drivers/pwm/pwm-sun4i.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * Driver for Allwinner sun4i Pulse Width Modulation Controller
  *
  * Copyright (C) 2014 Alexandre Belloni <alexandre.belloni@free-electrons.com>
  *
  * Limitations:
  * - When outputing the source clock directly, the PWM logic will be bypassed
  *   and the currently running period is not guaranteed to be completed
  */

 #include <linux/bitops.h>
 #include <linux/clk.h>
 #include <linux/delay.h>
 #include <linux/err.h>
 #include <linux/io.h>
 #include <linux/jiffies.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/of_device.h>
 #include <linux/platform_device.h>
 #include <linux/pwm.h>
 #include <linux/reset.h>
 #include <linux/slab.h>
 #include <linux/spinlock.h>
 #include <linux/time.h>

 #define PWM_CTRL_REG		0x0

 #define PWM_CH_PRD_BASE		0x4
 #define PWM_CH_PRD_OFFSET	0x4
 #define PWM_CH_PRD(ch)		(PWM_CH_PRD_BASE + PWM_CH_PRD_OFFSET * (ch))

 #define PWMCH_OFFSET		15
 #define PWM_PRESCAL_MASK	GENMASK(3, 0)
 #define PWM_PRESCAL_OFF		0
 #define PWM_EN			BIT(4)
 #define PWM_ACT_STATE		BIT(5)
 #define PWM_CLK_GATING		BIT(6)
 #define PWM_MODE		BIT(7)
 #define PWM_PULSE		BIT(8)
 #define PWM_BYPASS		BIT(9)

 #define PWM_RDY_BASE		28
 #define PWM_RDY_OFFSET		1
 #define PWM_RDY(ch)		BIT(PWM_RDY_BASE + PWM_RDY_OFFSET * (ch))

 #define PWM_PRD(prd)		(((prd) - 1) << 16)
 #define PWM_PRD_MASK		GENMASK(15, 0)

 #define PWM_DTY_MASK		GENMASK(15, 0)

 #define PWM_REG_PRD(reg)	((((reg) >> 16) & PWM_PRD_MASK) + 1)
 #define PWM_REG_DTY(reg)	((reg) & PWM_DTY_MASK)
 #define PWM_REG_PRESCAL(reg, chan)	(((reg) >> ((chan) * PWMCH_OFFSET)) & PWM_PRESCAL_MASK)

 #define BIT_CH(bit, chan)	((bit) << ((chan) * PWMCH_OFFSET))

 static const u32 prescaler_table[] = {
 	120,
 	180,
 	240,
 	360,
 	480,
 	0,
 	0,
 	0,
 	12000,
 	24000,
 	36000,
 	48000,
 	72000,
 	0,
 	0,
 	0, /* Actually 1 but tested separately */
 };

 struct sun4i_pwm_data {
 	bool has_prescaler_bypass;
 	bool has_direct_mod_clk_output;
 	unsigned int npwm;
 };

 struct sun4i_pwm_chip {
 	struct pwm_chip chip;
 	struct clk *bus_clk;
 	struct clk *clk;
 	struct reset_control *rst;
 	void __iomem *base;
 	spinlock_t ctrl_lock;
 	const struct sun4i_pwm_data *data;
 	unsigned long next_period[2];
 };

 static inline struct sun4i_pwm_chip *to_sun4i_pwm_chip(struct pwm_chip *chip)
 {
 	return container_of(chip, struct sun4i_pwm_chip, chip);
 }

 static inline u32 sun4i_pwm_readl(struct sun4i_pwm_chip *chip,
 				  unsigned long offset)
 {
 	return readl(chip->base + offset);
 }

 static inline void sun4i_pwm_writel(struct sun4i_pwm_chip *chip,
 				    u32 val, unsigned long offset)
 {
 	writel(val, chip->base + offset);
 }

 static void sun4i_pwm_get_state(struct pwm_chip *chip,
 				struct pwm_device *pwm,
 				struct pwm_state *state)
 {
 	struct sun4i_pwm_chip *sun4i_pwm = to_sun4i_pwm_chip(chip);
 	u64 clk_rate, tmp;
 	u32 val;
 	unsigned int prescaler;

 	clk_rate = clk_get_rate(sun4i_pwm->clk);

 	val = sun4i_pwm_readl(sun4i_pwm, PWM_CTRL_REG);

