tree: https://github.com/intel/linux-intel-lts.git 5.10/KMB-yocto head: e00ba07ec4720ed356ee8a0ae9a1f53f754b7577 commit: a34e97d69a97d031757c8e68207de5922d211f14 [8210/8457] Bug fixes for UART config: i386-randconfig-a013-20211209 (https://download.01.org/0day-ci/archive/20211210/202112100647.Xt7A5dsP-lk...) compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project 097a1cb1d5ebb3a0ec4bcaed8ba3ff6a8e33c00a) 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://github.com/intel/linux-intel-lts/commit/a34e97d69a97d031757c8e682... git remote add intel-lts https://github.com/intel/linux-intel-lts.git git fetch --no-tags intel-lts 5.10/KMB-yocto git checkout a34e97d69a97d031757c8e68207de5922d211f14 # 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=i386 SHELL=/bin/bash drivers/tty/serial/8250/ 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 >>): drivers/tty/serial/8250/8250_port.c:349:14: warning: no previous prototype for function 'au_serial_in' [-Wmissing-prototypes] unsigned int au_serial_in(struct uart_port *p, int offset) ^ drivers/tty/serial/8250/8250_port.c:349:1: note: declare 'static' if the function is not intended to be used outside of this translation unit unsigned int au_serial_in(struct uart_port *p, int offset) ^ static drivers/tty/serial/8250/8250_port.c:359:6: warning: no previous prototype for function 'au_serial_out' [-Wmissing-prototypes] void au_serial_out(struct uart_port *p, int offset, int value) ^ drivers/tty/serial/8250/8250_port.c:359:1: note: declare 'static' if the function is not intended to be used outside of this translation unit void au_serial_out(struct uart_port *p, int offset, int value) ^ static bool skip_rx = false; ^ 3 warnings generated. vim +/skip_rx +1890 drivers/tty/serial/8250/8250_port.c 33d9b8b23a73d5 Peter Hurley 2016-04-09 1881 b6830f6df8914f Peter Hurley 2015-06-27 1882 /* b6830f6df8914f Peter Hurley 2015-06-27 1883 * This handles the interrupt from one port. b6830f6df8914f Peter Hurley 2015-06-27 1884 */ b6830f6df8914f Peter Hurley 2015-06-27 1885 int serial8250_handle_irq(struct uart_port *port, unsigned int iir) b6830f6df8914f Peter Hurley 2015-06-27 1886 { b6830f6df8914f Peter Hurley 2015-06-27 1887 unsigned char status; b6830f6df8914f Peter Hurley 2015-06-27 1888 unsigned long flags; b6830f6df8914f Peter Hurley 2015-06-27 1889 struct uart_8250_port *up = up_to_u8250p(port); f19c3f6c8109b8 Vignesh Raghavendra 2020-03-19 @1890 bool skip_rx = false; b6830f6df8914f Peter Hurley 2015-06-27 1891 b6830f6df8914f Peter Hurley 2015-06-27 1892 if (iir & UART_IIR_NO_INT) b6830f6df8914f Peter Hurley 2015-06-27 1893 return 0; b6830f6df8914f Peter Hurley 2015-06-27 1894 b6830f6df8914f Peter Hurley 2015-06-27 1895 spin_lock_irqsave(&port->lock, flags); b6830f6df8914f Peter Hurley 2015-06-27 1896 b6830f6df8914f Peter Hurley 2015-06-27 1897 status = serial_port_in(port, UART_LSR); b6830f6df8914f Peter Hurley 2015-06-27 1898 f19c3f6c8109b8 Vignesh Raghavendra 2020-03-19 