Hi Arnd, First bad commit (maybe != root cause): tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master head: e783362eb54cd99b2cac8b3a9aeac942e6f6ac07 commit: 606b102876e3741851dfb09d53f3ee57f650a52c drm: fb_helper: fix CONFIG_FB dependency date: 4 months ago config: mips-randconfig-r002-20220120 (https://download.01.org/0day-ci/archive/20220123/202201231941.OMnmf2JQ-lk...) compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project f7b7138a62648f4019c55e4671682af1f851f295) 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 mips cross compiling tool for clang build # apt-get install binutils-mips-linux-gnu # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit... git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git git fetch --no-tags linus master git checkout 606b102876e3741851dfb09d53f3ee57f650a52c # save the config file to linux build tree mkdir build_dir COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=mips SHELL=/bin/bash 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 >>, old ones prefixed by <<): -- arch/mips/boot/compressed/decompress.c:42:6: warning: no previous prototype for function 'error' [-Wmissing-prototypes] void error(char *x) ^ arch/mips/boot/compressed/decompress.c:42:1: note: declare 'static' if the function is not intended to be used outside of this translation unit void error(char *x) ^ static In file included from arch/mips/boot/compressed/decompress.c:64: In file included from arch/mips/boot/compressed/../../../../lib/decompress_unlz4.c:10: int LZ4_decompress_safe_forceExtDict(const char *source, char *dest, ^ arch/mips/boot/compressed/../../../../lib/lz4/lz4_decompress.c:506:1: note: declare 'static' if the function is not intended to be used outside of this translation unit int LZ4_decompress_safe_forceExtDict(const char *source, char *dest, ^ static arch/mips/boot/compressed/decompress.c:85:6: warning: no previous prototype for function '__stack_chk_fail' [-Wmissing-prototypes] void __stack_chk_fail(void) ^ arch/mips/boot/compressed/decompress.c:85:1: note: declare 'static' if the function is not intended to be used outside of this translation unit void __stack_chk_fail(void) ^ static arch/mips/boot/compressed/decompress.c:90:6: warning: no previous prototype for function 'decompress_kernel' [-Wmissing-prototypes] void decompress_kernel(unsigned long boot_heap_start) ^ arch/mips/boot/compressed/decompress.c:90:1: note: declare 'static' if the function is not intended to be used outside of this translation unit void decompress_kernel(unsigned long boot_heap_start) ^ static 4 warnings generated. --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org