drivers/pwm/pwm-imx-tpm.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Copyright 2018-2019 NXP.
  *
  * Limitations:
  * - The TPM counter and period counter are shared between
  *   multiple channels, so all channels should use same period
  *   settings.
  * - Changes to polarity cannot be latched at the time of the
  *   next period start.
  * - Changing period and duty cycle together isn't atomic,
  *   with the wrong timing it might happen that a period is
  *   produced with old duty cycle but new period settings.
  */

 #include <linux/bitfield.h>
 #include <linux/bitops.h>
 #include <linux/clk.h>
 #include <linux/err.h>
 #include <linux/io.h>
 #include <linux/log2.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/of_address.h>
 #include <linux/platform_device.h>
 #include <linux/pwm.h>
 #include <linux/slab.h>

 #define PWM_IMX_TPM_PARAM	0x4
 #define PWM_IMX_TPM_GLOBAL	0x8
 #define PWM_IMX_TPM_SC		0x10
 #define PWM_IMX_TPM_CNT		0x14
 #define PWM_IMX_TPM_MOD		0x18
 #define PWM_IMX_TPM_CnSC(n)	(0x20 + (n) * 0x8)
 #define PWM_IMX_TPM_CnV(n)	(0x24 + (n) * 0x8)

 #define PWM_IMX_TPM_PARAM_CHAN			GENMASK(7, 0)

 #define PWM_IMX_TPM_SC_PS			GENMASK(2, 0)
 #define PWM_IMX_TPM_SC_CMOD			GENMASK(4, 3)
 #define PWM_IMX_TPM_SC_CMOD_INC_EVERY_CLK	FIELD_PREP(PWM_IMX_TPM_SC_CMOD, 1)
 #define PWM_IMX_TPM_SC_CPWMS			BIT(5)

 #define PWM_IMX_TPM_CnSC_CHF	BIT(7)
 #define PWM_IMX_TPM_CnSC_MSB	BIT(5)
 #define PWM_IMX_TPM_CnSC_MSA	BIT(4)

 /*
  * The reference manual describes this field as two separate bits. The
  * semantic of the two bits isn't orthogonal though, so they are treated
  * together as a 2-bit field here.
  */
 #define PWM_IMX_TPM_CnSC_ELS	GENMASK(3, 2)
 #define PWM_IMX_TPM_CnSC_ELS_INVERSED	FIELD_PREP(PWM_IMX_TPM_CnSC_ELS, 1)
 #define PWM_IMX_TPM_CnSC_ELS_NORMAL	FIELD_PREP(PWM_IMX_TPM_CnSC_ELS, 2)


 #define PWM_IMX_TPM_MOD_WIDTH	16
 #define PWM_IMX_TPM_MOD_MOD	GENMASK(PWM_IMX_TPM_MOD_WIDTH - 1, 0)

 struct imx_tpm_pwm_chip {
 	struct pwm_chip chip;
 	struct clk *clk;
 	void __iomem *base;
 	struct mutex lock;
 	u32 user_count;
 	u32 enable_count;
 	u32 real_period;
 };

 struct imx_tpm_pwm_param {
 	u8 prescale;
 	u32 mod;
 	u32 val;
 };

 static inline struct imx_tpm_pwm_chip *
 to_imx_tpm_pwm_chip(struct pwm_chip *chip)
 {
 	return container_of(chip, struct imx_tpm_pwm_chip, chip);
 }

 /*
  * This function determines for a given pwm_state *state that a consumer
  * might request the pwm_state *real_state that eventually is implemented
  * by the hardware and the necessary register values (in *p) to achieve
  * this.
  */
 static int pwm_imx_tpm_round_state(struct pwm_chip *chip,
 				   struct imx_tpm_pwm_param *p,
 				   struct pwm_state *real_state,
 				   const struct pwm_state *state)
 {
 	struct imx_tpm_pwm_chip *tpm = to_imx_tpm_pwm_chip(chip);
 	u32 rate, prescale, period_count, clock_unit;
 	u64 tmp;

 	rate = clk_get_rate(tpm->clk);
 	tmp = (u64)state->period * rate;
 	clock_unit = DIV_ROUND_CLOSEST_ULL(tmp, NSEC_PER_SEC);
 	if (clock_unit <= PWM_IMX_TPM_MOD_MOD)
 		prescale = 0;
 	else
 		prescale = ilog2(clock_unit) + 1 - PWM_IMX_TPM_MOD_WIDTH;

 	if ((!FIELD_FIT(PWM_IMX_TPM_SC_PS, prescale)))
 		return -ERANGE;
 	p->prescale = prescale;

 	period_count = (clock_unit + ((1 << prescale) >> 1)) >> prescale;
 	p->mod = period_count;

