linux-stable/include/linux/pwm.h
Boris Brezillon 5ec803edcb pwm: Add core infrastructure to allow atomic updates
Add an ->apply() method to the pwm_ops struct to allow PWM drivers to
implement atomic updates. This method is preferred over the ->enable(),
->disable() and ->config() methods if available.

Add the pwm_apply_state() function to the PWM user API.

Note that the pwm_apply_state() does not guarantee the atomicity of the
update operation, it all depends on the availability and implementation
of the ->apply() method.

pwm_enable/disable/set_polarity/config() are now implemented as wrappers
around the pwm_apply_state() function.

pwm_adjust_config() is allowing smooth handover between the bootloader
and the kernel. This function tries to adapt the current PWM state to
the PWM arguments coming from a PWM lookup table or a DT definition
without changing the duty_cycle/period proportion.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
[thierry.reding@gmail.com: fix a couple of typos]
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
2016-05-17 14:48:03 +02:00

536 lines
13 KiB
C

#ifndef __LINUX_PWM_H
#define __LINUX_PWM_H
#include <linux/err.h>
#include <linux/mutex.h>
#include <linux/of.h>
struct seq_file;
struct pwm_chip;
/**
* enum pwm_polarity - polarity of a PWM signal
* @PWM_POLARITY_NORMAL: a high signal for the duration of the duty-
* cycle, followed by a low signal for the remainder of the pulse
* period
* @PWM_POLARITY_INVERSED: a low signal for the duration of the duty-
* cycle, followed by a high signal for the remainder of the pulse
* period
*/
enum pwm_polarity {
PWM_POLARITY_NORMAL,
PWM_POLARITY_INVERSED,
};
/**
* struct pwm_args - board-dependent PWM arguments
* @period: reference period
* @polarity: reference polarity
*
* This structure describes board-dependent arguments attached to a PWM
* device. These arguments are usually retrieved from the PWM lookup table or
* device tree.
*
* Do not confuse this with the PWM state: PWM arguments represent the initial
* configuration that users want to use on this PWM device rather than the
* current PWM hardware state.
*/
struct pwm_args {
unsigned int period;
enum pwm_polarity polarity;
};
enum {
PWMF_REQUESTED = 1 << 0,
PWMF_EXPORTED = 1 << 1,
};
/*
* struct pwm_state - state of a PWM channel
* @period: PWM period (in nanoseconds)
* @duty_cycle: PWM duty cycle (in nanoseconds)
* @polarity: PWM polarity
* @enabled: PWM enabled status
*/
struct pwm_state {
unsigned int period;
unsigned int duty_cycle;
enum pwm_polarity polarity;
bool enabled;
};
/**
* struct pwm_device - PWM channel object
* @label: name of the PWM device
* @flags: flags associated with the PWM device
* @hwpwm: per-chip relative index of the PWM device
* @pwm: global index of the PWM device
* @chip: PWM chip providing this PWM device
* @chip_data: chip-private data associated with the PWM device
* @args: PWM arguments
* @state: curent PWM channel state
*/
struct pwm_device {
const char *label;
unsigned long flags;
unsigned int hwpwm;
unsigned int pwm;
struct pwm_chip *chip;
void *chip_data;
struct pwm_args args;
struct pwm_state state;
};
/**
* pwm_get_state() - retrieve the current PWM state
* @pwm: PWM device
* @state: state to fill with the current PWM state
*/
static inline void pwm_get_state(const struct pwm_device *pwm,
struct pwm_state *state)
{
*state = pwm->state;
}
static inline bool pwm_is_enabled(const struct pwm_device *pwm)
{
struct pwm_state state;
pwm_get_state(pwm, &state);
return state.enabled;
}
static inline void pwm_set_period(struct pwm_device *pwm, unsigned int period)
{
if (pwm)
pwm->state.period = period;
}
static inline unsigned int pwm_get_period(const struct pwm_device *pwm)
{
struct pwm_state state;
pwm_get_state(pwm, &state);
return state.period;
}
static inline void pwm_set_duty_cycle(struct pwm_device *pwm, unsigned int duty)
{
if (pwm)
pwm->state.duty_cycle = duty;
}
static inline unsigned int pwm_get_duty_cycle(const struct pwm_device *pwm)
{
struct pwm_state state;
pwm_get_state(pwm, &state);
return state.duty_cycle;
}
static inline enum pwm_polarity pwm_get_polarity(const struct pwm_device *pwm)
{
struct pwm_state state;
pwm_get_state(pwm, &state);
return state.polarity;
}
static inline void pwm_get_args(const struct pwm_device *pwm,
struct pwm_args *args)
{
*args = pwm->args;
}
/**
* struct pwm_ops - PWM controller operations
* @request: optional hook for requesting a PWM
