10  * With the prescaler setting you can select which bit of the counter is used
16  * | prescaler |  reset | counter bits | frequency | period length |
25  * - The hardware cannot generate a 100% duty cycle if the prescaler is 0.
26  * - The hardware cannot atomically set the prescaler and the counter value,
28  * - The counter is not reset if you switch the prescaler which leads
55 #define SL28CPLD_PWM_MAX_DUTY_CYCLE(prescaler)	(1 << (7 - (prescaler)))  argument
56 #define SL28CPLD_PWM_PERIOD(prescaler) \  argument
57 	(NSEC_PER_SEC / SL28CPLD_PWM_CLK * SL28CPLD_PWM_MAX_DUTY_CYCLE(prescaler))
64  *   max_period_ns = 1 << (7 - prescaler) / SL28CPLD_PWM_CLK * NSEC_PER_SEC
65  *   max_duty_cycle = 1 << (7 - prescaler)
99 	int prescaler;  in sl28cpld_pwm_get_state()  local
105 	prescaler = FIELD_GET(SL28CPLD_PWM_CTRL_PRESCALER_MASK, reg);  in sl28cpld_pwm_get_state()
106 	state->period = SL28CPLD_PWM_PERIOD(prescaler);  in sl28cpld_pwm_get_state()
113 	 * Sanitize values for the PWM core. Depending on the prescaler it  in sl28cpld_pwm_get_state()
129 	unsigned int cycle, prescaler;  in sl28cpld_pwm_apply()  local
139 	 * Calculate the prescaler. Pick the biggest period that isn't  in sl28cpld_pwm_apply()
142 	prescaler = DIV_ROUND_UP_ULL(SL28CPLD_PWM_PERIOD(0), state->period);  in sl28cpld_pwm_apply()
143 	prescaler = order_base_2(prescaler);  in sl28cpld_pwm_apply()
145 	if (prescaler > field_max(SL28CPLD_PWM_CTRL_PRESCALER_MASK))  in sl28cpld_pwm_apply()
148 	ctrl = FIELD_PREP(SL28CPLD_PWM_CTRL_PRESCALER_MASK, prescaler);  in sl28cpld_pwm_apply()
153 	cycle = min_t(unsigned int, cycle, SL28CPLD_PWM_MAX_DUTY_CYCLE(prescaler));  in sl28cpld_pwm_apply()
157 	 * cycle if the prescaler is 0. Set prescaler to 1 instead. We don't  in sl28cpld_pwm_apply()
160 	 * We don't need to check the actual prescaler setting, because only  in sl28cpld_pwm_apply()
161 	 * if the prescaler is 0 we can have this particular value.  in sl28cpld_pwm_apply()
170 	 * To avoid glitches when we switch the prescaler, we have to make sure  in sl28cpld_pwm_apply()
173 	 * Take the current prescaler (or the current period length) into  in sl28cpld_pwm_apply()
175 	 * prescaler first. If the period length is decreasing we have to  in sl28cpld_pwm_apply()