 	/* calculate real period HW can support */
 	tmp = (u64)period_count << prescale;
 	tmp *= NSEC_PER_SEC;
 	real_state->period = DIV_ROUND_CLOSEST_ULL(tmp, rate);

 	/*
 	 * if eventually the PWM output is inactive, either
 	 * duty cycle is 0 or status is disabled, need to
 	 * make sure the output pin is inactive.
 	 */
 	if (!state->enabled)
 		real_state->duty_cycle = 0;
 	else
 		real_state->duty_cycle = state->duty_cycle;

 	tmp = (u64)p->mod * real_state->duty_cycle;
 	p->val = DIV_ROUND_CLOSEST_ULL(tmp, real_state->period);

 	real_state->polarity = state->polarity;
 	real_state->enabled = state->enabled;

 	return 0;
 }

 static void pwm_imx_tpm_get_state(struct pwm_chip *chip,
 				  struct pwm_device *pwm,
 				  struct pwm_state *state)
 {
 	struct imx_tpm_pwm_chip *tpm = to_imx_tpm_pwm_chip(chip);
 	u32 rate, val, prescale;
 	u64 tmp;

 	/* get period */
 	state->period = tpm->real_period;

 	/* get duty cycle */
 	rate = clk_get_rate(tpm->clk);
 	val = readl(tpm->base + PWM_IMX_TPM_SC);
 	prescale = FIELD_GET(PWM_IMX_TPM_SC_PS, val);
 	tmp = readl(tpm->base + PWM_IMX_TPM_CnV(pwm->hwpwm));
 	tmp = (tmp << prescale) * NSEC_PER_SEC;
 	state->duty_cycle = DIV_ROUND_CLOSEST_ULL(tmp, rate);

 	/* get polarity */
 	val = readl(tpm->base + PWM_IMX_TPM_CnSC(pwm->hwpwm));
 	if ((val & PWM_IMX_TPM_CnSC_ELS) == PWM_IMX_TPM_CnSC_ELS_INVERSED)
 		state->polarity = PWM_POLARITY_INVERSED;
 	else
 		/*
 		 * Assume reserved values (2b00 and 2b11) to yield
 		 * normal polarity.
 		 */
 		state->polarity = PWM_POLARITY_NORMAL;

 	/* get channel status */
 	state->enabled = FIELD_GET(PWM_IMX_TPM_CnSC_ELS, val) ? true : false;
 }

 /* this function is supposed to be called with mutex hold */
 static int pwm_imx_tpm_apply_hw(struct pwm_chip *chip,
 				struct imx_tpm_pwm_param *p,
 				struct pwm_state *state,
 				struct pwm_device *pwm)
 {
 	struct imx_tpm_pwm_chip *tpm = to_imx_tpm_pwm_chip(chip);
 	bool period_update = false;
 	bool duty_update = false;
 	u32 val, cmod, cur_prescale;
 	unsigned long timeout;
 	struct pwm_state c;

 	if (state->period != tpm->real_period) {
 		/*
 		 * TPM counter is shared by multiple channels, so
 		 * prescale and period can NOT be modified when
 		 * there are multiple channels in use with different
 		 * period settings.
 		 */
 		if (tpm->user_count > 1)
 			return -EBUSY;

 		val = readl(tpm->base + PWM_IMX_TPM_SC);
 		cmod = FIELD_GET(PWM_IMX_TPM_SC_CMOD, val);
 		cur_prescale = FIELD_GET(PWM_IMX_TPM_SC_PS, val);
 		if (cmod && cur_prescale != p->prescale)
 			return -EBUSY;

 		/* set TPM counter prescale */
 		val &= ~PWM_IMX_TPM_SC_PS;
 		val |= FIELD_PREP(PWM_IMX_TPM_SC_PS, p->prescale);
 		writel(val, tpm->base + PWM_IMX_TPM_SC);

