Hi Piyush, FYI, the error/warning still remains. tree: https://github.com/Xilinx/linux-xlnx xlnx_rebase_v5.4 head: 2f686fa6c0bf7fa168dc45dd7ce1359217212911 commit: 782658c51bbcd85a39a5d9a51b57224f185d7670 [906/1765] usb: dwc3: Correct errors when dwc3 loaded as module config: x86_64-randconfig-r013-20210720 (attached as .config) compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project 87039c048c0cbc3d8cbba86187269b006bf2f373) reproduce (this is a W=1 build): wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross # install x86_64 cross compiling tool for clang build # apt-get install binutils-x86-64-linux-gnu # https://github.com/Xilinx/linux-xlnx/commit/782658c51bbcd85a39a5d9a51b572... git remote add xlnx https://github.com/Xilinx/linux-xlnx git fetch --no-tags xlnx xlnx_rebase_v5.4 git checkout 782658c51bbcd85a39a5d9a51b57224f185d7670 # save the attached .config to linux build tree mkdir build_dir COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross O=build_dir ARCH=x86_64 SHELL=/bin/bash M=drivers/usb/dwc3 If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All error/warnings (new ones prefixed by >>): In file included from drivers/usb/dwc3/core.c:36: drivers/usb/dwc3/core.h:1429:6: warning: no previous prototype for function 'dwc3_simple_wakeup_capable' [-Wmissing-prototypes] void dwc3_simple_wakeup_capable(struct device *dev, bool wakeup) ^ drivers/usb/dwc3/core.h:1429:1: note: declare 'static' if the function is not intended to be used outside of this translation unit void dwc3_simple_wakeup_capable(struct device *dev, bool wakeup) ^ static drivers/usb/dwc3/core.h:1431:6: warning: no previous prototype for function 'dwc3_set_simple_data' [-Wmissing-prototypes] void dwc3_set_simple_data(struct dwc3 *dwc) ^ drivers/usb/dwc3/core.h:1431:1: note: declare 'static' if the function is not intended to be used outside of this translation unit void dwc3_set_simple_data(struct dwc3 *dwc) ^ static void dwc3_simple_check_quirks(struct dwc3 *dwc) ^ drivers/usb/dwc3/core.h:1433:1: note: declare 'static' if the function is not intended to be used outside of this translation unit void dwc3_simple_check_quirks(struct dwc3 *dwc) ^ static 3 warnings generated. -- -- --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org