drivers/pwm/pwm_sam0_tc.c

/*
 * Copyright (c) 2024 Daikin Comfort Technologies North America, Inc.
 *
 * Heavily based on pwm_sam0_tcc.c, which is:
 * Copyright (c) 2020 Google LLC.
 *
 * SPDX-License-Identifier: Apache-2.0
 */

/*
 * PWM driver using the SAM0 Timer/Counter (TC) Supports the SAMD21 and SAMD5x series,
 * 8 and 16 bit counter size is supported.
 *
 * The 8-bit counter operates in Normal PWM (NPWM) mode, it supports pulse width and period
 * values between 0 and 255. It is ideal for applications requiring moderate frequency PWM,
 * however, it is not suitable for high-precision or low-frequency applications.
 *
 * The 16-bit counter operates in Match PWM (MPWM) mode to generate the PWM signal.
 * this mode sacrifices the timer's CC0 channel in order to achieve pulse width modulation.
 */

#define DT_DRV_COMPAT atmel_sam0_tc_pwm

#include <zephyr/kernel.h>
#include <zephyr/device.h>
#include <errno.h>
#include <zephyr/drivers/pwm.h>
#include <zephyr/drivers/pinctrl.h>
#include <soc.h>

/* clang-format off */

/* Static configuration */
struct pwm_sam0_config {
	Tc *regs;
	const struct pinctrl_dev_config *pcfg;
	uint8_t channels;
	uint8_t counter_size;
	uint16_t prescaler;
	uint32_t freq;
	volatile uint32_t *mclk;
	uint32_t mclk_mask;
	uint32_t gclk_gen;
	uint16_t gclk_id;
};

#define COUNTER_8BITS 8U

/* Wait for the peripheral to finish all commands */
static void wait_synchronization(Tc *regs, uint8_t counter_size)
{
	if (COUNTER_8BITS == counter_size) {
		while (regs->COUNT8.SYNCBUSY.reg != 0) {
		}
	} else {
		while (regs->COUNT16.SYNCBUSY.reg != 0) {
		}
	}
}

static int pwm_sam0_get_cycles_per_sec(const struct device *dev,
							uint32_t channel, uint64_t *cycles)
{
	const struct pwm_sam0_config *const cfg = dev->config;

	if (channel >= cfg->channels) {
		return -EINVAL;
	}

	*cycles = cfg->freq;

	return 0;
}

static int pwm_sam0_set_cycles(const struct device *dev, uint32_t channel, uint32_t period_cycles,
			       uint32_t pulse_cycles, pwm_flags_t flags)
{
	const struct pwm_sam0_config *const cfg = dev->config;
	Tc *regs = cfg->regs;
	uint8_t counter_size = cfg->counter_size;
	uint32_t top = 1 << counter_size;
	uint32_t invert_mask = 1 << channel;
	bool invert = ((flags & PWM_POLARITY_INVERTED) != 0);
	bool inverted;

	if (channel >= cfg->channels) {
		return -EINVAL;
	}
	if (period_cycles >= top || pulse_cycles >= top) {
		return -EINVAL;
	}

	/*
	 * Update the buffered width and period.  These will be automatically
	 * loaded on the next cycle.
	 */
	if (COUNTER_8BITS == counter_size) {
		inverted = ((regs->COUNT8.DRVCTRL.vec.INVEN & invert_mask) != 0);
		regs->COUNT8.CCBUF[channel].reg = TC_COUNT8_CCBUF_CCBUF(pulse_cycles);
		regs->COUNT8.PERBUF.reg = TC_COUNT8_PERBUF_PERBUF(period_cycles);
		wait_synchronization(regs, counter_size);

		if (invert != inverted) {
			regs->COUNT8.CTRLA.bit.ENABLE = 0;
			wait_synchronization(regs, counter_size);

			regs->COUNT8.DRVCTRL.vec.INVEN ^= invert_mask;
			regs->COUNT8.CTRLA.bit.ENABLE = 1;
			wait_synchronization(regs, counter_size);
		}
	} else {
		inverted = ((regs->COUNT16.DRVCTRL.vec.INVEN & invert_mask) != 0);
		regs->COUNT16.CCBUF[0].reg = TC_COUNT16_CCBUF_CCBUF(period_cycles);
		regs->COUNT16.CCBUF[1].reg = TC_COUNT16_CCBUF_CCBUF(pulse_cycles);
		wait_synchronization(regs, counter_size);

		if (invert != inverted) {
			regs->COUNT16.CTRLA.bit.ENABLE = 0;
			wait_synchronization(regs, counter_size);

			regs->COUNT16.DRVCTRL.vec.INVEN ^= invert_mask;
			regs->COUNT16.CTRLA.bit.ENABLE = 1;
			wait_synchronization(regs, counter_size);
		}
	}

	return 0;
}

static int pwm_sam0_init(const struct device *dev)
{
	const struct pwm_sam0_config *const cfg = dev->config;
	uint8_t counter_size = cfg->counter_size;
	Tc *regs = cfg->regs;
	int retval;

