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... 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(a)intel.com&gt; All warnings (new ones prefixed by >>): 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 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