[RFC PATCH 1/2] drivers: pwm: core: implement pwm mode
Claudiu Beznea
claudiu.beznea at microchip.com
Wed Apr 5 06:58:58 PDT 2017
Extends PWM framework to support PWM modes. The currently
implemented PWM modes were called PWM complementary mode
and PWM push-pull mode. For devices that have more than one
output per PWM channel:
- PWM complementary mode is standard working mode; in PWM
complementary mode the rising and falling edges of the
channels outputs have opposite levels, same duration and
same starting time.
- in PWM push-pull mode the channles outputs has same levels,
same duration and the rising edges are delayed until the
beginning of the next period.
A new member was added in pwm_state structure in order to
keep the new PWM argument.
For PWM channels with inputs in DT, the mode could also be
passed via DT. No new extra field need to be added in device
tree; since the signal polarity is passed as a flag via DT,
the filed used to pass information for PWM channel polarity
via DT is also used by PWM mode. Since, for the moment, only
the complementary and push-pull modes are implemented, only
one bit in flags used to pass polarity could also be used for
PWM mode. The other drivers are not affected by this change.
Signed-off-by: Claudiu Beznea <claudiu.beznea at microchip.com>
---
Documentation/pwm.txt | 24 +++++++++++++++++---
drivers/pwm/core.c | 13 +++++++++--
drivers/pwm/sysfs.c | 52 +++++++++++++++++++++++++++++++++++++++++++
include/dt-bindings/pwm/pwm.h | 1 +
include/linux/pwm.h | 37 ++++++++++++++++++++++++++++--
5 files changed, 120 insertions(+), 7 deletions(-)
diff --git a/Documentation/pwm.txt b/Documentation/pwm.txt
index 789b27c..1b6fc59 100644
--- a/Documentation/pwm.txt
+++ b/Documentation/pwm.txt
@@ -59,9 +59,9 @@ In addition to the PWM state, the PWM API also exposes PWM arguments, which
are the reference PWM config one should use on this PWM.
PWM arguments are usually platform-specific and allows the PWM user to only
care about dutycycle relatively to the full period (like, duty = 50% of the
-period). struct pwm_args contains 2 fields (period and polarity) and should
-be used to set the initial PWM config (usually done in the probe function
-of the PWM user). PWM arguments are retrieved with pwm_get_args().
+period). struct pwm_args contains 3 fields (period, polarity and mode) and
+should be used to set the initial PWM config (usually done in the probe
+function of the PWM user). PWM arguments are retrieved with pwm_get_args().
Using PWMs with the sysfs interface
-----------------------------------
@@ -100,6 +100,24 @@ enable - Enable/disable the PWM signal (read/write).
0 - disabled
1 - enabled
+mode - Set PWM signal type (for channels with more than one output
+ per channel)
+ complementary - for an output signal as follow:
+ __ __ __ __
+ PWMH __| |__| |__| |__| |__
+ __ __ __ __ __
+ PWML |__| |__| |__| |__|
+ <--T-->
+ Where T is the signal period.
+
+ push-pull - for an output signal as follows:
+ __ __
+ PWMH __| |________| |________
+ __ __
+ PWML ________| |________| |__
+ <--T-->
+ Where T is the signal period.
+
Implementing a PWM driver
-------------------------
diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index a0860b3..4efc92d 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -154,9 +154,14 @@ of_pwm_xlate_with_flags(struct pwm_chip *pc, const struct of_phandle_args *args)
pwm->args.period = args->args[1];
pwm->args.polarity = PWM_POLARITY_NORMAL;
+ pwm->args.mode = PWM_MODE_COMPLEMENTARY;
- if (args->args_count > 2 && args->args[2] & PWM_POLARITY_INVERTED)
- pwm->args.polarity = PWM_POLARITY_INVERSED;
+ if (args->args_count > 2) {
+ if (args->args[2] & PWM_POLARITY_INVERTED)
+ pwm->args.polarity = PWM_POLARITY_INVERSED;
+ if (args->args[2] & PWM_MODE_PUSHPULL)
+ pwm->args.mode = PWM_MODE_PUSH_PULL;
+ }
return pwm;
}
@@ -579,6 +584,8 @@ int pwm_adjust_config(struct pwm_device *pwm)
pwm_get_args(pwm, &pargs);
pwm_get_state(pwm, &state);
+ state.mode = pargs.mode;
+
/*
* If the current period is zero it means that either the PWM driver
* does not support initial state retrieval or the PWM has not yet
@@ -997,6 +1004,8 @@ static void pwm_dbg_show(struct pwm_chip *chip, struct seq_file *s)
seq_printf(s, " duty: %u ns", state.duty_cycle);
seq_printf(s, " polarity: %s",
state.polarity ? "inverse" : "normal");
+ seq_printf(s, " mode: %s",
+ state.mode ? "push-pull" : "complementary");
seq_puts(s, "\n");
}
diff --git a/drivers/pwm/sysfs.c b/drivers/pwm/sysfs.c
index a813239..58f02bf 100644
