DWC3 driver uses of_usb_get_phy_mode() which is implemented in drivers/usb/phy/of.c and in bare minimal configuration it might not be pulled in kernel binary.
In case of ARC or ARM this could be easily reproduced with "allnodefconfig" +CONFIG_USB=m +CONFIG_USB_DWC3=m. On building all ends-up with: ---------------------->8------------------ Kernel: arch/arm/boot/Image is ready Kernel: arch/arm/boot/zImage is ready Building modules, stage 2. MODPOST 5 modules ERROR: "of_usb_get_phy_mode" [drivers/usb/dwc3/dwc3.ko] undefined! make[1]: *** [__modpost] Error 1 make: *** [modules] Error 2 ---------------------->8------------------ Signed-off-by: Alexey Brodkin <[email protected]> Cc: Greg Kroah-Hartman <[email protected]> Cc: Masahiro Yamada <[email protected]> Cc: Geert Uytterhoeven <[email protected]> Cc: Nicolas Pitre <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Felipe Balbi <[email protected]> Cc: Felix Fietkau <[email protected]> Cc: Jeremy Kerr <[email protected]> Cc: [email protected] Cc: [email protected] --- drivers/Makefile | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/Makefile b/drivers/Makefile index 2eced9afba53..8f8bdc9e3d29 100644 --- a/drivers/Makefile +++ b/drivers/Makefile @@ -104,6 +104,7 @@ obj-$(CONFIG_USB_PHY) += usb/ obj-$(CONFIG_USB) += usb/ obj-$(CONFIG_PCI) += usb/ obj-$(CONFIG_USB_GADGET) += usb/ +obj-$(CONFIG_OF) += usb/ obj-$(CONFIG_SERIO) += input/serio/ obj-$(CONFIG_GAMEPORT) += input/gameport/ obj-$(CONFIG_INPUT) += input/ -- 2.7.4
