[PATCH RFC v4 01/15] pwm: core: export pwm_get_state_hw()

[David Lechner <dlechner@xxxxxxxxxxxx>]

Export the pwm_get_state_hw() function. This is useful in cases where
we want to know what the hardware is actually doing, rather than what
what we requested it should do.

Signed-off-by: David Lechner <dlechner@xxxxxxxxxxxx>
---

v4 changes: new patch in v4

And FYI for Uwe and Jonathan, there are a couple of other series
introducing PWM conversion triggers that could make use of this
so that the sampling_frequency attribute can return the actual rate
rather than the requested rate.

Already applied:
https://lore.kernel.org/linux-iio/20241015-ad7606_add_iio_backend_support-v5-4-654faf1ae08c@xxxxxxxxxxxx/

Under review:
https://lore.kernel.org/linux-iio/aea7f92b-3d12-4ced-b1c8-90bcf1d992d3@xxxxxxxxxxxx/T/#m1377d5acd7e996acd1f59038bdd09f0742d3ac35
---
 drivers/pwm/core.c  | 55 +++++++++++++++++++++++++++++++++++++----------------
 include/linux/pwm.h |  1 +
 2 files changed, 40 insertions(+), 16 deletions(-)

diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index 634be56e204b..a214d0165d09 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -718,7 +718,7 @@ int pwm_apply_atomic(struct pwm_device *pwm, const struct pwm_state *state)
 }
 EXPORT_SYMBOL_GPL(pwm_apply_atomic);
 
-static int pwm_get_state_hw(struct pwm_device *pwm, struct pwm_state *state)
+static int __pwm_get_state_hw(struct pwm_device *pwm, struct pwm_state *state)
 {
 	struct pwm_chip *chip = pwm->chip;
 	const struct pwm_ops *ops = chip->ops;
@@ -730,29 +730,50 @@ static int pwm_get_state_hw(struct pwm_device *pwm, struct pwm_state *state)
 
 		BUG_ON(WFHWSIZE < ops->sizeof_wfhw);
 
-		scoped_guard(pwmchip, chip) {
-
-			ret = __pwm_read_waveform(chip, pwm, &wfhw);
-			if (ret)
-				return ret;
+		ret = __pwm_read_waveform(chip, pwm, &wfhw);
+		if (ret)
+			return ret;
 
-			ret = __pwm_round_waveform_fromhw(chip, pwm, &wfhw, &wf);
-			if (ret)
-				return ret;
-		}
+		ret = __pwm_round_waveform_fromhw(chip, pwm, &wfhw, &wf);
+		if (ret)
+			return ret;
 
 		pwm_wf2state(&wf, state);
 
 	} else if (ops->get_state) {
-		scoped_guard(pwmchip, chip)
-			ret = ops->get_state(chip, pwm, state);
-
+		ret = ops->get_state(chip, pwm, state);
 		trace_pwm_get(pwm, state, ret);
 	}
 
 	return ret;
 }
 
+/**
+ * pwm_get_state_hw() - get the current PWM state from hardware
+ * @pwm: PWM device
+ * @state: state to fill with the current PWM state
+ *
+ * Similar to pwm_get_state() but reads the current PWM state from hardware
+ * instead of the requested state.
+ *
+ * Returns: 0 on success or a negative error code on failure.
+ * Context: May sleep.
+ */
+int pwm_get_state_hw(struct pwm_device *pwm, struct pwm_state *state)
+{
+	struct pwm_chip *chip = pwm->chip;
+
+	might_sleep();
+
+	guard(pwmchip)(chip);
+
+	if (!chip->operational)
+		return -ENODEV;
+
+	return __pwm_get_state_hw(pwm, state);
+}
+EXPORT_SYMBOL_GPL(pwm_get_state_hw);
+
 /**
  * pwm_adjust_config() - adjust the current PWM config to the PWM arguments
  * @pwm: PWM device
@@ -906,9 +927,11 @@ static int pwm_device_request(struct pwm_device *pwm, const char *label)
 		 */
 		struct pwm_state state = { 0, };
 
-		err = pwm_get_state_hw(pwm, &state);
-		if (!err)
-			pwm->state = state;
+		scoped_guard(pwmchip, chip) {
+			err = __pwm_get_state_hw(pwm, &state);
+			if (!err)
+				pwm->state = state;
+		}
 
 		if (IS_ENABLED(CONFIG_PWM_DEBUG))
 			pwm->last = pwm->state;
diff --git a/include/linux/pwm.h b/include/linux/pwm.h
index f1cb1e5b0a36..5bcbcf2911c3 100644
--- a/include/linux/pwm.h
+++ b/include/linux/pwm.h
@@ -370,6 +370,7 @@ int pwm_get_waveform_might_sleep(struct pwm_device *pwm, struct pwm_waveform *wf
 int pwm_set_waveform_might_sleep(struct pwm_device *pwm, const struct pwm_waveform *wf, bool exact);
 int pwm_apply_might_sleep(struct pwm_device *pwm, const struct pwm_state *state);
 int pwm_apply_atomic(struct pwm_device *pwm, const struct pwm_state *state);
+int pwm_get_state_hw(struct pwm_device *pwm, struct pwm_state *state);
 int pwm_adjust_config(struct pwm_device *pwm);
 
 /**

-- 
2.43.0