Hi Christoph,

FYI, the error/warning still remains.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   65f0d2414b7079556fbbcc070b3d1c9f9587606d
commit: 5ceda74093a5c1c3f42a02b894df031f3bbc9af1 dma-direct: rename and cleanup __phys_to_dma
date:   4 months ago
config: mips-randconfig-r023-20210113 (attached as .config)
compiler: mips-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=5ceda74093a5c1c3f42a02b894df031f3bbc9af1
        git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
        git fetch --no-tags linus master
        git checkout 5ceda74093a5c1c3f42a02b894df031f3bbc9af1
        # 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 <lkp@intel.com>

All warnings (new ones prefixed by >>):

>> arch/mips/bmips/dma.c:43:12: warning: no previous prototype for 'phys_to_dma' [-Wmissing-prototypes]
      43 | dma_addr_t phys_to_dma(struct device *dev, phys_addr_t pa)
         |            ^~~~~~~~~~~
   arch/mips/bmips/dma.c:55:13: warning: no previous prototype for 'dma_to_phys' [-Wmissing-prototypes]
      55 | phys_addr_t dma_to_phys(struct device *dev, dma_addr_t dma_addr)
         |             ^~~~~~~~~~~
   arch/mips/bmips/dma.c:67:6: warning: no previous prototype for 'arch_sync_dma_for_cpu_all' [-Wmissing-prototypes]
      67 | void arch_sync_dma_for_cpu_all(void)
         |      ^~~~~~~~~~~~~~~~~~~~~~~~~


vim +/phys_to_dma +43 arch/mips/bmips/dma.c

    42	
  > 43	dma_addr_t phys_to_dma(struct device *dev, phys_addr_t pa)
    44	{
    45		struct bmips_dma_range *r;
    46	
    47		for (r = bmips_dma_ranges; r && r->size; r++) {
    48			if (pa >= r->child_addr &&
    49			    pa < (r->child_addr + r->size))
    50				return pa - r->child_addr + r->parent_addr;
    51		}
    52		return pa;
    53	}
    54	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org