources[0].start = res->start;