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authorBoris Brezillon <boris.brezillon@free-electrons.com>2016-06-14 12:13:10 +0300
committerThierry Reding <thierry.reding@gmail.com>2016-07-08 18:52:19 +0300
commitf6f3bddf7b2b994a927808fcc5a3d07069c35956 (patch)
treeea4b977c05eee37a08393720a22e69e5c100c0f5 /include/linux/pwm.h
parenta6a0dbbcfa469cf3e5c4d9522106c0b7b9e9e373 (diff)
downloadlinux-f6f3bddf7b2b994a927808fcc5a3d07069c35956.tar.xz
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>
Diffstat (limited to 'include/linux/pwm.h')
-rw-r--r--include/linux/pwm.h55
1 files changed, 55 insertions, 0 deletions
diff --git a/include/linux/pwm.h b/include/linux/pwm.h
index a100f6e80738..fd1092729ed6 100644
--- a/include/linux/pwm.h
+++ b/include/linux/pwm.h
@@ -181,6 +181,61 @@ static inline void pwm_init_state(const struct pwm_device *pwm,
}
/**
+ * 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
* @free: optional hook for freeing a PWM