Commit 5ec803ed authored by Boris Brezillon's avatar Boris Brezillon Committed by Thierry Reding

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: default avatarBoris Brezillon <boris.brezillon@free-electrons.com>
[thierry.reding@gmail.com: fix a couple of typos]
Signed-off-by: default avatarThierry Reding <thierry.reding@gmail.com>
parent 15fa8a43
......@@ -226,6 +226,19 @@ void *pwm_get_chip_data(struct pwm_device *pwm)
}
EXPORT_SYMBOL_GPL(pwm_get_chip_data);
static bool pwm_ops_check(const struct pwm_ops *ops)
{
/* driver supports legacy, non-atomic operation */
if (ops->config && ops->enable && ops->disable)
return true;
/* driver supports atomic operation */
if (ops->apply)
return true;
return false;
}
/**
* pwmchip_add_with_polarity() - register a new PWM chip
* @chip: the PWM chip to add
......@@ -244,8 +257,10 @@ int pwmchip_add_with_polarity(struct pwm_chip *chip,
unsigned int i;
int ret;
if (!chip || !chip->dev || !chip->ops || !chip->ops->config ||
!chip->ops->enable || !chip->ops->disable || !chip->npwm)
if (!chip || !chip->dev || !chip->ops || !chip->npwm)
return -EINVAL;
if (!pwm_ops_check(chip->ops))
return -EINVAL;
mutex_lock(&pwm_lock);
......@@ -431,102 +446,138 @@ void pwm_free(struct pwm_device *pwm)
EXPORT_SYMBOL_GPL(pwm_free);
/**
* pwm_config() - change a PWM device configuration
* pwm_apply_state() - atomically apply a new state to a PWM device
* @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.
* @state: new state to apply. This can be adjusted by the PWM driver
* if the requested config is not achievable, for example,
* ->duty_cycle and ->period might be approximated.
*/
int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns)
int pwm_apply_state(struct pwm_device *pwm, struct pwm_state *state)
{
int err;
if (!pwm || duty_ns < 0 || period_ns <= 0 || duty_ns > period_ns)
if (!pwm)
return -EINVAL;
err = pwm->chip->ops->config(pwm->chip, pwm, duty_ns, period_ns);
if (err)
return err;
pwm->state.duty_cycle = duty_ns;
pwm->state.period = period_ns;
return 0;
}
EXPORT_SYMBOL_GPL(pwm_config);
if (!memcmp(state, &pwm->state, sizeof(*state)))
return 0;
/**
* 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.
*/
int pwm_set_polarity(struct pwm_device *pwm, enum pwm_polarity polarity)
{
int err;
if (pwm->chip->ops->apply) {
err = pwm->chip->ops->apply(pwm->chip, pwm, state);
if (err)
return err;
if (!pwm || !pwm->chip->ops)
return -EINVAL;
pwm->state = *state;
} else {
/*
* FIXME: restore the initial state in case of error.
*/
if (state->polarity != pwm->state.polarity) {
if (!pwm->chip->ops->set_polarity)
return -ENOTSUPP;
/*
* Changing the polarity of a running PWM is
* only allowed when the PWM driver implements
* ->apply().
*/
if (pwm->state.enabled) {
pwm->chip->ops->disable(pwm->chip, pwm);
pwm->state.enabled = false;
}
err = pwm->chip->ops->set_polarity(pwm->chip, pwm,
state->polarity);
if (err)
return err;
pwm->state.polarity = state->polarity;
}
if (!pwm->chip->ops->set_polarity)
return -ENOSYS;
if (state->period != pwm->state.period ||
state->duty_cycle != pwm->state.duty_cycle) {
err = pwm->chip->ops->config(pwm->chip, pwm,
state->duty_cycle,
state->period);
if (err)
return err;
if (pwm_is_enabled(pwm))
return -EBUSY;
pwm->state.duty_cycle = state->duty_cycle;
pwm->state.period = state->period;
}
err = pwm->chip->ops->set_polarity(pwm->chip, pwm, polarity);
if (err)
return err;
if (state->enabled != pwm->state.enabled) {
if (state->enabled) {
err = pwm->chip->ops->enable(pwm->chip, pwm);
if (err)
return err;
} else {
pwm->chip->ops->disable(pwm->chip, pwm);
}
pwm->state.polarity = polarity;
pwm->state.enabled = state->enabled;
}
}
return 0;
}
EXPORT_SYMBOL_GPL(pwm_set_polarity);
EXPORT_SYMBOL_GPL(pwm_apply_state);
/**
* pwm_enable() - start a PWM output toggling
* pwm_adjust_config() - adjust the current PWM config to the PWM arguments
* @pwm: PWM device
*
* Returns: 0 on success or a negative error code on failure.
