Hi Jiaxun, FYI, the error/warning still remains. tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master head: 44db63d1ad8d71c6932cbe007eb41f31c434d140 commit: b13812ddea615b6507beef24f76540c0c1143c5c MIPS: Loongson2ef: Disable Loongson MMI instructions date: 9 months ago config: mips-randconfig-r021-20210625 (attached as .config) compiler: mips64el-linux-gcc (GCC) 9.3.0 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 # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b13812ddea615b6507beef24f76540c0c1143c5c git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git git fetch --no-tags linus master git checkout b13812ddea615b6507beef24f76540c0c1143c5c # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=mips If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot All warnings (new ones prefixed by >>): >> arch/mips/loongson2ef/common/cs5536/cs5536_mfgpt.c:195:12: warning: no previous prototype for 'init_mfgpt_clocksource' [-Wmissing-prototypes] 195 | int __init init_mfgpt_clocksource(void) | ^~~~~~~~~~~~~~~~~~~~~~ vim +/init_mfgpt_clocksource +195 arch/mips/loongson2ef/common/cs5536/cs5536_mfgpt.c 916daba8a9f261 arch/mips/loongson/common/cs5536/cs5536_mfgpt.c Wu Zhangjin 2009-11-17 194 916daba8a9f261 arch/mips/loongson/common/cs5536/cs5536_mfgpt.c Wu Zhangjin 2009-11-17 @195 int __init init_mfgpt_clocksource(void) 916daba8a9f261 arch/mips/loongson/common/cs5536/cs5536_mfgpt.c Wu Zhangjin 2009-11-17 196 { 916daba8a9f261 arch/mips/loongson/common/cs5536/cs5536_mfgpt.c Wu Zhangjin 2009-11-17 197 if (num_possible_cpus() > 1) /* MFGPT does not scale! */ 916daba8a9f261 arch/mips/loongson/common/cs5536/cs5536_mfgpt.c Wu Zhangjin 2009-11-17 198 return 0; 916daba8a9f261 arch/mips/loongson/common/cs5536/cs5536_mfgpt.c Wu Zhangjin 2009-11-17 199 75c4fd8c7862f3 arch/mips/loongson/common/cs5536/cs5536_mfgpt.c John Stultz 2010-04-26 200 return clocksource_register_hz(&clocksource_mfgpt, MFGPT_TICK_RATE); 916daba8a9f261 arch/mips/loongson/common/cs5536/cs5536_mfgpt.c Wu Zhangjin 2009-11-17 201 } 916daba8a9f261 arch/mips/loongson/common/cs5536/cs5536_mfgpt.c Wu Zhangjin 2009-11-17 202 :::::: The code at line 195 was first introduced by commit :::::: 916daba8a9f2617ded8b9255e6b39f066ef60178 MIPS: Lemote 2F: Add cs5536 MFGPT timer support :::::: TO: Wu Zhangjin :::::: CC: Ralf Baechle --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org