 	/*
 	 * PWM chapter in H6 manual has a diagram which explains that if bypass
 	 * bit is set, no other setting has any meaning. Even more, experiment
 	 * proved that also enable bit is ignored in this case.
 	 */
 	if ((val & BIT_CH(PWM_BYPASS, pwm->hwpwm)) &&
 	    sun4i_pwm->data->has_direct_mod_clk_output) {
 		state->period = DIV_ROUND_UP_ULL(NSEC_PER_SEC, clk_rate);
 		state->duty_cycle = DIV_ROUND_UP_ULL(state->period, 2);
 		state->polarity = PWM_POLARITY_NORMAL;
 		state->enabled = true;
 		return;
 	}

 	if ((PWM_REG_PRESCAL(val, pwm->hwpwm) == PWM_PRESCAL_MASK) &&
 	    sun4i_pwm->data->has_prescaler_bypass)
 		prescaler = 1;
 	else
 		prescaler = prescaler_table[PWM_REG_PRESCAL(val, pwm->hwpwm)];

 	if (prescaler == 0)
 		return;

 	if (val & BIT_CH(PWM_ACT_STATE, pwm->hwpwm))
 		state->polarity = PWM_POLARITY_NORMAL;
 	else
 		state->polarity = PWM_POLARITY_INVERSED;

 	if ((val & BIT_CH(PWM_CLK_GATING | PWM_EN, pwm->hwpwm)) ==
 	    BIT_CH(PWM_CLK_GATING | PWM_EN, pwm->hwpwm))
 		state->enabled = true;
 	else
 		state->enabled = false;

 	val = sun4i_pwm_readl(sun4i_pwm, PWM_CH_PRD(pwm->hwpwm));

 	tmp = (u64)prescaler * NSEC_PER_SEC * PWM_REG_DTY(val);
 	state->duty_cycle = DIV_ROUND_CLOSEST_ULL(tmp, clk_rate);

 	tmp = (u64)prescaler * NSEC_PER_SEC * PWM_REG_PRD(val);
 	state->period = DIV_ROUND_CLOSEST_ULL(tmp, clk_rate);
 }

 static int sun4i_pwm_calculate(struct sun4i_pwm_chip *sun4i_pwm,
 			       const struct pwm_state *state,
 			       u32 *dty, u32 *prd, unsigned int *prsclr,
 			       bool *bypass)
 {
 	u64 clk_rate, div = 0;
 	unsigned int prescaler = 0;

 	clk_rate = clk_get_rate(sun4i_pwm->clk);

 	*bypass = sun4i_pwm->data->has_direct_mod_clk_output &&
 		  state->enabled &&
 		  (state->period * clk_rate >= NSEC_PER_SEC) &&
 		  (state->period * clk_rate < 2 * NSEC_PER_SEC) &&
 		  (state->duty_cycle * clk_rate * 2 >= NSEC_PER_SEC);

 	/* Skip calculation of other parameters if we bypass them */
 	if (*bypass)
 		return 0;

 	if (sun4i_pwm->data->has_prescaler_bypass) {
 		/* First, test without any prescaler when available */
 		prescaler = PWM_PRESCAL_MASK;
 		/*
 		 * When not using any prescaler, the clock period in nanoseconds
 		 * is not an integer so round it half up instead of
 		 * truncating to get less surprising values.
 		 */
 		div = clk_rate * state->period + NSEC_PER_SEC / 2;
 		do_div(div, NSEC_PER_SEC);
 		if (div - 1 > PWM_PRD_MASK)
 			prescaler = 0;
 	}

 	if (prescaler == 0) {
 		/* Go up from the first divider */
 		for (prescaler = 0; prescaler < PWM_PRESCAL_MASK; prescaler++) {
 			unsigned int pval = prescaler_table[prescaler];

 			if (!pval)
 				continue;

 			div = clk_rate;
 			do_div(div, pval);
 			div = div * state->period;
 			do_div(div, NSEC_PER_SEC);
 			if (div - 1 <= PWM_PRD_MASK)
 				break;
 		}

 		if (div - 1 > PWM_PRD_MASK)
 			return -EINVAL;
 	}

 	*prd = div;
 	div *= state->duty_cycle;
 	do_div(div, state->period);
 	*dty = div;
 	*prsclr = prescaler;

 	return 0;
 }

 static int sun4i_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 			   const struct pwm_state *state)
 {
 	struct sun4i_pwm_chip *sun4i_pwm = to_sun4i_pwm_chip(chip);
 	struct pwm_state cstate;
 	u32 ctrl, duty = 0, period = 0, val;
 	int ret;
 	unsigned int delay_us, prescaler = 0;
 	unsigned long now;
 	bool bypass;

 	pwm_get_state(pwm, &cstate);

 	if (!cstate.enabled) {
 		ret = clk_prepare_enable(sun4i_pwm->clk);
 		if (ret) {
 			dev_err(chip->dev, "failed to enable PWM clock\n");
 			return ret;
 		}
 	}

 	ret = sun4i_pwm_calculate(sun4i_pwm, state, &duty, &period, &prescaler,
 				  &bypass);
 	if (ret) {
 		dev_err(chip->dev, "period exceeds the maximum value\n");
 		if (!cstate.enabled)
 			clk_disable_unprepare(sun4i_pwm->clk);
 		return ret;
 	}

 	spin_lock(&sun4i_pwm->ctrl_lock);
 	ctrl = sun4i_pwm_readl(sun4i_pwm, PWM_CTRL_REG);

 	if (sun4i_pwm->data->has_direct_mod_clk_output) {
 		if (bypass) {
 			ctrl |= BIT_CH(PWM_BYPASS, pwm->hwpwm);
 			/* We can skip other parameter */
 			sun4i_pwm_writel(sun4i_pwm, ctrl, PWM_CTRL_REG);
 			spin_unlock(&sun4i_pwm->ctrl_lock);
 			return 0;
 		}

