[RFC PATCH 1/3] pwm: add duty offset support

From: Trevor Gamblin
Date: Thu Apr 04 2024 - 20:30:58 EST

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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@xxxxxxxxxxxx>
---
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

Next message: Dave Hansen: "Re: [PATCH] x86/cpufeatures: Add CPUID_LNX_5 to track recently added Linux-defined word"
Previous message: Trevor Gamblin: "[RFC PATCH 3/3] pwm: add pwm_config_full to pwm.h"
In reply to: Trevor Gamblin: "[RFC PATCH 3/3] pwm: add pwm_config_full to pwm.h"
Next in thread: Uwe Kleine-König: "Re: [RFC PATCH 0/3] pwm: add support for duty_offset"
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