path: root/drivers/pwm/core.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Generic pwmlib implementation
 *
 * Copyright (C) 2011 Sascha Hauer <s.hauer@pengutronix.de>
 * Copyright (C) 2011-2012 Avionic Design GmbH
 */

#include <linux/acpi.h>
#include <linux/module.h>
#include <linux/idr.h>
#include <linux/of.h>
#include <linux/pwm.h>
#include <linux/list.h>
#include <linux/mutex.h>
#include <linux/err.h>
#include <linux/slab.h>
#include <linux/device.h>
#include <linux/debugfs.h>
#include <linux/seq_file.h>

#include <dt-bindings/pwm/pwm.h>

#define CREATE_TRACE_POINTS
#include <trace/events/pwm.h>

/* protects access to pwm_chips */
static DEFINE_MUTEX(pwm_lock);

static DEFINE_IDR(pwm_chips);

static void pwm_apply_debug(struct pwm_device *pwm,
			    const struct pwm_state *state)
{
	struct pwm_state *last = &pwm->last;
	struct pwm_chip *chip = pwm->chip;
	struct pwm_state s1 = { 0 }, s2 = { 0 };
	int err;

	if (!IS_ENABLED(CONFIG_PWM_DEBUG))
		return;

	/* No reasonable diagnosis possible without .get_state() */
	if (!chip->ops->get_state)
		return;

	/*
	 * *state was just applied. Read out the hardware state and do some
	 * checks.
	 */

	err = chip->ops->get_state(chip, pwm, &s1);
	trace_pwm_get(pwm, &s1, err);
	if (err)
		/* If that failed there isn't much to debug */
		return;

	/*
	 * The lowlevel driver either ignored .polarity (which is a bug) or as
	 * best effort inverted .polarity and fixed .duty_cycle respectively.
	 * Undo this inversion and fixup for further tests.
	 */
	if (s1.enabled && s1.polarity != state->polarity) {
		s2.polarity = state->polarity;
		s2.duty_cycle = s1.period - s1.duty_cycle;
		s2.period = s1.period;
		s2.enabled = s1.enabled;
	} else {
		s2 = s1;
	}

	if (s2.polarity != state->polarity &&
	    state->duty_cycle < state->period)
		dev_warn(pwmchip_parent(chip), ".apply ignored .polarity\n");

	if (state->enabled &&
	    last->polarity == state->polarity &&
	    last->period > s2.period &&
	    last->period <= state->period)
		dev_warn(pwmchip_parent(chip),
			 ".apply didn't pick the best available period (requested: %llu, applied: %llu, possible: %llu)\n",
			 state->period, s2.period, last->period);

	if (state->enabled && state->period < s2.period)
		dev_warn(pwmchip_parent(chip),
			 ".apply is supposed to round down period (requested: %llu, applied: %llu)\n",
			 state->period, s2.period);

	if (state->enabled &&
	    last->polarity == state->polarity &&
	    last->period == s2.period &&
	    last->duty_cycle > s2.duty_cycle &&
	    last->duty_cycle <= state->duty_cycle)
		dev_warn(pwmchip_parent(chip),
			 ".apply didn't pick the best available duty cycle (requested: %llu/%llu, applied: %llu/%llu, possible: %llu/%llu)\n",
			 state->duty_cycle, state->period,
			 s2.duty_cycle, s2.period,
			 last->duty_cycle, last->period);

	if (state->enabled && state->duty_cycle < s2.duty_cycle)
		dev_warn(pwmchip_parent(chip),
			 ".apply is supposed to round down duty_cycle (requested: %llu/%llu, applied: %llu/%llu)\n",
			 state->duty_cycle, state->period,
			 s2.duty_cycle, s2.period);

	if (!state->enabled && s2.enabled && s2.duty_cycle > 0)
		dev_warn(pwmchip_parent(chip),
			 "requested disabled, but yielded enabled with duty > 0\n");

	/* reapply the state that the driver reported being configured. */
	err = chip->ops->apply(chip, pwm, &s1);
	trace_pwm_apply(pwm, &s1, err);
	if (err) {
		*last = s1;
		dev_err(pwmchip_parent(chip), "failed to reapply current setting\n");
		return;
	}

	*last = (struct pwm_state){ 0 };
	err = chip->ops->get_state(chip, pwm,