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>

4 files changed, 49 insertions, 9 deletions

diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index 7831bc6b51dd..680fbc795a0a 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -128,6 +128,13 @@ static int pwm_device_request(struct pwm_device *pwm, const char *label)
         set_bit(PWMF_REQUESTED, &pwm->flags);
         pwm->label = label;
 
+        /*
+         * FIXME: This should be removed once all PWM users properly make use
+         * of struct pwm_args to initialize the PWM device. As long as this is
+         * here, the PWM state and hardware state can get out of sync.
+         */
+        pwm_apply_args(pwm);
+
         return 0;
 }
 
@@ -146,12 +153,12 @@ of_pwm_xlate_with_flags(struct pwm_chip *pc, const struct of_phandle_args *args)
         if (IS_ERR(pwm))
                 return pwm;
 
-        pwm_set_period(pwm, args->args[1]);
+        pwm->args.period = args->args[1];
 
         if (args->args[2] & PWM_POLARITY_INVERTED)
-                pwm_set_polarity(pwm, PWM_POLARITY_INVERSED);
+                pwm->args.polarity = PWM_POLARITY_INVERSED;
         else
-                pwm_set_polarity(pwm, PWM_POLARITY_NORMAL);
+                pwm->args.polarity = PWM_POLARITY_NORMAL;
 
         return pwm;
 }
@@ -172,7 +179,7 @@ of_pwm_simple_xlate(struct pwm_chip *pc, const struct of_phandle_args *args)
         if (IS_ERR(pwm))
                 return pwm;
 
-        pwm_set_period(pwm, args->args[1]);
+        pwm->args.period = args->args[1];
 
         return pwm;
 }
@@ -747,13 +754,13 @@ struct pwm_device *pwm_get(struct device *dev, const char *con_id)
         if (!chip)
                 goto out;
 
+        pwm->args.period = chosen->period;
+        pwm->args.polarity = chosen->polarity;
+
         pwm = pwm_request_from_chip(chip, chosen->index, con_id ?: dev_id);
         if (IS_ERR(pwm))
                 goto out;
 
-        pwm_set_period(pwm, chosen->period);
-        pwm_set_polarity(pwm, chosen->polarity);
-
 out:
         mutex_unlock(&pwm_lookup_lock);
         return pwm;
diff --git a/drivers/pwm/pwm-clps711x.c b/drivers/pwm/pwm-clps711x.c
index a80c10803636..7d335422cfda 100644
--- a/drivers/pwm/pwm-clps711x.c
+++ b/drivers/pwm/pwm-clps711x.c
@@ -60,7 +60,7 @@ static int clps711x_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm)
                 return -EINVAL;
 
         /* Store constant period value */
-        pwm_set_period(pwm, DIV_ROUND_CLOSEST(NSEC_PER_SEC, freq));
+        pwm->args.period = DIV_ROUND_CLOSEST(NSEC_PER_SEC, freq);
 
         return 0;
 }
diff --git a/drivers/pwm/pwm-pxa.c b/drivers/pwm/pwm-pxa.c
index cb2f7024cf68..58b709f29130 100644
--- a/drivers/pwm/pwm-pxa.c
+++ b/drivers/pwm/pwm-pxa.c
@@ -160,7 +160,7 @@ pxa_pwm_of_xlate(struct pwm_chip *pc, const struct of_phandle_args *args)
         if (IS_ERR(pwm))
                 return pwm;
 
-        pwm_set_period(pwm, args->args[0]);
+        pwm->args.period = args->args[0];
 
         return pwm;
 }
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