usb: dwc3: Enable GBit Ethernet on Odroid XU4

[Jochen Sprickerhof <git@jochen.sprickerhof.de>]

Note that it only works with USB_XHCI_PLATFORM=y. Also it needs a hard
reset when coming from an unpatched kernel.

This was included in the original patch in
https://patchwork.kernel.org/patch/9992809/ but got dropped when
accepted in d8c80bb3b55b phy: exynos5-usbdrd: Calibrate LOS levels for
exynos5420/5800.

Old behaviour:

$ lsusb -t
/:  Bus 06.Port 1: Dev 1, Class=root_hub, Driver=xhci-hcd/1p, 5000M
/:  Bus 05.Port 1: Dev 1, Class=root_hub, Driver=xhci-hcd/1p, 480M
    |__ Port 1: Dev 2, If 0, Class=Vendor Specific Class, Driver=r8152, 480M

New behaviour:

$ lsusb -t
/:  Bus 06.Port 1: Dev 1, Class=root_hub, Driver=xhci-hcd/1p, 5000M
    |__ Port 1: Dev 2, If 0, Class=Vendor Specific Class, Driver=r8152, 5000M

Tested on Debian unstable using u-boot-exynos (2018.11+dfsg-2) and Linux
4.19.14.

Signed-off-by: Jochen Sprickerhof <git@jochen.sprickerhof.de>
---

Hi,

I'm not sure why this it only works with the driver compiled into the
kernel nor why it needs a hard reset or why it was the line was dropped
when the patch was accepted. Would be great to get some feedback of the
authors.

Cheers Jochen

 drivers/usb/dwc3/core.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index a1b126f90261..0008bccc30aa 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -1169,7 +1169,8 @@ static int dwc3_core_init_mode(struct dwc3 *dwc)
 				dev_err(dev, "failed to initialize host\n");
 			return ret;
 		}
-		phy_calibrate(dwc->usb2_generic_phy);
+		if (dwc->usb2_generic_phy)
+			phy_calibrate(dwc->usb2_generic_phy);
 		break;
 	case USB_DR_MODE_OTG:
 		INIT_WORK(&dwc->drd_work, __dwc3_set_mode);