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
committed by
Thierry Reding
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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