pwm: Add support referencing PWMs from ACPI

In analogy to referencing a GPIO using the "gpios" property from ACPI,
support referencing a PWM using the "pwms" property.

ACPI entries must look like
 Package () {"pwms", Package ()
     { <PWM device reference>, <PWM index>, <PWM period> [, <PWM flags>]}}

In contrast to the DT implementation, only _one_ PWM entry in the "pwms"
property is supported. As a consequence "pwm-names"-property and
con_id lookup aren't supported.

Support for ACPI is added via the firmware-node framework which is an
abstraction layer on top of ACPI/DT. To keep this patch clean, DT and
ACPI paths are kept separate. The firmware-node framework could be used
to unify both paths in a future patch.

To support leds-pwm driver, an additional method devm_fwnode_pwm_get()
which supports both ACPI and DT configuration is exported.

Signed-off-by: Nikolaus Voss <nikolaus.voss@loewensteinmedical.de>
[thierry.reding@gmail.com: fix build failures for !ACPI]
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

drivers/pwm/core.c

@@ -19,6 +19,7 @@
  *  the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+#include <linux/acpi.h>
 #include <linux/module.h>
 #include <linux/pwm.h>
 #include <linux/radix-tree.h>
@@ -750,6 +751,85 @@ put:
 }
 EXPORT_SYMBOL_GPL(of_pwm_get);
 
+#if IS_ENABLED(CONFIG_ACPI)
+static struct pwm_chip *device_to_pwmchip(struct device *dev)
+{
+	struct pwm_chip *chip;
+
+	mutex_lock(&pwm_lock);
+
+	list_for_each_entry(chip, &pwm_chips, list) {
+		struct acpi_device *adev = ACPI_COMPANION(chip->dev);
+
+		if ((chip->dev == dev) || (adev && &adev->dev == dev)) {
+			mutex_unlock(&pwm_lock);
+			return chip;
+		}
+	}
+
+	mutex_unlock(&pwm_lock);
+
+	return ERR_PTR(-EPROBE_DEFER);
+}
+#endif
+
+/**
+ * acpi_pwm_get() - request a PWM via parsing "pwms" property in ACPI
+ * @fwnode: firmware node to get the "pwm" property from
+ *
+ * Returns the PWM device parsed from the fwnode and index specified in the
+ * "pwms" property or a negative error-code on failure.
+ * Values parsed from the device tree are stored in the returned PWM device
+ * object.
+ *
+ * This is analogous to of_pwm_get() except con_id is not yet supported.
+ * ACPI entries must look like
+ * Package () {"pwms", Package ()
+ *     { <PWM device reference>, <PWM index>, <PWM period> [, <PWM flags>]}}
+ *
+ * Returns: A pointer to the requested PWM device or an ERR_PTR()-encoded
+ * error code on failure.
+ */
+static struct pwm_device *acpi_pwm_get(struct fwnode_handle *fwnode)
+{
+	struct pwm_device *pwm = ERR_PTR(-ENODEV);
+#if IS_ENABLED(CONFIG_ACPI)
+	struct fwnode_reference_args args;
+	struct acpi_device *acpi;
+	struct pwm_chip *chip;
+	int ret;
+
+	memset(&args, 0, sizeof(args));
+
+	ret = __acpi_node_get_property_reference(fwnode, "pwms", 0, 3, &args);
+	if (ret < 0)
+		return ERR_PTR(ret);
+
+	acpi = to_acpi_device_node(args.fwnode);
+	if (!acpi)
+		return ERR_PTR(-EINVAL);
+
+	if (args.nargs < 2)
+		return ERR_PTR(-EPROTO);
+
+	chip = device_to_pwmchip(&acpi->dev);
+	if (IS_ERR(chip))
+		return ERR_CAST(chip);
+
+	pwm = pwm_request_from_chip(chip, args.args[0], NULL);
+	if (IS_ERR(pwm))
+		return pwm;
+
+	pwm->args.period = args.args[1];
+	pwm->args.polarity = PWM_POLARITY_NORMAL;
+
+	if (args.nargs > 2 && args.args[2] & PWM_POLARITY_INVERTED)
+		pwm->args.polarity = PWM_POLARITY_INVERSED;
+#endif
+
+	return pwm;
+}
+
 /**
  * pwm_add_table() - register PWM device consumers
  * @table: array of consumers to register
@@ -814,6 +894,10 @@ struct pwm_device *pwm_get(struct device *dev, const char *con_id)
 	if (IS_ENABLED(CONFIG_OF) && dev && dev->of_node)
 		return of_pwm_get(dev, dev->of_node, con_id);
 
