pwm: Allow chips to support multiple PWMs

Many PWM controllers provide access to more than a single PWM output and
may even share some resource among them. Allowing a PWM chip to provide
multiple PWM devices enables better sharing of those resources. As a
side-effect this change allows easy integration with the device tree
where a given PWM can be looked up based on the PWM chip's phandle and a
corresponding index.

This commit modifies the PWM core to support multiple PWMs per struct
pwm_chip. It achieves this in a similar way to how gpiolib works, by
allowing PWM ranges to be requested dynamically (pwm_chip.base == -1) or
starting at a given offset (pwm_chip.base >= 0). A chip specifies how
many PWMs it controls using the npwm member. Each of the functions in
the pwm_ops structure gets an additional argument that specified the PWM
number (it can be converted to a per-chip index by subtracting the
chip's base).

The total maximum number of PWM devices is currently fixed to 1024 while
the data is actually stored in a radix tree, thus saving resources if
not all of them are used.
Reviewed-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Reviewed-by: Shawn Guo <shawn.guo@linaro.org>
[eric@eukrea.com: fix error handling in pwmchip_add]
Signed-off-by: Eric Bénard <eric@eukrea.com>
Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>

Documentation/pwm.txt

@@ -33,9 +33,12 @@ there only has been the barebone API meaning that each driver has
 to implement the pwm_*() functions itself. This means that it's impossible
 to have multiple PWM drivers in the system. For this reason it's mandatory
 for new drivers to use the generic PWM framework.
-A new PWM device can be added using pwmchip_add() and removed again with
-pwmchip_remove(). pwmchip_add() takes a filled in struct pwm_chip as
-argument which provides the ops and the pwm id to the framework.
+
+A new PWM controller/chip can be added using pwmchip_add() and removed
+again with pwmchip_remove(). pwmchip_add() takes a filled in struct
+pwm_chip as argument which provides a description of the PWM chip, the
+number of PWM devices provider by the chip and the chip-specific
+implementation of the supported PWM operations to the framework.
 
 Locking
 -------

drivers/pwm/core.c

@@ -2,6 +2,7 @@
  * Generic pwmlib implementation
  *
  * Copyright (C) 2011 Sascha Hauer <s.hauer@pengutronix.de>
+ * Copyright (C) 2011-2012 Avionic Design GmbH
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -20,66 +21,161 @@
 
 #include <linux/module.h>
 #include <linux/pwm.h>
+#include <linux/radix-tree.h>
 #include <linux/list.h>
 #include <linux/mutex.h>
 #include <linux/err.h>
 #include <linux/slab.h>
 #include <linux/device.h>
 
-struct pwm_device {
-	struct			pwm_chip *chip;
-	const char		*label;
-	unsigned long		flags;
-#define FLAG_REQUESTED	0
-#define FLAG_ENABLED	1
-	struct list_head	node;
-};
-
-static LIST_HEAD(pwm_list);
+#define MAX_PWMS 1024
 
 static DEFINE_MUTEX(pwm_lock);
+static LIST_HEAD(pwm_chips);
+static DECLARE_BITMAP(allocated_pwms, MAX_PWMS);
+static RADIX_TREE(pwm_tree, GFP_KERNEL);
 
-static struct pwm_device *_find_pwm(int pwm_id)
+static struct pwm_device *pwm_to_device(unsigned int pwm)
 {
-	struct pwm_device *pwm;
+	return radix_tree_lookup(&pwm_tree, pwm);
+}
+
+static int alloc_pwms(int pwm, unsigned int count)
+{
+	unsigned int from = 0;
+	unsigned int start;
+
+	if (pwm >= MAX_PWMS)
+		return -EINVAL;
+
+	if (pwm >= 0)
+		from = pwm;
 
-	list_for_each_entry(pwm, &pwm_list, node) {
-		if (pwm->chip->pwm_id == pwm_id)
-			return pwm;
+	start = bitmap_find_next_zero_area(allocated_pwms, MAX_PWMS, from,
+					   count, 0);
+
+	if (pwm >= 0 && start != pwm)
+		return -EEXIST;
+
+	if (start + count > MAX_PWMS)
+		return -ENOSPC;
+
+	return start;
+}
+
+static void free_pwms(struct pwm_chip *chip)
+{
+	unsigned int i;
+
+	for (i = 0; i < chip->npwm; i++) {
+		struct pwm_device *pwm = &chip->pwms[i];
+		radix_tree_delete(&pwm_tree, pwm->pwm);
 	}
 
