zephyr/include/drivers/pwm.h
Peter Bigot a4337bde28 drivers: pwm: clarify behavior
As written the specification when both period and pulse are zero is
inconsistent: allowed behavior would be to drive the pin at constant
active or constant inactive, depending on which condition was checked
first.

Clarify that driving constant active level requres a non-zero pulse
equal to period.

Signed-off-by: Peter Bigot <peter.bigot@nordicsemi.no>
2020-06-09 18:12:53 +02:00

197 lines
5.1 KiB
C

/*
* Copyright (c) 2016 Intel Corporation.
*
* SPDX-License-Identifier: Apache-2.0
*/
/**
* @file
* @brief Public PWM Driver APIs
*/
#ifndef ZEPHYR_INCLUDE_DRIVERS_PWM_H_
#define ZEPHYR_INCLUDE_DRIVERS_PWM_H_
/**
* @brief PWM Interface
* @defgroup pwm_interface PWM Interface
* @ingroup io_interfaces
* @{
*/
#include <errno.h>
#include <zephyr/types.h>
#include <stddef.h>
#include <device.h>
#include <dt-bindings/pwm/pwm.h>
#ifdef __cplusplus
extern "C" {
#endif
/**
* @brief Provides a type to hold PWM configuration flags.
*/
typedef uint8_t pwm_flags_t;
/**
* @typedef pwm_pin_set_t
* @brief Callback API upon setting the pin
* See @a pwm_pin_set_cycles() for argument description
*/
typedef int (*pwm_pin_set_t)(struct device *dev, uint32_t pwm,
uint32_t period_cycles, uint32_t pulse_cycles,
pwm_flags_t flags);
/**
* @typedef pwm_get_cycles_per_sec_t
* @brief Callback API upon getting cycles per second
* See @a pwm_get_cycles_per_sec() for argument description
*/
typedef int (*pwm_get_cycles_per_sec_t)(struct device *dev, uint32_t pwm,
uint64_t *cycles);
/** @brief PWM driver API definition. */
__subsystem struct pwm_driver_api {
pwm_pin_set_t pin_set;
pwm_get_cycles_per_sec_t get_cycles_per_sec;
};
/**
* @brief Set the period and pulse width for a single PWM output.
*
* Passing 0 as @p pulse will cause the pin to be driven to a constant
* inactive level.
* Passing a non-zero @p pulse equal to @p period will cause the pin
* to be driven to a constant active level.
*
* @param dev Pointer to the device structure for the driver instance.
* @param pwm PWM pin.
* @param period Period (in clock cycle) set to the PWM. HW specific.
* @param pulse Pulse width (in clock cycle) set to the PWM. HW specific.
* @param flags Flags for pin configuration (polarity).
*
* @retval 0 If successful.
* @retval Negative errno code if failure.
*/
__syscall int pwm_pin_set_cycles(struct device *dev, uint32_t pwm,
uint32_t period, uint32_t pulse, pwm_flags_t flags);
static inline int z_impl_pwm_pin_set_cycles(struct device *dev, uint32_t pwm,
uint32_t period, uint32_t pulse,
pwm_flags_t flags)
{
struct pwm_driver_api *api;
api = (struct pwm_driver_api *)dev->driver_api;
return api->pin_set(dev, pwm, period, pulse, flags);
}
/**
* @brief Get the clock rate (cycles per second) for a single PWM output.
*
* @param dev Pointer to the device structure for the driver instance.
* @param pwm PWM pin.
* @param cycles Pointer to the memory to store clock rate (cycles per sec).
* HW specific.
*
* @retval 0 If successful.
* @retval Negative errno code if failure.
*/
__syscall int pwm_get_cycles_per_sec(struct device *dev, uint32_t pwm,
uint64_t *cycles);
static inline int z_impl_pwm_get_cycles_per_sec(struct device *dev, uint32_t pwm,
uint64_t *cycles)
{
struct pwm_driver_api *api;
api = (struct pwm_driver_api *)dev->driver_api;
return api->get_cycles_per_sec(dev, pwm, cycles);
}
/**
* @brief Set the period and pulse width for a single PWM output.
*
* @param dev Pointer to the device structure for the driver instance.
* @param pwm PWM pin.
* @param period Period (in microseconds) set to the PWM.
* @param pulse Pulse width (in microseconds) set to the PWM.
* @param flags Flags for pin configuration (polarity).
*
* @retval 0 If successful.
* @retval Negative errno code if failure.
*/
static inline int pwm_pin_set_usec(struct device *dev, uint32_t pwm,
uint32_t period, uint32_t pulse,
pwm_flags_t flags)
{
uint64_t period_cycles, pulse_cycles, cycles_per_sec;
if (pwm_get_cycles_per_sec(dev, pwm, &cycles_per_sec) != 0) {
return -EIO;
}
period_cycles = (period * cycles_per_sec) / USEC_PER_SEC;
if (period_cycles >= ((uint64_t)1 << 32)) {
return -ENOTSUP;
}
pulse_cycles = (pulse * cycles_per_sec) / USEC_PER_SEC;
if (pulse_cycles >= ((uint64_t)1 << 32)) {
return -ENOTSUP;
}
return pwm_pin_set_cycles(dev, pwm, (uint32_t)period_cycles,
(uint32_t)pulse_cycles, flags);
}
/**
* @brief Set the period and pulse width for a single PWM output.
*
* @param dev Pointer to the device structure for the driver instance.
* @param pwm PWM pin.
* @param period Period (in nanoseconds) set to the PWM.
* @param pulse Pulse width (in nanoseconds) set to the PWM.
* @param flags Flags for pin configuration (polarity).
*
* @retval 0 If successful.
* @retval Negative errno code if failure.
*/
static inline int pwm_pin_set_nsec(struct device *dev, uint32_t pwm,
uint32_t period, uint32_t pulse,
pwm_flags_t flags)
{
uint64_t period_cycles, pulse_cycles, cycles_per_sec;
if (pwm_get_cycles_per_sec(dev, pwm, &cycles_per_sec) != 0) {
return -EIO;
}
period_cycles = (period * cycles_per_sec) / NSEC_PER_SEC;
if (period_cycles >= ((uint64_t)1 << 32)) {
return -ENOTSUP;
}
pulse_cycles = (pulse * cycles_per_sec) / NSEC_PER_SEC;
if (pulse_cycles >= ((uint64_t)1 << 32)) {
return -ENOTSUP;
}
return pwm_pin_set_cycles(dev, pwm, (uint32_t)period_cycles,
(uint32_t)pulse_cycles, flags);
}
#ifdef __cplusplus
}
#endif
/**
* @}
*/
#include <syscalls/pwm.h>
#endif /* ZEPHYR_INCLUDE_DRIVERS_PWM_H_ */