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From: Trevor Gamblin <tgamblin@baylibre.com>
To: linux-pwm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org,
	u.kleine-koenig@pengutronix.de,
	michael.hennerich@analog.com,
	nuno.sa@analog.com,
	tgamblin@baylibre.com,
	dlechner@baylibre.com
Subject: [RFC PATCH 1/3] pwm: add duty offset support
Date: Thu,  4 Apr 2024 20:30:23 -0400
Message-ID: <20240405003025.739603-2-tgamblin@baylibre.com>
In-Reply-To: <20240405003025.739603-1-tgamblin@baylibre.com>
References: <20240405003025.739603-1-tgamblin@baylibre.com>
Precedence: bulk
MIME-Version: 1.0
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Some PWM chips support a "phase" or "duty_offset" feature. This patch
continues adding support for configuring this property in the PWM
subsystem.

The pwm_chip struct gains a new supports_offset flag, which can be set
for compatible parts. This is checked in __pwm_apply, where attempts to
set duty_offset result in an EOPNOTSUPP if the flag is not set.

Functions duty_offset_show(), duty_offset_store(), and
pwm_get_duty_offset() are added to match what exists for duty_cycle.

Handle duty_offset in the new pwmchip char device logic.

Also add duty_offset to TP_printk in include/trace/events/pwm.h so that
it is reported with other properties when using the event tracing pipe
for debug.

Signed-off-by: Trevor Gamblin <tgamblin@baylibre.com>
---
 drivers/pwm/core.c         | 75 +++++++++++++++++++++++++++++++++++---
 include/linux/pwm.h        | 17 +++++++++
 include/trace/events/pwm.h |  6 ++-
 3 files changed, 90 insertions(+), 8 deletions(-)

diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index 2745941a008b..0e05518feb21 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -80,6 +80,7 @@ static void pwm_apply_debug(struct pwm_device *pwm,
 	 */
 	if (s1.enabled && s1.polarity != state->polarity) {
 		s2.polarity = state->polarity;
+		s2.duty_offset = s1.duty_cycle;
 		s2.duty_cycle = s1.period - s1.duty_cycle;
 		s2.period = s1.period;
 		s2.enabled = s1.enabled;
@@ -121,6 +122,23 @@ static void pwm_apply_debug(struct pwm_device *pwm,
 			 state->duty_cycle, state->period,
 			 s2.duty_cycle, s2.period);
 
+	if (state->enabled &&
+	    last->polarity == state->polarity &&
+	    last->period == s2.period &&
+	    last->duty_offset > s2.duty_offset &&
+	    last->duty_offset <= state->duty_offset)
+		dev_warn(pwmchip_parent(chip),
+			 ".apply didn't pick the best available duty offset (requested: %llu/%llu, applied: %llu/%llu, possible: %llu/%llu)\n",
+			 state->duty_offset, state->period,
+			 s2.duty_offset, s2.period,
+			 last->duty_offset, last->period);
+
+	if (state->enabled && state->duty_offset < s2.duty_offset)
+		dev_warn(pwmchip_parent(chip),
+			 ".apply is supposed to round down duty_offset (requested: %llu/%llu, applied: %llu/%llu)\n",
+			 state->duty_offset, state->period,
+			 s2.duty_offset, s2.period);
+
 	if (!state->enabled && s2.enabled && s2.duty_cycle > 0)
 		dev_warn(pwmchip_parent(chip),
 			 "requested disabled, but yielded enabled with duty > 0\n");
@@ -144,12 +162,13 @@ static void pwm_apply_debug(struct pwm_device *pwm,
 	if (s1.enabled != last->enabled ||
 	    s1.polarity != last->polarity ||
 	    (s1.enabled && s1.period != last->period) ||
+	    (s1.enabled && s1.duty_offset != last->duty_offset) ||
 	    (s1.enabled && s1.duty_cycle != last->duty_cycle)) {
 		dev_err(pwmchip_parent(chip),
-			".apply is not idempotent (ena=%d pol=%d %llu/%llu) -> (ena=%d pol=%d %llu/%llu)\n",
+			".apply is not idempotent (ena=%d pol=%d %llu/%llu/%llu) -> (ena=%d pol=%d %llu/%llu/%llu)\n",
 			s1.enabled, s1.polarity, s1.duty_cycle, s1.period,
-			last->enabled, last->polarity, last->duty_cycle,
-			last->period);
+			s1.duty_offset, last->enabled, last->polarity,
+			last->duty_cycle, last->period, last->duty_offset);
 	}
 }
 
