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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>
This commit is contained in:
Boris Brezillon
Thierry Reding
parent
15fa8a43c1
commit
5ec803edcb
@ -226,6 +226,19 @@ void *pwm_get_chip_data(struct pwm_device *pwm)
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}
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EXPORT_SYMBOL_GPL(pwm_get_chip_data);
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static bool pwm_ops_check(const struct pwm_ops *ops)
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{
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/* driver supports legacy, non-atomic operation */
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if (ops->config && ops->enable && ops->disable)
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return true;
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/* driver supports atomic operation */
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if (ops->apply)
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return true;
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return false;
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}
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/**
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* pwmchip_add_with_polarity() - register a new PWM chip
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* @chip: the PWM chip to add
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@ -244,8 +257,10 @@ int pwmchip_add_with_polarity(struct pwm_chip *chip,
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unsigned int i;
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int ret;
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if (!chip || !chip->dev || !chip->ops || !chip->ops->config ||
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!chip->ops->enable || !chip->ops->disable || !chip->npwm)
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if (!chip || !chip->dev || !chip->ops || !chip->npwm)
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return -EINVAL;
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if (!pwm_ops_check(chip->ops))
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return -EINVAL;
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mutex_lock(&pwm_lock);
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@ -431,102 +446,138 @@ void pwm_free(struct pwm_device *pwm)
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EXPORT_SYMBOL_GPL(pwm_free);
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/**
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* pwm_config() - change a PWM device configuration
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* pwm_apply_state() - atomically apply a new state to a PWM device
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* @pwm: PWM device
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* @duty_ns: "on" time (in nanoseconds)
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* @period_ns: duration (in nanoseconds) of one cycle
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*
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* Returns: 0 on success or a negative error code on failure.
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* @state: new state to apply. This can be adjusted by the PWM driver
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* if the requested config is not achievable, for example,
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* ->duty_cycle and ->period might be approximated.
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*/
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int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns)
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int pwm_apply_state(struct pwm_device *pwm, struct pwm_state *state)
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{
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int err;
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if (!pwm || duty_ns < 0 || period_ns <= 0 || duty_ns > period_ns)
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return -EINVAL;
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err = pwm->chip->ops->config(pwm->chip, pwm, duty_ns, period_ns);
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if (err)
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return err;
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pwm->state.duty_cycle = duty_ns;
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pwm->state.period = period_ns;
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return 0;
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}
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EXPORT_SYMBOL_GPL(pwm_config);
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/**
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* pwm_set_polarity() - configure the polarity of a PWM signal
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* @pwm: PWM device
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* @polarity: new polarity of the PWM signal
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*
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* Note that the polarity cannot be configured while the PWM device is
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* enabled.
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*
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* Returns: 0 on success or a negative error code on failure.
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*/
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int pwm_set_polarity(struct pwm_device *pwm, enum pwm_polarity polarity)
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{
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int err;
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if (!pwm || !pwm->chip->ops)
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return -EINVAL;
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if (!pwm->chip->ops->set_polarity)
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return -ENOSYS;
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if (pwm_is_enabled(pwm))
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return -EBUSY;
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err = pwm->chip->ops->set_polarity(pwm->chip, pwm, polarity);
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if (err)
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return err;
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pwm->state.polarity = polarity;
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return 0;
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}
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EXPORT_SYMBOL_GPL(pwm_set_polarity);
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/**
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* pwm_enable() - start a PWM output toggling
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* @pwm: PWM device
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*
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* Returns: 0 on success or a negative error code on failure.
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*/
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int pwm_enable(struct pwm_device *pwm)
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{
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int err = 0;
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if (!pwm)
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return -EINVAL;
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if (!pwm_is_enabled(pwm)) {
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err = pwm->chip->ops->enable(pwm->chip, pwm);
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if (!err)
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pwm->state.enabled = true;
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if (!memcmp(state, &pwm->state, sizeof(*state)))
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return 0;
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if (pwm->chip->ops->apply) {
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err = pwm->chip->ops->apply(pwm->chip, pwm, state);
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if (err)
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return err;
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pwm->state = *state;
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} else {
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/*
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* FIXME: restore the initial state in case of error.
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*/
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if (state->polarity != pwm->state.polarity) {
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if (!pwm->chip->ops->set_polarity)
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return -ENOTSUPP;
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/*
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* Changing the polarity of a running PWM is
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* only allowed when the PWM driver implements
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* ->apply().