* @free: optional hook for freeing a PWM
* @config: configure duty cycles and period length for this PWM
* @set_polarity: configure the polarity of this PWM
* @enable: enable PWM output toggling
* @disable: disable PWM output toggling
* @apply: atomically apply a new PWM config. The state argument
* should be adjusted with the real hardware config (if the
* approximate the period or duty_cycle value, state should
* reflect it)
* @get_state: get the current PWM state. This function is only
* called once per PWM device when the PWM chip is
* registered.
* @dbg_show: optional routine to show contents in debugfs
* @owner: helps prevent removal of modules exporting active PWMs
*/
struct pwm_ops {
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 (*set_polarity)(struct pwm_chip *chip, struct pwm_device *pwm,
enum pwm_polarity polarity);
int (*enable)(struct pwm_chip *chip, struct pwm_device *pwm);
void (*disable)(struct pwm_chip *chip, struct pwm_device *pwm);
int (*apply)(struct pwm_chip *chip, struct pwm_device *pwm,
struct pwm_state *state);
void (*get_state)(struct pwm_chip *chip, struct pwm_device *pwm,
struct pwm_state *state);
#ifdef CONFIG_DEBUG_FS
void (*dbg_show)(struct pwm_chip *chip, struct seq_file *s);
#endif
struct module *owner;
};
/**
* 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
* @of_xlate: request a PWM device given a device tree PWM specifier
* @of_pwm_n_cells: number of cells expected in the device tree PWM specifier
* @can_sleep: must be true if the .config(), .enable() or .disable()
* operations may sleep
*/
struct pwm_chip {
struct device *dev;
struct list_head list;
const struct pwm_ops *ops;
int base;
unsigned int npwm;
struct pwm_device *pwms;
struct pwm_device * (*of_xlate)(struct pwm_chip *pc,
const struct of_phandle_args *args);
unsigned int of_pwm_n_cells;
bool can_sleep;
};
#if IS_ENABLED(CONFIG_PWM)
/* PWM user APIs */
struct pwm_device *pwm_request(int pwm_id, const char *label);
void pwm_free(struct pwm_device *pwm);
int pwm_apply_state(struct pwm_device *pwm, struct pwm_state *state);
int pwm_adjust_config(struct pwm_device *pwm);
/**
* pwm_config() - change a PWM device configuration
* @pwm: PWM device
* @duty_ns: "on" time (in nanoseconds)
* @period_ns: duration (in nanoseconds) of one cycle
*
* Returns: 0 on success or a negative error code on failure.
*/
static inline int pwm_config(struct pwm_device *pwm, int duty_ns,
int period_ns)
{
struct pwm_state state;
if (!pwm)
return -EINVAL;
pwm_get_state(pwm, &state);
if (state.duty_cycle == duty_ns && state.period == period_ns)
return 0;
state.duty_cycle = duty_ns;
state.period = period_ns;
return pwm_apply_state(pwm, &state);
}
/**
* pwm_set_polarity() - configure the polarity of a PWM signal
* @pwm: PWM device
* @polarity: new polarity of the PWM signal
*
* Note that the polarity cannot be configured while the PWM device is
* enabled.
*
* Returns: 0 on success or a negative error code on failure.
*/
static inline int pwm_set_polarity(struct pwm_device *pwm,
enum pwm_polarity polarity)
{
struct pwm_state state;
if (!pwm)
return -EINVAL;
pwm_get_state(pwm, &state);
if (state.polarity == polarity)
return 0;
/*
* Changing the polarity of a running PWM without adjusting the
* dutycycle/period value is a bit risky (can introduce glitches).
* Return -EBUSY in this case.
* Note that this is allowed when using pwm_apply_state() because
* the user specifies all the parameters.
*/
if (state.enabled)
return -EBUSY;
state.polarity = polarity;
return pwm_apply_state(pwm, &state);
}
/**
* pwm_enable() - start a PWM output toggling
* @pwm: PWM device
*
* Returns: 0 on success or a negative error code on failure.
*/
static inline int pwm_enable(struct pwm_device *pwm)
{
struct pwm_state state;
if (!pwm)
return -EINVAL;
pwm_get_state(pwm, &state);
if (state.enabled)
return 0;
state.enabled = true;
return pwm_apply_state(pwm, &state);
}
/**
* pwm_disable() - stop a PWM output toggling
* @pwm: PWM device
*/
static inline void pwm_disable(struct pwm_device *pwm)
{
struct pwm_state state;
if (!pwm)
return;
pwm_get_state(pwm, &state);
if (!state.enabled)
return;
state.enabled = false;
pwm_apply_state(pwm, &state);
}
/* PWM provider APIs */
int pwm_set_chip_data(struct pwm_device *pwm, void *data);
void *pwm_get_chip_data(struct pwm_device *pwm);
int pwmchip_add_with_polarity(struct pwm_chip *chip,
enum pwm_polarity polarity);
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);
