pwm: Add different PWM output types support
Normally, PWM channel has fixed output until software request to change
its settings. There are some PWM devices which their outputs could be
changed autonomously according to a predefined pattern programmed in
hardware. Add pwm_output_type enum type to identify these two different
PWM types and add relevant helper functions to set and get PWM output
types and pattern.
Change-Id: Ia1f914a45ab4f4dd7be037a395eeb89d0e65a80e
Signed-off-by: Fenglin Wu <fenglinw@codeaurora.org>
diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index 172ef82..17b808c 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -285,6 +285,7 @@
pwm->pwm = chip->base + i;
pwm->hwpwm = i;
pwm->state.polarity = polarity;
+ pwm->state.output_type = PWM_OUTPUT_FIXED;
if (chip->ops->get_state)
chip->ops->get_state(chip, pwm, &pwm->state);
@@ -498,6 +499,31 @@
pwm->state.polarity = state->polarity;
}
+ if (state->output_type != pwm->state.output_type) {
+ if (!pwm->chip->ops->set_output_type)
+ return -ENOTSUPP;
+
+ err = pwm->chip->ops->set_output_type(pwm->chip, pwm,
+ state->output_type);
+ if (err)
+ return err;
+
+ pwm->state.output_type = state->output_type;
+ }
+
+ if (state->output_pattern != pwm->state.output_pattern &&
+ state->output_pattern != NULL) {
+ if (!pwm->chip->ops->set_output_pattern)
+ return -ENOTSUPP;
+
+ err = pwm->chip->ops->set_output_pattern(pwm->chip,
+ pwm, state->output_pattern);
+ if (err)
+ return err;
+
+ pwm->state.output_pattern = state->output_pattern;
+ }
+
if (state->period != pwm->state.period ||
state->duty_cycle != pwm->state.duty_cycle) {
err = pwm->chip->ops->config(pwm->chip, pwm,
diff --git a/drivers/pwm/sysfs.c b/drivers/pwm/sysfs.c
index a813239..ea2b53d 100644
--- a/drivers/pwm/sysfs.c
+++ b/drivers/pwm/sysfs.c
@@ -223,11 +223,60 @@
return sprintf(buf, "%u %u\n", result.period, result.duty_cycle);
}
+static ssize_t output_type_show(struct device *child,
+ struct device_attribute *attr,
+ char *buf)
+{
+ const struct pwm_device *pwm = child_to_pwm_device(child);
+ const char *output_type = "unknown";
+ struct pwm_state state;
+
+ pwm_get_state(pwm, &state);
+ switch (state.output_type) {
+ case PWM_OUTPUT_FIXED:
+ output_type = "fixed";
+ break;
+ case PWM_OUTPUT_MODULATED:
+ output_type = "modulated";
+ break;
+ default:
+ break;
+ }
+
+ return snprintf(buf, PAGE_SIZE, "%s\n", output_type);
+}
+
+static ssize_t output_type_store(struct device *child,
+ struct device_attribute *attr,
+ const char *buf, size_t size)
+{
+ struct pwm_export *export = child_to_pwm_export(child);
+ struct pwm_device *pwm = export->pwm;
+ struct pwm_state state;
+ int ret = -EINVAL;
+
+ mutex_lock(&export->lock);
+ pwm_get_state(pwm, &state);
+ if (sysfs_streq(buf, "fixed"))
+ state.output_type = PWM_OUTPUT_FIXED;
+ else if (sysfs_streq(buf, "modulated"))
+ state.output_type = PWM_OUTPUT_MODULATED;
+ else
+ goto unlock;
+
+ ret = pwm_apply_state(pwm, &state);
+unlock:
+ mutex_unlock(&export->lock);
+
+ return ret ? : size;
+}
+
static DEVICE_ATTR_RW(period);
static DEVICE_ATTR_RW(duty_cycle);
static DEVICE_ATTR_RW(enable);
static DEVICE_ATTR_RW(polarity);
static DEVICE_ATTR_RO(capture);
+static DEVICE_ATTR_RW(output_type);
static struct attribute *pwm_attrs[] = {
&dev_attr_period.attr,
@@ -235,6 +284,7 @@
&dev_attr_enable.attr,
&dev_attr_polarity.attr,