--- a/drivers/pwm/sysfs.c
+++ b/drivers/pwm/sysfs.c
@@ -223,11 +223,62 @@ static ssize_t capture_show(struct device *child,
return sprintf(buf, "%u %u\n", result.period, result.duty_cycle);
}
+static ssize_t mode_show(struct device *child,
+ struct device_attribute *attr,
+ char *buf)
+{
+ const struct pwm_device *pwm = child_to_pwm_device(child);
+ const char *mode = "unknown";
+ struct pwm_state state;
+
+ pwm_get_state(pwm, &state);
+
+ switch (state.mode) {
+ case PWM_MODE_COMPLEMENTARY:
+ mode = "complementary";
+ break;
+
+ case PWM_MODE_PUSH_PULL:
+ mode = "push-pull";
+ break;
+ }
+
+ return sprintf(buf, "%s\n", mode);
+}
+
+static ssize_t mode_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;
+ enum pwm_mode mode;
+ struct pwm_state state;
+ int ret;
+
+ if (sysfs_streq(buf, "complementary"))
+ mode = PWM_MODE_COMPLEMENTARY;
+ else if (sysfs_streq(buf, "push-pull"))
+ mode = PWM_MODE_PUSH_PULL;
+ else
+ return -EINVAL;
+
+ mutex_lock(&export->lock);
+ pwm_get_state(pwm, &state);
+ state.mode = mode;
+ ret = pwm_apply_state(pwm, &state);
+ 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(mode);
static struct attribute *pwm_attrs[] = {
&dev_attr_period.attr,
@@ -235,6 +286,7 @@ static struct attribute *pwm_attrs[] = {
&dev_attr_enable.attr,
&dev_attr_polarity.attr,
&dev_attr_capture.attr,
+ &dev_attr_mode.attr,
NULL
};
ATTRIBUTE_GROUPS(pwm);
diff --git a/include/dt-bindings/pwm/pwm.h b/include/dt-bindings/pwm/pwm.h
index 96f49e8..83bb884 100644
--- a/include/dt-bindings/pwm/pwm.h
+++ b/include/dt-bindings/pwm/pwm.h
@@ -10,5 +10,6 @@
#define _DT_BINDINGS_PWM_PWM_H
#define PWM_POLARITY_INVERTED (1 << 0)
+#define PWM_MODE_PUSHPULL (1 << 1)
#endif
diff --git a/include/linux/pwm.h b/include/linux/pwm.h
index 08fad7c..d924e55 100644
--- a/include/linux/pwm.h
+++ b/include/linux/pwm.h
@@ -25,9 +25,23 @@ enum pwm_polarity {
};
/**
+ * enum pwm_mode - PWM mode
+ * @PWM_MODE_COMPLEMENTARY: rising and falling edges of the complementary
+ * PWM channels have opposite levels, same duration and same starting time
+ * @PWM_MODE_PUSH_PULL: rising and falling edges of the complementary PWM
+ * channels have same levels, same duration and are delayed until the
+ * beginning of the next period
+ */
+enum pwm_mode {
+ PWM_MODE_COMPLEMENTARY,
+ PWM_MODE_PUSH_PULL,
+};
+
+/**
* struct pwm_args - board-dependent PWM arguments
* @period: reference period
* @polarity: reference polarity
+ * @mode: pwm mode
*
* This structure describes board-dependent arguments attached to a PWM
* device. These arguments are usually retrieved from the PWM lookup table or
@@ -40,6 +54,7 @@ enum pwm_polarity {
struct pwm_args {
unsigned int period;
enum pwm_polarity polarity;
+ enum pwm_mode mode;
};
enum {
@@ -52,12 +67,14 @@ enum {
* @period: PWM period (in nanoseconds)
* @duty_cycle: PWM duty cycle (in nanoseconds)
* @polarity: PWM polarity
+ * @mode: PWM mode
* @enabled: PWM enabled status
*/
struct pwm_state {
unsigned int period;
unsigned int duty_cycle;
enum pwm_polarity polarity;
+ enum pwm_mode mode;
bool enabled;
};
@@ -143,6 +160,21 @@ static inline enum pwm_polarity pwm_get_polarity(const struct pwm_device *pwm)
return state.polarity;
}
+static inline void pwm_set_mode(struct pwm_device *pwm, enum pwm_mode mode)
+{
+ if (pwm)
+ pwm->state.mode = mode;
+}
+
+static inline enum pwm_mode pwm_get_mode(const struct pwm_device *pwm)
+{
+ struct pwm_state state;
+
+ pwm_get_state(pwm, &state);
+
+ return state.mode;
+}
+
static inline void pwm_get_args(const struct pwm_device *pwm,
struct pwm_args *args)
{
@@ -156,8 +188,8 @@ static inline void pwm_get_args(const struct pwm_device *pwm,
*
* This functions prepares a state that can later be tweaked and applied
* to the PWM device with pwm_apply_state(). This is a convenient function
- * that first retrieves the current PWM state and the replaces the period
- * and polarity fields with the reference values defined in pwm->args.
+ * that first retrieves the current PWM state and the replaces the period,
+ * polarity and mode fields with the reference values defined in pwm->args.
* Once the function returns, you can adjust the ->enabled and ->duty_cycle
* fields according to your needs before calling pwm_apply_state().
*
@@ -180,6 +212,7 @@ static inline void pwm_init_state(const struct pwm_device *pwm,
state->period = args.period;
state->polarity = args.polarity;
state->duty_cycle = 0;
+ state->mode = args.mode;
}
/**
--
2.7.4
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