Re: drivers/clk/clk-k210.c:717:6: warning: variable 'reg' set but not used

[Damien Le Moal <Damien.LeMoal@wdc.com>]

On 2021/06/03 18:35, kernel test robot wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   324c92e5e0ee0e993bdb106fac407846ed677f6b
> commit: c6ca7616f7d5c2ce166280107ba74db1d528fcb7 clk: Add RISC-V Canaan Kendryte K210 clock driver
> date:   3 months ago
> config: riscv-randconfig-r033-20210603 (attached as .config)
> compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project d8e0ae9a76a62bdc6117630d59bf9967ac9bb4ea)
> 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 riscv cross compiling tool for clang build
>         # apt-get install binutils-riscv64-linux-gnu
>         # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c6ca7616f7d5c2ce166280107ba74db1d528fcb7
>         git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
>         git fetch --no-tags linus master
>         git checkout c6ca7616f7d5c2ce166280107ba74db1d528fcb7
>         # save the attached .config to linux build tree
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=riscv 
> 
> 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 >>):
> 
>    In file included from drivers/clk/clk-k210.c:8:
>    In file included from include/linux/io.h:13:
>    In file included from arch/riscv/include/asm/io.h:149:
>    include/asm-generic/io.h:556:9: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
>            return inb(addr);
>                   ^~~~~~~~~
>    arch/riscv/include/asm/io.h:55:76: note: expanded from macro 'inb'
>    #define inb(c)          ({ u8  __v; __io_pbr(); __v = readb_cpu((void*)(PCI_IOBASE + (c))); __io_par(__v); __v; })
>                                                                            ~~~~~~~~~~ ^
>    arch/riscv/include/asm/mmio.h:87:48: note: expanded from macro 'readb_cpu'
>    #define readb_cpu(c)            ({ u8  __r = __raw_readb(c); __r; })
>                                                             ^
>    In file included from drivers/clk/clk-k210.c:8:
>    In file included from include/linux/io.h:13:
>    In file included from arch/riscv/include/asm/io.h:149:
>    include/asm-generic/io.h:564:9: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
>            return inw(addr);
>                   ^~~~~~~~~
>    arch/riscv/include/asm/io.h:56:76: note: expanded from macro 'inw'
>    #define inw(c)          ({ u16 __v; __io_pbr(); __v = readw_cpu((void*)(PCI_IOBASE + (c))); __io_par(__v); __v; })
>                                                                            ~~~~~~~~~~ ^
>    arch/riscv/include/asm/mmio.h:88:76: note: expanded from macro 'readw_cpu'
>    #define readw_cpu(c)            ({ u16 __r = le16_to_cpu((__force __le16)__raw_readw(c)); __r; })
>                                                                                         ^
>    include/uapi/linux/byteorder/little_endian.h:36:51: note: expanded from macro '__le16_to_cpu'
>    #define __le16_to_cpu(x) ((__force __u16)(__le16)(x))
>                                                      ^
>    In file included from drivers/clk/clk-k210.c:8:
>    In file included from include/linux/io.h:13:
>    In file included from arch/riscv/include/asm/io.h:149:
>    include/asm-generic/io.h:572:9: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
>            return inl(addr);
>                   ^~~~~~~~~
>    arch/riscv/include/asm/io.h:57:76: note: expanded from macro 'inl'
>    #define inl(c)          ({ u32 __v; __io_pbr(); __v = readl_cpu((void*)(PCI_IOBASE + (c))); __io_par(__v); __v; })
>                                                                            ~~~~~~~~~~ ^
>    arch/riscv/include/asm/mmio.h:89:76: note: expanded from macro 'readl_cpu'
>    #define readl_cpu(c)            ({ u32 __r = le32_to_cpu((__force __le32)__raw_readl(c)); __r; })
>                                                                                         ^
>    include/uapi/linux/byteorder/little_endian.h:34:51: note: expanded from macro '__le32_to_cpu'
>    #define __le32_to_cpu(x) ((__force __u32)(__le32)(x))
