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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: Boris Brezillon <boris.brezillon@free-electrons.com>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
This commit is contained in:
Boris Brezillon 2016-06-14 11:13:10 +02:00 committed by Thierry Reding
parent a6a0dbbcfa
commit f6f3bddf7b
1 changed files with 55 additions and 0 deletions
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55
include/linux/pwm.h
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@ -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