 		/*
 		 * set period count:
 		 * if the PWM is disabled (CMOD[1:0] = 2b00), then MOD register
 		 * is updated when MOD register is written.
 		 *
 		 * if the PWM is enabled (CMOD[1:0] ≠ 2b00), the period length
 		 * is latched into hardware when the next period starts.
 		 */
 		writel(p->mod, tpm->base + PWM_IMX_TPM_MOD);
 		tpm->real_period = state->period;
 		period_update = true;
 	}

 	pwm_imx_tpm_get_state(chip, pwm, &c);

 	/* polarity is NOT allowed to be changed if PWM is active */
 	if (c.enabled && c.polarity != state->polarity)
 		return -EBUSY;

 	if (state->duty_cycle != c.duty_cycle) {
 		/*
 		 * set channel value:
 		 * if the PWM is disabled (CMOD[1:0] = 2b00), then CnV register
 		 * is updated when CnV register is written.
 		 *
 		 * if the PWM is enabled (CMOD[1:0] ≠ 2b00), the duty length
 		 * is latched into hardware when the next period starts.
 		 */
 		writel(p->val, tpm->base + PWM_IMX_TPM_CnV(pwm->hwpwm));
 		duty_update = true;
 	}

 	/* make sure MOD & CnV registers are updated */
 	if (period_update || duty_update) {
 		timeout = jiffies + msecs_to_jiffies(tpm->real_period /
 						     NSEC_PER_MSEC + 1);
 		while (readl(tpm->base + PWM_IMX_TPM_MOD) != p->mod
 		       || readl(tpm->base + PWM_IMX_TPM_CnV(pwm->hwpwm))
 		       != p->val) {
 			if (time_after(jiffies, timeout))
 				return -ETIME;
 			cpu_relax();
 		}
 	}

 	/*
 	 * polarity settings will enabled/disable output status
 	 * immediately, so if the channel is disabled, need to
 	 * make sure MSA/MSB/ELS are set to 0 which means channel
 	 * disabled.
 	 */
 	val = readl(tpm->base + PWM_IMX_TPM_CnSC(pwm->hwpwm));
 	val &= ~(PWM_IMX_TPM_CnSC_ELS | PWM_IMX_TPM_CnSC_MSA |
 		 PWM_IMX_TPM_CnSC_MSB);
 	if (state->enabled) {
 		/*
 		 * set polarity (for edge-aligned PWM modes)
 		 *
 		 * ELS[1:0] = 2b10 yields normal polarity behaviour,
 		 * ELS[1:0] = 2b01 yields inversed polarity.
 		 * The other values are reserved.
 		 */
 		val |= PWM_IMX_TPM_CnSC_MSB;
 		val |= (state->polarity == PWM_POLARITY_NORMAL) ?
 			PWM_IMX_TPM_CnSC_ELS_NORMAL :
 			PWM_IMX_TPM_CnSC_ELS_INVERSED;
 	}
 	writel(val, tpm->base + PWM_IMX_TPM_CnSC(pwm->hwpwm));

 	/* control the counter status */
 	if (state->enabled != c.enabled) {
 		val = readl(tpm->base + PWM_IMX_TPM_SC);
 		if (state->enabled) {
 			if (++tpm->enable_count == 1)
 				val |= PWM_IMX_TPM_SC_CMOD_INC_EVERY_CLK;
 		} else {
 			if (--tpm->enable_count == 0)
 				val &= ~PWM_IMX_TPM_SC_CMOD;
 		}
 		writel(val, tpm->base + PWM_IMX_TPM_SC);
 	}

 	return 0;
 }

 static int pwm_imx_tpm_apply(struct pwm_chip *chip,
 			     struct pwm_device *pwm,
 			     const struct pwm_state *state)
 {
 	struct imx_tpm_pwm_chip *tpm = to_imx_tpm_pwm_chip(chip);
 	struct imx_tpm_pwm_param param;
 	struct pwm_state real_state;
 	int ret;

 	ret = pwm_imx_tpm_round_state(chip, &param, &real_state, state);
 	if (ret)
 		return ret;

 	mutex_lock(&tpm->lock);
 	ret = pwm_imx_tpm_apply_hw(chip, &param, &real_state, pwm);
 	mutex_unlock(&tpm->lock);

 	return ret;
 }

 static int pwm_imx_tpm_request(struct pwm_chip *chip, struct pwm_device *pwm)
 {
 	struct imx_tpm_pwm_chip *tpm = to_imx_tpm_pwm_chip(chip);

