drivers/clk/clk-k210.c:717:6: warning: variable 'reg' set but not used
Palmer Dabbelt
palmerdabbelt at google.com
Fri Jun 11 20:55:41 PDT 2021
On Thu, 03 Jun 2021 03:03:14 PDT (-0700), Damien Le Moal wrote:
>> 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 at 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() ?
I have no idea what's going on here. When I try to re-build that config
I don't get any warnings or errors. That said...
>> 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);
Isn't reg unused here? That's one of the warnings.
The void* casting has been there for a while and looks like a real bug,
but asm-generic adopted our {in,out}{bwlq} implementation so I'm just
going to toss ours. I'm not quite sure why the generic ones aren't
doing arithmetic on void*, but I'm not getting warnings.
>> 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
>
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