pwm-lpc18xx-sct.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * NXP LPC18xx State Configurable Timer - Pulse Width Modulator driver
 *
 * Copyright (c) 2015 Ariel D'Alessandro <ariel@vanguardiasur.com>
 *
 * Notes
 * =====
 * NXP LPC18xx provides a State Configurable Timer (SCT) which can be configured
 * as a Pulse Width Modulator.
 *
 * SCT supports 16 outputs, 16 events and 16 registers. Each event will be
 * triggered when its related register matches the SCT counter value, and it
 * will set or clear a selected output.
 *
 * One of the events is preselected to generate the period, thus the maximum
 * number of simultaneous channels is limited to 15. Notice that period is
 * global to all the channels, thus PWM driver will refuse setting different
 * values to it, unless there's only one channel requested.
 */

#include <linux/clk.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/pwm.h>

/* LPC18xx SCT registers */
#define LPC18XX_PWM_CONFIG		0x000
#define LPC18XX_PWM_CONFIG_UNIFY	BIT(0)
#define LPC18XX_PWM_CONFIG_NORELOAD	BIT(7)

#define LPC18XX_PWM_CTRL		0x004
#define LPC18XX_PWM_CTRL_HALT		BIT(2)
#define LPC18XX_PWM_BIDIR		BIT(4)
#define LPC18XX_PWM_PRE_SHIFT		5
#define LPC18XX_PWM_PRE_MASK		(0xff << LPC18XX_PWM_PRE_SHIFT)
#define LPC18XX_PWM_PRE(x)		(x << LPC18XX_PWM_PRE_SHIFT)

#define LPC18XX_PWM_LIMIT		0x008

#define LPC18XX_PWM_RES_BASE		0x058
#define LPC18XX_PWM_RES_SHIFT(_ch)	(_ch * 2)
#define LPC18XX_PWM_RES(_ch, _action)	(_action << LPC18XX_PWM_RES_SHIFT(_ch))
#define LPC18XX_PWM_RES_MASK(_ch)	(0x3 << LPC18XX_PWM_RES_SHIFT(_ch))

#define LPC18XX_PWM_MATCH_BASE		0x100
#define LPC18XX_PWM_MATCH(_ch)		(LPC18XX_PWM_MATCH_BASE + _ch * 4)

#define LPC18XX_PWM_MATCHREL_BASE	0x200
#define LPC18XX_PWM_MATCHREL(_ch)	(LPC18XX_PWM_MATCHREL_BASE + _ch * 4)

#define LPC18XX_PWM_EVSTATEMSK_BASE	0x300
#define LPC18XX_PWM_EVSTATEMSK(_ch)	(LPC18XX_PWM_EVSTATEMSK_BASE + _ch * 8)
#define LPC18XX_PWM_EVSTATEMSK_ALL	0xffffffff

#define LPC18XX_PWM_EVCTRL_BASE		0x304
#define LPC18XX_PWM_EVCTRL(_ev)		(LPC18XX_PWM_EVCTRL_BASE + _ev * 8)

#define LPC18XX_PWM_EVCTRL_MATCH(_ch)	_ch

#define LPC18XX_PWM_EVCTRL_COMB_SHIFT	12
#define LPC18XX_PWM_EVCTRL_COMB_MATCH	(0x1 << LPC18XX_PWM_EVCTRL_COMB_SHIFT)

#define LPC18XX_PWM_OUTPUTSET_BASE	0x500
#define LPC18XX_PWM_OUTPUTSET(_ch)	(LPC18XX_PWM_OUTPUTSET_BASE + _ch * 8)

#define LPC18XX_PWM_OUTPUTCL_BASE	0x504
#define LPC18XX_PWM_OUTPUTCL(_ch)	(LPC18XX_PWM_OUTPUTCL_BASE + _ch * 8)

/* LPC18xx SCT unified counter */
#define LPC18XX_PWM_TIMER_MAX		0xffffffff

/* LPC18xx SCT events */
#define LPC18XX_PWM_EVENT_PERIOD	0
#define LPC18XX_PWM_EVENT_MAX		16

