Hi Sunyeal, kernel test robot noticed the following build warnings: https://git-scm.com/docs/git-format-patch#_base_tree_information] url: https://github.com/intel-lab-lkp/linux/commits/Sunyeal-Hong/dt-bindings-clock-add-Exynos-Auto-v920-SoC-CMU-bindings/20240708-072150 base: https://git.kernel.org/pub/scm/linux/kernel/git/krzk/linux.git for-next patch link: https://lore.kernel.org/r/20240707231331.3433340-4-sunyeal.hong%40samsung.com patch subject: [PATCH v2 3/4] clk: samsung: clk-pll: Add support for pll_531x config: arc-randconfig-r071-20240719 (https://download.01.org/0day-ci/archive/20240720/202407200028.5AADGhmj-lkp@xxxxxxxxx/config) compiler: arc-elf-gcc (GCC) 13.2.0 If you fix the issue in a separate patch/commit (i.e. not just a new version of the same patch/commit), kindly add following tags | Reported-by: kernel test robot <lkp@xxxxxxxxx> | Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx> | Closes: https://lore.kernel.org/r/202407200028.5AADGhmj-lkp@xxxxxxxxx/ smatch warnings: drivers/clk/samsung/clk-pll.c:1292 samsung_pll531x_recalc_rate() warn: mask and shift to zero: expr='fdiv >> 31' vim +1292 drivers/clk/samsung/clk-pll.c 5c788df7a25de7 Sunyeal Hong 2024-07-08 1277 static unsigned long samsung_pll531x_recalc_rate(struct clk_hw *hw, 5c788df7a25de7 Sunyeal Hong 2024-07-08 1278 unsigned long parent_rate) 5c788df7a25de7 Sunyeal Hong 2024-07-08 1279 { 5c788df7a25de7 Sunyeal Hong 2024-07-08 1280 struct samsung_clk_pll *pll = to_clk_pll(hw); 5c788df7a25de7 Sunyeal Hong 2024-07-08 1281 u32 mdiv, pdiv, sdiv, pll_con0, pll_con8; 5c788df7a25de7 Sunyeal Hong 2024-07-08 1282 s32 fdiv; 5c788df7a25de7 Sunyeal Hong 2024-07-08 1283 u64 fout = parent_rate; 5c788df7a25de7 Sunyeal Hong 2024-07-08 1284 5c788df7a25de7 Sunyeal Hong 2024-07-08 1285 pll_con0 = readl_relaxed(pll->con_reg); 5c788df7a25de7 Sunyeal Hong 2024-07-08 1286 pll_con8 = readl_relaxed(pll->con_reg + 20); 5c788df7a25de7 Sunyeal Hong 2024-07-08 1287 mdiv = (pll_con0 >> PLL531X_MDIV_SHIFT) & PLL531X_MDIV_MASK; 5c788df7a25de7 Sunyeal Hong 2024-07-08 1288 pdiv = (pll_con0 >> PLL531X_PDIV_SHIFT) & PLL531X_PDIV_MASK; 5c788df7a25de7 Sunyeal Hong 2024-07-08 1289 sdiv = (pll_con0 >> PLL531X_SDIV_SHIFT) & PLL531X_SDIV_MASK; 5c788df7a25de7 Sunyeal Hong 2024-07-08 1290 fdiv = (s32)(pll_con8 & PLL531X_FDIV_MASK); PLL531X_FDIV_MASK is 0xffff. Was this supposed to be a cast to s16 instead of s32? Why is fdiv signed? Shifting negative values is undefined in C. 5c788df7a25de7 Sunyeal Hong 2024-07-08 1291 5c788df7a25de7 Sunyeal Hong 2024-07-08 @1292 if (fdiv >> 31) It's really unclear what's happening here. If I had to guess, I'd say that this was testing to see if fdiv was negative. 5c788df7a25de7 Sunyeal Hong 2024-07-08 1293 mdiv--; 5c788df7a25de7 Sunyeal Hong 2024-07-08 1294 5c788df7a25de7 Sunyeal Hong 2024-07-08 1295 fout *= ((u64)mdiv << 24) + (fdiv >> 8); ^^^^^^^^^ More shifting. 5c788df7a25de7 Sunyeal Hong 2024-07-08 1296 do_div(fout, (pdiv << sdiv)); 5c788df7a25de7 Sunyeal Hong 2024-07-08 1297 fout >>= 24; 5c788df7a25de7 Sunyeal Hong 2024-07-08 1298 5c788df7a25de7 Sunyeal Hong 2024-07-08 1299 return (unsigned long)fout; 5c788df7a25de7 Sunyeal Hong 2024-07-08 1300 } -- 0-DAY CI Kernel Test Service https://github.com/intel/lkp-tests/wiki
