summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
-rw-r--r--drivers/pwm/Kconfig9
-rw-r--r--drivers/pwm/core.c135
-rw-r--r--include/linux/pwm.h4
3 files changed, 140 insertions, 8 deletions
diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index 30190beeb6e9..e21834f44a29 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -33,6 +33,15 @@ config PWM_SYSFS
bool
default y if SYSFS
+config PWM_DEBUG
+ bool "PWM lowlevel drivers additional checks and debug messages"
+ depends on DEBUG_KERNEL
+ help
+ This option enables some additional checks to help lowlevel driver
+ authors to get their callbacks implemented correctly.
+ It is expected to introduce some runtime overhead and diagnostic
+ output to the kernel log, so only enable while working on a driver.
+
config PWM_AB8500
tristate "AB8500 PWM support"
depends on AB8500_CORE && ARCH_U8500
diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index 5a7f6598c05f..e9b9283cff28 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -120,6 +120,9 @@ static int pwm_device_request(struct pwm_device *pwm, const char *label)
if (pwm->chip->ops->get_state) {
pwm->chip->ops->get_state(pwm->chip, pwm, &pwm->state);
trace_pwm_get(pwm, &pwm->state);
+
+ if (IS_ENABLED(PWM_DEBUG))
+ pwm->last = pwm->state;
}
set_bit(PWMF_REQUESTED, &pwm->flags);
@@ -232,17 +235,28 @@ void *pwm_get_chip_data(struct pwm_device *pwm)
}
EXPORT_SYMBOL_GPL(pwm_get_chip_data);
-static bool pwm_ops_check(const struct pwm_ops *ops)
+static bool pwm_ops_check(const struct pwm_chip *chip)
{
+
+ const struct pwm_ops *ops = chip->ops;
+
/* driver supports legacy, non-atomic operation */
- if (ops->config && ops->enable && ops->disable)
- return true;
+ if (ops->config && ops->enable && ops->disable) {
+ if (IS_ENABLED(CONFIG_PWM_DEBUG))
+ dev_warn(chip->dev,
+ "Driver needs updating to atomic API\n");
- /* driver supports atomic operation */
- if (ops->apply)
return true;
+ }
- return false;
+ if (!ops->apply)
+ return false;
+
+ if (IS_ENABLED(CONFIG_PWM_DEBUG) && !ops->get_state)
+ dev_warn(chip->dev,
+ "Please implement the .get_state() callback\n");
+
+ return true;
}
/**
@@ -266,7 +280,7 @@ int pwmchip_add_with_polarity(struct pwm_chip *chip,
if (!chip || !chip->dev || !chip->ops || !chip->npwm)
return -EINVAL;
- if (!pwm_ops_check(chip->ops))
+ if (!pwm_ops_check(chip))
return -EINVAL;
mutex_lock(&pwm_lock);
@@ -450,6 +464,107 @@ void pwm_free(struct pwm_device *pwm)
}
EXPORT_SYMBOL_GPL(pwm_free);
+void pwm_apply_state_debug(struct pwm_device *pwm,
+ const struct pwm_state *state)
+{
+ struct pwm_state *last = &pwm->last;
+ struct pwm_chip *chip = pwm->chip;
+ struct pwm_state s1, s2;
+ int err;
+
+ if (!IS_ENABLED(CONFIG_PWM_DEBUG))
+ return;
+
+ /* No reasonable diagnosis possible without .get_state() */
+ if (!chip->ops->get_state)
+ return;
+
+ /*
+ * *state was just applied. Read out the hardware state and do some
+ * checks.
+ */
+
+ chip->ops->get_state(chip, pwm, &s1);
+ trace_pwm_get(pwm, &s1);
+
+ /*
+ * The lowlevel driver either ignored .polarity (which is a bug) or as
+ * best effort inverted .polarity and fixed .duty_cycle respectively.
+ * Undo this inversion and fixup for further tests.
