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Commit f051c466 authored by Thierry Reding's avatar Thierry Reding
Browse files

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: default avatarMark Brown <broonie@opensource.wolfsonmicro.com>
Reviewed-by: default avatarShawn Guo <shawn.guo@linaro.org>
[eric@eukrea.com: fix error handling in pwmchip_add]
Signed-off-by: default avatarEric Bénard <eric@eukrea.com>
Signed-off-by: default avatarThierry Reding <thierry.reding@avionic-design.de>
parent 0c2498f1

Documentation/pwm.txt

+6 −3
Original line number Diff line number Diff line
@@ -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

+190 −77
Original line number Diff line number Diff line
@@ -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);

}



	list_for_each_entry(pwm, &pwm_list, node) {

		if (pwm->chip->pwm_id == pwm_id)

			return 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;



	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);

	}



	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;

		}

	}



	return NULL;

	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;



		radix_tree_insert(&pwm_tree, pwm->pwm, pwm);

	}



	bitmap_set(allocated_pwms, chip->base, chip->npwm);



	if (ret)

		kfree(pwm);

	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)) {

		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

+58 −13
Original line number Diff line number Diff line
@@ -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 */