 		ctrl &= ~BIT_CH(PWM_BYPASS, pwm->hwpwm);
 	}

 	if (PWM_REG_PRESCAL(ctrl, pwm->hwpwm) != prescaler) {
 		/* Prescaler changed, the clock has to be gated */
 		ctrl &= ~BIT_CH(PWM_CLK_GATING, pwm->hwpwm);
 		sun4i_pwm_writel(sun4i_pwm, ctrl, PWM_CTRL_REG);

 		ctrl &= ~BIT_CH(PWM_PRESCAL_MASK, pwm->hwpwm);
 		ctrl |= BIT_CH(prescaler, pwm->hwpwm);
 	}

 	val = (duty & PWM_DTY_MASK) | PWM_PRD(period);
 	sun4i_pwm_writel(sun4i_pwm, val, PWM_CH_PRD(pwm->hwpwm));
 	sun4i_pwm->next_period[pwm->hwpwm] = jiffies +
 		usecs_to_jiffies(cstate.period / 1000 + 1);

 	if (state->polarity != PWM_POLARITY_NORMAL)
 		ctrl &= ~BIT_CH(PWM_ACT_STATE, pwm->hwpwm);
 	else
 		ctrl |= BIT_CH(PWM_ACT_STATE, pwm->hwpwm);

 	ctrl |= BIT_CH(PWM_CLK_GATING, pwm->hwpwm);

 	if (state->enabled) {
 		ctrl |= BIT_CH(PWM_EN, pwm->hwpwm);
 	} else {
 		ctrl &= ~BIT_CH(PWM_EN, pwm->hwpwm);
 		ctrl &= ~BIT_CH(PWM_CLK_GATING, pwm->hwpwm);
 	}

 	sun4i_pwm_writel(sun4i_pwm, ctrl, PWM_CTRL_REG);

 	spin_unlock(&sun4i_pwm->ctrl_lock);

 	if (state->enabled)
 		return 0;

 	/* We need a full period to elapse before disabling the channel. */
 	now = jiffies;
 	if (time_before(now, sun4i_pwm->next_period[pwm->hwpwm])) {
 		delay_us = jiffies_to_usecs(sun4i_pwm->next_period[pwm->hwpwm] -
 					   now);
 		if ((delay_us / 500) > MAX_UDELAY_MS)
 			msleep(delay_us / 1000 + 1);
 		else
 			usleep_range(delay_us, delay_us * 2);
 	}

 	spin_lock(&sun4i_pwm->ctrl_lock);
 	ctrl = sun4i_pwm_readl(sun4i_pwm, PWM_CTRL_REG);
 	ctrl &= ~BIT_CH(PWM_CLK_GATING, pwm->hwpwm);
 	ctrl &= ~BIT_CH(PWM_EN, pwm->hwpwm);
 	sun4i_pwm_writel(sun4i_pwm, ctrl, PWM_CTRL_REG);
 	spin_unlock(&sun4i_pwm->ctrl_lock);

 	clk_disable_unprepare(sun4i_pwm->clk);

 	return 0;
 }

 static const struct pwm_ops sun4i_pwm_ops = {
 	.apply = sun4i_pwm_apply,
 	.get_state = sun4i_pwm_get_state,
 	.owner = THIS_MODULE,
 };

 static const struct sun4i_pwm_data sun4i_pwm_dual_nobypass = {
 	.has_prescaler_bypass = false,
 	.npwm = 2,
 };

 static const struct sun4i_pwm_data sun4i_pwm_dual_bypass = {
 	.has_prescaler_bypass = true,
 	.npwm = 2,
 };

 static const struct sun4i_pwm_data sun4i_pwm_single_bypass = {
 	.has_prescaler_bypass = true,
 	.npwm = 1,
 };

 static const struct sun4i_pwm_data sun50i_a64_pwm_data = {
 	.has_prescaler_bypass = true,
 	.has_direct_mod_clk_output = true,
 	.npwm = 1,
 };

 static const struct sun4i_pwm_data sun50i_h6_pwm_data = {
 	.has_prescaler_bypass = true,
 	.has_direct_mod_clk_output = true,
 	.npwm = 2,
 };

 static const struct of_device_id sun4i_pwm_dt_ids[] = {
 	{
 		.compatible = "allwinner,sun4i-a10-pwm",
 		.data = &sun4i_pwm_dual_nobypass,
 	}, {
 		.compatible = "allwinner,sun5i-a10s-pwm",
 		.data = &sun4i_pwm_dual_bypass,
 	}, {
 		.compatible = "allwinner,sun5i-a13-pwm",
 		.data = &sun4i_pwm_single_bypass,
 	}, {
 		.compatible = "allwinner,sun7i-a20-pwm",
 		.data = &sun4i_pwm_dual_bypass,
 	}, {
 		.compatible = "allwinner,sun8i-h3-pwm",
 		.data = &sun4i_pwm_single_bypass,
 	}, {
 		.compatible = "allwinner,sun50i-a64-pwm",
 		.data = &sun50i_a64_pwm_data,
 	}, {
 		.compatible = "allwinner,sun50i-h6-pwm",
 		.data = &sun50i_h6_pwm_data,
 	}, {
 		/* sentinel */
 	},
 };
 MODULE_DEVICE_TABLE(of, sun4i_pwm_dt_ids);

 static int sun4i_pwm_probe(struct platform_device *pdev)
 {
 	struct sun4i_pwm_chip *pwm;
 	struct resource *res;
 	int ret;

