[PATCH 08/10] pwm: core: add pulse feature to the PWM framework

Olliver Schinagl
2015-10-26T21:35:03Z

From: Olliver Schinagl <oliver@schinagl.nl>

Some hardware PWM's have the possibility to only send out one (or more)
pulses. This can be quite a useful feature in case one wants or needs
only a single pulse, but at the exact width.

Additionally, if multiple pulses are possible, outputting a fixed amount
of pulses can be useful for various timing specific purposes.

A few new functions have been expanded or added for this new behavior.

* pwm_config() now takes an additional parameter to setup the number of
pulses to output. The driver may force this to 0 or 1
for if example if this feature is not or only partially
supported
* pwm_[sg]et_pulse_count() get or set the number of pulses the pwm
framework is configured for
* pwm_get_pulse_count_max() get the maximum number of pulses the pwm
driver supports
* pwm_pulse() Tell the PWM to emit a pre-configured number of pulses
* pwm_pulse_done() an internal function for drivers to call when
they have completed their pre-configured number
of pulses
* pwm_is_pulsing() tells the callers if the pwm is busy pulsing,
yielding a little more information than just
pwm_is_enabled()

Signed-off-by: Olliver Schinagl <oliver@schinagl.nl>
---
drivers/pwm/core.c | 30 +++++++++++++++++++----
drivers/pwm/pwm-gpio.c | 3 ++-
drivers/pwm/pwm-sun4i.c | 3 ++-
drivers/pwm/sysfs.c | 58 ++++++++++++++++++++++++++++++++++++++++++--
include/linux/pwm.h | 64 ++++++++++++++++++++++++++++++++++++++++++++++---
5 files changed, 147 insertions(+), 11 deletions(-)

diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index 3f9df3e..e2c1c0a 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -432,22 +432,29 @@ EXPORT_SYMBOL_GPL(pwm_free);
* @pwm: PWM device
* @duty_ns: "on" time (in nanoseconds)
* @period_ns: duration (in nanoseconds) of one cycle
+ * @pulse_count: number of pulses (periods) to output on pwm_pulse
*
* Returns: 0 on success or a negative error code on failure.
*/
-int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns)
+int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns,
+ unsigned int pulse_count)
{
int err;

if (!pwm || duty_ns < 0 || period_ns <= 0 || duty_ns > period_ns)
return -EINVAL;

- err = pwm->chip->ops->config(pwm->chip, pwm, duty_ns, period_ns);
+ if (pulse_count > pwm->pulse_count_max)
+ return -EINVAL;
+
+ err = pwm->chip->ops->config(pwm->chip, pwm, duty_ns,
+ period_ns, pulse_count);
if (err)
return err;

pwm->duty_cycle = duty_ns;
pwm->period = period_ns;
+ pwm->pulse_count = pulse_count;

return 0;
}
@@ -487,6 +494,18 @@ int pwm_set_polarity(struct pwm_device *pwm, enum pwm_polarity polarity)
EXPORT_SYMBOL_GPL(pwm_set_polarity);

/**
+ * pwm_pulse_done() - notify the PWM framework that pulse_count pulses are done
+ * @pwm: PWM device
+ */
+void pwm_pulse_done(struct pwm_device *pwm)
+{
+ if (pwm && !test_and_clear_bit(PWMF_ENABLED | PWMF_PULSING,
+ &pwm->flags))
+ return pwm->chip->ops->disable(pwm->chip, pwm);
+}
+EXPORT_SYMBOL_GPL(pwm_pulse_done);
+
+/**
* pwm_enable() - start a PWM output toggling
* @pwm: PWM device
*
@@ -494,7 +513,9 @@ EXPORT_SYMBOL_GPL(pwm_set_polarity);
*/
int pwm_enable(struct pwm_device *pwm)
{
- if (pwm && !test_and_set_bit(PWMF_ENABLED, &pwm->flags))
+ if (pwm && !test_and_set_bit(
+ PWMF_ENABLED | !pwm->pulse_count ? : PWMF_PULSING,
+ &pwm->flags))
return pwm->chip->ops->enable(pwm->chip, pwm);

return pwm ? 0 : -EINVAL;
@@ -507,7 +528,8 @@ EXPORT_SYMBOL_GPL(pwm_enable);
*/
void pwm_disable(struct pwm_device *pwm)
{
- if (pwm && test_and_clear_bit(PWMF_ENABLED, &pwm->flags))
+ if (pwm && test_and_clear_bit(PWMF_ENABLED | PWMF_PULSING,
+ &pwm->flags))
pwm->chip->ops->disable(pwm->chip, pwm);
}
EXPORT_SYMBOL_GPL(pwm_disable);
diff --git a/drivers/pwm/pwm-gpio.c b/drivers/pwm/pwm-gpio.c
index 8b588fb..cf4b170 100644
--- a/drivers/pwm/pwm-gpio.c
+++ b/drivers/pwm/pwm-gpio.c
@@ -84,7 +84,7 @@ enum hrtimer_restart gpio_pwm_timer(struct hrtimer *timer)
}

static int gpio_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
- int duty_ns, int period_ns)
+ int duty_ns, int period_ns, unsigned int count)
{
struct gpio_pwm_data *gpio_data = pwm_get_chip_data(pwm);