* This function will adjust the PWM config to the PWM arguments provided
* by the DT or PWM lookup table. This is particularly useful to adapt
* the bootloader config to the Linux one.
*/
int pwm_enable(struct pwm_device *pwm)
int pwm_adjust_config(struct pwm_device *pwm)
{
int err = 0;
struct pwm_state state;
struct pwm_args pargs;
if (!pwm)
return -EINVAL;
pwm_get_args(pwm, &pargs);
pwm_get_state(pwm, &state);
/*
* If the current period is zero it means that either the PWM driver
* does not support initial state retrieval or the PWM has not yet
* been configured.
*
* In either case, we setup the new period and polarity, and assign a
* duty cycle of 0.
*/
if (!state.period) {
state.duty_cycle = 0;
state.period = pargs.period;
state.polarity = pargs.polarity;
if (!pwm_is_enabled(pwm)) {
err = pwm->chip->ops->enable(pwm->chip, pwm);
if (!err)
pwm->state.enabled = true;
return pwm_apply_state(pwm, &state);
}
return err;
}
EXPORT_SYMBOL_GPL(pwm_enable);
/*
* Adjust the PWM duty cycle/period based on the period value provided
* in PWM args.
*/
if (pargs.period != state.period) {
u64 dutycycle = (u64)state.duty_cycle * pargs.period;
/**
* pwm_disable() - stop a PWM output toggling
* @pwm: PWM device
*/
void pwm_disable(struct pwm_device *pwm)
{
if (!pwm)
return;
do_div(dutycycle, state.period);
state.duty_cycle = dutycycle;
state.period = pargs.period;
}
if (pwm_is_enabled(pwm)) {
pwm->chip->ops->disable(pwm->chip, pwm);
pwm->state.enabled = false;
/*
* If the polarity changed, we should also change the duty cycle.
*/
if (pargs.polarity != state.polarity) {
state.polarity = pargs.polarity;
state.duty_cycle = state.period - state.duty_cycle;
}
return pwm_apply_state(pwm, &state);
}
EXPORT_SYMBOL_GPL(pwm_disable);
EXPORT_SYMBOL_GPL(pwm_adjust_config);
static struct pwm_chip *of_node_to_pwmchip(struct device_node *np)
{
......
......@@ -5,59 +5,7 @@
#include <linux/mutex.h>
#include <linux/of.h>
struct pwm_device;
struct seq_file;
#if IS_ENABLED(CONFIG_PWM)
/*
* pwm_request - request a PWM device
*/
struct pwm_device *pwm_request(int pwm_id, const char *label);
/*
* pwm_free - free a PWM device
*/
void pwm_free(struct pwm_device *pwm);
/*
* pwm_config - change a PWM device configuration
*/
int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns);
/*
* pwm_enable - start a PWM output toggling
*/
int pwm_enable(struct pwm_device *pwm);
/*
* pwm_disable - stop a PWM output toggling
*/
void pwm_disable(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_config(struct pwm_device *pwm, int duty_ns, int period_ns)
{
return -EINVAL;
}
static inline int pwm_enable(struct pwm_device *pwm)
{
return -EINVAL;
}
static inline void pwm_disable(struct pwm_device *pwm)
{
}
#endif
struct pwm_chip;
/**
......@@ -184,11 +132,6 @@ static inline unsigned int pwm_get_duty_cycle(const struct pwm_device *pwm)
return state.duty_cycle;
}
/*
* pwm_set_polarity - configure the polarity of a PWM signal
*/
int pwm_set_polarity(struct pwm_device *pwm, enum pwm_polarity polarity);
static inline enum pwm_polarity pwm_get_polarity(const struct pwm_device *pwm)
{
struct pwm_state state;
......@@ -204,34 +147,6 @@ static inline void pwm_get_args(const struct pwm_device *pwm,
*args = pwm->args;
}
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_ops - PWM controller operations
* @request: optional hook for requesting a PWM
......@@ -240,6 +155,10 @@ static inline void pwm_apply_args(struct pwm_device *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.
......@@ -255,6 +174,8 @@ struct pwm_ops {
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
......@@ -292,6 +213,115 @@ struct pwm_chip {
};
#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);
......@@ -317,6 +347,47 @@ 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;
......@@ -388,6 +459,34 @@ static inline bool pwm_can_sleep(struct pwm_device *pwm)
}
#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;
......
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