On Mon, Dec 03, 2018 at 11:45:12AM +0800, Yu Chen wrote:

quoted

The Type-C drivers use USB role switch API to inform the
system about the negotiated data role, so registering a role
switch in the DRD code in order to support platforms with
USB Type-C connectors.

Cc: Felipe Balbi <balbi@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Yu Chen <chenyu56@huawei.com>
Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>

--
v0:
The patch is provided by Heikki Krogerus. I modified and test it
on Hikey960 platform.
--
---
 drivers/usb/dwc3/core.h |  2 ++
 drivers/usb/dwc3/drd.c  | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 51 insertions(+)

You need to select USB_ROLE_SWITCH in Kconfig:

diff --git a/drivers/usb/dwc3/Kconfig b/drivers/usb/dwc3/Kconfig
index 1a0404fda596..3a0cb9f1f38a 100644
--- a/drivers/usb/dwc3/Kconfig
+++ b/drivers/usb/dwc3/Kconfig

@@ -42,6 +42,7 @@ config USB_DWC3_DUAL_ROLE
        bool "Dual Role mode"
        depends on ((USB=y || USB=USB_DWC3) && (USB_GADGET=y || USB_GADGET=USB_DWC3))
        depends on (EXTCON=y || EXTCON=USB_DWC3)
+       select USB_ROLE_SWITCH
        help
          This is the default mode of working of DWC3 controller where
          both host and gadget features are enabled.