-	return NULL;
+	bitmap_clear(allocated_pwms, chip->base, chip->npwm);
+
+	kfree(chip->pwms);
+	chip->pwms = NULL;
+}
+
+static int pwm_device_request(struct pwm_device *pwm, const char *label)
+{
+	int err;
+
+	if (test_bit(PWMF_REQUESTED, &pwm->flags))
+		return -EBUSY;
+
+	if (!try_module_get(pwm->chip->ops->owner))
+		return -ENODEV;
+
+	if (pwm->chip->ops->request) {
+		err = pwm->chip->ops->request(pwm->chip, pwm);
+		if (err) {
+			module_put(pwm->chip->ops->owner);
+			return err;
+		}
+	}
+
+	set_bit(PWMF_REQUESTED, &pwm->flags);
+	pwm->label = label;
+
+	return 0;
+}
+
+/**
+ * pwm_set_chip_data() - set private chip data for a PWM
+ * @pwm: PWM device
+ * @data: pointer to chip-specific data
+ */
+int pwm_set_chip_data(struct pwm_device *pwm, void *data)
+{
+	if (!pwm)
+		return -EINVAL;
+
+	pwm->chip_data = data;
+
+	return 0;
+}
+
+/**
+ * pwm_get_chip_data() - get private chip data for a PWM
+ * @pwm: PWM device
+ */
+void *pwm_get_chip_data(struct pwm_device *pwm)
+{
+	return pwm ? pwm->chip_data : NULL;
 }
 
 /**
  * pwmchip_add() - register a new PWM chip
  * @chip: the PWM chip to add
+ *
+ * Register a new PWM chip. If chip->base < 0 then a dynamically assigned base
+ * will be used.
  */
 int pwmchip_add(struct pwm_chip *chip)
 {
 	struct pwm_device *pwm;
-	int ret = 0;
-
-	pwm = kzalloc(sizeof(*pwm), GFP_KERNEL);
-	if (!pwm)
-		return -ENOMEM;
+	unsigned int i;
+	int ret;
 
-	pwm->chip = chip;
+	if (!chip || !chip->dev || !chip->ops || !chip->ops->config ||
+	    !chip->ops->enable || !chip->ops->disable)
+		return -EINVAL;
 
 	mutex_lock(&pwm_lock);
 
-	if (chip->pwm_id >= 0 && _find_pwm(chip->pwm_id)) {
-		ret = -EBUSY;
+	ret = alloc_pwms(chip->base, chip->npwm);
+	if (ret < 0)
+		goto out;
+
+	chip->pwms = kzalloc(chip->npwm * sizeof(*pwm), GFP_KERNEL);
+	if (!chip->pwms) {
+		ret = -ENOMEM;
 		goto out;
 	}
 
-	list_add_tail(&pwm->node, &pwm_list);
-out:
-	mutex_unlock(&pwm_lock);
+	chip->base = ret;
+
+	for (i = 0; i < chip->npwm; i++) {
+		pwm = &chip->pwms[i];
+
+		pwm->chip = chip;
+		pwm->pwm = chip->base + i;
+		pwm->hwpwm = i;
 
-	if (ret)
-		kfree(pwm);
+		radix_tree_insert(&pwm_tree, pwm->pwm, pwm);
+	}
+
+	bitmap_set(allocated_pwms, chip->base, chip->npwm);
+
+	INIT_LIST_HEAD(&chip->list);
+	list_add(&chip->list, &pwm_chips);
 
+	ret = 0;
+
+out:
+	mutex_unlock(&pwm_lock);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(pwmchip_add);
@@ -93,28 +189,25 @@ EXPORT_SYMBOL_GPL(pwmchip_add);
  */
 int pwmchip_remove(struct pwm_chip *chip)
 {
-	struct pwm_device *pwm;
+	unsigned int i;
 	int ret = 0;
 
 	mutex_lock(&pwm_lock);
 
-	pwm = _find_pwm(chip->pwm_id);
-	if (!pwm) {
-		ret = -ENOENT;
-		goto out;
-	}
+	for (i = 0; i < chip->npwm; i++) {
+		struct pwm_device *pwm = &chip->pwms[i];
 
-	if (test_bit(FLAG_REQUESTED, &pwm->flags)) {
-		ret = -EBUSY;
-		goto out;
+		if (test_bit(PWMF_REQUESTED, &pwm->flags)) {
+			ret = -EBUSY;
+			goto out;
+		}
 	}
 
-	list_del(&pwm->node);
+	list_del_init(&chip->list);
+	free_pwms(chip);
 
