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authorBoris Brezillon <boris.brezillon@free-electrons.com>2016-04-14 21:17:41 +0200
committerThierry Reding <thierry.reding@gmail.com>2016-05-17 14:48:03 +0200
commit5ec803edcb703fe379836f13560b79dfac79b01d (patch)
treeee69e2156e03337bd928e151a5c5a39aa44baeb2 /drivers/pwm
parent15fa8a43c147213a9563903c87b29671035eb6e8 (diff)
downloadlinux-5ec803edcb703fe379836f13560b79dfac79b01d.tar.bz2
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>
Diffstat (limited to 'drivers/pwm')
-rw-r--r--drivers/pwm/core.c187
1 files changed, 119 insertions, 68 deletions
diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index a909c64ee863..729d457861fd 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 +446,138 @@ 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)
{