pwm: Introduce the pwm_args concept

Currently the PWM core mixes the current PWM state with the per-platform
reference config (specified through the PWM lookup table, DT definition
or directly hardcoded in PWM drivers).

Create a struct pwm_args to store this reference configuration, so that
PWM users can differentiate between the current and reference
configurations.

Patch all places where pwm->args should be initialized. We keep the
pwm_set_polarity/period() calls until all PWM users are patched to use
pwm_args instead of pwm_get_period/polarity().

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
[thierry.reding@gmail.com: reword kerneldoc comments]
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

1 files changed, 33 insertions, 0 deletions

diff --git a/include/linux/pwm.h b/include/linux/pwm.h
index cfc3ed46cad2..b78d27c42629 100644
--- a/include/linux/pwm.h
+++ b/include/linux/pwm.h
@@ -74,6 +74,24 @@ enum pwm_polarity {
 	PWM_POLARITY_INVERSED,
 };
 
+/**
+ * struct pwm_args - board-dependent PWM arguments
+ * @period: reference period
+ * @polarity: reference polarity
+ *
+ * This structure describes board-dependent arguments attached to a PWM
+ * device. These arguments are usually retrieved from the PWM lookup table or
+ * device tree.
+ *
+ * Do not confuse this with the PWM state: PWM arguments represent the initial
+ * configuration that users want to use on this PWM device rather than the
+ * current PWM hardware state.
+ */
+struct pwm_args {
+	unsigned int period;
+	enum pwm_polarity polarity;
+};
+
 enum {
 	PWMF_REQUESTED = 1 << 0,
 	PWMF_ENABLED = 1 << 1,
@@ -92,6 +110,7 @@ enum {
  * @period: period of the PWM signal (in nanoseconds)
  * @duty_cycle: duty cycle of the PWM signal (in nanoseconds)
  * @polarity: polarity of the PWM signal
+ * @args: PWM arguments
  */
 struct pwm_device {
 	const char *label;
@@ -105,6 +124,8 @@ struct pwm_device {
 	unsigned int period;
 	unsigned int duty_cycle;
 	enum pwm_polarity polarity;
+
+	struct pwm_args args;
 };
 
 static inline bool pwm_is_enabled(const struct pwm_device *pwm)
@@ -144,6 +165,18 @@ static inline enum pwm_polarity pwm_get_polarity(const struct pwm_device *pwm)
 	return pwm ? pwm->polarity : PWM_POLARITY_NORMAL;
 }
 
+static inline void pwm_get_args(const struct pwm_device *pwm,
+				struct pwm_args *args)
+{
+	*args = pwm->args;
+}
+
+static inline void pwm_apply_args(struct pwm_device *pwm)
+{
+	pwm_set_period(pwm, pwm->args.period);
+	pwm_set_polarity(pwm, pwm->args.polarity);
+}
+
 /**
  * struct pwm_ops - PWM controller operations
  * @request: optional hook for requesting a PWM