-	kfree(pwm);
 out:
 	mutex_unlock(&pwm_lock);
-
 	return ret;
 }
 EXPORT_SYMBOL_GPL(pwmchip_remove);
@@ -124,50 +217,64 @@ EXPORT_SYMBOL_GPL(pwmchip_remove);
  * @pwm_id: global PWM device index
  * @label: PWM device label
  */
-struct pwm_device *pwm_request(int pwm_id, const char *label)
+struct pwm_device *pwm_request(int pwm, const char *label)
 {
-	struct pwm_device *pwm;
-	int ret;
+	struct pwm_device *dev;
+	int err;
+
+	if (pwm < 0 || pwm >= MAX_PWMS)
+		return ERR_PTR(-EINVAL);
 
 	mutex_lock(&pwm_lock);
 
-	pwm = _find_pwm(pwm_id);
-	if (!pwm) {
-		pwm = ERR_PTR(-ENOENT);
+	dev = pwm_to_device(pwm);
+	if (!dev) {
+		dev = ERR_PTR(-EPROBE_DEFER);
 		goto out;
 	}
 
-	if (test_bit(FLAG_REQUESTED, &pwm->flags)) {
-		pwm = ERR_PTR(-EBUSY);
-		goto out;
-	}
+	err = pwm_device_request(dev, label);
+	if (err < 0)
+		dev = ERR_PTR(err);
 
-	if (!try_module_get(pwm->chip->ops->owner)) {
-		pwm = ERR_PTR(-ENODEV);
-		goto out;
-	}
+out:
+	mutex_unlock(&pwm_lock);
 
-	if (pwm->chip->ops->request) {
-		ret = pwm->chip->ops->request(pwm->chip);
-		if (ret) {
-			pwm = ERR_PTR(ret);
-			goto out_put;
-		}
-	}
+	return dev;
+}
+EXPORT_SYMBOL_GPL(pwm_request);
 
-	pwm->label = label;
-	set_bit(FLAG_REQUESTED, &pwm->flags);
+/**
+ * pwm_request_from_chip() - request a PWM device relative to a PWM chip
+ * @chip: PWM chip
+ * @index: per-chip index of the PWM to request
+ * @label: a literal description string of this PWM
+ *
+ * Returns the PWM at the given index of the given PWM chip. A negative error
+ * code is returned if the index is not valid for the specified PWM chip or
+ * if the PWM device cannot be requested.
+ */
+struct pwm_device *pwm_request_from_chip(struct pwm_chip *chip,
+					 unsigned int index,
+					 const char *label)
+{
+	struct pwm_device *pwm;
+	int err;
 
-	goto out;
+	if (!chip || index >= chip->npwm)
+		return ERR_PTR(-EINVAL);
 
-out_put:
-	module_put(pwm->chip->ops->owner);
-out:
-	mutex_unlock(&pwm_lock);
+	mutex_lock(&pwm_lock);
+	pwm = &chip->pwms[index];
 
+	err = pwm_device_request(pwm, label);
+	if (err < 0)
+		pwm = ERR_PTR(err);
+
+	mutex_unlock(&pwm_lock);
 	return pwm;
 }
-EXPORT_SYMBOL_GPL(pwm_request);
+EXPORT_SYMBOL_GPL(pwm_request_from_chip);
 
 /**
  * pwm_free() - free a PWM device
@@ -177,11 +284,14 @@ void pwm_free(struct pwm_device *pwm)
 {
 	mutex_lock(&pwm_lock);
 
-	if (!test_and_clear_bit(FLAG_REQUESTED, &pwm->flags)) {
+	if (!test_and_clear_bit(PWMF_REQUESTED, &pwm->flags)) {
 		pr_warning("PWM device already freed\n");
 		goto out;
 	}
 
+	if (pwm->chip->ops->free)
+		pwm->chip->ops->free(pwm->chip, pwm);
+
 	pwm->label = NULL;
 
 	module_put(pwm->chip->ops->owner);
@@ -198,7 +308,10 @@ EXPORT_SYMBOL_GPL(pwm_free);
  */
 int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns)
 {
-	return pwm->chip->ops->config(pwm->chip, duty_ns, period_ns);
+	if (!pwm || period_ns == 0 || duty_ns > period_ns)
+		return -EINVAL;
+
+	return pwm->chip->ops->config(pwm->chip, pwm, duty_ns, period_ns);
 }
 EXPORT_SYMBOL_GPL(pwm_config);
 
