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Subject[PATCH v2 2/3] PWM framework: add support referencing PWMs from ACPI
Date
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>
---
drivers/pwm/core.c | 113 ++++++++++++++++++++++++++++++++++++++++++++
include/linux/pwm.h | 9 ++++
2 files changed, 122 insertions(+)

diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index 275b5f399a1a..5fed419d0833 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -6,6 +6,7 @@
* Copyright (C) 2011-2012 Avionic Design GmbH
*/

+#include <linux/acpi.h>
#include <linux/module.h>
#include <linux/pwm.h>
#include <linux/radix-tree.h>
@@ -700,6 +701,76 @@ struct pwm_device *of_pwm_get(struct device_node *np, const char *con_id)
}
EXPORT_SYMBOL_GPL(of_pwm_get);

+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);
+}
+
+/**
+ * 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 fwnode_reference_args args;
+ struct pwm_chip *chip;
+ struct pwm_device *pwm = ERR_PTR(-ENODEV);
+ int ret;
+
+ memset(&args, 0, sizeof(args));
+ ret = __acpi_node_get_property_reference(fwnode, "pwms", 0, 3, &args);
+
+ if (!to_acpi_device_node(args.fwnode))
+ return ERR_PTR(-EINVAL);
+
+ if (args.nargs < 2)
+ return ERR_PTR(-EPROTO);
+
+ chip = device_to_pwmchip(&to_acpi_device_node(args.fwnode)->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;
+
+ return pwm;
+}
+
/**
* pwm_add_table() - register PWM device consumers
* @table: array of consumers to register
@@ -763,6 +834,10 @@ 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->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
@@ -942,6 +1017,44 @@ 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(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;
diff --git a/include/linux/pwm.h b/include/linux/pwm.h
index eaa5c6e3fc9f..1a635916cdfb 100644
--- a/include/linux/pwm.h
+++ b/include/linux/pwm.h
@@ -411,6 +411,9 @@ 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)
@@ -516,6 +519,12 @@ 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)
{
}
--
2.17.1
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