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Commit f6f3bddf authored by Boris Brezillon's avatar Boris Brezillon Committed by Thierry Reding
Browse files

pwm: Add relative duty cycle manipulation helpers 



The PWM framework expects PWM users to configure the duty cycle in nano-
seconds, but many users want to express the duty cycle relatively to the
period value (i.e. duty_cycle = 33% of the period).

Add the pwm_{get,set}_relative_duty_cycle() helpers to ease this kind of
conversion.

Signed-off-by: default avatarBoris Brezillon <boris.brezillon@free-electrons.com>
Tested-by: default avatarHeiko Stuebner <heiko@sntech.de>
Signed-off-by: default avatarThierry Reding <thierry.reding@gmail.com>
parent a6a0dbbc

include/linux/pwm.h

+55 −0
Original line number Diff line number Diff line
@@ -180,6 +180,61 @@ static inline void pwm_init_state(const struct pwm_device *pwm, 
	state->duty_cycle = 0;

}



/**

 * pwm_get_relative_duty_cycle() - Get a relative duty cycle value

 * @state: PWM state to extract the duty cycle from

 * @scale: target scale of the relative duty cycle

 *

 * This functions converts the absolute duty cycle stored in @state (expressed

 * in nanosecond) into a value relative to the period.

 *

 * For example if you want to get the duty_cycle expressed in percent, call:

 *

 * pwm_get_state(pwm, &state);

 * duty = pwm_get_relative_duty_cycle(&state, 100);

 */

static inline unsigned int

pwm_get_relative_duty_cycle(const struct pwm_state *state, unsigned int scale)

{

	if (!state->period)

		return 0;



	return DIV_ROUND_CLOSEST_ULL((u64)state->duty_cycle * scale,

				     state->period);

}



/**

 * pwm_set_relative_duty_cycle() - Set a relative duty cycle value

 * @state: PWM state to fill

 * @duty_cycle: relative duty cycle value

 * @scale: scale in which @duty_cycle is expressed

 *

 * This functions converts a relative into an absolute duty cycle (expressed

 * in nanoseconds), and puts the result in state->duty_cycle.

 *

 * For example if you want to configure a 50% duty cycle, call:

 *

 * pwm_init_state(pwm, &state);

 * pwm_set_relative_duty_cycle(&state, 50, 100);

 * pwm_apply_state(pwm, &state);

 *

 * This functions returns -EINVAL if @duty_cycle and/or @scale are

 * inconsistent (@scale == 0 or @duty_cycle > @scale).

 */

static inline int

pwm_set_relative_duty_cycle(struct pwm_state *state, unsigned int duty_cycle,

			    unsigned int scale)

{

	if (!scale || duty_cycle > scale)

		return -EINVAL;



	state->duty_cycle = DIV_ROUND_CLOSEST_ULL((u64)duty_cycle *

						  state->period,

						  scale);



	return 0;

}



/**

 * struct pwm_ops - PWM controller operations

 * @request: optional hook for requesting a PWM