pwm: Add PWM capture support

Supply a PWM capture callback op in order to pass back information
obtained by running analysis on a PWM signal. This would normally (at
least during testing) be called from the sysfs routines with a view to
printing out PWM capture data which has been encoded into a string.
Signed-off-by: Lee Jones <lee.jones@linaro.org>
[thierry.reding@gmail.com: make capture data unsigned int for symmetry]
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

drivers/pwm/core.c

@@ -524,6 +524,33 @@ int pwm_apply_state(struct pwm_device *pwm, struct pwm_state *state)
 }
 EXPORT_SYMBOL_GPL(pwm_apply_state);
 
+/**
+ * pwm_capture() - capture and report a PWM signal
+ * @pwm: PWM device
+ * @result: structure to fill with capture result
+ * @timeout: time to wait, in milliseconds, before giving up on capture
+ *
+ * Returns: 0 on success or a negative error code on failure.
+ */
+int pwm_capture(struct pwm_device *pwm, struct pwm_capture *result,
+		unsigned long timeout)
+{
+	int err;
+
+	if (!pwm || !pwm->chip->ops)
+		return -EINVAL;
+
+	if (!pwm->chip->ops->capture)
+		return -ENOSYS;
+
+	mutex_lock(&pwm_lock);
+	err = pwm->chip->ops->capture(pwm->chip, pwm, result, timeout);
+	mutex_unlock(&pwm_lock);
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(pwm_capture);
+
 /**
  * pwm_adjust_config() - adjust the current PWM config to the PWM arguments
  * @pwm: PWM device

include/linux/pwm.h

@@ -5,7 +5,9 @@
 #include <linux/mutex.h>
 #include <linux/of.h>
 
+struct pwm_capture;
 struct seq_file;
+
 struct pwm_chip;
 
 /**
@@ -153,6 +155,7 @@ static inline void pwm_get_args(const struct pwm_device *pwm,
  * @free: optional hook for freeing a PWM
  * @config: configure duty cycles and period length for this PWM
  * @set_polarity: configure the polarity of this PWM
+ * @capture: capture and report PWM signal
  * @enable: enable PWM output toggling
  * @disable: disable PWM output toggling
  * @apply: atomically apply a new PWM config. The state argument
@@ -172,6 +175,8 @@ struct pwm_ops {
 		      int duty_ns, int period_ns);
 	int (*set_polarity)(struct pwm_chip *chip, struct pwm_device *pwm,
 			    enum pwm_polarity polarity);
+	int (*capture)(struct pwm_chip *chip, struct pwm_device *pwm,
+		       struct pwm_capture *result, unsigned long timeout);
 	int (*enable)(struct pwm_chip *chip, struct pwm_device *pwm);
 	void (*disable)(struct pwm_chip *chip, struct pwm_device *pwm);
 	int (*apply)(struct pwm_chip *chip, struct pwm_device *pwm,
@@ -212,6 +217,16 @@ struct pwm_chip {
 	bool can_sleep;
 };
 
+/**
+ * struct pwm_capture - PWM capture data
+ * @period: period of the PWM signal (in nanoseconds)
+ * @duty_cycle: duty cycle of the PWM signal (in nanoseconds)
+ */
+struct pwm_capture {
+	unsigned int period;
+	unsigned int duty_cycle;
+};
+
 #if IS_ENABLED(CONFIG_PWM)
 /* PWM user APIs */
 struct pwm_device *pwm_request(int pwm_id, const char *label);
@@ -322,6 +337,8 @@ static inline void pwm_disable(struct pwm_device *pwm)
 
 
 /* PWM provider APIs */
+int pwm_capture(struct pwm_device *pwm, struct pwm_capture *result,
+		unsigned long timeout);
 int pwm_set_chip_data(struct pwm_device *pwm, void *data);
 void *pwm_get_chip_data(struct pwm_device *pwm);
 
@@ -373,6 +390,13 @@ static inline int pwm_config(struct pwm_device *pwm, int duty_ns,
 	return -EINVAL;
 }
 
+static inline int pwm_capture(struct pwm_device *pwm,
+			      struct pwm_capture *result,
+			      unsigned long timeout)
+{
+	return -EINVAL;
+}
+
 static inline int pwm_set_polarity(struct pwm_device *pwm,
 				   enum pwm_polarity polarity)
 {