Re: [PATCH v13 4/5] pwm: sifive: Fix rounding issues in apply and get_state functions

[kernel test robot <lkp@intel.com>]

Hi Nylon,

kernel test robot noticed the following build errors:

[auto build test ERROR on robh/for-next]
[also build test ERROR on linus/master v6.15-rc5 next-20250507]
[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/Nylon-Chen/riscv-dts-sifive-unleashed-unmatched-Remove-PWM-controlled-LED-s-active-low-properties/20250423-165906
base:   https://git.kernel.org/pub/scm/linux/kernel/git/robh/linux.git for-next
patch link:    https://lore.kernel.org/r/20250423090446.294846-5-nylon.chen%40sifive.com
patch subject: [PATCH v13 4/5] pwm: sifive: Fix rounding issues in apply and get_state functions
config: hexagon-allmodconfig (https://download.01.org/0day-ci/archive/20250508/202505080303.dBfU5YMS-lkp@intel.com/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/20250508/202505080303.dBfU5YMS-lkp@intel.com/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@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202505080303.dBfU5YMS-lkp@intel.com/

All error/warnings (new ones prefixed by >>):

>> drivers/pwm/pwm-sifive.c:161:2: warning: comparison of distinct pointer types ('typeof ((frac)) *' (aka 'unsigned int *') and 'uint64_t *' (aka 'unsigned long long *')) [-Wcompare-distinct-pointer-types]
     161 |         do_div(frac, state->period);
         |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~
   include/asm-generic/div64.h:183:28: note: expanded from macro 'do_div'
     183 |         (void)(((typeof((n)) *)0) == ((uint64_t *)0));  \
         |                ~~~~~~~~~~~~~~~~~~ ^  ~~~~~~~~~~~~~~~
>> drivers/pwm/pwm-sifive.c:161:2: error: incompatible pointer types passing 'u32 *' (aka 'unsigned int *') to parameter of type 'uint64_t *' (aka 'unsigned long long *') [-Werror,-Wincompatible-pointer-types]
     161 |         do_div(frac, state->period);
         |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~
   include/asm-generic/div64.h:199:22: note: expanded from macro 'do_div'
     199 |                 __rem = __div64_32(&(n), __base);       \
         |                                    ^~~~
   include/asm-generic/div64.h:174:38: note: passing argument to parameter 'dividend' here
     174 | extern uint32_t __div64_32(uint64_t *dividend, uint32_t divisor);
         |                                      ^
>> drivers/pwm/pwm-sifive.c:161:2: warning: shift count >= width of type [-Wshift-count-overflow]
     161 |         do_div(frac, state->period);
         |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~
   include/asm-generic/div64.h:195:25: note: expanded from macro 'do_div'
     195 |         } else if (likely(((n) >> 32) == 0)) {          \
         |                                ^  ~~
   include/linux/compiler.h:76:40: note: expanded from macro 'likely'
      76 | # define likely(x)      __builtin_expect(!!(x), 1)
         |                                             ^
   2 warnings and 1 error generated.


vim +161 drivers/pwm/pwm-sifive.c

   131	
   132	static int pwm_sifive_apply(struct pwm_chip *chip, struct pwm_device *pwm,
   133				    const struct pwm_state *state)
   134	{
   135		struct pwm_sifive_ddata *ddata = pwm_sifive_chip_to_ddata(chip);
   136		struct pwm_state cur_state;
   137		unsigned int duty_cycle;
   138		unsigned long long num;
   139		bool enabled;
   140		int ret = 0;
   141		u32 frac, inactive;
   142	
   143		if (state->polarity != PWM_POLARITY_NORMAL)
   144			return -EINVAL;
   145	
   146		cur_state = pwm->state;
   147		enabled = cur_state.enabled;
   148	
   149		duty_cycle = state->duty_cycle;
   150		if (!state->enabled)
   151			duty_cycle = 0;
   152	
   153		/*
   154		 * The problem of output producing mixed setting as mentioned at top,
   155		 * occurs here. To minimize the window for this problem, we are
   156		 * calculating the register values first and then writing them
   157		 * consecutively
   158		 */
   159		num = (u64)duty_cycle * (1U << PWM_SIFIVE_CMPWIDTH);
   160		frac = num;
 > 161		do_div(frac, state->period);
   162		/* The hardware cannot generate a 0% duty cycle */
   163		frac = min(frac, (1U << PWM_SIFIVE_CMPWIDTH) - 1);
   164		inactive = (1U << PWM_SIFIVE_CMPWIDTH) - 1 - frac;
   165	
   166		mutex_lock(&ddata->lock);
   167		if (state->period != ddata->approx_period) {
   168			/*
   169			 * Don't let a 2nd user change the period underneath the 1st user.
   170			 * However if ddate->approx_period == 0 this is the first time we set
   171			 * any period, so let whoever gets here first set the period so other
   172			 * users who agree on the period won't fail.
   173			 */
   174			if (ddata->user_count != 1 && ddata->approx_period) {
   175				mutex_unlock(&ddata->lock);
   176				return -EBUSY;
   177			}
   178			ddata->approx_period = state->period;
   179			pwm_sifive_update_clock(ddata, clk_get_rate(ddata->clk));
   180		}
   181		mutex_unlock(&ddata->lock);
   182	
   183		/*
   184		 * If the PWM is enabled the clk is already on. So only enable it
   185		 * conditionally to have it on exactly once afterwards independent of
   186		 * the PWM state.
   187		 */
   188		if (!enabled) {
   189			ret = clk_enable(ddata->clk);
   190			if (ret) {
   191				dev_err(pwmchip_parent(chip), "Enable clk failed\n");
   192				return ret;
   193			}
   194		}
   195	
   196		writel(inactive, ddata->regs + PWM_SIFIVE_PWMCMP(pwm->hwpwm));
   197	
   198		if (!state->enabled)
   199			clk_disable(ddata->clk);
   200	
   201		return 0;
   202	}
   203	

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