 	mutex_lock(&tpm->lock);
 	tpm->user_count++;
 	mutex_unlock(&tpm->lock);

 	return 0;
 }

 static void pwm_imx_tpm_free(struct pwm_chip *chip, struct pwm_device *pwm)
 {
 	struct imx_tpm_pwm_chip *tpm = to_imx_tpm_pwm_chip(chip);

 	mutex_lock(&tpm->lock);
 	tpm->user_count--;
 	mutex_unlock(&tpm->lock);
 }

 static const struct pwm_ops imx_tpm_pwm_ops = {
 	.request = pwm_imx_tpm_request,
 	.free = pwm_imx_tpm_free,
 	.get_state = pwm_imx_tpm_get_state,
 	.apply = pwm_imx_tpm_apply,
 	.owner = THIS_MODULE,
 };

 static int pwm_imx_tpm_probe(struct platform_device *pdev)
 {
 	struct imx_tpm_pwm_chip *tpm;
 	int ret;
 	u32 val;

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

 	platform_set_drvdata(pdev, tpm);

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

 	tpm->clk = devm_clk_get(&pdev->dev, NULL);
 	if (IS_ERR(tpm->clk)) {
 		ret = PTR_ERR(tpm->clk);
 		if (ret != -EPROBE_DEFER)
 			dev_err(&pdev->dev,
 				"failed to get PWM clock: %d\n", ret);
 		return ret;
 	}

 	ret = clk_prepare_enable(tpm->clk);
 	if (ret) {
 		dev_err(&pdev->dev,
 			"failed to prepare or enable clock: %d\n", ret);
 		return ret;
 	}

 	tpm->chip.dev = &pdev->dev;
 	tpm->chip.ops = &imx_tpm_pwm_ops;
 	tpm->chip.base = -1;
 	tpm->chip.of_xlate = of_pwm_xlate_with_flags;
 	tpm->chip.of_pwm_n_cells = 3;

 	/* get number of channels */
 	val = readl(tpm->base + PWM_IMX_TPM_PARAM);
 	tpm->chip.npwm = FIELD_GET(PWM_IMX_TPM_PARAM_CHAN, val);

 	mutex_init(&tpm->lock);

 	ret = pwmchip_add(&tpm->chip);
 	if (ret) {
 		dev_err(&pdev->dev, "failed to add PWM chip: %d\n", ret);
 		clk_disable_unprepare(tpm->clk);
 	}

 	return ret;
 }

 static int pwm_imx_tpm_remove(struct platform_device *pdev)
 {
 	struct imx_tpm_pwm_chip *tpm = platform_get_drvdata(pdev);
 	int ret = pwmchip_remove(&tpm->chip);

 	clk_disable_unprepare(tpm->clk);

 	return ret;
 }

 static int __maybe_unused pwm_imx_tpm_suspend(struct device *dev)
 {
 	struct imx_tpm_pwm_chip *tpm = dev_get_drvdata(dev);

 	if (tpm->enable_count > 0)
 		return -EBUSY;

 	clk_disable_unprepare(tpm->clk);

 	return 0;
 }

 static int __maybe_unused pwm_imx_tpm_resume(struct device *dev)
 {
 	struct imx_tpm_pwm_chip *tpm = dev_get_drvdata(dev);
 	int ret = 0;

 	ret = clk_prepare_enable(tpm->clk);
 	if (ret)
 		dev_err(dev,
 			"failed to prepare or enable clock: %d\n",
 			ret);

 	return ret;
 }

 static SIMPLE_DEV_PM_OPS(imx_tpm_pwm_pm,
 			 pwm_imx_tpm_suspend, pwm_imx_tpm_resume);

 static const struct of_device_id imx_tpm_pwm_dt_ids[] = {
 	{ .compatible = "fsl,imx7ulp-pwm", },
 	{ /* sentinel */ }
 };
 MODULE_DEVICE_TABLE(of, imx_tpm_pwm_dt_ids);

 static struct platform_driver imx_tpm_pwm_driver = {
 	.driver = {
 		.name = "imx7ulp-tpm-pwm",
 		.of_match_table = imx_tpm_pwm_dt_ids,
 		.pm = &imx_tpm_pwm_pm,
 	},
 	.probe	= pwm_imx_tpm_probe,
 	.remove = pwm_imx_tpm_remove,
 };
 module_platform_driver(imx_tpm_pwm_driver);