+	/* then lookup via ACPI */
+	if (dev && is_acpi_node(dev->fwnode))
+		return acpi_pwm_get(dev->fwnode);
+
 	/*
 	 * We look up the provider in the static table typically provided by
 	 * board setup code. We first try to lookup the consumer device by
@@ -999,6 +1083,44 @@ struct pwm_device *devm_of_pwm_get(struct device *dev, struct device_node *np,
 }
 EXPORT_SYMBOL_GPL(devm_of_pwm_get);
 
+/**
+ * devm_fwnode_pwm_get() - request a resource managed PWM from firmware node
+ * @dev: device for PWM consumer
+ * @fwnode: firmware node to get the PWM from
+ * @con_id: consumer name
+ *
+ * Returns the PWM device parsed from the firmware node. See of_pwm_get() and
+ * acpi_pwm_get() for a detailed description.
+ *
+ * Returns: A pointer to the requested PWM device or an ERR_PTR()-encoded
+ * error code on failure.
+ */
+struct pwm_device *devm_fwnode_pwm_get(struct device *dev,
+				       struct fwnode_handle *fwnode,
+				       const char *con_id)
+{
+	struct pwm_device **ptr, *pwm = ERR_PTR(-ENODEV);
+
+	ptr = devres_alloc(devm_pwm_release, sizeof(*ptr), GFP_KERNEL);
+	if (!ptr)
+		return ERR_PTR(-ENOMEM);
+
+	if (is_of_node(fwnode))
+		pwm = of_pwm_get(dev, to_of_node(fwnode), con_id);
+	else if (is_acpi_node(fwnode))
+		pwm = acpi_pwm_get(fwnode);
+
+	if (!IS_ERR(pwm)) {
+		*ptr = pwm;
+		devres_add(dev, ptr);
+	} else {
+		devres_free(ptr);
+	}
+
+	return pwm;
+}
+EXPORT_SYMBOL_GPL(devm_fwnode_pwm_get);
+
 static int devm_pwm_match(struct device *dev, void *res, void *data)
 {
 	struct pwm_device **p = res;

include/linux/pwm.h

@@ -412,6 +412,9 @@ void pwm_put(struct pwm_device *pwm);
 struct pwm_device *devm_pwm_get(struct device *dev, const char *con_id);
 struct pwm_device *devm_of_pwm_get(struct device *dev, struct device_node *np,
 				   const char *con_id);
+struct pwm_device *devm_fwnode_pwm_get(struct device *dev,
+				       struct fwnode_handle *fwnode,
+				       const char *con_id);
 void devm_pwm_put(struct device *dev, struct pwm_device *pwm);
 #else
 static inline struct pwm_device *pwm_request(int pwm_id, const char *label)
@@ -518,6 +521,13 @@ static inline struct pwm_device *devm_of_pwm_get(struct device *dev,
 	return ERR_PTR(-ENODEV);
 }
 
+static inline struct pwm_device *
+devm_fwnode_pwm_get(struct device *dev, struct fwnode_handle *fwnode,
+		    const char *con_id)
+{
+	return ERR_PTR(-ENODEV);
+}
+
 static inline void devm_pwm_put(struct device *dev, struct pwm_device *pwm)
 {
 }