[kbuild-all] drivers/tty/serial/ucc_uart.c:286:6: warning: no previous prototype for 'qe_uart_set_mctrl'

Hi Rasmus, First bad commit (maybe != root cause): tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master head: 07a56bb875afbe39dabbf6ba7b83783d166863db commit: 5a35435ef4e6e4bd2aabd6706b146b298a9cffe5 soc: fsl: qe: remove PPC32 dependency from CONFIG_QUICC_ENGINE date: 7 months ago config: c6x-randconfig-r011-20200717 (attached as .config) compiler: c6x-elf-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 git checkout 5a35435ef4e6e4bd2aabd6706b146b298a9cffe5 # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=c6x If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All warnings (new ones prefixed by >>): 286 | void qe_uart_set_mctrl(struct uart_port *port, unsigned int mctrl) | ^~~~~~~~~~~~~~~~~ vim +/qe_uart_set_mctrl +286 drivers/tty/serial/ucc_uart.c d7584ed2b994a5 drivers/serial/ucc_uart.c Timur Tabi 2008-01-15 278 d7584ed2b994a5 drivers/serial/ucc_uart.c Timur Tabi 2008-01-15 279 /* d7584ed2b994a5 drivers/serial/ucc_uart.c Timur Tabi 2008-01-15 280 * Set the modem control lines d7584ed2b994a5 drivers/serial/ucc_uart.c Timur Tabi 2008-01-15 281 * d7584ed2b994a5 drivers/serial/ucc_uart.c Timur Tabi 2008-01-15 282 * Although the QE can control the modem control lines (e.g. CTS), we d7584ed2b994a5 drivers/serial/ucc_uart.c Timur Tabi 2008-01-15 283 * don't need that support. This function must exist, however, otherwise d7584ed2b994a5 drivers/serial/ucc_uart.c Timur Tabi 2008-01-15 284 * the kernel will panic. d7584ed2b994a5 drivers/serial/ucc_uart.c Timur Tabi 2008-01-15 285 */ d7584ed2b994a5 drivers/serial/ucc_uart.c Timur Tabi 2008-01-15 @286 void qe_uart_set_mctrl(struct uart_port *port, unsigned int mctrl) d7584ed2b994a5 drivers/serial/ucc_uart.c Timur Tabi 2008-01-15 287 { d7584ed2b994a5 drivers/serial/ucc_uart.c Timur Tabi 2008-01-15 288 } d7584ed2b994a5 drivers/serial/ucc_uart.c Timur Tabi 2008-01-15 289 :::::: The code at line 286 was first introduced by commit :::::: d7584ed2b994a572326650b0c4d2c25961e6f49d [POWERPC] qe-uart: add support for Freescale QUICCEngine UART :::::: TO: Timur Tabi <timur(a)freescale.com&gt; :::::: CC: Kumar Gala <galak(a)kernel.crashing.org&gt; --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org