lkml.org 
[lkml]   [2016]   [Mar]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH v5 18/46] pwm: add the core infrastructure to allow atomic update
    Date
    Add an ->apply() method to the pwm_ops struct to allow PWM drivers to
    implement atomic update.
    This method will be 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.

    Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
    ---
    drivers/pwm/core.c | 155 ++++++++++++++++++---------------------
    include/linux/pwm.h | 207 +++++++++++++++++++++++++++++++++++++---------------
    2 files changed, 220 insertions(+), 142 deletions(-)

    diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
    index a909c64..62e6b3c 100644
    --- a/drivers/pwm/core.c
    +++ b/drivers/pwm/core.c
    @@ -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 +446,72 @@ 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)
    - 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);
    -
    -/**
    - * 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 || !pwm->chip->ops)
    - return -EINVAL;
    -
    - if (!pwm->chip->ops->set_polarity)
    - return -ENOSYS;
    -
    - if (pwm_is_enabled(pwm))
    - return -EBUSY;
    -
    - err = pwm->chip->ops->set_polarity(pwm->chip, pwm, polarity);
    - if (err)
    - return err;
    -
    - pwm->state.polarity = polarity;
    -
    - return 0;
    -}
    -EXPORT_SYMBOL_GPL(pwm_set_polarity);
    -
    -/**
    - * pwm_enable() - start a PWM output toggling
    - * @pwm: PWM device
    - *
    - * Returns: 0 on success or a negative error code on failure.
    - */
    -int pwm_enable(struct pwm_device *pwm)
    -{
    - int err = 0;
    -
    if (!pwm)
    return -EINVAL;

    - if (!pwm_is_enabled(pwm)) {
    - err = pwm->chip->ops->enable(pwm->chip, pwm);
    - if (!err)
    - pwm->state.enabled = true;
    - }
    + if (!memcmp(state, &pwm->state, sizeof(*state)))
    + return 0;

    - return err;
    -}
    -EXPORT_SYMBOL_GPL(pwm_enable);
    + if (pwm->chip->ops->apply) {
    + err = pwm->chip->ops->apply(pwm->chip, pwm, state);
    + if (err)
    + return err;
    + } 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)
    + return -EBUSY;
    +
    + err = pwm->chip->ops->set_polarity(pwm->chip, pwm,
    + state->polarity);
    + if (err)
    + return err;
    + }

    -/**
    - * pwm_disable() - stop a PWM output toggling
    - * @pwm: PWM device
    - */
    -void pwm_disable(struct pwm_device *pwm)
    -{
    - if (!pwm)
    - return;
    + if (state->period != pwm->state.period ||
    + state->duty_cycle != pwm->state.duty_cycle) {
    + err = pwm->chip->ops->config(pwm->chip, pwm,
    + state->period,
    + state->duty_cycle);
    + if (err)
    + return err;
    + }

    - if (pwm_is_enabled(pwm)) {
    - pwm->chip->ops->disable(pwm->chip, pwm);
    - pwm->state.enabled = false;
    + 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 = *state;
    + return 0;
    }
    -EXPORT_SYMBOL_GPL(pwm_disable);
    +EXPORT_SYMBOL_GPL(pwm_apply_state);

    static struct pwm_chip *of_node_to_pwmchip(struct device_node *np)
    {
    diff --git a/include/linux/pwm.h b/include/linux/pwm.h
    index ceedcf8..4aad4eb 100644
    --- a/include/linux/pwm.h
    +++ b/include/linux/pwm.h
    @@ -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;

    /**
    @@ -183,11 +131,6 @@ static inline unsigned int pwm_get_duty_cycle(const struct pwm_device *pwm)
    return pstate.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 pstate;
    @@ -211,6 +154,10 @@ static inline void pwm_get_args(const 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.
    @@ -226,6 +173,8 @@ 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 *pstate);
    #ifdef CONFIG_DEBUG_FS
    @@ -263,6 +212,114 @@ 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);
    +
    +/**
    + * 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 pstate;
    +
    + if (!pwm)
    + return -EINVAL;
    +
    + pwm_get_state(pwm, &pstate);
    + if (pstate.duty_cycle == duty_ns && pstate.period == period_ns)
    + return 0;
    +
    + pstate.duty_cycle = duty_ns;
    + pstate.period = period_ns;
    + return pwm_apply_state(pwm, &pstate);
    +}
    +
    +/**
    + * 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 pstate;
    +
    + if (!pwm)
    + return -EINVAL;
    +
    + pwm_get_state(pwm, &pstate);
    + if (pstate.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 (pstate.enabled)
    + return -EBUSY;
    +
    + pstate.polarity = polarity;
    + return pwm_apply_state(pwm, &pstate);
    +}
    +
    +/**
    + * 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 pstate;
    +
    + if (!pwm)
    + return -EINVAL;
    +
    + pwm_get_state(pwm, &pstate);
    + if (pstate.enabled)
    + return 0;
    +
    + pstate.enabled = true;
    + return pwm_apply_state(pwm, &pstate);
    +}
    +
    +/**
    + * pwm_disable() - stop a PWM output toggling
    + * @pwm: PWM device
    + */
    +static inline void pwm_disable(struct pwm_device *pwm)
    +{
    + struct pwm_state pstate;
    +
    + if (!pwm)
    + return;
    +
    + pwm_get_state(pwm, &pstate);
    + if (!pstate.enabled)
    + return;
    +
    + pstate.enabled = false;
    + pwm_apply_state(pwm, &pstate);
    +}
    +
    +
    +/* PWM provider APIs */
    int pwm_set_chip_data(struct pwm_device *pwm, void *data);
    void *pwm_get_chip_data(struct pwm_device *pwm);

    @@ -288,6 +345,42 @@ 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_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;
    --
    2.5.0
    \
     
     \ /
      Last update: 2016-03-30 22:21    [W:9.053 / U:0.016 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site