@@ -208,10 +321,10 @@ EXPORT_SYMBOL_GPL(pwm_config);
  */
 int pwm_enable(struct pwm_device *pwm)
 {
-	if (!test_and_set_bit(FLAG_ENABLED, &pwm->flags))
-		return pwm->chip->ops->enable(pwm->chip);
+	if (pwm && !test_and_set_bit(PWMF_ENABLED, &pwm->flags))
+		return pwm->chip->ops->enable(pwm->chip, pwm);
 
-	return 0;
+	return pwm ? 0 : -EINVAL;
 }
 EXPORT_SYMBOL_GPL(pwm_enable);
 
@@ -221,7 +334,7 @@ EXPORT_SYMBOL_GPL(pwm_enable);
  */
 void pwm_disable(struct pwm_device *pwm)
 {
-	if (test_and_clear_bit(FLAG_ENABLED, &pwm->flags))
-		pwm->chip->ops->disable(pwm->chip);
+	if (pwm && test_and_clear_bit(PWMF_ENABLED, &pwm->flags))
+		pwm->chip->ops->disable(pwm->chip, pwm);
 }
 EXPORT_SYMBOL_GPL(pwm_disable);

include/linux/pwm.h

@@ -31,6 +31,33 @@ void pwm_disable(struct pwm_device *pwm);
 #ifdef CONFIG_PWM
 struct pwm_chip;
 
+enum {
+	PWMF_REQUESTED = 1 << 0,
+	PWMF_ENABLED = 1 << 1,
+};
+
+struct pwm_device {
+	const char		*label;
+	unsigned long		flags;
+	unsigned int		hwpwm;
+	unsigned int		pwm;
+	struct pwm_chip		*chip;
+	void			*chip_data;
+
+	unsigned int		period; /* in nanoseconds */
+};
+
+static inline void pwm_set_period(struct pwm_device *pwm, unsigned int period)
+{
+	if (pwm)
+		pwm->period = period;
+}
+
+static inline unsigned int pwm_get_period(struct pwm_device *pwm)
+{
+	return pwm ? pwm->period : 0;
+}
+
 /**
  * struct pwm_ops - PWM controller operations
  * @request: optional hook for requesting a PWM
@@ -41,29 +68,47 @@ struct pwm_chip;
  * @owner: helps prevent removal of modules exporting active PWMs
  */
 struct pwm_ops {
-	int			(*request)(struct pwm_chip *chip);
-	void			(*free)(struct pwm_chip *chip);
-	int			(*config)(struct pwm_chip *chip, int duty_ns,
-						int period_ns);
-	int			(*enable)(struct pwm_chip *chip);
-	void			(*disable)(struct pwm_chip *chip);
+	int			(*request)(struct pwm_chip *chip,
+					   struct pwm_device *pwm);
+	void			(*free)(struct pwm_chip *chip,
+					struct pwm_device *pwm);
+	int			(*config)(struct pwm_chip *chip,
+					  struct pwm_device *pwm,
+					  int duty_ns, int period_ns);
+	int			(*enable)(struct pwm_chip *chip,
+					  struct pwm_device *pwm);
+	void			(*disable)(struct pwm_chip *chip,
+					   struct pwm_device *pwm);
 	struct module		*owner;
 };
 
 /**
- * struct pwm_chip - abstract a PWM
- * @pwm_id: global PWM device index
- * @label: PWM device label
- * @ops: controller operations
+ * struct pwm_chip - abstract a PWM controller
+ * @dev: device providing the PWMs
+ * @list: list node for internal use
+ * @ops: callbacks for this PWM controller
+ * @base: number of first PWM controlled by this chip
+ * @npwm: number of PWMs controlled by this chip
+ * @pwms: array of PWM devices allocated by the framework
  */
 struct pwm_chip {
-	int			pwm_id;
-	const char		*label;
-	struct pwm_ops		*ops;
+	struct device		*dev;
+	struct list_head	list;
+	const struct pwm_ops	*ops;
+	int			base;
+	unsigned int		npwm;
+
+	struct pwm_device	*pwms;
 };
 
+int pwm_set_chip_data(struct pwm_device *pwm, void *data);
+void *pwm_get_chip_data(struct pwm_device *pwm);
+
 int pwmchip_add(struct pwm_chip *chip);
 int pwmchip_remove(struct pwm_chip *chip);
+struct pwm_device *pwm_request_from_chip(struct pwm_chip *chip,
+					 unsigned int index,
+					 const char *label);
 #endif
 
 #endif /* __LINUX_PWM_H */