 MODULE_AUTHOR("Anson Huang <Anson.Huang@nxp.com>");
 MODULE_DESCRIPTION("i.MX TPM PWM Driver");
 MODULE_LICENSE("GPL v2");
	// SPDX-License-Identifier: GPL-2.0
	/*
	* Copyright 2018-2019 NXP.
	*
	* Limitations:
	* - The TPM counter and period counter are shared between
	* multiple channels, so all channels should use same period
	* settings.
	* - Changes to polarity cannot be latched at the time of the
	* next period start.
	* - Changing period and duty cycle together isn't atomic,
	* with the wrong timing it might happen that a period is
	* produced with old duty cycle but new period settings.
	*/

	#include <linux/bitfield.h>
	#include <linux/bitops.h>
	#include <linux/clk.h>
	#include <linux/err.h>
	#include <linux/io.h>
	#include <linux/log2.h>
	#include <linux/module.h>
	#include <linux/of.h>
	#include <linux/of_address.h>
	#include <linux/platform_device.h>
	#include <linux/pwm.h>
	#include <linux/slab.h>

	#define PWM_IMX_TPM_PARAM 0x4
	#define PWM_IMX_TPM_GLOBAL 0x8
	#define PWM_IMX_TPM_SC 0x10
	#define PWM_IMX_TPM_CNT 0x14
	#define PWM_IMX_TPM_MOD 0x18
	#define PWM_IMX_TPM_CnSC(n) (0x20 + (n) * 0x8)
	#define PWM_IMX_TPM_CnV(n) (0x24 + (n) * 0x8)

	#define PWM_IMX_TPM_PARAM_CHAN GENMASK(7, 0)

	#define PWM_IMX_TPM_SC_PS GENMASK(2, 0)
	#define PWM_IMX_TPM_SC_CMOD GENMASK(4, 3)
	#define PWM_IMX_TPM_SC_CMOD_INC_EVERY_CLK FIELD_PREP(PWM_IMX_TPM_SC_CMOD, 1)
	#define PWM_IMX_TPM_SC_CPWMS BIT(5)

	#define PWM_IMX_TPM_CnSC_CHF BIT(7)
	#define PWM_IMX_TPM_CnSC_MSB BIT(5)
	#define PWM_IMX_TPM_CnSC_MSA BIT(4)

	/*
	* The reference manual describes this field as two separate bits. The
	* semantic of the two bits isn't orthogonal though, so they are treated
	* together as a 2-bit field here.
	*/
	#define PWM_IMX_TPM_CnSC_ELS GENMASK(3, 2)
	#define PWM_IMX_TPM_CnSC_ELS_INVERSED FIELD_PREP(PWM_IMX_TPM_CnSC_ELS, 1)
	#define PWM_IMX_TPM_CnSC_ELS_NORMAL FIELD_PREP(PWM_IMX_TPM_CnSC_ELS, 2)


	#define PWM_IMX_TPM_MOD_WIDTH 16
	#define PWM_IMX_TPM_MOD_MOD GENMASK(PWM_IMX_TPM_MOD_WIDTH - 1, 0)

	struct imx_tpm_pwm_chip {
	struct pwm_chip chip;
	struct clk *clk;
	void __iomem *base;
	struct mutex lock;
	u32 user_count;
	u32 enable_count;
	u32 real_period;
	};

	struct imx_tpm_pwm_param {
	u8 prescale;
	u32 mod;
	u32 val;
	};

	static inline struct imx_tpm_pwm_chip *
	to_imx_tpm_pwm_chip(struct pwm_chip *chip)
	{
	return container_of(chip, struct imx_tpm_pwm_chip, chip);
	}

