[PATCH v6 02/17] pwm: Allow chips to support multiple PWMs
Thierry Reding
thierry.reding at avionic-design.de
Wed Apr 11 01:06:25 EST 2012
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.
Signed-off-by: Thierry Reding <thierry.reding at avionic-design.de>
Reviewed-by: Mark Brown <broonie at opensource.wolfsonmicro.com>
Reviewed-by: Shawn Guo <shawn.guo at linaro.org>
---
Changes in v5:
- add sanity checks to pwmchip_add()
- make pwm_chip.pwm_ops constant
- remove unused pwm_request_from_device() function
- check for valid chip in pwm_request_from_chip()
- add sanity checks to pwm_config(), pwm_enable() and pwm_disable()
- update Documentation/pwm.txt
- use deferred driver probing if pwm_request() cannot find a PWM
Changes in v4:
- remove OF-specific code to preserve bisectability
- add pwm_request_from_device() and pwm_request_from_chip() functions
- refactor PWM requesting code
- store period in struct pwm_device and get rid of the unused struct
pwm_spec
Changes in v3:
- get rid of pwm_desc structure and keep only struct pwm_device
- keep a list of pwm_chip structures for fast and easy lookup
- pass struct pwm_device directly to pwm_ops
- add debugfs file
Changes in v2:
- add 'struct device *dev' field to pwm_chip, drop label field
- use radix tree for PWM descriptors
- add pwm_set_chip_data() and pwm_get_chip_data() functions to allow
storing and retrieving chip-specific per-PWM data
Documentation/pwm.txt | 9 +-
drivers/pwm/core.c | 263 ++++++++++++++++++++++++++++++++++---------------
include/linux/pwm.h | 71 ++++++++++---
3 files changed, 250 insertions(+), 93 deletions(-)
diff --git a/Documentation/pwm.txt b/Documentation/pwm.txt
index 03e39d1..48f598a 100644
--- a/Documentation/pwm.txt
+++ b/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
-------
diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index 0b8a38e..8688754 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -2,6 +2,7 @@
* Generic pwmlib implementation
*
* Copyright (C) 2011 Sascha Hauer <s.hauer at 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 +21,157 @@
#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;
+
+ 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;
+}
- list_for_each_entry(pwm, &pwm_list, node) {
- if (pwm->chip->pwm_id == pwm_id)
- return pwm;
+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)
+ return -ENOMEM;
+
+ 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);
}
- list_add_tail(&pwm->node, &pwm_list);
-out:
- mutex_unlock(&pwm_lock);
+ bitmap_set(allocated_pwms, chip->base, chip->npwm);
- if (ret)
- kfree(pwm);
+ INIT_LIST_HEAD(&chip->list);
+ list_add(&chip->list, &pwm_chips);
+out:
+ mutex_unlock(&pwm_lock);
return ret;
}
EXPORT_SYMBOL_GPL(pwmchip_add);
@@ -93,28 +185,25 @@ 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 +213,64 @@ 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 +280,14 @@ 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 +304,10 @@ 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 +317,10 @@ 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 +330,7 @@ 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);
diff --git a/include/linux/pwm.h b/include/linux/pwm.h
index 1f308a1..5710391 100644
--- a/include/linux/pwm.h
+++ b/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 */
--
1.7.9.6
More information about the devicetree-discuss
mailing list