Hi "Maciej,

I love your patch! Perhaps something to improve:

[auto build test WARNING on linus/master]
[also build test WARNING on v5.13-rc6 next-20210616]
[cannot apply to tty/tty-testing]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Maciej-W-Rozycki/serial-8250-Fixes-for-Oxford-Semiconductor-950-UARTs/20210616-201047
base:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 94f0b2d4a1d0c52035aef425da5e022bd2cb1c71
config: x86_64-randconfig-b001-20210615 (attached as .config)
compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project 64720f57bea6a6bf033feef4a5751ab9c0c3b401)
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/0day-ci/linux/commit/d3a55e8397b71f343ef931cd098d42a13faf9047
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Maciej-W-Rozycki/serial-8250-Fixes-for-Oxford-Semiconductor-950-UARTs/20210616-201047
        git checkout d3a55e8397b71f343ef931cd098d42a13faf9047
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=x86_64 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

>> drivers/tty/serial/8250/8250_pci.c:1258:18: warning: implicit conversion from 'int' to 'unsigned char' changes value from -129 to 127 [-Wconstant-conversion]
                   up->mcr_mask = ~UART_MCR_CLKSEL;
                                ~ ^~~~~~~~~~~~~~~~
   1 warning generated.


vim +1258 drivers/tty/serial/8250/8250_pci.c

  1241	
  1242	/*
  1243	 * For Tornado devices we force MCR[7] set for the Divide-by-M N/8 baud rate
  1244	 * generator prescaler (CPR and CPR2).  Otherwise no prescaler would be used.
  1245	 */
  1246	static int pci_oxsemi_tornado_setup(struct serial_private *priv,
  1247					    const struct pciserial_board *board,
  1248					    struct uart_8250_port *up, int idx)
  1249	{
  1250		struct pci_dev *dev = priv->dev;
  1251	
  1252		/* OxSemi Tornado devices are all 0xCxxx */
  1253		if (dev->vendor == PCI_VENDOR_ID_OXSEMI &&
  1254		    (dev->device & 0xF000) == 0xC000) {
  1255			up->port.get_divisor = pci_oxsemi_tornado_get_divisor;
  1256			up->port.set_divisor = pci_oxsemi_tornado_set_divisor;
  1257	
> 1258			up->mcr_mask = ~UART_MCR_CLKSEL;
  1259			up->mcr_force = UART_MCR_CLKSEL;
  1260		}
  1261	
  1262		return pci_default_setup(priv, board, up, idx);
  1263	}
  1264	

---
0-DAY CI Kernel Test Service, Intel Corporation
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