@@ -202,6 +202,7 @@ static int gpio_pwm_probe(struct platform_device *pdev)
hrtimer++;

pwm_set_chip_data(&gpio_chip->chip.pwms[i], gpio_data);
+ pwm_set_pulse_count_max(&gpio_chip->chip.pwms[i], UINT_MAX);
}
if (!hrtimer)
dev_warn(&pdev->dev, "unable to use High-Resolution timer,");
diff --git a/drivers/pwm/pwm-sun4i.c b/drivers/pwm/pwm-sun4i.c
index 4d84d9d..6347ca8 100644
--- a/drivers/pwm/pwm-sun4i.c
+++ b/drivers/pwm/pwm-sun4i.c
@@ -97,7 +97,8 @@ static inline void sun4i_pwm_writel(struct sun4i_pwm_chip *chip,
}

static int sun4i_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
- int duty_ns, int period_ns)
+ int duty_ns, int period_ns,
+ unsigned int pulse_count)
{
struct sun4i_pwm_chip *sun4i_pwm = to_sun4i_pwm_chip(chip);
u32 prd, dty, val, clk_gate;
diff --git a/drivers/pwm/sysfs.c b/drivers/pwm/sysfs.c
index 9c90886..9b7413c 100644
--- a/drivers/pwm/sysfs.c
+++ b/drivers/pwm/sysfs.c
@@ -61,7 +61,8 @@ static ssize_t period_store(struct device *child,
if (ret)
return ret;

- ret = pwm_config(pwm, pwm_get_duty_cycle(pwm), val);
+ ret = pwm_config(pwm, pwm_get_duty_cycle(pwm),
+ val, pwm_get_pulse_count(pwm));

return ret ? : size;
}
@@ -87,7 +88,8 @@ static ssize_t duty_cycle_store(struct device *child,
if (ret)
return ret;

- ret = pwm_config(pwm, val, pwm_get_period(pwm));
+ ret = pwm_config(pwm, val, pwm_get_period(pwm),
+ pwm_get_pulse_count(pwm));

return ret ? : size;
}
@@ -167,16 +169,68 @@ static ssize_t polarity_store(struct device *child,
return ret ? : size;
}

+static ssize_t pulse_count_show(struct device *child,
+ struct device_attribute *attr,
+ char *buf)
+{
+ const struct pwm_device *pwm = child_to_pwm_device(child);
+
+ return sprintf(buf, "%u\n", pwm_get_pulse_count(pwm));
+}
+
+static ssize_t pulse_count_store(struct device *child,
+ struct device_attribute *attr,
+ const char *buf, size_t size)
+{
+ struct pwm_device *pwm = child_to_pwm_device(child);
+ unsigned int val;
+ int ret;
+
+ ret = kstrtouint(buf, 0, &val);
+ if (ret)
+ return ret;
+
+ ret = pwm_config(pwm, pwm_get_duty_cycle(pwm),
+ pwm_get_period(pwm), val);
+
+ return ret ? : size;
+
+}
+
+static ssize_t pulse_count_max_show(struct device *child,
+ struct device_attribute *attr,
+ char *buf)
+{
+ const struct pwm_device *pwm = child_to_pwm_device(child);
+
+ return sprintf(buf, "%u\n", pwm_get_pulse_count_max(pwm));
+}
+
+static ssize_t pulsing_show(struct device *child,
+ struct device_attribute *attr,
+ char *buf)
+{
+ const struct pwm_device *pwm = child_to_pwm_device(child);
+
+ return sprintf(buf, "%d\n", pwm_is_pulsing(pwm));
+}
+
static DEVICE_ATTR_RW(period);
static DEVICE_ATTR_RW(duty_cycle);
static DEVICE_ATTR_RW(enable);
static DEVICE_ATTR_RW(polarity);
+static DEVICE_ATTR_RW(pulse_count);
+static DEVICE_ATTR_RO(pulse_count_max);
+static DEVICE_ATTR_RO(pulsing);