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

 	pwm->data = of_device_get_match_data(&pdev->dev);
 	if (!pwm->data)
 		return -ENODEV;

 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	pwm->base = devm_ioremap_resource(&pdev->dev, res);
 	if (IS_ERR(pwm->base))
 		return PTR_ERR(pwm->base);

 	/*
 	 * All hardware variants need a source clock that is divided and
 	 * then feeds the counter that defines the output wave form. In the
 	 * device tree this clock is either unnamed or called "mod".
 	 * Some variants (e.g. H6) need another clock to access the
 	 * hardware registers; this is called "bus".
 	 * So we request "mod" first (and ignore the corner case that a
 	 * parent provides a "mod" clock while the right one would be the
 	 * unnamed one of the PWM device) and if this is not found we fall
 	 * back to the first clock of the PWM.
 	 */
 	pwm->clk = devm_clk_get_optional(&pdev->dev, "mod");
 	if (IS_ERR(pwm->clk)) {
 		if (PTR_ERR(pwm->clk) != -EPROBE_DEFER)
 			dev_err(&pdev->dev, "get mod clock failed %pe\n",
 				pwm->clk);
 		return PTR_ERR(pwm->clk);
 	}

 	if (!pwm->clk) {
 		pwm->clk = devm_clk_get(&pdev->dev, NULL);
 		if (IS_ERR(pwm->clk)) {
 			if (PTR_ERR(pwm->clk) != -EPROBE_DEFER)
 				dev_err(&pdev->dev, "get unnamed clock failed %pe\n",
 					pwm->clk);
 			return PTR_ERR(pwm->clk);
 		}
 	}

 	pwm->bus_clk = devm_clk_get_optional(&pdev->dev, "bus");
 	if (IS_ERR(pwm->bus_clk)) {
 		if (PTR_ERR(pwm->bus_clk) != -EPROBE_DEFER)
 			dev_err(&pdev->dev, "get bus clock failed %pe\n",
 				pwm->bus_clk);
 		return PTR_ERR(pwm->bus_clk);
 	}

 	pwm->rst = devm_reset_control_get_optional_shared(&pdev->dev, NULL);
 	if (IS_ERR(pwm->rst)) {
 		if (PTR_ERR(pwm->rst) != -EPROBE_DEFER)
 			dev_err(&pdev->dev, "get reset failed %pe\n",
 				pwm->rst);
 		return PTR_ERR(pwm->rst);
 	}

 	/* Deassert reset */
 	ret = reset_control_deassert(pwm->rst);
 	if (ret) {
 		dev_err(&pdev->dev, "cannot deassert reset control: %pe\n",
 			ERR_PTR(ret));
 		return ret;
 	}

 	/*
 	 * We're keeping the bus clock on for the sake of simplicity.
 	 * Actually it only needs to be on for hardware register accesses.
 	 */
 	ret = clk_prepare_enable(pwm->bus_clk);
 	if (ret) {
 		dev_err(&pdev->dev, "cannot prepare and enable bus_clk %pe\n",
 			ERR_PTR(ret));
 		goto err_bus;
 	}

 	pwm->chip.dev = &pdev->dev;
 	pwm->chip.ops = &sun4i_pwm_ops;
 	pwm->chip.base = -1;
 	pwm->chip.npwm = pwm->data->npwm;
 	pwm->chip.of_xlate = of_pwm_xlate_with_flags;
 	pwm->chip.of_pwm_n_cells = 3;

 	spin_lock_init(&pwm->ctrl_lock);

 	ret = pwmchip_add(&pwm->chip);
 	if (ret < 0) {
 		dev_err(&pdev->dev, "failed to add PWM chip: %d\n", ret);
 		goto err_pwm_add;
 	}

 	platform_set_drvdata(pdev, pwm);

 	return 0;

 err_pwm_add:
 	clk_disable_unprepare(pwm->bus_clk);
 err_bus:
 	reset_control_assert(pwm->rst);

 	return ret;
 }

 static int sun4i_pwm_remove(struct platform_device *pdev)
 {
 	struct sun4i_pwm_chip *pwm = platform_get_drvdata(pdev);
 	int ret;

 	ret = pwmchip_remove(&pwm->chip);
 	if (ret)
 		return ret;

 	clk_disable_unprepare(pwm->bus_clk);
 	reset_control_assert(pwm->rst);

 	return 0;
 }

 static struct platform_driver sun4i_pwm_driver = {
 	.driver = {
 		.name = "sun4i-pwm",
 		.of_match_table = sun4i_pwm_dt_ids,
 	},
 	.probe = sun4i_pwm_probe,
 	.remove = sun4i_pwm_remove,
 };
 module_platform_driver(sun4i_pwm_driver);