>                                                      ^
>    In file included from drivers/clk/clk-k210.c:8:
>    In file included from include/linux/io.h:13:
>    In file included from arch/riscv/include/asm/io.h:149:
>    include/asm-generic/io.h:580:2: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
>            outb(value, addr);
>            ^~~~~~~~~~~~~~~~~
>    arch/riscv/include/asm/io.h:59:68: note: expanded from macro 'outb'
>    #define outb(v,c)       ({ __io_pbw(); writeb_cpu((v),(void*)(PCI_IOBASE + (c))); __io_paw(); })
>                                                                  ~~~~~~~~~~ ^
>    arch/riscv/include/asm/mmio.h:91:52: note: expanded from macro 'writeb_cpu'
>    #define writeb_cpu(v, c)        ((void)__raw_writeb((v), (c)))
>                                                              ^
>    In file included from drivers/clk/clk-k210.c:8:
>    In file included from include/linux/io.h:13:
>    In file included from arch/riscv/include/asm/io.h:149:
>    include/asm-generic/io.h:588:2: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
>            outw(value, addr);
>            ^~~~~~~~~~~~~~~~~
>    arch/riscv/include/asm/io.h:60:68: note: expanded from macro 'outw'
>    #define outw(v,c)       ({ __io_pbw(); writew_cpu((v),(void*)(PCI_IOBASE + (c))); __io_paw(); })
>                                                                  ~~~~~~~~~~ ^
>    arch/riscv/include/asm/mmio.h:92:76: note: expanded from macro 'writew_cpu'
>    #define writew_cpu(v, c)        ((void)__raw_writew((__force u16)cpu_to_le16(v), (c)))
>                                                                                      ^
>    In file included from drivers/clk/clk-k210.c:8:
>    In file included from include/linux/io.h:13:
>    In file included from arch/riscv/include/asm/io.h:149:
>    include/asm-generic/io.h:596:2: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
>            outl(value, addr);
>            ^~~~~~~~~~~~~~~~~
>    arch/riscv/include/asm/io.h:61:68: note: expanded from macro 'outl'
>    #define outl(v,c)       ({ __io_pbw(); writel_cpu((v),(void*)(PCI_IOBASE + (c))); __io_paw(); })
>                                                                  ~~~~~~~~~~ ^
>    arch/riscv/include/asm/mmio.h:93:76: note: expanded from macro 'writel_cpu'
>    #define writel_cpu(v, c)        ((void)__raw_writel((__force u32)cpu_to_le32(v), (c)))
>                                                                                      ^
>    In file included from drivers/clk/clk-k210.c:8:
>    In file included from include/linux/io.h:13:
>    In file included from arch/riscv/include/asm/io.h:149:
>    include/asm-generic/io.h:1005:55: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
>            return (port > MMIO_UPPER_LIMIT) ? NULL : PCI_IOBASE + port;
>                                                      ~~~~~~~~~~ ^
>>> drivers/clk/clk-k210.c:717:6: warning: variable 'reg' set but not used [-Wunused-but-set-variable]
>            u32 reg;
>                ^
>    8 warnings generated.
> 
> 
> vim +/reg +717 drivers/clk/clk-k210.c
> 
>    710	
>    711	static int k210_clk_set_parent(struct clk_hw *hw, u8 index)
>    712	{
>    713		struct k210_clk *kclk = to_k210_clk(hw);
>    714		struct k210_sysclk *ksc = kclk->ksc;
>    715		struct k210_clk_cfg *cfg = &k210_clk_cfgs[kclk->id];
>    716		unsigned long flags;
>  > 717		u32 reg;

Palmer,

I do not think this driver is the real cause of this error. Did something change
recently with risc-v mmio readl()/writel() ?

>    718	
>    719		spin_lock_irqsave(&ksc->clk_lock, flags);
>    720		reg = readl(ksc->regs + cfg->mux_reg);
>    721		if (index)
>    722			reg |= BIT(cfg->mux_bit);
>    723		else
>    724			reg &= ~BIT(cfg->mux_bit);
>    725		spin_unlock_irqrestore(&ksc->clk_lock, flags);
>    726	
>    727		return 0;
>    728	}
>    729	
> 
> ---
> 0-DAY CI Kernel Test Service, Intel Corporation
> https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
> 


-- 
Damien Le Moal
Western Digital Research