reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/pci/pci.git/commit/?id=8ba5de8db3acd06e35c42ecd0becc38134348df3
        git remote add pci https://git.kernel.org/pub/scm/linux/kernel/git/pci/pci.git
        git fetch --no-tags pci controller/dwc-rcar-gen4
        git checkout 8ba5de8db3acd06e35c42ecd0becc38134348df3

        # install sparc64 cross compiling tool for clang build
        # apt-get install binutils-sparc64-linux-gnu
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests

        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-20 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=sparc64 olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-20 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=sparc64 SHELL=/bin/bash drivers/pci/controller/dwc/