 MODULE_ALIAS("platform:sun4i-pwm");
 MODULE_AUTHOR("Alexandre Belloni <alexandre.belloni@free-electrons.com>");
 MODULE_DESCRIPTION("Allwinner sun4i PWM driver");
 MODULE_LICENSE("GPL v2");
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* Driver for Allwinner sun4i Pulse Width Modulation Controller
	*
	* Copyright (C) 2014 Alexandre Belloni <alexandre.belloni@free-electrons.com>
	*
	* Limitations:
	* - When outputing the source clock directly, the PWM logic will be bypassed
	* and the currently running period is not guaranteed to be completed
	*/

	#include <linux/bitops.h>
	#include <linux/clk.h>
	#include <linux/delay.h>
	#include <linux/err.h>
	#include <linux/io.h>
	#include <linux/jiffies.h>
	#include <linux/module.h>
	#include <linux/of.h>
	#include <linux/of_device.h>
	#include <linux/platform_device.h>
	#include <linux/pwm.h>
	#include <linux/reset.h>
	#include <linux/slab.h>
	#include <linux/spinlock.h>
	#include <linux/time.h>

	#define PWM_CTRL_REG 0x0

	#define PWM_CH_PRD_BASE 0x4
	#define PWM_CH_PRD_OFFSET 0x4
	#define PWM_CH_PRD(ch) (PWM_CH_PRD_BASE + PWM_CH_PRD_OFFSET * (ch))

	#define PWMCH_OFFSET 15
	#define PWM_PRESCAL_MASK GENMASK(3, 0)
	#define PWM_PRESCAL_OFF 0
	#define PWM_EN BIT(4)
	#define PWM_ACT_STATE BIT(5)
	#define PWM_CLK_GATING BIT(6)
	#define PWM_MODE BIT(7)
	#define PWM_PULSE BIT(8)
	#define PWM_BYPASS BIT(9)

	#define PWM_RDY_BASE 28
	#define PWM_RDY_OFFSET 1
	#define PWM_RDY(ch) BIT(PWM_RDY_BASE + PWM_RDY_OFFSET * (ch))

	#define PWM_PRD(prd) (((prd) - 1) << 16)
	#define PWM_PRD_MASK GENMASK(15, 0)

	#define PWM_DTY_MASK GENMASK(15, 0)

	#define PWM_REG_PRD(reg) ((((reg) >> 16) & PWM_PRD_MASK) + 1)
	#define PWM_REG_DTY(reg) ((reg) & PWM_DTY_MASK)
	#define PWM_REG_PRESCAL(reg, chan) (((reg) >> ((chan) * PWMCH_OFFSET)) & PWM_PRESCAL_MASK)

	#define BIT_CH(bit, chan) ((bit) << ((chan) * PWMCH_OFFSET))

	static const u32 prescaler_table[] = {
	120,
	180,
	240,
	360,
	480,
	0,
	0,
	0,
	12000,
	24000,
	36000,
	48000,
	72000,
	0,
	0,
	0, /* Actually 1 but tested separately */
	};

	struct sun4i_pwm_data {
	bool has_prescaler_bypass;
	bool has_direct_mod_clk_output;
	unsigned int npwm;
	};

	struct sun4i_pwm_chip {
	struct pwm_chip chip;
	struct clk *bus_clk;
	struct clk *clk;
	struct reset_control *rst;
	void __iomem *base;
	spinlock_t ctrl_lock;
	const struct sun4i_pwm_data *data;
	unsigned long next_period[2];
	};

	static inline struct sun4i_pwm_chip to_sun4i_pwm_chip(struct pwm_chip chip)
	{
	return container_of(chip, struct sun4i_pwm_chip, chip);
	}

	static inline u32 sun4i_pwm_readl(struct sun4i_pwm_chip *chip,
	unsigned long offset)
	{
	return readl(chip->base + offset);
	}

	static inline void sun4i_pwm_writel(struct sun4i_pwm_chip *chip,
	u32 val, unsigned long offset)
	{
	writel(val, chip->base + offset);
	}

	static void sun4i_pwm_get_state(struct pwm_chip *chip,
	struct pwm_device *pwm,
	struct pwm_state *state)
	{
	struct sun4i_pwm_chip *sun4i_pwm = to_sun4i_pwm_chip(chip);
	u64 clk_rate, tmp;
	u32 val;
	unsigned int prescaler;

	clk_rate = clk_get_rate(sun4i_pwm->clk);

	val = sun4i_pwm_readl(sun4i_pwm, PWM_CTRL_REG);