#define LPC18XX_NUM_PWMS		16

/* SCT conflict resolution */
enum lpc18xx_pwm_res_action {
	LPC18XX_PWM_RES_NONE,
	LPC18XX_PWM_RES_SET,
	LPC18XX_PWM_RES_CLEAR,
	LPC18XX_PWM_RES_TOGGLE,
};

struct lpc18xx_pwm_data {
	unsigned int duty_event;
};

struct lpc18xx_pwm_chip {
	struct device *dev;
	struct pwm_chip chip;
	void __iomem *base;
	struct clk *pwm_clk;
	unsigned long clk_rate;
	unsigned int period_ns;
	unsigned int min_period_ns;
	u64 max_period_ns;
	unsigned int period_event;
	unsigned long event_map;
	struct mutex res_lock;
	struct mutex period_lock;
	struct lpc18xx_pwm_data channeldata[LPC18XX_NUM_PWMS];
};

static inline struct lpc18xx_pwm_chip *
to_lpc18xx_pwm_chip(struct pwm_chip *chip)
{
	return container_of(chip, struct lpc18xx_pwm_chip, chip);
}

static inline void lpc18xx_pwm_writel(struct lpc18xx_pwm_chip *lpc18xx_pwm,
				      u32 reg, u32 val)
{
	writel(val, lpc18xx_pwm->base + reg);
}

static inline u32 lpc18xx_pwm_readl(struct lpc18xx_pwm_chip *lpc18xx_pwm,
				    u32 reg)
{
	return readl(lpc18xx_pwm->base + reg);
}

static void lpc18xx_pwm_set_conflict_res(struct lpc18xx_pwm_chip *lpc18xx_pwm,
					 struct pwm_device *pwm,
					 enum lpc18xx_pwm_res_action action)
{
	u32 val;

	mutex_lock(&lpc18xx_pwm->res_lock);

	/*
	 * Simultaneous set and clear may happen on an output, that is the case
	 * when duty_ns == period_ns. LPC18xx SCT allows to set a conflict
	 * resolution action to be taken in such a case.
	 */
	val = lpc18xx_pwm_readl(lpc18xx_pwm, LPC18XX_PWM_RES_BASE);
	val &= ~LPC18XX_PWM_RES_MASK(pwm->hwpwm);
	val |= LPC18XX_PWM_RES(pwm->hwpwm, action);
	lpc18xx_pwm_writel(lpc18xx_pwm, LPC18XX_PWM_RES_BASE, val);

	mutex_unlock(&lpc18xx_pwm->res_lock);
}

static void lpc18xx_pwm_config_period(struct pwm_chip *chip, u64 period_ns)
{
	struct lpc18xx_pwm_chip *lpc18xx_pwm = to_lpc18xx_pwm_chip(chip);
	u32 val;

	/*
	 * With clk_rate < NSEC_PER_SEC this cannot overflow.
	 * With period_ns < max_period_ns this also fits into an u32.
	 * As period_ns >= min_period_ns = DIV_ROUND_UP(NSEC_PER_SEC, lpc18xx_pwm->clk_rate);
	 * we have val >= 1.
	 */
	val = mul_u64_u64_div_u64(period_ns, lpc18xx_pwm->clk_rate, NSEC_PER_SEC);

	lpc18xx_pwm_writel(lpc18xx_pwm,
			   LPC18XX_PWM_MATCH(lpc18xx_pwm->period_event),
			   val - 1);

	lpc18xx_pwm_writel(lpc18xx_pwm,
			   LPC18XX_PWM_MATCHREL(lpc18xx_pwm->period_event),
			   val - 1);
}

static void lpc18xx_pwm_config_duty(struct pwm_chip *chip,
				    struct pwm_device *pwm, u64 duty_ns)
{
	struct lpc18xx_pwm_chip *lpc18xx_pwm = to_lpc18xx_pwm_chip(chip);
	struct lpc18xx_pwm_data *lpc18xx_data = &lpc18xx_pwm->channeldata[pwm->hwpwm];
	u32 val;