+ */
+ if (s1.enabled && s1.polarity != state->polarity) {
+ s2.polarity = state->polarity;
+ s2.duty_cycle = s1.period - s1.duty_cycle;
+ s2.period = s1.period;
+ s2.enabled = s1.enabled;
+ } else {
+ s2 = s1;
+ }
+
+ if (s2.polarity != state->polarity &&
+ state->duty_cycle < state->period)
+ dev_warn(chip->dev, ".apply ignored .polarity\n");
+
+ if (state->enabled &&
+ last->polarity == state->polarity &&
+ last->period > s2.period &&
+ last->period <= state->period)
+ dev_warn(chip->dev,
+ ".apply didn't pick the best available period (requested: %u, applied: %u, possible: %u)\n",
+ state->period, s2.period, last->period);
+
+ if (state->enabled && state->period < s2.period)
+ dev_warn(chip->dev,
+ ".apply is supposed to round down period (requested: %u, applied: %u)\n",
+ state->period, s2.period);
+
+ if (state->enabled &&
+ last->polarity == state->polarity &&
+ last->period == s2.period &&
+ last->duty_cycle > s2.duty_cycle &&
+ last->duty_cycle <= state->duty_cycle)
+ dev_warn(chip->dev,
+ ".apply didn't pick the best available duty cycle (requested: %u/%u, applied: %u/%u, possible: %u/%u)\n",
+ state->duty_cycle, state->period,
+ s2.duty_cycle, s2.period,
+ last->duty_cycle, last->period);
+
+ if (state->enabled && state->duty_cycle < s2.duty_cycle)
+ dev_warn(chip->dev,
+ ".apply is supposed to round down duty_cycle (requested: %u/%u, applied: %u/%u)\n",
+ state->duty_cycle, state->period,
+ s2.duty_cycle, s2.period);
+
+ if (!state->enabled && s2.enabled && s2.duty_cycle > 0)
+ dev_warn(chip->dev,
+ "requested disabled, but yielded enabled with duty > 0");
+
+ /* reapply the state that the driver reported being configured. */
+ err = chip->ops->apply(chip, pwm, &s1);
+ if (err) {
+ *last = s1;
+ dev_err(chip->dev, "failed to reapply current setting\n");
+ return;
+ }
+
+ trace_pwm_apply(pwm, &s1);
+
+ chip->ops->get_state(chip, pwm, last);
+ trace_pwm_get(pwm, last);
+
+ /* reapplication of the current state should give an exact match */
+ if (s1.enabled != last->enabled ||
+ s1.polarity != last->polarity ||
+ (s1.enabled && s1.period != last->period) ||
+ (s1.enabled && s1.duty_cycle != last->duty_cycle)) {
+ dev_err(chip->dev,
+ ".apply is not idempotent (ena=%d pol=%d %u/%u) -> (ena=%d pol=%d %u/%u)\n",
+ s1.enabled, s1.polarity, s1.duty_cycle, s1.period,
+ last->enabled, last->polarity, last->duty_cycle,
+ last->period);
+ }
+}
+
/**
* pwm_apply_state() - atomically apply a new state to a PWM device
* @pwm: PWM device
@@ -480,6 +595,12 @@ int pwm_apply_state(struct pwm_device *pwm, const struct pwm_state *state)
trace_pwm_apply(pwm, state);
pwm->state = *state;
+
+ /*
+ * only do this after pwm->state was applied as some
+ * implementations of .get_state depend on this
+ */
+ pwm_apply_state_debug(pwm, state);
} else {
/*
* FIXME: restore the initial state in case of error.
diff --git a/include/linux/pwm.h b/include/linux/pwm.h
index 0ef808d925bb..2635b2a55090 100644
--- a/include/linux/pwm.h
+++ b/include/linux/pwm.h
@@ -71,7 +71,8 @@ struct pwm_state {
* @chip: PWM chip providing this PWM device
* @chip_data: chip-private data associated with the PWM device
* @args: PWM arguments
- * @state: curent PWM channel state
+ * @state: last applied state
+ * @last: last implemented state (for PWM_DEBUG)
*/
struct pwm_device {
const char *label;
@@ -83,6 +84,7 @@ struct pwm_device {
struct pwm_args args;
struct pwm_state state;
+ struct pwm_state last;
};
/**