struct pwm_device *of_pwm_xlate_with_flags(struct pwm_chip *pc,
const struct of_phandle_args *args);
struct pwm_device *pwm_get(struct device *dev, const char *con_id);
struct pwm_device *of_pwm_get(struct device_node *np, const char *con_id);
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);
void devm_pwm_put(struct device *dev, struct pwm_device *pwm);
bool pwm_can_sleep(struct pwm_device *pwm);
#else
static inline struct pwm_device *pwm_request(int pwm_id, const char *label)
{
return ERR_PTR(-ENODEV);
}
static inline void pwm_free(struct pwm_device *pwm)
{
}
static inline int pwm_apply_state(struct pwm_device *pwm,
const struct pwm_state *state)
{
return -ENOTSUPP;
}
static inline int pwm_adjust_config(struct pwm_device *pwm)
{
return -ENOTSUPP;
}
static inline int pwm_config(struct pwm_device *pwm, int duty_ns,
int period_ns)
{
return -EINVAL;
}
static inline int pwm_set_polarity(struct pwm_device *pwm,
enum pwm_polarity polarity)
{
return -ENOTSUPP;
}
static inline int pwm_enable(struct pwm_device *pwm)
{
return -EINVAL;
}
static inline void pwm_disable(struct pwm_device *pwm)
{
}
static inline int pwm_set_chip_data(struct pwm_device *pwm, void *data)
{
return -EINVAL;
}
static inline void *pwm_get_chip_data(struct pwm_device *pwm)
{
return NULL;
}
static inline int pwmchip_add(struct pwm_chip *chip)
{
return -EINVAL;
}
static inline int pwmchip_add_inversed(struct pwm_chip *chip)
{
return -EINVAL;
}
static inline int pwmchip_remove(struct pwm_chip *chip)
{
return -EINVAL;
}
static inline struct pwm_device *pwm_request_from_chip(struct pwm_chip *chip,
unsigned int index,
const char *label)
{
return ERR_PTR(-ENODEV);
}
static inline struct pwm_device *pwm_get(struct device *dev,
const char *consumer)
{
return ERR_PTR(-ENODEV);
}
static inline struct pwm_device *of_pwm_get(struct device_node *np,
const char *con_id)
{
return ERR_PTR(-ENODEV);
}
static inline void pwm_put(struct pwm_device *pwm)
{
}
static inline struct pwm_device *devm_pwm_get(struct device *dev,
const char *consumer)
{
return ERR_PTR(-ENODEV);
}
static inline struct pwm_device *devm_of_pwm_get(struct device *dev,
struct device_node *np,
const char *con_id)
{
return ERR_PTR(-ENODEV);
}
static inline void devm_pwm_put(struct device *dev, struct pwm_device *pwm)
{
}
static inline bool pwm_can_sleep(struct pwm_device *pwm)
{
return false;
}
#endif
static inline void pwm_apply_args(struct pwm_device *pwm)
{
/*
* PWM users calling pwm_apply_args() expect to have a fresh config
* where the polarity and period are set according to pwm_args info.
* The problem is, polarity can only be changed when the PWM is
* disabled.
*
* PWM drivers supporting hardware readout may declare the PWM device
* as enabled, and prevent polarity setting, which changes from the
* existing behavior, where all PWM devices are declared as disabled
* at startup (even if they are actually enabled), thus authorizing
* polarity setting.
*
* Instead of setting ->enabled to false, we call pwm_disable()
* before pwm_set_polarity() to ensure that everything is configured
* as expected, and the PWM is really disabled when the user request
* it.
*
* Note that PWM users requiring a smooth handover between the
* bootloader and the kernel (like critical regulators controlled by
* PWM devices) will have to switch to the atomic API and avoid calling
* pwm_apply_args().
*/
pwm_disable(pwm);
pwm_set_polarity(pwm, pwm->args.polarity);
}
struct pwm_lookup {
struct list_head list;
const char *provider;
unsigned int index;
const char *dev_id;
const char *con_id;
unsigned int period;
enum pwm_polarity polarity;
};
#define PWM_LOOKUP(_provider, _index, _dev_id, _con_id, _period, _polarity) \
{ \
.provider = _provider, \
.index = _index, \
.dev_id = _dev_id, \
.con_id = _con_id, \
.period = _period, \
.polarity = _polarity \
}
#if IS_ENABLED(CONFIG_PWM)
void pwm_add_table(struct pwm_lookup *table, size_t num);
void pwm_remove_table(struct pwm_lookup *table, size_t num);
#else
static inline void pwm_add_table(struct pwm_lookup *table, size_t num)
{
}
static inline void pwm_remove_table(struct pwm_lookup *table, size_t num)
{
}
#endif
#ifdef CONFIG_PWM_SYSFS
void pwmchip_sysfs_export(struct pwm_chip *chip);
void pwmchip_sysfs_unexport(struct pwm_chip *chip);
#else
static inline void pwmchip_sysfs_export(struct pwm_chip *chip)
{
}
static inline void pwmchip_sysfs_unexport(struct pwm_chip *chip)
{
}
#endif /* CONFIG_PWM_SYSFS */
#endif /* __LINUX_PWM_H */