	/*
	* PWM chapter in H6 manual has a diagram which explains that if bypass
	* bit is set, no other setting has any meaning. Even more, experiment
	* proved that also enable bit is ignored in this case.
	*/
	if ((val & BIT_CH(PWM_BYPASS, pwm->hwpwm)) &&
	sun4i_pwm->data->has_direct_mod_clk_output) {
	state->period = DIV_ROUND_UP_ULL(NSEC_PER_SEC, clk_rate);
	state->duty_cycle = DIV_ROUND_UP_ULL(state->period, 2);
	state->polarity = PWM_POLARITY_NORMAL;
	state->enabled = true;
	return;
	}

	if ((PWM_REG_PRESCAL(val, pwm->hwpwm) == PWM_PRESCAL_MASK) &&
	sun4i_pwm->data->has_prescaler_bypass)
	prescaler = 1;
	else
	prescaler = prescaler_table[PWM_REG_PRESCAL(val, pwm->hwpwm)];

	if (prescaler == 0)
	return;

	if (val & BIT_CH(PWM_ACT_STATE, pwm->hwpwm))
	state->polarity = PWM_POLARITY_NORMAL;
	else
	state->polarity = PWM_POLARITY_INVERSED;

	if ((val & BIT_CH(PWM_CLK_GATING \| PWM_EN, pwm->hwpwm)) ==
	BIT_CH(PWM_CLK_GATING \| PWM_EN, pwm->hwpwm))
	state->enabled = true;
	else
	state->enabled = false;

	val = sun4i_pwm_readl(sun4i_pwm, PWM_CH_PRD(pwm->hwpwm));

	tmp = (u64)prescaler * NSEC_PER_SEC * PWM_REG_DTY(val);
	state->duty_cycle = DIV_ROUND_CLOSEST_ULL(tmp, clk_rate);

	tmp = (u64)prescaler * NSEC_PER_SEC * PWM_REG_PRD(val);
	state->period = DIV_ROUND_CLOSEST_ULL(tmp, clk_rate);
	}

	static int sun4i_pwm_calculate(struct sun4i_pwm_chip *sun4i_pwm,
	const struct pwm_state *state,
	u32 dty, u32 prd, unsigned int *prsclr,
	bool *bypass)
	{
	u64 clk_rate, div = 0;
	unsigned int prescaler = 0;

	clk_rate = clk_get_rate(sun4i_pwm->clk);

	*bypass = sun4i_pwm->data->has_direct_mod_clk_output &&
	state->enabled &&
	(state->period * clk_rate >= NSEC_PER_SEC) &&
	(state->period * clk_rate < 2 * NSEC_PER_SEC) &&
	(state->duty_cycle * clk_rate * 2 >= NSEC_PER_SEC);

	/* Skip calculation of other parameters if we bypass them */
	if (*bypass)
	return 0;

	if (sun4i_pwm->data->has_prescaler_bypass) {
	/* First, test without any prescaler when available */
	prescaler = PWM_PRESCAL_MASK;
	/*
	* When not using any prescaler, the clock period in nanoseconds
	* is not an integer so round it half up instead of
	* truncating to get less surprising values.
	*/
	div = clk_rate * state->period + NSEC_PER_SEC / 2;
	do_div(div, NSEC_PER_SEC);
	if (div - 1 > PWM_PRD_MASK)
	prescaler = 0;
	}

	if (prescaler == 0) {
	/* Go up from the first divider */
	for (prescaler = 0; prescaler < PWM_PRESCAL_MASK; prescaler++) {
	unsigned int pval = prescaler_table[prescaler];

	if (!pval)
	continue;

	div = clk_rate;
	do_div(div, pval);
	div = div * state->period;
	do_div(div, NSEC_PER_SEC);
	if (div - 1 <= PWM_PRD_MASK)
	break;
	}

	if (div - 1 > PWM_PRD_MASK)
	return -EINVAL;
	}

	*prd = div;
	div *= state->duty_cycle;
	do_div(div, state->period);
	*dty = div;
	*prsclr = prescaler;

	return 0;
	}

	static int sun4i_pwm_apply(struct pwm_chip chip, struct pwm_device pwm,
	const struct pwm_state *state)
	{
	struct sun4i_pwm_chip *sun4i_pwm = to_sun4i_pwm_chip(chip);
	struct pwm_state cstate;
	u32 ctrl, duty = 0, period = 0, val;
	int ret;
	unsigned int delay_us, prescaler = 0;
	unsigned long now;
	bool bypass;

	pwm_get_state(pwm, &cstate);

	if (!cstate.enabled) {
	ret = clk_prepare_enable(sun4i_pwm->clk);
	if (ret) {
	dev_err(chip->dev, "failed to enable PWM clock\n");
	return ret;
	}
	}

	ret = sun4i_pwm_calculate(sun4i_pwm, state, &duty, &period, &prescaler,
	&bypass);
	if (ret) {
	dev_err(chip->dev, "period exceeds the maximum value\n");
	if (!cstate.enabled)
	clk_disable_unprepare(sun4i_pwm->clk);
	return ret;
	}

	spin_lock(&sun4i_pwm->ctrl_lock);
	ctrl = sun4i_pwm_readl(sun4i_pwm, PWM_CTRL_REG);

	if (sun4i_pwm->data->has_direct_mod_clk_output) {
	if (bypass) {
	ctrl \|= BIT_CH(PWM_BYPASS, pwm->hwpwm);
	/* We can skip other parameter */
	sun4i_pwm_writel(sun4i_pwm, ctrl, PWM_CTRL_REG);
	spin_unlock(&sun4i_pwm->ctrl_lock);
	return 0;
	}