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*/
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if (pwm->state.enabled) {
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pwm->chip->ops->disable(pwm->chip, pwm);
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pwm->state.enabled = false;
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}
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err = pwm->chip->ops->set_polarity(pwm->chip, pwm,
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state->polarity);
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if (err)
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return err;
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pwm->state.polarity = state->polarity;
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}
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if (state->period != pwm->state.period ||
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state->duty_cycle != pwm->state.duty_cycle) {
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err = pwm->chip->ops->config(pwm->chip, pwm,
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state->duty_cycle,
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state->period);
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if (err)
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return err;
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pwm->state.duty_cycle = state->duty_cycle;
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pwm->state.period = state->period;
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}
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if (state->enabled != pwm->state.enabled) {
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if (state->enabled) {
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err = pwm->chip->ops->enable(pwm->chip, pwm);
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if (err)
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return err;
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} else {
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pwm->chip->ops->disable(pwm->chip, pwm);
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}
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pwm->state.enabled = state->enabled;
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}
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}
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return err;
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return 0;
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}
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EXPORT_SYMBOL_GPL(pwm_enable);
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EXPORT_SYMBOL_GPL(pwm_apply_state);
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/**
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* pwm_disable() - stop a PWM output toggling
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* pwm_adjust_config() - adjust the current PWM config to the PWM arguments
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* @pwm: PWM device
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*
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* This function will adjust the PWM config to the PWM arguments provided
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* by the DT or PWM lookup table. This is particularly useful to adapt
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* the bootloader config to the Linux one.
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*/
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void pwm_disable(struct pwm_device *pwm)
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int pwm_adjust_config(struct pwm_device *pwm)
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{
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if (!pwm)
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return;
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struct pwm_state state;
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struct pwm_args pargs;
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if (pwm_is_enabled(pwm)) {
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pwm->chip->ops->disable(pwm->chip, pwm);
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pwm->state.enabled = false;
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pwm_get_args(pwm, &pargs);
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pwm_get_state(pwm, &state);
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/*
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* If the current period is zero it means that either the PWM driver
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* does not support initial state retrieval or the PWM has not yet
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* been configured.
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*
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* In either case, we setup the new period and polarity, and assign a
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* duty cycle of 0.
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*/
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if (!state.period) {
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state.duty_cycle = 0;
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state.period = pargs.period;
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state.polarity = pargs.polarity;
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return pwm_apply_state(pwm, &state);
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}
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/*
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* Adjust the PWM duty cycle/period based on the period value provided
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* in PWM args.
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*/
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if (pargs.period != state.period) {
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u64 dutycycle = (u64)state.duty_cycle * pargs.period;
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do_div(dutycycle, state.period);
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state.duty_cycle = dutycycle;
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state.period = pargs.period;
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}
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/*
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* If the polarity changed, we should also change the duty cycle.
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*/
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if (pargs.polarity != state.polarity) {
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state.polarity = pargs.polarity;
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state.duty_cycle = state.period - state.duty_cycle;
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}
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return pwm_apply_state(pwm, &state);
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}
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EXPORT_SYMBOL_GPL(pwm_disable);
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EXPORT_SYMBOL_GPL(pwm_adjust_config);
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static struct pwm_chip *of_node_to_pwmchip(struct device_node *np)
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{
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@ -5,59 +5,7 @@
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#include <linux/mutex.h>
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#include <linux/of.h>
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struct pwm_device;
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struct seq_file;
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#if IS_ENABLED(CONFIG_PWM)
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/*
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* pwm_request - request a PWM device
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*/
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struct pwm_device *pwm_request(int pwm_id, const char *label);
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/*
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* pwm_free - free a PWM device
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*/
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void pwm_free(struct pwm_device *pwm);
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/*
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* pwm_config - change a PWM device configuration
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*/
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int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns);
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/*
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* pwm_enable - start a PWM output toggling
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*/
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int pwm_enable(struct pwm_device *pwm);
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/*
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* pwm_disable - stop a PWM output toggling
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*/
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void pwm_disable(struct pwm_device *pwm);
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#else
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static inline struct pwm_device *pwm_request(int pwm_id, const char *label)
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{
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return ERR_PTR(-ENODEV);
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}
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static inline void pwm_free(struct pwm_device *pwm)
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{
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}
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static inline int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns)
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{
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return -EINVAL;
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}
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static inline int pwm_enable(struct pwm_device *pwm)
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{
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return -EINVAL;
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}
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static inline void pwm_disable(struct pwm_device *pwm)
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{
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}
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#endif
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struct pwm_chip;
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/**
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@ -184,11 +132,6 @@ static inline unsigned int pwm_get_duty_cycle(const struct pwm_device *pwm)
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return state.duty_cycle;
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}
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/*
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* pwm_set_polarity - configure the polarity of a PWM signal
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*/
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int pwm_set_polarity(struct pwm_device *pwm, enum pwm_polarity polarity);
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static inline enum pwm_polarity pwm_get_polarity(const struct pwm_device *pwm)
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{
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struct pwm_state state;
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@ -204,34 +147,6 @@ static inline void pwm_get_args(const struct pwm_device *pwm,
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*args = pwm->args;
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}
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static inline void pwm_apply_args(struct pwm_device *pwm)
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{
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/*
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* PWM users calling pwm_apply_args() expect to have a fresh config
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* where the polarity and period are set according to pwm_args info.
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* The problem is, polarity can only be changed when the PWM is
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* disabled.
