Hi Aleksandr, kernel test robot noticed the following build warnings: [auto build test WARNING on robh/for-next] [also build test WARNING on sunxi/sunxi/for-next linus/master v6.8-rc2 next-20240202] [If your patch is applied to the wrong git tree, kindly drop us a note. And when submitting patch, we suggest to use '--base' as documented in https://git-scm.com/docs/git-format-patch#_base_tree_information] url: https://github.com/intel-lab-lkp/linux/commits/Aleksandr-Shubin/dt-bindings-pwm-Add-binding-for-Allwinner-D1-T113-S3-R329-PWM-controller/20240131-210313 base: https://git.kernel.org/pub/scm/linux/kernel/git/robh/linux.git for-next patch link: https://lore.kernel.org/r/20240131125920.2879433-3-privatesub2%40gmail.com patch subject: [PATCH v8 2/3] pwm: Add Allwinner's D1/T113-S3/R329 SoCs PWM support config: x86_64-allyesconfig (https://download.01.org/0day-ci/archive/20240203/202402032222.BiIrD3g4-lkp@xxxxxxxxx/config) compiler: clang version 17.0.6 (https://github.com/llvm/llvm-project 6009708b4367171ccdbf4b5905cb6a803753fe18) reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240203/202402032222.BiIrD3g4-lkp@xxxxxxxxx/reproduce) 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> | Closes: https://lore.kernel.org/oe-kbuild-all/202402032222.BiIrD3g4-lkp@xxxxxxxxx/ All warnings (new ones prefixed by >>): >> drivers/pwm/pwm-sun20i.c:47: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst * SUN20I_PWM_MAGIC is used to quickly compute the values of the clock dividers vim +47 drivers/pwm/pwm-sun20i.c 45 46 /** > 47 * SUN20I_PWM_MAGIC is used to quickly compute the values of the clock dividers 48 * div_m (SUN20I_PWM_CLK_CFG_DIV_M) & prescale_k (SUN20I_PWM_CTL_PRESCAL_K) 49 * without using a loop. These dividers limit the # of cycles in a period 50 * to SUN20I_PWM_PCNTR_SIZE by applying a scaling factor of 51 * 1/(div_m * (prescale_k + 1)) to the clock source. 52 * 53 * SUN20I_PWM_MAGIC is derived by solving for div_m and prescale_k 54 * such that for a given requested period, 55 * 56 * i) div_m is minimized for any prescale_k ≤ SUN20I_PWM_CTL_PRESCAL_K_MAX, 57 * ii) prescale_k is minimized. 58 * 59 * The derivation proceeds as follows, with val = # of cycles for reqested 60 * period: 61 * 62 * for a given value of div_m we want the smallest prescale_k such that 63 * 64 * (val >> div_m) // (prescale_k + 1) ≤ 65536 (SUN20I_PWM_PCNTR_SIZE) 65 * 66 * This is equivalent to: 67 * 68 * (val >> div_m) ≤ 65536 * (prescale_k + 1) + prescale_k 69 * ⟺ (val >> div_m) ≤ 65537 * prescale_k + 65536 70 * ⟺ (val >> div_m) - 65536 ≤ 65537 * prescale_k 71 * ⟺ ((val >> div_m) - 65536) / 65537 ≤ prescale_k 72 * 73 * As prescale_k is integer, this becomes 74 * 75 * ((val >> div_m) - 65536) // 65537 ≤ prescale_k 76 * 77 * And is minimized at 78 * 79 * ((val >> div_m) - 65536) // 65537 80 * 81 * Now we pick the smallest div_m that satifies prescale_k ≤ 255 82 * (i.e SUN20I_PWM_CTL_PRESCAL_K_MAX), 83 * 84 * ((val >> div_m) - 65536) // 65537 ≤ 255 85 * ⟺ (val >> div_m) - 65536 ≤ 255 * 65537 + 65536 86 * ⟺ val >> div_m ≤ 255 * 65537 + 2 * 65536 87 * ⟺ val >> div_m < (255 * 65537 + 2 * 65536 + 1) 88 * ⟺ div_m = fls((val) / (255 * 65537 + 2 * 65536 + 1)) 89 * 90 * Suggested by Uwe Kleine-König 91 */ 92 #define SUN20I_PWM_MAGIC (255 * 65537 + 2 * 65536 + 1) 93 -- 0-DAY CI Kernel Test Service https://github.com/intel/lkp-tests/wiki