	/*
	 * With clk_rate <= NSEC_PER_SEC this cannot overflow.
	 * With duty_ns <= period_ns < max_period_ns this also fits into an u32.
	 */
	val = mul_u64_u64_div_u64(duty_ns, lpc18xx_pwm->clk_rate, NSEC_PER_SEC);

	lpc18xx_pwm_writel(lpc18xx_pwm,
			   LPC18XX_PWM_MATCH(lpc18xx_data->duty_event),
			   val);

	lpc18xx_pwm_writel(lpc18xx_pwm,
			   LPC18XX_PWM_MATCHREL(lpc18xx_data->duty_event),
			   val);
}

static int lpc18xx_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
			      int duty_ns, int period_ns)
{
	struct lpc18xx_pwm_chip *lpc18xx_pwm = to_lpc18xx_pwm_chip(chip);
	int requested_events, i;

	if (period_ns < lpc18xx_pwm->min_period_ns ||
	    period_ns > lpc18xx_pwm->max_period_ns) {
		dev_err(chip->dev, "period %d not in range\n", period_ns);
		return -ERANGE;
	}

	mutex_lock(&lpc18xx_pwm->period_lock);

	requested_events = bitmap_weight(&lpc18xx_pwm->event_map,
					 LPC18XX_PWM_EVENT_MAX);

	/*
	 * The PWM supports only a single period for all PWM channels.
	 * Once the period is set, it can only be changed if no more than one
	 * channel is requested at that moment.
	 */
	if (requested_events > 2 && lpc18xx_pwm->period_ns != period_ns &&
	    lpc18xx_pwm->period_ns) {
		dev_err(chip->dev, "conflicting period requested for PWM %u\n",
			pwm->hwpwm);
		mutex_unlock(&lpc18xx_pwm->period_lock);
		return -EBUSY;
	}

	if ((requested_events <= 2 && lpc18xx_pwm->period_ns != period_ns) ||
	    !lpc18xx_pwm->period_ns) {
		lpc18xx_pwm->period_ns = period_ns;
		for (i = 0; i < chip->npwm; i++)
			pwm_set_period(&chip->pwms[i], period_ns);
		lpc18xx_pwm_config_period(chip, period_ns);
	}

	mutex_unlock(&lpc18xx_pwm->period_lock);

	lpc18xx_pwm_config_duty(chip, pwm, duty_ns);

	return 0;
}

static int lpc18xx_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm, enum pwm_polarity polarity)
{
	struct lpc18xx_pwm_chip *lpc18xx_pwm = to_lpc18xx_pwm_chip(chip);
	struct lpc18xx_pwm_data *lpc18xx_data = &lpc18xx_pwm->channeldata[pwm->hwpwm];
	enum lpc18xx_pwm_res_action res_action;
	unsigned int set_event, clear_event;

	lpc18xx_pwm_writel(lpc18xx_pwm,
			   LPC18XX_PWM_EVCTRL(lpc18xx_data->duty_event),
			   LPC18XX_PWM_EVCTRL_MATCH(lpc18xx_data->duty_event) |
			   LPC18XX_PWM_EVCTRL_COMB_MATCH);

	lpc18xx_pwm_writel(lpc18xx_pwm,
			   LPC18XX_PWM_EVSTATEMSK(lpc18xx_data->duty_event),
			   LPC18XX_PWM_EVSTATEMSK_ALL);

	if (polarity == PWM_POLARITY_NORMAL) {
		set_event = lpc18xx_pwm->period_event;
		clear_event = lpc18xx_data->duty_event;
		res_action = LPC18XX_PWM_RES_SET;
	} else {
		set_event = lpc18xx_data->duty_event;
		clear_event = lpc18xx_pwm->period_event;
		res_action = LPC18XX_PWM_RES_CLEAR;
	}

	lpc18xx_pwm_writel(lpc18xx_pwm, LPC18XX_PWM_OUTPUTSET(pwm->hwpwm),
			   BIT(set_event));
	lpc18xx_pwm_writel(lpc18xx_pwm, LPC18XX_PWM_OUTPUTCL(pwm->hwpwm),
			   BIT(clear_event));
	lpc18xx_pwm_set_conflict_res(lpc18xx_pwm, pwm, res_action);

	return 0;
}

static void lpc18xx_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
{
	struct lpc18xx_pwm_chip *lpc18xx_pwm = to_lpc18xx_pwm_chip(chip);
	struct lpc18xx_pwm_data *lpc18xx_data = &lpc18xx_pwm->channeldata[pwm->hwpwm];

	lpc18xx_pwm_writel(lpc18xx_pwm,
			   LPC18XX_PWM_EVCTRL(lpc18xx_data->duty_event), 0);
	lpc18xx_pwm_writel(lpc18xx_pwm, LPC18XX_PWM_OUTPUTSET(pwm->hwpwm), 0);
	lpc18xx_pwm_writel(lpc18xx_pwm, LPC18XX_PWM_OUTPUTCL(pwm->hwpwm), 0);
}