1899 /* f19c3f6c8109b8 Vignesh Raghavendra 2020-03-19 1900 * If port is stopped and there are no error conditions in the f19c3f6c8109b8 Vignesh Raghavendra 2020-03-19 1901 * FIFO, then don't drain the FIFO, as this may lead to TTY buffer f19c3f6c8109b8 Vignesh Raghavendra 2020-03-19 1902 * overflow. Not servicing, RX FIFO would trigger auto HW flow f19c3f6c8109b8 Vignesh Raghavendra 2020-03-19 1903 * control when FIFO occupancy reaches preset threshold, thus f19c3f6c8109b8 Vignesh Raghavendra 2020-03-19 1904 * halting RX. This only works when auto HW flow control is f19c3f6c8109b8 Vignesh Raghavendra 2020-03-19 1905 * available. f19c3f6c8109b8 Vignesh Raghavendra 2020-03-19 1906 */ f19c3f6c8109b8 Vignesh Raghavendra 2020-03-19 1907 if (!(status & (UART_LSR_FIFOE | UART_LSR_BRK_ERROR_BITS)) && f19c3f6c8109b8 Vignesh Raghavendra 2020-03-19 1908 (port->status & (UPSTAT_AUTOCTS | UPSTAT_AUTORTS)) && f19c3f6c8109b8 Vignesh Raghavendra 2020-03-19 1909 !(port->read_status_mask & UART_LSR_DR)) f19c3f6c8109b8 Vignesh Raghavendra 2020-03-19 1910 skip_rx = true; f19c3f6c8109b8 Vignesh Raghavendra 2020-03-19 1911 a34e97d69a97d0 Aman Kumar 2021-03-09 1912 if (port->iir_rdi) { a34e97d69a97d0 Aman Kumar 2021-03-09 1913 if (status & (UART_LSR_DR | UART_LSR_BI) && a34e97d69a97d0 Aman Kumar 2021-03-09 1914 iir & UART_IIR_RDI) { 33d9b8b23a73d5 Peter Hurley 2016-04-09 1915 if (!up->dma || handle_rx_dma(up, iir)) b6830f6df8914f Peter Hurley 2015-06-27 1916 status = serial8250_rx_chars(up, status); b6830f6df8914f Peter Hurley 2015-06-27 1917 } a34e97d69a97d0 Aman Kumar 2021-03-09 1918 } else { a34e97d69a97d0 Aman Kumar 2021-03-09 1919 if (status & (UART_LSR_DR | UART_LSR_BI)) { a34e97d69a97d0 Aman Kumar 2021-03-09 1920 if (!up->dma || handle_rx_dma(up, iir)) a34e97d69a97d0 Aman Kumar 2021-03-09 1921 status = serial8250_rx_chars(up, status); a34e97d69a97d0 Aman Kumar 2021-03-09 1922 } a34e97d69a97d0 Aman Kumar 2021-03-09 1923 } b6830f6df8914f Peter Hurley 2015-06-27 1924 serial8250_modem_status(up); db1b5bc047b3ca Rautkoski Kimmo EXT 2019-05-24 1925 if ((!up->dma || up->dma->tx_err) && (status & UART_LSR_THRE) && db1b5bc047b3ca Rautkoski Kimmo EXT 2019-05-24 1926 (up->ier & UART_IER_THRI)) b6830f6df8914f Peter Hurley 2015-06-27 1927 serial8250_tx_chars(up); b6830f6df8914f Peter Hurley 2015-06-27 1928 596f63da42b928 Douglas Anderson 2018-10-30 1929 uart_unlock_and_check_sysrq(port, flags); b6830f6df8914f Peter Hurley 2015-06-27 1930 return 1; b6830f6df8914f Peter Hurley 2015-06-27 1931 } b6830f6df8914f Peter Hurley 2015-06-27 1932 EXPORT_SYMBOL_GPL(serial8250_handle_irq); b6830f6df8914f Peter Hurley 2015-06-27 1933 :::::: The code at line 1890 was first introduced by commit :::::: f19c3f6c8109b8bab000afd35580929958e087a9 serial: 8250_port: Don't service RX FIFO if throttled :::::: TO: Vignesh Raghavendra <vigneshr(a)ti.com&gt; :::::: CC: Greg Kroah-Hartman <gregkh(a)linuxfoundation.org&gt; --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org