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*
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* PWM drivers supporting hardware readout may declare the PWM device
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* as enabled, and prevent polarity setting, which changes from the
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* existing behavior, where all PWM devices are declared as disabled
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* at startup (even if they are actually enabled), thus authorizing
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* polarity setting.
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*
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* Instead of setting ->enabled to false, we call pwm_disable()
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* before pwm_set_polarity() to ensure that everything is configured
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* as expected, and the PWM is really disabled when the user request
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* it.
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*
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* Note that PWM users requiring a smooth handover between the
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* bootloader and the kernel (like critical regulators controlled by
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* PWM devices) will have to switch to the atomic API and avoid calling
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* pwm_apply_args().
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*/
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pwm_disable(pwm);
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pwm_set_polarity(pwm, pwm->args.polarity);
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}
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/**
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* struct pwm_ops - PWM controller operations
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* @request: optional hook for requesting a PWM
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@ -240,6 +155,10 @@ static inline void pwm_apply_args(struct pwm_device *pwm)
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* @set_polarity: configure the polarity of this PWM
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* @enable: enable PWM output toggling
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* @disable: disable PWM output toggling
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* @apply: atomically apply a new PWM config. The state argument
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* should be adjusted with the real hardware config (if the
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* approximate the period or duty_cycle value, state should
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* reflect it)
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* @get_state: get the current PWM state. This function is only
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* called once per PWM device when the PWM chip is
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* registered.
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@ -255,6 +174,8 @@ struct pwm_ops {
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enum pwm_polarity polarity);
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int (*enable)(struct pwm_chip *chip, struct pwm_device *pwm);
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void (*disable)(struct pwm_chip *chip, struct pwm_device *pwm);
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int (*apply)(struct pwm_chip *chip, struct pwm_device *pwm,
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struct pwm_state *state);
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void (*get_state)(struct pwm_chip *chip, struct pwm_device *pwm,
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struct pwm_state *state);
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#ifdef CONFIG_DEBUG_FS
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@ -292,6 +213,115 @@ struct pwm_chip {
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};
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#if IS_ENABLED(CONFIG_PWM)
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/* PWM user APIs */
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struct pwm_device *pwm_request(int pwm_id, const char *label);
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void pwm_free(struct pwm_device *pwm);
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int pwm_apply_state(struct pwm_device *pwm, struct pwm_state *state);
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int pwm_adjust_config(struct pwm_device *pwm);
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/**
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* pwm_config() - change a PWM device configuration
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* @pwm: PWM device
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* @duty_ns: "on" time (in nanoseconds)
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* @period_ns: duration (in nanoseconds) of one cycle
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*
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* Returns: 0 on success or a negative error code on failure.
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*/
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static inline int pwm_config(struct pwm_device *pwm, int duty_ns,
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int period_ns)
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{
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struct pwm_state state;
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if (!pwm)
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return -EINVAL;
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pwm_get_state(pwm, &state);
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if (state.duty_cycle == duty_ns && state.period == period_ns)
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return 0;
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state.duty_cycle = duty_ns;
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state.period = period_ns;
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return pwm_apply_state(pwm, &state);
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}
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/**
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* pwm_set_polarity() - configure the polarity of a PWM signal
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* @pwm: PWM device
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* @polarity: new polarity of the PWM signal
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*
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* Note that the polarity cannot be configured while the PWM device is
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* enabled.
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*
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* Returns: 0 on success or a negative error code on failure.
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*/
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static inline int pwm_set_polarity(struct pwm_device *pwm,
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enum pwm_polarity polarity)
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{
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struct pwm_state state;
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if (!pwm)
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return -EINVAL;
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pwm_get_state(pwm, &state);
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if (state.polarity == polarity)
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return 0;
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/*
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* Changing the polarity of a running PWM without adjusting the
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* dutycycle/period value is a bit risky (can introduce glitches).
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* Return -EBUSY in this case.
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* Note that this is allowed when using pwm_apply_state() because
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* the user specifies all the parameters.
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*/
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if (state.enabled)
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return -EBUSY;
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state.polarity = polarity;
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return pwm_apply_state(pwm, &state);
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}
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/**
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* pwm_enable() - start a PWM output toggling
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* @pwm: PWM device
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*
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* Returns: 0 on success or a negative error code on failure.
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*/
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static inline int pwm_enable(struct pwm_device *pwm)
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{
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struct pwm_state state;
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if (!pwm)
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return -EINVAL;
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pwm_get_state(pwm, &state);
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if (state.enabled)
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return 0;
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state.enabled = true;
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return pwm_apply_state(pwm, &state);
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}
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/**
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* pwm_disable() - stop a PWM output toggling
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* @pwm: PWM device
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*/
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static inline void pwm_disable(struct pwm_device *pwm)
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{
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struct pwm_state state;
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if (!pwm)
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return;
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|
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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;
|
||||
|
||||
Loading…
Reference in New Issue
Block a user