[PATCH RCC 1/6] pwm: Add different PWM output types support

Martin Botka
2020-07-24T21:37:49Z

From: Fenglin Wu <fenglinw@codeaurora.org>

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.

Signed-off-by: Fenglin Wu <fenglinw@codeaurora.org>
[konradybcio@gmail.com: Fast-forward from kernel 4.14 to 5.8]
Signed-off-by: Konrad Dybcio <konradybcio@gmail.com>
Signed-off-by: Martin Botka <martin.botka1@gmail.com>
---
drivers/pwm/core.c | 26 +++++++++++++++++
drivers/pwm/sysfs.c | 50 ++++++++++++++++++++++++++++++++
include/linux/pwm.h | 69 +++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 145 insertions(+)

diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index 004b2ea9b5fd..f3aa44106962 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -304,6 +304,7 @@ int pwmchip_add_with_polarity(struct pwm_chip *chip,
pwm->pwm = chip->base + i;
pwm->hwpwm = i;
pwm->state.polarity = polarity;
+ pwm->state.output_type = PWM_OUTPUT_FIXED;

radix_tree_insert(&pwm_tree, pwm->pwm, pwm);
}
@@ -627,6 +628,31 @@ int pwm_apply_state(struct pwm_device *pwm, const struct pwm_state *state)
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 = chip->ops->config(pwm->chip, pwm,
diff --git a/drivers/pwm/sysfs.c b/drivers/pwm/sysfs.c
index 2389b8669846..4ee1e81db0bc 100644
--- a/drivers/pwm/sysfs.c
+++ b/drivers/pwm/sysfs.c
@@ -215,11 +215,60 @@ static ssize_t capture_show(struct device *child,
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,
@@ -227,6 +276,7 @@ static struct attribute *pwm_attrs[] = {
&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 2635b2a55090..10a102efadc4 100644
--- a/include/linux/pwm.h
+++ b/include/linux/pwm.h
@@ -48,6 +48,29 @@ enum {
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)
@@ -59,6 +82,8 @@ struct pwm_state {
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;
};

@@ -146,6 +171,26 @@ static inline enum pwm_polarity pwm_get_polarity(const struct pwm_device *pwm)
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)
{
@@ -254,6 +299,9 @@ pwm_set_relative_duty_cycle(struct pwm_state *state, unsigned int duty_cycle,
* @set_polarity: configure the polarity of this PWM
* @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
*/
struct pwm_ops {
int (*request)(struct pwm_chip *chip, struct pwm_device *pwm);
@@ -273,6 +321,13 @@ struct pwm_ops {
enum pwm_polarity polarity);
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);
};

/**
@@ -318,6 +373,20 @@ void pwm_free(struct pwm_device *pwm);
int pwm_apply_state(struct pwm_device *pwm, const struct pwm_state *state);
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
--
2.27.0