	ctrl &= ~BIT_CH(PWM_BYPASS, pwm->hwpwm);
	}

	if (PWM_REG_PRESCAL(ctrl, pwm->hwpwm) != prescaler) {
	/* Prescaler changed, the clock has to be gated */
	ctrl &= ~BIT_CH(PWM_CLK_GATING, pwm->hwpwm);
	sun4i_pwm_writel(sun4i_pwm, ctrl, PWM_CTRL_REG);

	ctrl &= ~BIT_CH(PWM_PRESCAL_MASK, pwm->hwpwm);
	ctrl \|= BIT_CH(prescaler, pwm->hwpwm);
	}

	val = (duty & PWM_DTY_MASK) \| PWM_PRD(period);
	sun4i_pwm_writel(sun4i_pwm, val, PWM_CH_PRD(pwm->hwpwm));
	sun4i_pwm->next_period[pwm->hwpwm] = jiffies +
	usecs_to_jiffies(cstate.period / 1000 + 1);

	if (state->polarity != PWM_POLARITY_NORMAL)
	ctrl &= ~BIT_CH(PWM_ACT_STATE, pwm->hwpwm);
	else
	ctrl \|= BIT_CH(PWM_ACT_STATE, pwm->hwpwm);

	ctrl \|= BIT_CH(PWM_CLK_GATING, pwm->hwpwm);

	if (state->enabled) {
	ctrl \|= BIT_CH(PWM_EN, pwm->hwpwm);
	} else {
	ctrl &= ~BIT_CH(PWM_EN, pwm->hwpwm);
	ctrl &= ~BIT_CH(PWM_CLK_GATING, pwm->hwpwm);
	}

	sun4i_pwm_writel(sun4i_pwm, ctrl, PWM_CTRL_REG);

	spin_unlock(&sun4i_pwm->ctrl_lock);

	if (state->enabled)
	return 0;

	/* We need a full period to elapse before disabling the channel. */
	now = jiffies;
	if (time_before(now, sun4i_pwm->next_period[pwm->hwpwm])) {
	delay_us = jiffies_to_usecs(sun4i_pwm->next_period[pwm->hwpwm] -
	now);
	if ((delay_us / 500) > MAX_UDELAY_MS)
	msleep(delay_us / 1000 + 1);
	else
	usleep_range(delay_us, delay_us * 2);
	}

	spin_lock(&sun4i_pwm->ctrl_lock);
	ctrl = sun4i_pwm_readl(sun4i_pwm, PWM_CTRL_REG);
	ctrl &= ~BIT_CH(PWM_CLK_GATING, pwm->hwpwm);
	ctrl &= ~BIT_CH(PWM_EN, pwm->hwpwm);
	sun4i_pwm_writel(sun4i_pwm, ctrl, PWM_CTRL_REG);
	spin_unlock(&sun4i_pwm->ctrl_lock);

	clk_disable_unprepare(sun4i_pwm->clk);

	return 0;
	}

	static const struct pwm_ops sun4i_pwm_ops = {
	.apply = sun4i_pwm_apply,
	.get_state = sun4i_pwm_get_state,
	.owner = THIS_MODULE,
	};

	static const struct sun4i_pwm_data sun4i_pwm_dual_nobypass = {
	.has_prescaler_bypass = false,
	.npwm = 2,
	};

	static const struct sun4i_pwm_data sun4i_pwm_dual_bypass = {
	.has_prescaler_bypass = true,
	.npwm = 2,
	};

	static const struct sun4i_pwm_data sun4i_pwm_single_bypass = {
	.has_prescaler_bypass = true,
	.npwm = 1,
	};

	static const struct sun4i_pwm_data sun50i_a64_pwm_data = {
	.has_prescaler_bypass = true,
	.has_direct_mod_clk_output = true,
	.npwm = 1,
	};

	static const struct sun4i_pwm_data sun50i_h6_pwm_data = {
	.has_prescaler_bypass = true,
	.has_direct_mod_clk_output = true,
	.npwm = 2,
	};

	static const struct of_device_id sun4i_pwm_dt_ids[] = {
	{
	.compatible = "allwinner,sun4i-a10-pwm",
	.data = &sun4i_pwm_dual_nobypass,
	}, {
	.compatible = "allwinner,sun5i-a10s-pwm",
	.data = &sun4i_pwm_dual_bypass,
	}, {
	.compatible = "allwinner,sun5i-a13-pwm",
	.data = &sun4i_pwm_single_bypass,
	}, {
	.compatible = "allwinner,sun7i-a20-pwm",
	.data = &sun4i_pwm_dual_bypass,
	}, {
	.compatible = "allwinner,sun8i-h3-pwm",
	.data = &sun4i_pwm_single_bypass,
	}, {
	.compatible = "allwinner,sun50i-a64-pwm",
	.data = &sun50i_a64_pwm_data,
	}, {
	.compatible = "allwinner,sun50i-h6-pwm",
	.data = &sun50i_h6_pwm_data,
	}, {
	/* sentinel */
	},
	};
	MODULE_DEVICE_TABLE(of, sun4i_pwm_dt_ids);

	static int sun4i_pwm_probe(struct platform_device *pdev)
	{
	struct sun4i_pwm_chip *pwm;
	struct resource *res;
	int ret;

