[PATCH] PWM: Add support for configuring polarity of PWM

From: Philip, Avinash
Date: Wed Jul 18 2012 - 09:08:45 EST


Duty cycle inversion of PWM wave should achieved through PWM polarity
inversion. Also polarity of PWM wave should configurable from slave
drivers,

Configure polarity
1. PWM_POLARITY_NORMAL -> duty ns defines ON period of PWM wave
2. PWM_POLARITY_INVERSE -> duty ns defines OFF period of PWM wave.

This patch adds support for configuring PWM polarity in PWM frame work.

Signed-off-by: Philip, Avinash <avinashphilip@xxxxxx>
---
Configuring polarity to be done with PWM device disabled, if not
failure reported.

If PWM device is enabled while configuring polarity, disabling and
re_enabling make it complex. Whoever uses this API has to taken
care of the basic rules.

Discussions related to this can found at
http://www.spinics.net/lists/kernel/msg1372110.html

:100644 100644 ecb7690... 24d5495... M drivers/pwm/core.c
:100644 100644 21d076c... 2e4e960... M include/linux/pwm.h
drivers/pwm/core.c | 32 ++++++++++++++++++++++++++++++++
include/linux/pwm.h | 15 +++++++++++++++
2 files changed, 47 insertions(+), 0 deletions(-)

diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index ecb7690..24d5495 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -379,6 +379,38 @@ int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns)
EXPORT_SYMBOL_GPL(pwm_config);

/**
+ * pwm_set_polarity() - change PWM device Polarity
+ * @pwm: PWM device
+ * @polarity: Configure polarity of PWM
+ *
+ * Polarity to be configured with PWM device disabled.
+ */
+int pwm_set_polarity(struct pwm_device *pwm, int polarity)
+{
+ int pwm_flags = PWM_POLARITY_NORMAL;
+
+ if (!pwm || !pwm->chip->ops->set_polarity)
+ return -EINVAL;
+
+ if (test_bit(PWMF_ENABLED, &pwm->flags)) {
+ dev_err(pwm->chip->dev,
+ "Polarity configuration Failed!, PWM device enabled\n");
+ return -EBUSY;
+ }
+
+ if (polarity == PWM_POLARITY_INVERSE)
+ pwm_flags = PWM_POLARITY_INVERSE;
+
+ if (!pwm_flags)
+ clear_bit(PWMF_POLARITY_INVERSE, &pwm->flags);
+ else
+ set_bit(PWMF_POLARITY_INVERSE, &pwm->flags);
+
+ return pwm->chip->ops->set_polarity(pwm->chip, pwm, polarity);
+}
+EXPORT_SYMBOL_GPL(pwm_set_polarity);
+
+/**
* pwm_enable() - start a PWM output toggling
* @pwm: PWM device
*/
diff --git a/include/linux/pwm.h b/include/linux/pwm.h
index 21d076c..2e4e960 100644
--- a/include/linux/pwm.h
+++ b/include/linux/pwm.h
@@ -21,6 +21,16 @@ void pwm_free(struct pwm_device *pwm);
*/
int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns);

+enum {
+ PWM_POLARITY_NORMAL, /* ON period depends on duty_ns */
+ PWM_POLARITY_INVERSE, /* OFF period depends on duty_ns */
+};
+
+/*
+ * pwm_set_polarity - set polarity of PWM device
+ */
+int pwm_set_polarity(struct pwm_device *pwm, int polarity);
+
/*
* pwm_enable - start a PWM output toggling
*/
@@ -37,6 +47,7 @@ struct pwm_chip;
enum {
PWMF_REQUESTED = 1 << 0,
PWMF_ENABLED = 1 << 1,
+ PWMF_POLARITY_INVERSE = 1 << 2,
};

struct pwm_device {
@@ -66,6 +77,7 @@ static inline unsigned int pwm_get_period(struct pwm_device *pwm)
* @request: optional hook for requesting a PWM
* @free: optional hook for freeing a PWM
* @config: configure duty cycles and period length for this PWM
+ * @set_polarity: configure polarity of PWM
* @enable: enable PWM output toggling
* @disable: disable PWM output toggling
* @dbg_show: optional routine to show contents in debugfs
@@ -79,6 +91,9 @@ struct pwm_ops {
int (*config)(struct pwm_chip *chip,
struct pwm_device *pwm,
int duty_ns, int period_ns);
+ int (*set_polarity)(struct pwm_chip *chip,
+ struct pwm_device *pwm,
+ int polarity);
int (*enable)(struct pwm_chip *chip,
struct pwm_device *pwm);
void (*disable)(struct pwm_chip *chip,
--
1.7.1

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/