	/*
	* This function determines for a given pwm_state *state that a consumer
	* might request the pwm_state *real_state that eventually is implemented
	* by the hardware and the necessary register values (in *p) to achieve
	* this.
	*/
	static int pwm_imx_tpm_round_state(struct pwm_chip *chip,
	struct imx_tpm_pwm_param *p,
	struct pwm_state *real_state,
	const struct pwm_state *state)
	{
	struct imx_tpm_pwm_chip *tpm = to_imx_tpm_pwm_chip(chip);
	u32 rate, prescale, period_count, clock_unit;
	u64 tmp;

	rate = clk_get_rate(tpm->clk);
	tmp = (u64)state->period * rate;
	clock_unit = DIV_ROUND_CLOSEST_ULL(tmp, NSEC_PER_SEC);
	if (clock_unit <= PWM_IMX_TPM_MOD_MOD)
	prescale = 0;
	else
	prescale = ilog2(clock_unit) + 1 - PWM_IMX_TPM_MOD_WIDTH;

	if ((!FIELD_FIT(PWM_IMX_TPM_SC_PS, prescale)))
	return -ERANGE;
	p->prescale = prescale;

	period_count = (clock_unit + ((1 << prescale) >> 1)) >> prescale;
	p->mod = period_count;

	/* calculate real period HW can support */
	tmp = (u64)period_count << prescale;
	tmp *= NSEC_PER_SEC;
	real_state->period = DIV_ROUND_CLOSEST_ULL(tmp, rate);

	/*
	* if eventually the PWM output is inactive, either
	* duty cycle is 0 or status is disabled, need to
	* make sure the output pin is inactive.
	*/
	if (!state->enabled)
	real_state->duty_cycle = 0;
	else
	real_state->duty_cycle = state->duty_cycle;

	tmp = (u64)p->mod * real_state->duty_cycle;
	p->val = DIV_ROUND_CLOSEST_ULL(tmp, real_state->period);

	real_state->polarity = state->polarity;
	real_state->enabled = state->enabled;

	return 0;
	}

	static void pwm_imx_tpm_get_state(struct pwm_chip *chip,
	struct pwm_device *pwm,
	struct pwm_state *state)
	{
	struct imx_tpm_pwm_chip *tpm = to_imx_tpm_pwm_chip(chip);
	u32 rate, val, prescale;
	u64 tmp;

	/* get period */
	state->period = tpm->real_period;

	/* get duty cycle */
	rate = clk_get_rate(tpm->clk);
	val = readl(tpm->base + PWM_IMX_TPM_SC);
	prescale = FIELD_GET(PWM_IMX_TPM_SC_PS, val);
	tmp = readl(tpm->base + PWM_IMX_TPM_CnV(pwm->hwpwm));
	tmp = (tmp << prescale) * NSEC_PER_SEC;
	state->duty_cycle = DIV_ROUND_CLOSEST_ULL(tmp, rate);

	/* get polarity */
	val = readl(tpm->base + PWM_IMX_TPM_CnSC(pwm->hwpwm));
	if ((val & PWM_IMX_TPM_CnSC_ELS) == PWM_IMX_TPM_CnSC_ELS_INVERSED)
	state->polarity = PWM_POLARITY_INVERSED;
	else
	/*
	* Assume reserved values (2b00 and 2b11) to yield
	* normal polarity.
	*/
	state->polarity = PWM_POLARITY_NORMAL;

	/* get channel status */
	state->enabled = FIELD_GET(PWM_IMX_TPM_CnSC_ELS, val) ? true : false;
	}

	/* this function is supposed to be called with mutex hold */
	static int pwm_imx_tpm_apply_hw(struct pwm_chip *chip,
	struct imx_tpm_pwm_param *p,
	struct pwm_state *state,
	struct pwm_device *pwm)
	{
	struct imx_tpm_pwm_chip *tpm = to_imx_tpm_pwm_chip(chip);
	bool period_update = false;
	bool duty_update = false;
	u32 val, cmod, cur_prescale;
	unsigned long timeout;
	struct pwm_state c;

	if (state->period != tpm->real_period) {
	/*
	* TPM counter is shared by multiple channels, so
	* prescale and period can NOT be modified when
	* there are multiple channels in use with different
	* period settings.
	*/
	if (tpm->user_count > 1)
	return -EBUSY;

	val = readl(tpm->base + PWM_IMX_TPM_SC);
	cmod = FIELD_GET(PWM_IMX_TPM_SC_CMOD, val);
	cur_prescale = FIELD_GET(PWM_IMX_TPM_SC_PS, val);
	if (cmod && cur_prescale != p->prescale)
	return -EBUSY;

	/* set TPM counter prescale */
	val &= ~PWM_IMX_TPM_SC_PS;
	val \|= FIELD_PREP(PWM_IMX_TPM_SC_PS, p->prescale);
	writel(val, tpm->base + PWM_IMX_TPM_SC);

