Re: [clk:clk-sunplus 1/1] drivers/clk/clk-sp7021.c:316:8: warning: result of comparison of constant 18446744073709551615 with expression of type 'typeof (_Generic((_m), char: (unsigned char)0, unsigned char: (unsigned char)0, signed char: (unsigned char)0, unsigned short: (unsigne...

[Nathan Chancellor <nathan@kernel.org>]

On Wed, Mar 22, 2023 at 10:39:06AM -0700, Stephen Boyd wrote:
> Quoting kernel test robot (2023-03-22 04:17:48)
> > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/clk/linux.git clk-sunplus
> > head:   d54c1fd4a51e8fbc7f9da86b0cd338a4f7cd2bb2
> > commit: d54c1fd4a51e8fbc7f9da86b0cd338a4f7cd2bb2 [1/1] clk: Add Sunplus SP7021 clock driver
> > config: mips-randconfig-r012-20230322 (https://download.01.org/0day-ci/archive/20230322/202303221947.pXP2v4xJ-lkp@intel.com/config)
> > compiler: clang version 17.0.0 (https://github.com/llvm/llvm-project 67409911353323ca5edf2049ef0df54132fa1ca7)
> > 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 mips cross compiling tool for clang build
> >         # apt-get install binutils-mipsel-linux-gnu
> >         # https://git.kernel.org/pub/scm/linux/kernel/git/clk/linux.git/commit/?id=d54c1fd4a51e8fbc7f9da86b0cd338a4f7cd2bb2
> >         git remote add clk https://git.kernel.org/pub/scm/linux/kernel/git/clk/linux.git
> >         git fetch --no-tags clk clk-sunplus
> >         git checkout d54c1fd4a51e8fbc7f9da86b0cd338a4f7cd2bb2
> >         # save the config file
> >         mkdir build_dir && cp config build_dir/.config
> >         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=mips olddefconfig
> >         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=mips SHELL=/bin/bash drivers/clk/
> > 
> > If you fix the issue, kindly add following tag where applicable
> > | Reported-by: kernel test robot <lkp@intel.com>
> > | Link: https://lore.kernel.org/oe-kbuild-all/202303221947.pXP2v4xJ-lkp@intel.com/
> > 
> 
> Does this fix it?
> 
> ---8<---
> diff --git a/drivers/clk/clk-sp7021.c b/drivers/clk/clk-sp7021.c
> index 8fec14120105..caabbf5e2197 100644
> --- a/drivers/clk/clk-sp7021.c
> +++ b/drivers/clk/clk-sp7021.c
> @@ -30,9 +30,9 @@ enum {
>  	P_MAX
>  };
>  
> -#define MASK_SEL_FRA	GENMASK(1, 1)
> -#define MASK_SDM_MOD	GENMASK(2, 2)
> -#define MASK_PH_SEL	GENMASK(4, 4)
> +#define MASK_SEL_FRA	BITMASK(1)
> +#define MASK_SDM_MOD	BITMASK(2)
> +#define MASK_PH_SEL	BITMASK(4)
>  #define MASK_NFRA	GENMASK(12, 6)
>  #define MASK_DIVR	GENMASK(8, 7)
>  #define MASK_DIVN	GENMASK(7, 0)
> 

No (BITMASK did not exist but BIT_MASK does). It looks like clang is
complaining that mask is an unsigned int and it is being compared
against ~0ull, which will always be false. This makes the warning go
away for me, which is similar to commit cfd6fb45cfaf ("crypto: ccree -
avoid out-of-range warnings from clang"), but I am not sure if that is
correct or not.

diff --git a/drivers/clk/clk-sp7021.c b/drivers/clk/clk-sp7021.c
index 8fec14120105..11d22043ddd7 100644
--- a/drivers/clk/clk-sp7021.c
+++ b/drivers/clk/clk-sp7021.c
@@ -41,7 +41,7 @@ enum {
 /* HIWORD_MASK FIELD_PREP */
 #define HWM_FIELD_PREP(mask, value)		\
 ({						\
-	u32 _m = mask;				\
+	u64 _m = mask;				\
 	(_m << 16) | FIELD_PREP(_m, value);	\
 })
 

For the record, this only happens under W=1 but I think we would like to
eventually enable this warning so it would be good to avoid introducing
new instances.

Cheers,
Nathan