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

	pwm->data = of_device_get_match_data(&pdev->dev);
	if (!pwm->data)
	return -ENODEV;

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	pwm->base = devm_ioremap_resource(&pdev->dev, res);
	if (IS_ERR(pwm->base))
	return PTR_ERR(pwm->base);

	/*
	* All hardware variants need a source clock that is divided and
	* then feeds the counter that defines the output wave form. In the
	* device tree this clock is either unnamed or called "mod".
	* Some variants (e.g. H6) need another clock to access the
	* hardware registers; this is called "bus".
	* So we request "mod" first (and ignore the corner case that a
	* parent provides a "mod" clock while the right one would be the
	* unnamed one of the PWM device) and if this is not found we fall
	* back to the first clock of the PWM.
	*/
	pwm->clk = devm_clk_get_optional(&pdev->dev, "mod");
	if (IS_ERR(pwm->clk)) {
	if (PTR_ERR(pwm->clk) != -EPROBE_DEFER)
	dev_err(&pdev->dev, "get mod clock failed %pe\n",
	pwm->clk);
	return PTR_ERR(pwm->clk);
	}

	if (!pwm->clk) {
	pwm->clk = devm_clk_get(&pdev->dev, NULL);
	if (IS_ERR(pwm->clk)) {
	if (PTR_ERR(pwm->clk) != -EPROBE_DEFER)
	dev_err(&pdev->dev, "get unnamed clock failed %pe\n",
	pwm->clk);
	return PTR_ERR(pwm->clk);
	}
	}

	pwm->bus_clk = devm_clk_get_optional(&pdev->dev, "bus");
	if (IS_ERR(pwm->bus_clk)) {
	if (PTR_ERR(pwm->bus_clk) != -EPROBE_DEFER)
	dev_err(&pdev->dev, "get bus clock failed %pe\n",
	pwm->bus_clk);
	return PTR_ERR(pwm->bus_clk);
	}

	pwm->rst = devm_reset_control_get_optional_shared(&pdev->dev, NULL);
	if (IS_ERR(pwm->rst)) {
	if (PTR_ERR(pwm->rst) != -EPROBE_DEFER)
	dev_err(&pdev->dev, "get reset failed %pe\n",
	pwm->rst);
	return PTR_ERR(pwm->rst);
	}

	/* Deassert reset */
	ret = reset_control_deassert(pwm->rst);
	if (ret) {
	dev_err(&pdev->dev, "cannot deassert reset control: %pe\n",
	ERR_PTR(ret));
	return ret;
	}

	/*
	* We're keeping the bus clock on for the sake of simplicity.
	* Actually it only needs to be on for hardware register accesses.
	*/
	ret = clk_prepare_enable(pwm->bus_clk);
	if (ret) {
	dev_err(&pdev->dev, "cannot prepare and enable bus_clk %pe\n",
	ERR_PTR(ret));
	goto err_bus;
	}

	pwm->chip.dev = &pdev->dev;
	pwm->chip.ops = &sun4i_pwm_ops;
	pwm->chip.base = -1;
	pwm->chip.npwm = pwm->data->npwm;
	pwm->chip.of_xlate = of_pwm_xlate_with_flags;
	pwm->chip.of_pwm_n_cells = 3;

	spin_lock_init(&pwm->ctrl_lock);

	ret = pwmchip_add(&pwm->chip);
	if (ret < 0) {
	dev_err(&pdev->dev, "failed to add PWM chip: %d\n", ret);
	goto err_pwm_add;
	}

	platform_set_drvdata(pdev, pwm);

	return 0;

	err_pwm_add:
	clk_disable_unprepare(pwm->bus_clk);
	err_bus:
	reset_control_assert(pwm->rst);

	return ret;
	}

	static int sun4i_pwm_remove(struct platform_device *pdev)
	{
	struct sun4i_pwm_chip *pwm = platform_get_drvdata(pdev);
	int ret;

	ret = pwmchip_remove(&pwm->chip);
	if (ret)
	return ret;

	clk_disable_unprepare(pwm->bus_clk);
	reset_control_assert(pwm->rst);

	return 0;
	}

	static struct platform_driver sun4i_pwm_driver = {
	.driver = {
	.name = "sun4i-pwm",
	.of_match_table = sun4i_pwm_dt_ids,
	},
	.probe = sun4i_pwm_probe,
	.remove = sun4i_pwm_remove,
	};
	module_platform_driver(sun4i_pwm_driver);

	MODULE_ALIAS("platform:sun4i-pwm");
	MODULE_AUTHOR("Alexandre Belloni <alexandre.belloni@free-electrons.com>");
	MODULE_DESCRIPTION("Allwinner sun4i PWM driver");
	MODULE_LICENSE("GPL v2");