static struct attribute *pwm_attrs[] = {
&dev_attr_period.attr,
&dev_attr_duty_cycle.attr,
&dev_attr_enable.attr,
&dev_attr_polarity.attr,
+ &dev_attr_pulse_count.attr,
+ &dev_attr_pulse_count_max.attr,
+ &dev_attr_pulsing.attr,
NULL
};
ATTRIBUTE_GROUPS(pwm);
diff --git a/include/linux/pwm.h b/include/linux/pwm.h
index 29315ad..c6042cf 100644
--- a/include/linux/pwm.h
+++ b/include/linux/pwm.h
@@ -22,7 +22,13 @@ void pwm_free(struct pwm_device *pwm);
/*
* pwm_config - change a PWM device configuration
*/
-int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns);
+int pwm_config(struct pwm_device *pwm, int duty_ns,
+ int period_ns, unsigned int pulse_count);
+
+/*
+ * pwm_pulse_done - notify the PWM framework that pulse_count pulses are done
+ */
+void pwm_pulse_done(struct pwm_device *pwm);

/*
* pwm_enable - start a PWM output toggling
@@ -43,7 +49,8 @@ static inline void pwm_free(struct pwm_device *pwm)
{
}

-static inline int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns)
+static inline int pwm_config(struct pwm_device *pwm, int duty_ns,
+ int period_ns, unsigned int pulse_count)
{
return -EINVAL;
}
@@ -53,6 +60,11 @@ static inline int pwm_enable(struct pwm_device *pwm)
return -EINVAL;
}

+static inline int pwm_pulse_done(struct pwm_device *pwm)
+{
+ return -EINVAL;
+}
+
static inline void pwm_disable(struct pwm_device *pwm)
{
}
@@ -78,6 +90,7 @@ enum {
PWMF_REQUESTED = BIT(0),
PWMF_ENABLED = BIT(1),
PWMF_EXPORTED = BIT(2),
+ PWMF_PULSING = BIT(3),
};

/**
@@ -91,6 +104,8 @@ 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
+ * @pulse_count: number of PWM pulses to toggle
+ * @pulse_count_max: maximum number of pulses that can be set to pulse
*/
struct pwm_device {
const char *label;
@@ -103,6 +118,8 @@ struct pwm_device {
unsigned int period;
unsigned int duty_cycle;
enum pwm_polarity polarity;
+ unsigned int pulse_count;
+ unsigned int pulse_count_max;
};

static inline bool pwm_is_enabled(const struct pwm_device *pwm)
@@ -110,6 +127,11 @@ static inline bool pwm_is_enabled(const struct pwm_device *pwm)
return test_bit(PWMF_ENABLED, &pwm->flags);
}

+static inline bool pwm_is_pulsing(const struct pwm_device *pwm)
+{
+ return test_bit(PWMF_ENABLED | PWMF_PULSING, &pwm->flags);
+}
+
static inline void pwm_set_period(struct pwm_device *pwm, unsigned int period)
{
if (pwm)
@@ -142,6 +164,42 @@ static inline enum pwm_polarity pwm_get_polarity(const struct pwm_device *pwm)
return pwm ? pwm->polarity : PWM_POLARITY_NORMAL;
}

+/*
+ * pwm_set_pulse_count - configure the number of pulses of a pwm_pulse
+ */
+static inline void pwm_set_pulse_count(struct pwm_device *pwm,
+ unsigned int pulse_count)
+{
+ if (pwm)
+ pwm->pulse_count = 0;
+}
+
+/*
+ * pwm_get_pulse_count - retrieve the number of pules to pulse of a pwm_pulse
+ */
+static inline unsigned int pwm_get_pulse_count(const struct pwm_device *pwm)
+{
+ return pwm ? pwm->pulse_count : 0;
+}
+
+/*
+ * pwm_get_pulse_count_max - retrieve the maximum number of pulses
+ */
+static inline unsigned int pwm_get_pulse_count_max(const struct pwm_device *pwm)
+{
+ return pwm ? pwm->pulse_count_max : 0;
+}
+
+/*
+ * pwm_set_pulse_count_max - set the maximum number of pulses
+ */
+static inline void pwm_set_pulse_count_max(struct pwm_device *pwm,
+ unsigned int pulse_count_max)
+{
+ if (pwm)
+ pwm->pulse_count_max = pulse_count_max;
+}
+
/**
* struct pwm_ops - PWM controller operations
* @request: optional hook for requesting a PWM
@@ -157,7 +215,7 @@ struct pwm_ops {
int (*request)(struct pwm_chip *chip, struct pwm_device *pwm);
void (*free)(struct pwm_chip *chip, struct pwm_device *pwm);
int (*config)(struct pwm_chip *chip, struct pwm_device *pwm,
- int duty_ns, int period_ns);
+ int duty_ns, int period_ns, unsigned int pulse_count);
int (*set_polarity)(struct pwm_chip *chip, struct pwm_device *pwm,
enum pwm_polarity polarity);
int (*enable)(struct pwm_chip *chip, struct pwm_device *pwm);
--
2.6.1