	/*
	* set period count:
	* if the PWM is disabled (CMOD[1:0] = 2b00), then MOD register
	* is updated when MOD register is written.
	*
	* if the PWM is enabled (CMOD[1:0] ≠ 2b00), the period length
	* is latched into hardware when the next period starts.
	*/
	writel(p->mod, tpm->base + PWM_IMX_TPM_MOD);
	tpm->real_period = state->period;
	period_update = true;
	}

	pwm_imx_tpm_get_state(chip, pwm, &c);

	/* polarity is NOT allowed to be changed if PWM is active */
	if (c.enabled && c.polarity != state->polarity)
	return -EBUSY;

	if (state->duty_cycle != c.duty_cycle) {
	/*
	* set channel value:
	* if the PWM is disabled (CMOD[1:0] = 2b00), then CnV register
	* is updated when CnV register is written.
	*
	* if the PWM is enabled (CMOD[1:0] ≠ 2b00), the duty length
	* is latched into hardware when the next period starts.
	*/
	writel(p->val, tpm->base + PWM_IMX_TPM_CnV(pwm->hwpwm));
	duty_update = true;
	}

	/* make sure MOD & CnV registers are updated */
	if (period_update \|\| duty_update) {
	timeout = jiffies + msecs_to_jiffies(tpm->real_period /
	NSEC_PER_MSEC + 1);
	while (readl(tpm->base + PWM_IMX_TPM_MOD) != p->mod
	\|\| readl(tpm->base + PWM_IMX_TPM_CnV(pwm->hwpwm))
	!= p->val) {
	if (time_after(jiffies, timeout))
	return -ETIME;
	cpu_relax();
	}
	}

	/*
	* polarity settings will enabled/disable output status
	* immediately, so if the channel is disabled, need to
	* make sure MSA/MSB/ELS are set to 0 which means channel
	* disabled.
	*/
	val = readl(tpm->base + PWM_IMX_TPM_CnSC(pwm->hwpwm));
	val &= ~(PWM_IMX_TPM_CnSC_ELS \| PWM_IMX_TPM_CnSC_MSA \|
	PWM_IMX_TPM_CnSC_MSB);
	if (state->enabled) {
	/*
	* set polarity (for edge-aligned PWM modes)
	*
	* ELS[1:0] = 2b10 yields normal polarity behaviour,
	* ELS[1:0] = 2b01 yields inversed polarity.
	* The other values are reserved.
	*/
	val \|= PWM_IMX_TPM_CnSC_MSB;
	val \|= (state->polarity == PWM_POLARITY_NORMAL) ?
	PWM_IMX_TPM_CnSC_ELS_NORMAL :
	PWM_IMX_TPM_CnSC_ELS_INVERSED;
	}
	writel(val, tpm->base + PWM_IMX_TPM_CnSC(pwm->hwpwm));

	/* control the counter status */
	if (state->enabled != c.enabled) {
	val = readl(tpm->base + PWM_IMX_TPM_SC);
	if (state->enabled) {
	if (++tpm->enable_count == 1)
	val \|= PWM_IMX_TPM_SC_CMOD_INC_EVERY_CLK;
	} else {
	if (--tpm->enable_count == 0)
	val &= ~PWM_IMX_TPM_SC_CMOD;
	}
	writel(val, tpm->base + PWM_IMX_TPM_SC);
	}

	return 0;
	}

	static int pwm_imx_tpm_apply(struct pwm_chip *chip,
	struct pwm_device *pwm,
	const struct pwm_state *state)
	{
	struct imx_tpm_pwm_chip *tpm = to_imx_tpm_pwm_chip(chip);
	struct imx_tpm_pwm_param param;
	struct pwm_state real_state;
	int ret;

	ret = pwm_imx_tpm_round_state(chip, &param, &real_state, state);
	if (ret)
	return ret;

	mutex_lock(&tpm->lock);
	ret = pwm_imx_tpm_apply_hw(chip, &param, &real_state, pwm);
	mutex_unlock(&tpm->lock);

	return ret;
	}

	static int pwm_imx_tpm_request(struct pwm_chip chip, struct pwm_device pwm)
	{
	struct imx_tpm_pwm_chip *tpm = to_imx_tpm_pwm_chip(chip);

	mutex_lock(&tpm->lock);
	tpm->user_count++;
	mutex_unlock(&tpm->lock);

