kernel/drivers/pwm/pwm-bcm-iproc.c

// SPDX-License-Identifier: GPL-2.0-only
// Copyright (C) 2016 Broadcom

#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/math64.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/pwm.h>

#define IPROC_PWM_CTRL_OFFSET			0x00
#define IPROC_PWM_CTRL_TYPE_SHIFT(ch)		(15 + (ch))
#define IPROC_PWM_CTRL_POLARITY_SHIFT(ch)	(8 + (ch))
#define IPROC_PWM_CTRL_EN_SHIFT(ch)		(ch)

#define IPROC_PWM_PERIOD_OFFSET(ch)		(0x04 + ((ch) << 3))
#define IPROC_PWM_PERIOD_MIN			0x02
#define IPROC_PWM_PERIOD_MAX			0xffff

#define IPROC_PWM_DUTY_CYCLE_OFFSET(ch)		(0x08 + ((ch) << 3))
#define IPROC_PWM_DUTY_CYCLE_MIN		0x00
#define IPROC_PWM_DUTY_CYCLE_MAX		0xffff

#define IPROC_PWM_PRESCALE_OFFSET		0x24
#define IPROC_PWM_PRESCALE_BITS			0x06
#define IPROC_PWM_PRESCALE_SHIFT(ch)		((3 - (ch)) * \
						 IPROC_PWM_PRESCALE_BITS)
#define IPROC_PWM_PRESCALE_MASK(ch)		(IPROC_PWM_PRESCALE_MAX << \
						 IPROC_PWM_PRESCALE_SHIFT(ch))
#define IPROC_PWM_PRESCALE_MIN			0x00
#define IPROC_PWM_PRESCALE_MAX			0x3f

struct iproc_pwmc {
	void __iomem *base;
	struct clk *clk;
};

static inline struct iproc_pwmc *to_iproc_pwmc(struct pwm_chip *chip)
{
	return pwmchip_get_drvdata(chip);
}

static void iproc_pwmc_enable(struct iproc_pwmc *ip, unsigned int channel)
{
	u32 value;

	value = readl(ip->base + IPROC_PWM_CTRL_OFFSET);
	value |= 1 << IPROC_PWM_CTRL_EN_SHIFT(channel);
	writel(value, ip->base + IPROC_PWM_CTRL_OFFSET);

	/* must be a 400 ns delay between clearing and setting enable bit */
	ndelay(400);
}

static void iproc_pwmc_disable(struct iproc_pwmc *ip, unsigned int channel)
{
	u32 value;

	value = readl(ip->base + IPROC_PWM_CTRL_OFFSET);
	value &= ~(1 << IPROC_PWM_CTRL_EN_SHIFT(channel));
	writel(value, ip->base + IPROC_PWM_CTRL_OFFSET);

	/* must be a 400 ns delay between clearing and setting enable bit */
	ndelay(400);
}

static int iproc_pwmc_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
				struct pwm_state *state)
{
	struct iproc_pwmc *ip = to_iproc_pwmc(chip);
	u64 tmp, multi, rate;
	u32 value, prescale;

	value = readl(ip->base + IPROC_PWM_CTRL_OFFSET);

	if (value & BIT(IPROC_PWM_CTRL_EN_SHIFT(pwm->hwpwm)))
		state->enabled = true;
	else
		state->enabled = false;

	if (value & BIT(IPROC_PWM_CTRL_POLARITY_SHIFT(pwm->hwpwm)))
		state->polarity = PWM_POLARITY_NORMAL;
	else
		state->polarity = PWM_POLARITY_INVERSED;

	rate = clk_get_rate(ip->clk);
	if (rate == 0) {
		state->period = 0;
		state->duty_cycle = 0;
		return 0;
	}

	value = readl(ip->base + IPROC_PWM_PRESCALE_OFFSET);
	prescale = value >> IPROC_PWM_PRESCALE_SHIFT(pwm->hwpwm);
	prescale &= IPROC_PWM_PRESCALE_MAX;

	multi = NSEC_PER_SEC * (prescale + 1);

	value = readl(ip->base + IPROC_PWM_PERIOD_OFFSET(pwm->hwpwm));
	tmp = (value & IPROC_PWM_PERIOD_MAX) * multi;
	state->period = div64_u64(tmp, rate);

	value = readl(ip->base + IPROC_PWM_DUTY_CYCLE_OFFSET(pwm->hwpwm));
	tmp = (value & IPROC_PWM_PERIOD_MAX) * multi;
	state->duty_cycle = div64_u64(tmp, rate);

	return 0;
}

static int iproc_pwmc_apply(struct pwm_chip *chip, struct pwm_device *pwm,
			    const struct pwm_state *state)
{
	unsigned long prescale = IPROC_PWM_PRESCALE_MIN;
	struct iproc_pwmc *ip = to_iproc_pwmc(chip);
	u32 value, period, duty;
	u64 rate;

	rate = clk_get_rate(ip->clk);