&dev_attr_capture.attr,
+ &dev_attr_output_type.attr,
NULL
};
ATTRIBUTE_GROUPS(pwm);
diff --git a/include/linux/pwm.h b/include/linux/pwm.h
index 2c6c511..6c0168b 100644
--- a/include/linux/pwm.h
+++ b/include/linux/pwm.h
@@ -47,6 +47,29 @@
PWMF_EXPORTED = 1 << 1,
};
+/**
+ * enum pwm_output_type - output type of the PWM signal
+ * @PWM_OUTPUT_FIXED: PWM output is fixed until a change request
+ * @PWM_OUTPUT_MODULATED: PWM output is modulated in hardware
+ * autonomously with a predefined pattern
+ */
+enum pwm_output_type {
+ PWM_OUTPUT_FIXED = 1 << 0,
+ PWM_OUTPUT_MODULATED = 1 << 1,
+};
+
+/**
+ * struct pwm_output_pattern - PWM duty pattern for MODULATED duty type
+ * @duty_pattern: PWM duty cycles in the pattern for duty modulation
+ * @num_entries: number of entries in the pattern
+ * @cycles_per_duty: number of PWM period cycles an entry stays at
+ */
+struct pwm_output_pattern {
+ unsigned int *duty_pattern;
+ unsigned int num_entries;
+ unsigned int cycles_per_duty;
+};
+
/*
* struct pwm_state - state of a PWM channel
* @period: PWM period (in nanoseconds)
@@ -58,6 +81,8 @@
unsigned int period;
unsigned int duty_cycle;
enum pwm_polarity polarity;
+ enum pwm_output_type output_type;
+ struct pwm_output_pattern *output_pattern;
bool enabled;
};
@@ -143,6 +168,26 @@
return state.polarity;
}
+static inline enum pwm_output_type pwm_get_output_type(
+ const struct pwm_device *pwm)
+{
+ struct pwm_state state;
+
+ pwm_get_state(pwm, &state);
+
+ return state.output_type;
+}
+
+static inline struct pwm_output_pattern *pwm_get_output_pattern(
+ struct pwm_device *pwm)
+{
+ struct pwm_state state;
+
+ pwm_get_state(pwm, &state);
+
+ return pwm->state.output_pattern ?: NULL;
+}
+
static inline void pwm_get_args(const struct pwm_device *pwm,
struct pwm_args *args)
{
@@ -246,6 +291,9 @@
* @capture: capture and report PWM signal
* @enable: enable PWM output toggling
* @disable: disable PWM output toggling
+ * @get_output_type_supported: get the supported output type
+ * @set_output_type: set PWM output type
+ * @set_output_pattern: set the pattern for the modulated output
* @apply: atomically apply a new PWM config. The state argument
* should be adjusted with the real hardware config (if the
* approximate the period or duty_cycle value, state should
@@ -267,6 +315,13 @@
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 (*get_output_type_supported)(struct pwm_chip *chip,
+ struct pwm_device *pwm);
+ int (*set_output_type)(struct pwm_chip *chip, struct pwm_device *pwm,
+ enum pwm_output_type output_type);
+ int (*set_output_pattern)(struct pwm_chip *chip,
+ struct pwm_device *pwm,
+ struct pwm_output_pattern *output_pattern);
int (*apply)(struct pwm_chip *chip, struct pwm_device *pwm,
struct pwm_state *state);
void (*get_state)(struct pwm_chip *chip, struct pwm_device *pwm,
@@ -323,6 +378,21 @@
int pwm_adjust_config(struct pwm_device *pwm);
/**
+ * pwm_output_type_support()
+ * @pwm: PWM device
+ *
+ * Returns: output types supported by the PWM device
+ */
+static inline int pwm_get_output_type_supported(struct pwm_device *pwm)
+{
+ if (pwm->chip->ops->get_output_type_supported != NULL)
+ return pwm->chip->ops->
+ get_output_type_supported(pwm->chip, pwm);
+ else
+ return PWM_OUTPUT_FIXED;
+}
+
+/**
* pwm_config() - change a PWM device configuration
* @pwm: PWM device
* @duty_ns: "on" time (in nanoseconds)