	return 0;
	}

	static void pwm_imx_tpm_free(struct pwm_chip chip, struct pwm_device pwm)
	{
	struct imx_tpm_pwm_chip *tpm = to_imx_tpm_pwm_chip(chip);

	mutex_lock(&tpm->lock);
	tpm->user_count--;
	mutex_unlock(&tpm->lock);
	}

	static const struct pwm_ops imx_tpm_pwm_ops = {
	.request = pwm_imx_tpm_request,
	.free = pwm_imx_tpm_free,
	.get_state = pwm_imx_tpm_get_state,
	.apply = pwm_imx_tpm_apply,
	.owner = THIS_MODULE,
	};

	static int pwm_imx_tpm_probe(struct platform_device *pdev)
	{
	struct imx_tpm_pwm_chip *tpm;
	int ret;
	u32 val;

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

	platform_set_drvdata(pdev, tpm);

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

	tpm->clk = devm_clk_get(&pdev->dev, NULL);
	if (IS_ERR(tpm->clk)) {
	ret = PTR_ERR(tpm->clk);
	if (ret != -EPROBE_DEFER)
	dev_err(&pdev->dev,
	"failed to get PWM clock: %d\n", ret);
	return ret;
	}

	ret = clk_prepare_enable(tpm->clk);
	if (ret) {
	dev_err(&pdev->dev,
	"failed to prepare or enable clock: %d\n", ret);
	return ret;
	}

	tpm->chip.dev = &pdev->dev;
	tpm->chip.ops = &imx_tpm_pwm_ops;
	tpm->chip.base = -1;
	tpm->chip.of_xlate = of_pwm_xlate_with_flags;
	tpm->chip.of_pwm_n_cells = 3;

	/* get number of channels */
	val = readl(tpm->base + PWM_IMX_TPM_PARAM);
	tpm->chip.npwm = FIELD_GET(PWM_IMX_TPM_PARAM_CHAN, val);

	mutex_init(&tpm->lock);

	ret = pwmchip_add(&tpm->chip);
	if (ret) {
	dev_err(&pdev->dev, "failed to add PWM chip: %d\n", ret);
	clk_disable_unprepare(tpm->clk);
	}

	return ret;
	}

	static int pwm_imx_tpm_remove(struct platform_device *pdev)
	{
	struct imx_tpm_pwm_chip *tpm = platform_get_drvdata(pdev);
	int ret = pwmchip_remove(&tpm->chip);

	clk_disable_unprepare(tpm->clk);

	return ret;
	}

	static int __maybe_unused pwm_imx_tpm_suspend(struct device *dev)
	{
	struct imx_tpm_pwm_chip *tpm = dev_get_drvdata(dev);

	if (tpm->enable_count > 0)
	return -EBUSY;

	clk_disable_unprepare(tpm->clk);

	return 0;
	}

	static int __maybe_unused pwm_imx_tpm_resume(struct device *dev)
	{
	struct imx_tpm_pwm_chip *tpm = dev_get_drvdata(dev);
	int ret = 0;

	ret = clk_prepare_enable(tpm->clk);
	if (ret)
	dev_err(dev,
	"failed to prepare or enable clock: %d\n",
	ret);

	return ret;
	}

	static SIMPLE_DEV_PM_OPS(imx_tpm_pwm_pm,
	pwm_imx_tpm_suspend, pwm_imx_tpm_resume);

	static const struct of_device_id imx_tpm_pwm_dt_ids[] = {
	{ .compatible = "fsl,imx7ulp-pwm", },
	{ /* sentinel */ }
	};
	MODULE_DEVICE_TABLE(of, imx_tpm_pwm_dt_ids);

	static struct platform_driver imx_tpm_pwm_driver = {
	.driver = {
	.name = "imx7ulp-tpm-pwm",
	.of_match_table = imx_tpm_pwm_dt_ids,
	.pm = &imx_tpm_pwm_pm,
	},
	.probe = pwm_imx_tpm_probe,
	.remove = pwm_imx_tpm_remove,
	};
	module_platform_driver(imx_tpm_pwm_driver);

	MODULE_AUTHOR("Anson Huang <Anson.Huang@nxp.com>");
	MODULE_DESCRIPTION("i.MX TPM PWM Driver");
	MODULE_LICENSE("GPL v2");