	/*
	 * Find period count, duty count and prescale to suit duty_cycle and
	 * period. This is done according to formulas described below:
	 *
	 * period_ns = 10^9 * (PRESCALE + 1) * PC / PWM_CLK_RATE
	 * duty_ns = 10^9 * (PRESCALE + 1) * DC / PWM_CLK_RATE
	 *
	 * PC = (PWM_CLK_RATE * period_ns) / (10^9 * (PRESCALE + 1))
	 * DC = (PWM_CLK_RATE * duty_ns) / (10^9 * (PRESCALE + 1))
	 */
	while (1) {
		u64 value, div;

		div = NSEC_PER_SEC * (prescale + 1);
		value = rate * state->period;
		period = div64_u64(value, div);
		value = rate * state->duty_cycle;
		duty = div64_u64(value, div);

		if (period < IPROC_PWM_PERIOD_MIN)
			return -EINVAL;

		if (period <= IPROC_PWM_PERIOD_MAX &&
		     duty <= IPROC_PWM_DUTY_CYCLE_MAX)
			break;

		/* Otherwise, increase prescale and recalculate counts */
		if (++prescale > IPROC_PWM_PRESCALE_MAX)
			return -EINVAL;
	}

	iproc_pwmc_disable(ip, pwm->hwpwm);

	/* Set prescale */
	value = readl(ip->base + IPROC_PWM_PRESCALE_OFFSET);
	value &= ~IPROC_PWM_PRESCALE_MASK(pwm->hwpwm);
	value |= prescale << IPROC_PWM_PRESCALE_SHIFT(pwm->hwpwm);
	writel(value, ip->base + IPROC_PWM_PRESCALE_OFFSET);

	/* set period and duty cycle */
	writel(period, ip->base + IPROC_PWM_PERIOD_OFFSET(pwm->hwpwm));
	writel(duty, ip->base + IPROC_PWM_DUTY_CYCLE_OFFSET(pwm->hwpwm));

	/* set polarity */
	value = readl(ip->base + IPROC_PWM_CTRL_OFFSET);

	if (state->polarity == PWM_POLARITY_NORMAL)
		value |= 1 << IPROC_PWM_CTRL_POLARITY_SHIFT(pwm->hwpwm);
	else
		value &= ~(1 << IPROC_PWM_CTRL_POLARITY_SHIFT(pwm->hwpwm));

	writel(value, ip->base + IPROC_PWM_CTRL_OFFSET);

	if (state->enabled)
		iproc_pwmc_enable(ip, pwm->hwpwm);

	return 0;
}

static const struct pwm_ops iproc_pwm_ops = {
	.apply = iproc_pwmc_apply,
	.get_state = iproc_pwmc_get_state,
};

static int iproc_pwmc_probe(struct platform_device *pdev)
{
	struct pwm_chip *chip;
	struct iproc_pwmc *ip;
	unsigned int i;
	u32 value;
	int ret;

	chip = devm_pwmchip_alloc(&pdev->dev, 4, sizeof(*ip));
	if (IS_ERR(chip))
		return PTR_ERR(chip);
	ip = to_iproc_pwmc(chip);

	platform_set_drvdata(pdev, ip);

	chip->ops = &iproc_pwm_ops;

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

	ip->clk = devm_clk_get_enabled(&pdev->dev, NULL);
	if (IS_ERR(ip->clk))
		return dev_err_probe(&pdev->dev, PTR_ERR(ip->clk),
				     "failed to get clock\n");

	/* Set full drive and normal polarity for all channels */
	value = readl(ip->base + IPROC_PWM_CTRL_OFFSET);

	for (i = 0; i < chip->npwm; i++) {
		value &= ~(1 << IPROC_PWM_CTRL_TYPE_SHIFT(i));
		value |= 1 << IPROC_PWM_CTRL_POLARITY_SHIFT(i);
	}

	writel(value, ip->base + IPROC_PWM_CTRL_OFFSET);

	ret = devm_pwmchip_add(&pdev->dev, chip);
	if (ret < 0)
		return dev_err_probe(&pdev->dev, ret,
				     "failed to add PWM chip\n");

	return 0;
}

static const struct of_device_id bcm_iproc_pwmc_dt[] = {
	{ .compatible = "brcm,iproc-pwm" },
	{ },
};
MODULE_DEVICE_TABLE(of, bcm_iproc_pwmc_dt);

static struct platform_driver iproc_pwmc_driver = {
	.driver = {
		.name = "bcm-iproc-pwm",
		.of_match_table = bcm_iproc_pwmc_dt,
	},
	.probe = iproc_pwmc_probe,
};
module_platform_driver(iproc_pwmc_driver);

MODULE_AUTHOR("Yendapally Reddy Dhananjaya Reddy <yendapally.reddy@broadcom.com>");
MODULE_DESCRIPTION("Broadcom iProc PWM driver");
MODULE_LICENSE("GPL v2");