Merge tag 'pwm/for-6.14-rc1-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/ukleinek/linux

Pull pwm fixes from Uwe Kleine-König:
 "Two fixes.

  Conor Dooley found and fixed a problem in the pwm-microchip-core
  driver that existed since the driver's birth in v6.5-rc1. It's about a
  corner case that only happens if two pwm devices of the same chip are
  set to the same long period.

  The other problem is about the new pwm API that currently is only
  supported by two hardware drivers. The fix prevents a NULL pointer
  exception if one of the new functions is called for a pwm device with
  a driver that only provides the old callbacks"

* tag 'pwm/for-6.14-rc1-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/ukleinek/linux:
  pwm: Ensure callbacks exist before calling them
  pwm: microchip-core: fix incorrect comparison with max period

3 files changed, 29 insertions, 3 deletions

diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index 675b252d9c8c..99d0bc693315 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -242,6 +242,9 @@ int pwm_round_waveform_might_sleep(struct pwm_device *pwm, struct pwm_waveform *
 
 	BUG_ON(WFHWSIZE < ops->sizeof_wfhw);
 
+	if (!pwmchip_supports_waveform(chip))
+		return -EOPNOTSUPP;
+
 	if (!pwm_wf_valid(wf))
 		return -EINVAL;
 
@@ -294,6 +297,9 @@ int pwm_get_waveform_might_sleep(struct pwm_device *pwm, struct pwm_waveform *wf
 
 	BUG_ON(WFHWSIZE < ops->sizeof_wfhw);
 
+	if (!pwmchip_supports_waveform(chip) || !ops->read_waveform)
+		return -EOPNOTSUPP;
+
 	guard(pwmchip)(chip);
 
 	if (!chip->operational)
@@ -320,6 +326,9 @@ static int __pwm_set_waveform(struct pwm_device *pwm,
 
 	BUG_ON(WFHWSIZE < ops->sizeof_wfhw);
 
+	if (!pwmchip_supports_waveform(chip))
+		return -EOPNOTSUPP;
+
 	if (!pwm_wf_valid(wf))
 		return -EINVAL;
 
@@ -592,7 +601,7 @@ static int __pwm_apply(struct pwm_device *pwm, const struct pwm_state *state)
 	    state->usage_power == pwm->state.usage_power)
 		return 0;
 
-	if (ops->write_waveform) {
+	if (pwmchip_supports_waveform(chip)) {
 		struct pwm_waveform wf;
 		char wfhw[WFHWSIZE];
 
@@ -746,7 +755,7 @@ int pwm_get_state_hw(struct pwm_device *pwm, struct pwm_state *state)
 	if (!chip->operational)
 		return -ENODEV;
 
-	if (ops->read_waveform) {
+	if (pwmchip_supports_waveform(chip) && ops->read_waveform) {
 		char wfhw[WFHWSIZE];
 		struct pwm_waveform wf;
 
diff --git a/drivers/pwm/pwm-microchip-core.c b/drivers/pwm/pwm-microchip-core.c
index c1f2287b8e97..12821b4bbf97 100644
--- a/drivers/pwm/pwm-microchip-core.c
+++ b/drivers/pwm/pwm-microchip-core.c
@@ -327,7 +327,7 @@ static int mchp_core_pwm_apply_locked(struct pwm_chip *chip, struct pwm_device *
 		 * mchp_core_pwm_calc_period().
 		 * The period is locked and we cannot change this, so we abort.
 		 */
-		if (hw_period_steps == MCHPCOREPWM_PERIOD_STEPS_MAX)
+		if (hw_period_steps > MCHPCOREPWM_PERIOD_STEPS_MAX)
 			return -EINVAL;
 
 		prescale = hw_prescale;
diff --git a/include/linux/pwm.h b/include/linux/pwm.h
index 6853e29d9674..a2df509056ac 100644
--- a/include/linux/pwm.h
+++ b/include/linux/pwm.h
@@ -347,6 +347,23 @@ struct pwm_chip {
 	struct pwm_device pwms[] __counted_by(npwm);
 };
 
+/**
+ * pwmchip_supports_waveform() - checks if the given chip supports waveform callbacks
+ * @chip: The pwm_chip to test
+ *
+ * Returns true iff the pwm chip support the waveform functions like
+ * pwm_set_waveform_might_sleep() and pwm_round_waveform_might_sleep()
+ */
+static inline bool pwmchip_supports_waveform(struct pwm_chip *chip)
+{
+	/*
+	 * only check for .write_waveform(). If that is available,
+	 * .round_waveform_tohw() and .round_waveform_fromhw() asserted to be
+	 * available, too, in pwmchip_add().
+	 */
+	return chip->ops->write_waveform != NULL;
+}
+
 static inline struct device *pwmchip_parent(const struct pwm_chip *chip)
 {
 	return chip->dev.parent;