pwm_mcux_sctimer.c

/*
 * Copyright (c) 2021, NXP
 *
 * SPDX-License-Identifier: Apache-2.0
 */


#define DT_DRV_COMPAT nxp_sctimer_pwm

#include <errno.h>
#include <zephyr/drivers/pwm.h>
#include <fsl_sctimer.h>
#include <fsl_clock.h>
#include <zephyr/drivers/pinctrl.h>
#include <zephyr/drivers/clock_control.h>

#include <zephyr/logging/log.h>

LOG_MODULE_REGISTER(pwm_mcux_sctimer, CONFIG_PWM_LOG_LEVEL);

#define CHANNEL_COUNT FSL_FEATURE_SCT_NUMBER_OF_OUTPUTS

/* Constant identifying that no event number has been set */
#define EVENT_NOT_SET FSL_FEATURE_SCT_NUMBER_OF_EVENTS

struct pwm_mcux_sctimer_config {
	SCT_Type *base;
	uint32_t prescale;
	const struct pinctrl_dev_config *pincfg;
	const struct device *clock_dev;
	clock_control_subsys_t clock_subsys;
};

struct pwm_mcux_sctimer_data {
	uint32_t event_number[CHANNEL_COUNT];
	sctimer_pwm_signal_param_t channel[CHANNEL_COUNT];
	uint32_t match_period;
	uint32_t configured_chan;
};

/* Helper to setup channel that has not previously been configured for PWM */
static int mcux_sctimer_new_channel(const struct device *dev,
				    uint32_t channel, uint32_t period_cycles,
				    uint32_t duty_cycle)
{
	const struct pwm_mcux_sctimer_config *config = dev->config;
	struct pwm_mcux_sctimer_data *data = dev->data;
	uint32_t clock_freq;
	uint32_t pwm_freq;

	data->match_period = period_cycles;

	if (clock_control_get_rate(config->clock_dev, config->clock_subsys,
				&clock_freq)) {
		return -EINVAL;
	}

	pwm_freq = (clock_freq / config->prescale) / period_cycles;

	if (pwm_freq == 0) {
		LOG_ERR("Could not set up pwm_freq=%d", pwm_freq);
		return -EINVAL;
	}

	SCTIMER_StopTimer(config->base, kSCTIMER_Counter_U);

	LOG_DBG("SETUP dutycycle to %u\n", duty_cycle);
	data->channel[channel].dutyCyclePercent = duty_cycle;
	if (SCTIMER_SetupPwm(config->base, &data->channel[channel],
			     kSCTIMER_EdgeAlignedPwm, pwm_freq,
			     clock_freq, &data->event_number[channel]) == kStatus_Fail) {
		LOG_ERR("Could not set up pwm");
		return -ENOTSUP;
	}

	SCTIMER_StartTimer(config->base, kSCTIMER_Counter_U);
	data->configured_chan++;
	return 0;
}

static int mcux_sctimer_pwm_set_cycles(const struct device *dev,
				       uint32_t channel, uint32_t period_cycles,
				       uint32_t pulse_cycles, pwm_flags_t flags)
{
	const struct pwm_mcux_sctimer_config *config = dev->config;
	struct pwm_mcux_sctimer_data *data = dev->data;
	uint8_t duty_cycle;
	int ret;

	if (channel >= CHANNEL_COUNT) {
		LOG_ERR("Invalid channel");
		return -EINVAL;
	}

	if (period_cycles == 0) {
		LOG_ERR("Channel can not be set to inactive level");
		return -ENOTSUP;
	}

	if ((flags & PWM_POLARITY_INVERTED) == 0) {
		data->channel[channel].level = kSCTIMER_HighTrue;
	} else {
		data->channel[channel].level = kSCTIMER_LowTrue;
	}

	duty_cycle = 100 * pulse_cycles / period_cycles;

	if (duty_cycle == 0 && data->configured_chan == 1) {
		/* Only one channel is active. We can turn off the SCTimer
		 * global counter.
		 */
		SCT_Type *base = config->base;

		/* Stop timer so we can set output directly */
		SCTIMER_StopTimer(base, kSCTIMER_Counter_U);

		/* Set the output to inactive State */
		if (data->channel[channel].level == kSCTIMER_HighTrue) {
			base->OUTPUT &= ~(1UL << channel);
		} else {
			base->OUTPUT |= (1UL << channel);
		}