	*cfg->mclk |= cfg->mclk_mask;

#ifdef MCLK
	GCLK->PCHCTRL[cfg->gclk_id].reg = GCLK_PCHCTRL_CHEN
					| GCLK_PCHCTRL_GEN(cfg->gclk_gen);
#else
	GCLK->CLKCTRL.reg = GCLK_CLKCTRL_CLKEN
			  | GCLK_CLKCTRL_GEN(cfg->gclk_gen)
			  | GCLK_CLKCTRL_ID(cfg->gclk_id);
#endif

	retval = pinctrl_apply_state(cfg->pcfg, PINCTRL_STATE_DEFAULT);
	if (retval < 0) {
		return retval;
	}

	if (COUNTER_8BITS == counter_size) {
		regs->COUNT8.CTRLA.bit.SWRST = 1;
		wait_synchronization(regs, counter_size);

		regs->COUNT8.CTRLA.reg = cfg->prescaler | TC_CTRLA_MODE_COUNT8 |
						TC_CTRLA_PRESCSYNC_PRESC;
		regs->COUNT8.WAVE.reg = TC_WAVE_WAVEGEN_NPWM;
		regs->COUNT8.PER.reg = TC_COUNT8_PER_PER(1);

		regs->COUNT8.CTRLA.bit.ENABLE = 1;
		wait_synchronization(regs, counter_size);
	} else {
		regs->COUNT16.CTRLA.bit.SWRST = 1;
		wait_synchronization(regs, counter_size);

		regs->COUNT16.CTRLA.reg = cfg->prescaler | TC_CTRLA_MODE_COUNT16 |
						TC_CTRLA_PRESCSYNC_PRESC;
		regs->COUNT16.WAVE.reg = TC_WAVE_WAVEGEN_MPWM;
		regs->COUNT16.CC[0].reg = TC_COUNT16_CC_CC(1);

		regs->COUNT16.CTRLA.bit.ENABLE = 1;
		wait_synchronization(regs, cfg->counter_size);
	}

	return 0;
}

static DEVICE_API(pwm, pwm_sam0_driver_api) = {
	.set_cycles = pwm_sam0_set_cycles,
	.get_cycles_per_sec = pwm_sam0_get_cycles_per_sec,
};

#define ASSIGNED_CLOCKS_CELL_BY_NAME						\
	ATMEL_SAM0_DT_INST_ASSIGNED_CLOCKS_CELL_BY_NAME

#define PWM_SAM0_INIT(inst)							\
	PINCTRL_DT_INST_DEFINE(inst);						\
										\
	static const struct pwm_sam0_config pwm_sam0_config_##inst = {		\
		.regs = (Tc *)DT_INST_REG_ADDR(inst),				\
		.pcfg = PINCTRL_DT_INST_DEV_CONFIG_GET(inst),			\
		.channels = DT_INST_PROP(inst, channels),			\
		.counter_size = DT_INST_PROP(inst, counter_size),		\
		.prescaler = UTIL_CAT(TC_CTRLA_PRESCALER_DIV,			\
				      DT_INST_PROP(inst, prescaler)),		\
		.freq = SOC_ATMEL_SAM0_GCLK0_FREQ_HZ /				\
			DT_INST_PROP(inst, prescaler),		\
		.gclk_gen = ASSIGNED_CLOCKS_CELL_BY_NAME(inst, gclk, gen),	\
		.gclk_id = DT_INST_CLOCKS_CELL_BY_NAME(inst, gclk, id),		\
		.mclk = ATMEL_SAM0_DT_INST_MCLK_PM_REG_ADDR_OFFSET(inst),	\
		.mclk_mask = ATMEL_SAM0_DT_INST_MCLK_PM_PERIPH_MASK(inst, bit),	\
	};									\
										\
	DEVICE_DT_INST_DEFINE(inst, &pwm_sam0_init, NULL,			\
			      NULL, &pwm_sam0_config_##inst,			\
			      POST_KERNEL, CONFIG_PWM_TC_INIT_PRIORITY,		\
			      &pwm_sam0_driver_api);

DT_INST_FOREACH_STATUS_OKAY(PWM_SAM0_INIT)

/* clang-format on */