@@ -164,13 +183,17 @@ static int __pwm_apply(struct pwm_device *pwm, const struct pwm_state *state)
 	int err;
 
 	if (!pwm || !state || !state->period ||
-	    state->duty_cycle > state->period)
+	    state->duty_offset + state->duty_cycle > state->period)
 		return -EINVAL;
 
 	chip = pwm->chip;
 
+	if (!chip->supports_offset && state->duty_offset)
+		return -EOPNOTSUPP;
+
 	if (state->period == pwm->state.period &&
 	    state->duty_cycle == pwm->state.duty_cycle &&
+	    state->duty_offset == pwm->state.duty_offset &&
 	    state->polarity == pwm->state.polarity &&
 	    state->enabled == pwm->state.enabled &&
 	    state->usage_power == pwm->state.usage_power)
@@ -292,10 +315,11 @@ int pwm_adjust_config(struct pwm_device *pwm)
 	 * been configured.
 	 *
 	 * In either case, we setup the new period and polarity, and assign a
-	 * duty cycle of 0.
+	 * duty cycle and offset of 0.
 	 */
 	if (!state.period) {
 		state.duty_cycle = 0;
+		state.duty_offset = 0;
 		state.period = pargs.period;
 		state.polarity = pargs.polarity;
 
@@ -617,6 +641,41 @@ static ssize_t duty_cycle_store(struct device *pwm_dev,
 	return ret ? : size;
 }
 
+static ssize_t duty_offset_show(struct device *pwm_dev,
+			       struct device_attribute *attr,
+			       char *buf)
+{
+	const struct pwm_device *pwm = pwm_from_dev(pwm_dev);
+	struct pwm_state state;
+
+	pwm_get_state(pwm, &state);
+
+	return sysfs_emit(buf, "%llu\n", state.duty_offset);
+}
+
+static ssize_t duty_offset_store(struct device *pwm_dev,
+				struct device_attribute *attr,
+				const char *buf, size_t size)
+{
+	struct pwm_export *export = pwmexport_from_dev(pwm_dev);
+	struct pwm_device *pwm = export->pwm;
+	struct pwm_state state;
+	u64 val;
+	int ret;
+
+	ret = kstrtou64(buf, 0, &val);
+	if (ret)
+		return ret;
+
+	mutex_lock(&export->lock);
+	pwm_get_state(pwm, &state);
+	state.duty_offset = val;
+	ret = pwm_apply_might_sleep(pwm, &state);
+	mutex_unlock(&export->lock);
+
+	return ret ? : size;
+}
+
 static ssize_t enable_show(struct device *pwm_dev,
 			   struct device_attribute *attr,
 			   char *buf)
@@ -731,6 +790,7 @@ static ssize_t capture_show(struct device *pwm_dev,
 
 static DEVICE_ATTR_RW(period);
 static DEVICE_ATTR_RW(duty_cycle);
+static DEVICE_ATTR_RW(duty_offset);
 static DEVICE_ATTR_RW(enable);
 static DEVICE_ATTR_RW(polarity);
 static DEVICE_ATTR_RO(capture);
@@ -738,6 +798,7 @@ static DEVICE_ATTR_RO(capture);
 static struct attribute *pwm_attrs[] = {
 	&dev_attr_period.attr,
 	&dev_attr_duty_cycle.attr,
+	&dev_attr_duty_offset.attr,
 	&dev_attr_enable.attr,
 	&dev_attr_polarity.attr,
 	&dev_attr_capture.attr,
@@ -1290,7 +1351,7 @@ static long pwm_cdev_ioctl(struct file *file, unsigned int cmd, unsigned long ar
 			if (state.enabled) {
 				cstate.period = state.period;
 				if (state.polarity == PWM_POLARITY_NORMAL) {
-					cstate.duty_offset = 0;
+					cstate.duty_offset = state.duty_offset;
 					cstate.duty_cycle = state.duty_cycle;
 				} else {
 					cstate.duty_offset = state.duty_cycle;
@@ -1356,6 +1417,7 @@ static long pwm_cdev_ioctl(struct file *file, unsigned int cmd, unsigned long ar
 				state.period = cstate.period;
 				state.polarity = PWM_POLARITY_NORMAL;
 				state.duty_cycle = cstate.duty_cycle;
+				state.duty_offset = cstate.duty_offset;
 			} else {
 				state.enabled = false;
 			}
@@ -1991,6 +2053,7 @@ static void pwm_dbg_show(struct pwm_chip *chip, struct seq_file *s)
 
 		seq_printf(s, " period: %llu ns", state.period);
 		seq_printf(s, " duty: %llu ns", state.duty_cycle);
+		seq_printf(s, " duty_offset: %llu ns", state.duty_offset);
 		seq_printf(s, " polarity: %s",
 			   state.polarity ? "inverse" : "normal");
 