		return 0;
	}

	/* SCTimer has some unique restrictions when operation as a PWM output.
	 * The peripheral is based around a single counter, with a block of
	 * match registers that can trigger corresponding events. When used
	 * as a PWM peripheral, MCUX SDK sets up the SCTimer as follows:
	 * - one match register is used to set PWM output high, and reset
	 *   SCtimer counter. This sets the PWM period
	 * - one match register is used to set PWM output low. This sets the
	 *   pulse length
	 *
	 * This means that when configured, multiple channels must have the
	 * same PWM period, since they all share the same SCTimer counter.
	 */
	if (period_cycles != data->match_period &&
	    data->event_number[channel] == EVENT_NOT_SET &&
	    data->match_period == 0U) {
		/* No PWM signals have been configured. We can set up the first
		 * PWM output using the MCUX SDK.
		 */
		ret = mcux_sctimer_new_channel(dev, channel, period_cycles,
					       duty_cycle);
		if (ret < 0) {
			return ret;
		}
	} else if (data->event_number[channel] == EVENT_NOT_SET) {
		/* We have already configured a PWM signal, but this channel
		 * has not been setup. We can only support this channel
		 * if the period matches that of other PWM signals.
		 */
		if (period_cycles != data->match_period) {
			LOG_ERR("Only one PWM period is supported between "
				"multiple channels");
			return -ENOTSUP;
		}
		/* Setup PWM output using MCUX SDK */
		ret = mcux_sctimer_new_channel(dev, channel, period_cycles,
					       duty_cycle);
	} else if (period_cycles != data->match_period) {
		uint32_t period_event = data->event_number[channel];
		/* We are reconfiguring the period of a configured channel
		 * MCUX SDK does not provide support for this feature, and
		 * we cannot do this safely if multiple channels are setup.
		 */
		if (data->configured_chan != 1) {
			LOG_ERR("Cannot change PWM period when multiple "
				"channels active");
			return -ENOTSUP;
		}

		/* To make this change, we can simply set the MATCHREL
		 * registers for the period match, and the next match
		 * (which the SDK will setup as the pulse match event)
		 */
		SCTIMER_StopTimer(config->base, kSCTIMER_Counter_U);
		config->base->MATCHREL[period_event] = period_cycles - 1U;
		config->base->MATCHREL[period_event + 1] = pulse_cycles - 1U;
		SCTIMER_StartTimer(config->base, kSCTIMER_Counter_U);
		data->match_period = period_cycles;
	} else {
		/* Only duty cycle needs to be updated */
		SCTIMER_UpdatePwmDutycycle(config->base, channel, duty_cycle,
					   data->event_number[channel]);
	}

	return 0;
}

static int mcux_sctimer_pwm_get_cycles_per_sec(const struct device *dev,
					       uint32_t channel,
					       uint64_t *cycles)
{
	const struct pwm_mcux_sctimer_config *config = dev->config;
	uint32_t clock_freq;

	if (clock_control_get_rate(config->clock_dev, config->clock_subsys,
				&clock_freq)) {
		return -EINVAL;
	}

	*cycles = clock_freq / config->prescale;

	return 0;
}

static int mcux_sctimer_pwm_init(const struct device *dev)
{
	const struct pwm_mcux_sctimer_config *config = dev->config;
	struct pwm_mcux_sctimer_data *data = dev->data;
	sctimer_config_t pwm_config;
	status_t status;
	int i;
	int err;

	err = pinctrl_apply_state(config->pincfg, PINCTRL_STATE_DEFAULT);
	if (err) {
		return err;
	}

	SCTIMER_GetDefaultConfig(&pwm_config);

	pwm_config.prescale_l = config->prescale - 1;

	status = SCTIMER_Init(config->base, &pwm_config);
	if (status != kStatus_Success) {
		LOG_ERR("Unable to init PWM");
		return -EIO;
	}

	for (i = 0; i < CHANNEL_COUNT; i++) {
		data->channel[i].output = i;
		data->channel[i].level = kSCTIMER_HighTrue;
		data->channel[i].dutyCyclePercent = 0;
		data->event_number[i] = EVENT_NOT_SET;
	}
	data->match_period = 0;
	data->configured_chan = 0;

	return 0;
}

static DEVICE_API(pwm, pwm_mcux_sctimer_driver_api) = {
	.set_cycles = mcux_sctimer_pwm_set_cycles,
	.get_cycles_per_sec = mcux_sctimer_pwm_get_cycles_per_sec,
};

#define PWM_MCUX_SCTIMER_DEVICE_INIT_MCUX(n)						\
	PINCTRL_DT_INST_DEFINE(n);							\
	static struct pwm_mcux_sctimer_data pwm_mcux_sctimer_data_##n;			\
											\
	static const struct pwm_mcux_sctimer_config pwm_mcux_sctimer_config_##n = {	\
		.base = (SCT_Type *)DT_INST_REG_ADDR(n),				\
		.prescale = DT_INST_PROP(n, prescaler),					\
		.pincfg = PINCTRL_DT_INST_DEV_CONFIG_GET(n),				\
		.clock_dev = DEVICE_DT_GET(DT_INST_CLOCKS_CTLR(n)),		\
		.clock_subsys = (clock_control_subsys_t)DT_INST_CLOCKS_CELL(n, name),\
	};										\
											\
	DEVICE_DT_INST_DEFINE(n,							\
			      mcux_sctimer_pwm_init,					\
			      NULL,							\
			      &pwm_mcux_sctimer_data_##n,				\
			      &pwm_mcux_sctimer_config_##n,				\
			      POST_KERNEL, CONFIG_PWM_INIT_PRIORITY,			\
			      &pwm_mcux_sctimer_driver_api);

DT_INST_FOREACH_STATUS_OKAY(PWM_MCUX_SCTIMER_DEVICE_INIT_MCUX)