static int lpc18xx_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm)
{
	struct lpc18xx_pwm_chip *lpc18xx_pwm = to_lpc18xx_pwm_chip(chip);
	struct lpc18xx_pwm_data *lpc18xx_data = &lpc18xx_pwm->channeldata[pwm->hwpwm];
	unsigned long event;

	event = find_first_zero_bit(&lpc18xx_pwm->event_map,
				    LPC18XX_PWM_EVENT_MAX);

	if (event >= LPC18XX_PWM_EVENT_MAX) {
		dev_err(lpc18xx_pwm->dev,
			"maximum number of simultaneous channels reached\n");
		return -EBUSY;
	}

	set_bit(event, &lpc18xx_pwm->event_map);
	lpc18xx_data->duty_event = event;

	return 0;
}

static void lpc18xx_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
{
	struct lpc18xx_pwm_chip *lpc18xx_pwm = to_lpc18xx_pwm_chip(chip);
	struct lpc18xx_pwm_data *lpc18xx_data = &lpc18xx_pwm->channeldata[pwm->hwpwm];

	clear_bit(lpc18xx_data->duty_event, &lpc18xx_pwm->event_map);
}

static int lpc18xx_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
			     const struct pwm_state *state)
{
	int err;
	bool enabled = pwm->state.enabled;

	if (state->polarity != pwm->state.polarity && pwm->state.enabled) {
		lpc18xx_pwm_disable(chip, pwm);
		enabled = false;
	}

	if (!state->enabled) {
		if (enabled)
			lpc18xx_pwm_disable(chip, pwm);

		return 0;
	}

	err = lpc18xx_pwm_config(pwm->chip, pwm, state->duty_cycle, state->period);
	if (err)
		return err;

	if (!enabled)
		err = lpc18xx_pwm_enable(chip, pwm, state->polarity);

	return err;
}
static const struct pwm_ops lpc18xx_pwm_ops = {
	.apply = lpc18xx_pwm_apply,
	.request = lpc18xx_pwm_request,
	.free = lpc18xx_pwm_free,
	.owner = THIS_MODULE,
};

static const struct of_device_id lpc18xx_pwm_of_match[] = {
	{ .compatible = "nxp,lpc1850-sct-pwm" },
	{}
};
MODULE_DEVICE_TABLE(of, lpc18xx_pwm_of_match);

static int lpc18xx_pwm_probe(struct platform_device *pdev)
{
	struct lpc18xx_pwm_chip *lpc18xx_pwm;
	int ret;
	u64 val;

	lpc18xx_pwm = devm_kzalloc(&pdev->dev, sizeof(*lpc18xx_pwm),
				   GFP_KERNEL);
	if (!lpc18xx_pwm)
		return -ENOMEM;

	lpc18xx_pwm->dev = &pdev->dev;

	lpc18xx_pwm->base = devm_platform_ioremap_resource(pdev, 0);
	if (IS_ERR(lpc18xx_pwm->base))
		return PTR_ERR(lpc18xx_pwm->base);

	lpc18xx_pwm->pwm_clk = devm_clk_get(&pdev->dev, "pwm");
	if (IS_ERR(lpc18xx_pwm->pwm_clk))
		return dev_err_probe(&pdev->dev, PTR_ERR(lpc18xx_pwm->pwm_clk),
				     "failed to get pwm clock\n");

	ret = clk_prepare_enable(lpc18xx_pwm->pwm_clk);
	if (ret < 0)
		return dev_err_probe(&pdev->dev, ret,
				     "could not prepare or enable pwm clock\n");

	lpc18xx_pwm->clk_rate = clk_get_rate(lpc18xx_pwm->pwm_clk);
	if (!lpc18xx_pwm->clk_rate) {
		ret = dev_err_probe(&pdev->dev,
				    -EINVAL, "pwm clock has no frequency\n");
		goto disable_pwmclk;
	}