diff --git a/include/linux/pwm.h b/include/linux/pwm.h
index a58db7011807..e0e5960f91ba 100644
--- a/include/linux/pwm.h
+++ b/include/linux/pwm.h
@@ -51,6 +51,7 @@ enum {
  * struct pwm_state - state of a PWM channel
  * @period: PWM period (in nanoseconds)
  * @duty_cycle: PWM duty cycle (in nanoseconds)
+ * @duty_offset: PWM duty offset (in nanoseconds)
  * @polarity: PWM polarity
  * @enabled: PWM enabled status
  * @usage_power: If set, the PWM driver is only required to maintain the power
@@ -61,6 +62,7 @@ enum {
 struct pwm_state {
 	u64 period;
 	u64 duty_cycle;
+	u64 duty_offset;
 	enum pwm_polarity polarity;
 	bool enabled;
 	bool usage_power;
@@ -130,6 +132,15 @@ static inline u64 pwm_get_duty_cycle(const struct pwm_device *pwm)
 	return state.duty_cycle;
 }
 
+static inline u64 pwm_get_duty_offset(const struct pwm_device *pwm)
+{
+	struct pwm_state state;
+
+	pwm_get_state(pwm, &state);
+
+	return state.duty_offset;
+}
+
 static inline enum pwm_polarity pwm_get_polarity(const struct pwm_device *pwm)
 {
 	struct pwm_state state;
@@ -161,6 +172,9 @@ static inline void pwm_get_args(const struct pwm_device *pwm,
  * ->duty_cycle value exceed the pwm_args->period one, which would trigger
  * an error if the user calls pwm_apply_might_sleep() without adjusting ->duty_cycle
  * first.
+ *
+ * ->duty_offset is likewise set to zero to avoid inconsistent default
+ *  states.
  */
 static inline void pwm_init_state(const struct pwm_device *pwm,
 				  struct pwm_state *state)
@@ -176,6 +190,7 @@ static inline void pwm_init_state(const struct pwm_device *pwm,
 	state->period = args.period;
 	state->polarity = args.polarity;
 	state->duty_cycle = 0;
+	state->duty_offset = 0;
 	state->usage_power = false;
 }
 
@@ -275,6 +290,7 @@ struct pwm_ops {
  * @npwm: number of PWMs controlled by this chip
  * @of_xlate: request a PWM device given a device tree PWM specifier
  * @atomic: can the driver's ->apply() be called in atomic context
+ * @supports_offset: does the driver support duty cycle offset
  * @uses_pwmchip_alloc: signals if pwmchip_allow was used to allocate this chip
  * @operational: signals if the chip can be used (or is already deregistered)
  * @nonatomic_lock: mutex for nonatomic chips
@@ -292,6 +308,7 @@ struct pwm_chip {
 	struct pwm_device * (*of_xlate)(struct pwm_chip *chip,
 					const struct of_phandle_args *args);
 	bool atomic;
+	bool supports_offset;
 
 	/* only used internally by the PWM framework */
 	bool uses_pwmchip_alloc;
diff --git a/include/trace/events/pwm.h b/include/trace/events/pwm.h
index 12b35e4ff917..2d25ac5de816 100644
--- a/include/trace/events/pwm.h
+++ b/include/trace/events/pwm.h
@@ -18,6 +18,7 @@ DECLARE_EVENT_CLASS(pwm,
 		__field(struct pwm_device *, pwm)
 		__field(u64, period)
 		__field(u64, duty_cycle)
+		__field(u64, duty_offset)
 		__field(enum pwm_polarity, polarity)
 		__field(bool, enabled)
 		__field(int, err)
@@ -27,13 +28,14 @@ DECLARE_EVENT_CLASS(pwm,
 		__entry->pwm = pwm;
 		__entry->period = state->period;
 		__entry->duty_cycle = state->duty_cycle;
+		__entry->duty_offset = state->duty_offset;
 		__entry->polarity = state->polarity;
 		__entry->enabled = state->enabled;
 		__entry->err = err;
 	),
 
-	TP_printk("%p: period=%llu duty_cycle=%llu polarity=%d enabled=%d err=%d",
-		  __entry->pwm, __entry->period, __entry->duty_cycle,
+	TP_printk("%p: period=%llu duty_cycle=%llu duty_offset=%llu polarity=%d enabled=%d err=%d",
+		  __entry->pwm, __entry->period, __entry->duty_cycle, __entry->duty_offset,
 		  __entry->polarity, __entry->enabled, __entry->err)
 
 );
-- 
2.44.0