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    Subject[PATCH v4 20/24] 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_get_state(), pwm_get_default_state() and pwm_apply_state()
    functions for PWM users to be able to use the atomic update feature.

    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.

    Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
    Tested-by: Heiko Stuebner <heiko@sntech.de>
    ---
    drivers/pwm/core.c | 124 +++++++++++++++++++++++++++++++++++++++++++++++++---
    include/linux/pwm.h | 27 ++++++++++++
    2 files changed, 146 insertions(+), 5 deletions(-)

    diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
    index ce8b373..fbc71d3 100644
    --- a/drivers/pwm/core.c
    +++ b/drivers/pwm/core.c
    @@ -46,6 +46,12 @@ static struct pwm_device *pwm_to_device(unsigned int pwm)
    return radix_tree_lookup(&pwm_tree, pwm);
    }

    +static void pwm_set_state(struct pwm_device *pwm,
    + const struct pwm_state *state)
    +{
    + pwm->state = *state;
    +}
    +
    static int alloc_pwms(int pwm, unsigned int count)
    {
    unsigned int from = 0;
    @@ -226,6 +232,19 @@ 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 +263,10 @@ 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);
    @@ -446,7 +467,19 @@ int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns)
    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 (pwm->chip->ops->apply) {
    + struct pwm_state state;
    +
    + pwm_get_state(pwm, &state);
    + state.period = period_ns;
    + state.duty_cycle = duty_ns;
    +
    + err = pwm->chip->ops->apply(pwm->chip, pwm, &state);
    + } else {
    + err = pwm->chip->ops->config(pwm->chip, pwm, duty_ns,
    + period_ns);
    + }
    +
    if (err)
    return err;

    @@ -474,6 +507,18 @@ int pwm_set_polarity(struct pwm_device *pwm, enum pwm_polarity polarity)
    if (!pwm || !pwm->chip->ops)
    return -EINVAL;

    + if (pwm->chip->ops->apply) {
    + struct pwm_state state;
    +
    + pwm_get_state(pwm, &state);
    + state.polarity = polarity;
    + err = pwm->chip->ops->apply(pwm->chip, pwm, &state);
    + if (!err)
    + pwm->state.polarity = polarity;
    +
    + return err;
    + }
    +
    if (!pwm->chip->ops->set_polarity)
    return -ENOSYS;

    @@ -512,7 +557,17 @@ int pwm_enable(struct pwm_device *pwm)
    mutex_lock(&pwm->lock);

    if (!pwm_is_enabled(pwm)) {
    - err = pwm->chip->ops->enable(pwm->chip, pwm);
    + if (pwm->chip->ops->apply) {
    + struct pwm_state state;
    +
    + pwm_get_state(pwm, &state);
    + state.enabled = true;
    +
    + err = pwm->chip->ops->apply(pwm->chip, pwm, &state);
    + } else {
    + err = pwm->chip->ops->enable(pwm->chip, pwm);
    + }
    +
    if (!err)
    pwm->state.enabled = true;
    }
    @@ -535,7 +590,16 @@ void pwm_disable(struct pwm_device *pwm)
    mutex_lock(&pwm->lock);

    if (pwm_is_enabled(pwm)) {
    - pwm->chip->ops->disable(pwm->chip, pwm);
    + if (pwm->chip->ops->apply) {
    + struct pwm_state state;
    +
    + pwm_get_state(pwm, &state);
    + state.enabled = false;
    +
    + pwm->chip->ops->apply(pwm->chip, pwm, &state);
    + } else {
    + pwm->chip->ops->disable(pwm->chip, pwm);
    + }
    pwm->state.enabled = false;
    }

    @@ -543,6 +607,56 @@ void pwm_disable(struct pwm_device *pwm)
    }
    EXPORT_SYMBOL_GPL(pwm_disable);

    +/**
    + * pwm_apply_state() - atomically apply a new state to a PWM device
    + * @pwm: PWM device
    + * @state: new state to apply
    + */
    +int pwm_apply_state(struct pwm_device *pwm, const struct pwm_state *state)
    +{
    + int err = 0;
    +
    + if (!pwm)
    + return -EINVAL;
    +
    + if (!memcmp(state, &pwm->state, sizeof(*state)))
    + return 0;
    +
    + if (pwm->chip->ops->apply) {
    + err = pwm->chip->ops->apply(pwm->chip, pwm, state);
    + if (!err)
    + pwm_set_state(pwm, state);
    + } else {
    + /*
    + * FIXME: restore the initial state in case of error.
    + */
    + if (state->polarity != pwm->state.polarity) {
    + pwm_disable(pwm);
    + err = pwm_set_polarity(pwm, state->polarity);
    + if (err)
    + goto out;
    + }
    +
    + if (state->period != pwm->state.period ||
    + state->duty_cycle != pwm->state.duty_cycle) {
    + err = pwm_config(pwm, state->period, state->duty_cycle);
    + if (err)
    + goto out;
    + }
    +
    + if (state->enabled != pwm->state.enabled) {
    + if (state->enabled)
    + err = pwm_enable(pwm);
    + else
    + pwm_disable(pwm);
    + }
    + }
    +
    +out:
    + return err;
    +}
    +EXPORT_SYMBOL_GPL(pwm_apply_state);
    +
    static struct pwm_chip *of_node_to_pwmchip(struct device_node *np)
    {
    struct pwm_chip *chip;
    diff --git a/include/linux/pwm.h b/include/linux/pwm.h
    index caa0ffe..5e7b378 100644
    --- a/include/linux/pwm.h
    +++ b/include/linux/pwm.h
    @@ -174,6 +174,30 @@ static inline enum pwm_polarity pwm_get_polarity(const struct pwm_device *pwm)
    return pwm ? pwm->state.polarity : PWM_POLARITY_NORMAL;
    }

    +int pwm_apply_state(struct pwm_device *pwm, const 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(struct pwm_device *pwm,
    + struct pwm_state *state)
    +{
    + *state = pwm->state;
    +}
    +
    +/**
    + * pwm_get_default_state() - retrieve the default PWM state
    + * @pwm: PWM device
    + * @state: state to fill with the default PWM state
    + */
    +static inline void pwm_get_default_state(struct pwm_device *pwm,
    + struct pwm_state *state)
    +{
    + *state = pwm->default_state;
    +}
    +
    /**
    * struct pwm_ops - PWM controller operations
    * @request: optional hook for requesting a PWM
    @@ -182,6 +206,7 @@ static inline enum pwm_polarity pwm_get_polarity(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
    * @reset_state: reset the current PWM state (pwm->state) to the actual
    * hardware state. This function is only called once per
    * PWM device when the PWM chip is registered.
    @@ -197,6 +222,8 @@ 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,
    + const struct pwm_state *state);
    void (*reset_state)(struct pwm_chip *chip, struct pwm_device *pwm);
    #ifdef CONFIG_DEBUG_FS
    void (*dbg_show)(struct pwm_chip *chip, struct seq_file *s);
    --
    2.1.4


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