	/*
	 * If clkrate is too fast, the calculations in .apply() might overflow.
	 */
	if (lpc18xx_pwm->clk_rate > NSEC_PER_SEC) {
		ret = dev_err_probe(&pdev->dev, -EINVAL, "pwm clock to fast\n");
		goto disable_pwmclk;
	}

	mutex_init(&lpc18xx_pwm->res_lock);
	mutex_init(&lpc18xx_pwm->period_lock);

	lpc18xx_pwm->max_period_ns =
		mul_u64_u64_div_u64(NSEC_PER_SEC, LPC18XX_PWM_TIMER_MAX, lpc18xx_pwm->clk_rate);

	lpc18xx_pwm->min_period_ns = DIV_ROUND_UP(NSEC_PER_SEC,
						  lpc18xx_pwm->clk_rate);

	lpc18xx_pwm->chip.dev = &pdev->dev;
	lpc18xx_pwm->chip.ops = &lpc18xx_pwm_ops;
	lpc18xx_pwm->chip.npwm = LPC18XX_NUM_PWMS;

	/* SCT counter must be in unify (32 bit) mode */
	lpc18xx_pwm_writel(lpc18xx_pwm, LPC18XX_PWM_CONFIG,
			   LPC18XX_PWM_CONFIG_UNIFY);

	/*
	 * Everytime the timer counter reaches the period value, the related
	 * event will be triggered and the counter reset to 0.
	 */
	set_bit(LPC18XX_PWM_EVENT_PERIOD, &lpc18xx_pwm->event_map);
	lpc18xx_pwm->period_event = LPC18XX_PWM_EVENT_PERIOD;

	lpc18xx_pwm_writel(lpc18xx_pwm,
			   LPC18XX_PWM_EVSTATEMSK(lpc18xx_pwm->period_event),
			   LPC18XX_PWM_EVSTATEMSK_ALL);

	val = LPC18XX_PWM_EVCTRL_MATCH(lpc18xx_pwm->period_event) |
	      LPC18XX_PWM_EVCTRL_COMB_MATCH;
	lpc18xx_pwm_writel(lpc18xx_pwm,
			   LPC18XX_PWM_EVCTRL(lpc18xx_pwm->period_event), val);

	lpc18xx_pwm_writel(lpc18xx_pwm, LPC18XX_PWM_LIMIT,
			   BIT(lpc18xx_pwm->period_event));

	val = lpc18xx_pwm_readl(lpc18xx_pwm, LPC18XX_PWM_CTRL);
	val &= ~LPC18XX_PWM_BIDIR;
	val &= ~LPC18XX_PWM_CTRL_HALT;
	val &= ~LPC18XX_PWM_PRE_MASK;
	val |= LPC18XX_PWM_PRE(0);
	lpc18xx_pwm_writel(lpc18xx_pwm, LPC18XX_PWM_CTRL, val);

	ret = pwmchip_add(&lpc18xx_pwm->chip);
	if (ret < 0) {
		dev_err_probe(&pdev->dev, ret, "pwmchip_add failed\n");
		goto disable_pwmclk;
	}

	platform_set_drvdata(pdev, lpc18xx_pwm);

	return 0;

disable_pwmclk:
	clk_disable_unprepare(lpc18xx_pwm->pwm_clk);
	return ret;
}

static void lpc18xx_pwm_remove(struct platform_device *pdev)
{
	struct lpc18xx_pwm_chip *lpc18xx_pwm = platform_get_drvdata(pdev);
	u32 val;

	pwmchip_remove(&lpc18xx_pwm->chip);

	val = lpc18xx_pwm_readl(lpc18xx_pwm, LPC18XX_PWM_CTRL);
	lpc18xx_pwm_writel(lpc18xx_pwm, LPC18XX_PWM_CTRL,
			   val | LPC18XX_PWM_CTRL_HALT);

	clk_disable_unprepare(lpc18xx_pwm->pwm_clk);
}

static struct platform_driver lpc18xx_pwm_driver = {
	.driver = {
		.name = "lpc18xx-sct-pwm",
		.of_match_table = lpc18xx_pwm_of_match,
	},
	.probe = lpc18xx_pwm_probe,
	.remove_new = lpc18xx_pwm_remove,
};
module_platform_driver(lpc18xx_pwm_driver);

MODULE_AUTHOR("Ariel D'Alessandro <ariel@vanguardiasur.com.ar>");
MODULE_DESCRIPTION("NXP LPC18xx PWM driver");
MODULE_LICENSE("GPL v2");