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

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * drivers/pwm/pwm-tegra.c
  *
  * Tegra pulse-width-modulation controller driver
  *
  * Copyright (c) 2010-2020, NVIDIA Corporation.
  * Based on arch/arm/plat-mxc/pwm.c by Sascha Hauer <s.hauer@pengutronix.de>
  *
  * Overview of Tegra Pulse Width Modulator Register:
  * 1. 13-bit: Frequency division (SCALE)
  * 2. 8-bit : Pulse division (DUTY)
  * 3. 1-bit : Enable bit
  *
  * The PWM clock frequency is divided by 256 before subdividing it based
  * on the programmable frequency division value to generate the required
  * frequency for PWM output. The maximum output frequency that can be
  * achieved is (max rate of source clock) / 256.
  * e.g. if source clock rate is 408 MHz, maximum output frequency can be:
  * 408 MHz/256 = 1.6 MHz.
  * This 1.6 MHz frequency can further be divided using SCALE value in PWM.
  *
  * PWM pulse width: 8 bits are usable [23:16] for varying pulse width.
  * To achieve 100% duty cycle, program Bit [24] of this register to
  * 1’b1. In which case the other bits [23:16] are set to don't care.
  *
  * Limitations:
  * -	When PWM is disabled, the output is driven to inactive.
  * -	It does not allow the current PWM period to complete and
  *	stops abruptly.
  *
  * -	If the register is reconfigured while PWM is running,
  *	it does not complete the currently running period.
  *
  * -	If the user input duty is beyond acceptible limits,
  *	-EINVAL is returned.
  */

 #include <linux/clk.h>
 #include <linux/err.h>
 #include <linux/io.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/pm_opp.h>
 #include <linux/pwm.h>
 #include <linux/platform_device.h>
 #include <linux/pinctrl/consumer.h>
 #include <linux/pm_runtime.h>
 #include <linux/slab.h>
 #include <linux/reset.h>

 #include <soc/tegra/common.h>

 #define PWM_ENABLE	(1 << 31)
 #define PWM_DUTY_WIDTH	8
 #define PWM_DUTY_SHIFT	16
 #define PWM_SCALE_WIDTH	13
 #define PWM_SCALE_SHIFT	0

 struct tegra_pwm_soc {
 	unsigned int num_channels;

 	/* Maximum IP frequency for given SoCs */
 	unsigned long max_frequency;
 };

 struct tegra_pwm_chip {
 	struct pwm_chip chip;
 	struct device *dev;

 	struct clk *clk;
 	struct reset_control*rst;

 	unsigned long clk_rate;
 	unsigned long min_period_ns;

 	void __iomem *regs;

 	const struct tegra_pwm_soc *soc;
 };

 static inline struct tegra_pwm_chip *to_tegra_pwm_chip(struct pwm_chip *chip)
 {
 	return container_of(chip, struct tegra_pwm_chip, chip);
 }

 static inline u32 pwm_readl(struct tegra_pwm_chip *pc, unsigned int offset)
 {
 	return readl(pc->regs + (offset << 4));
 }

 static inline void pwm_writel(struct tegra_pwm_chip *pc, unsigned int offset, u32 value)
 {
 	writel(value, pc->regs + (offset << 4));
 }

 static int tegra_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
 			    int duty_ns, int period_ns)
 {
 	struct tegra_pwm_chip *pc = to_tegra_pwm_chip(chip);
 	unsigned long long c = duty_ns;
 	unsigned long rate, required_clk_rate;
 	u32 val = 0;
 	int err;

 	/*
 	 * Convert from duty_ns / period_ns to a fixed number of duty ticks
 	 * per (1 << PWM_DUTY_WIDTH) cycles and make sure to round to the
 	 * nearest integer during division.
 	 */
 	c *= (1 << PWM_DUTY_WIDTH);
 	c = DIV_ROUND_CLOSEST_ULL(c, period_ns);

 	val = (u32)c << PWM_DUTY_SHIFT;

 	/*
 	 *  min period = max clock limit >> PWM_DUTY_WIDTH
 	 */
 	if (period_ns < pc->min_period_ns)
 		return -EINVAL;

 	/*
 	 * Compute the prescaler value for which (1 << PWM_DUTY_WIDTH)
 	 * cycles at the PWM clock rate will take period_ns nanoseconds.
 	 *
 	 * num_channels: If single instance of PWM controller has multiple
 	 * channels (e.g. Tegra210 or older) then it is not possible to
 	 * configure separate clock rates to each of the channels, in such
 	 * case the value stored during probe will be referred.
 	 *
 	 * If every PWM controller instance has one channel respectively, i.e.
 	 * nums_channels == 1 then only the clock rate can be modified
 	 * dynamically (e.g. Tegra186 or Tegra194).
 	 */
 	if (pc->soc->num_channels == 1) {
 		/*
 		 * Rate is multiplied with 2^PWM_DUTY_WIDTH so that it matches
 		 * with the maximum possible rate that the controller can
 		 * provide. Any further lower value can be derived by setting
 		 * PFM bits[0:12].
 		 *
 		 * required_clk_rate is a reference rate for source clock and
 		 * it is derived based on user requested period. By setting the
 		 * source clock rate as required_clk_rate, PWM controller will
 		 * be able to configure the requested period.
 		 */
 		required_clk_rate = DIV_ROUND_UP_ULL((u64)NSEC_PER_SEC << PWM_DUTY_WIDTH,
 						     period_ns);

 		if (required_clk_rate > clk_round_rate(pc->clk, required_clk_rate))
 			/*
 			 * required_clk_rate is a lower bound for the input
 			 * rate; for lower rates there is no value for PWM_SCALE
 			 * that yields a period less than or equal to the
 			 * requested period. Hence, for lower rates, double the
 			 * required_clk_rate to get a clock rate that can meet
 			 * the requested period.
 			 */
 			required_clk_rate *= 2;

 		err = dev_pm_opp_set_rate(pc->dev, required_clk_rate);
 		if (err < 0)
 			return -EINVAL;

 		/* Store the new rate for further references */
 		pc->clk_rate = clk_get_rate(pc->clk);
 	}

 	/* Consider precision in PWM_SCALE_WIDTH rate calculation */
 	rate = mul_u64_u64_div_u64(pc->clk_rate, period_ns,
 				   (u64)NSEC_PER_SEC << PWM_DUTY_WIDTH);

 	/*
 	 * Since the actual PWM divider is the register's frequency divider
 	 * field plus 1, we need to decrement to get the correct value to
 	 * write to the register.
 	 */
 	if (rate > 0)
 		rate--;
 	else
 		return -EINVAL;

 	/*
 	 * Make sure that the rate will fit in the register's frequency
 	 * divider field.
 	 */
 	if (rate >> PWM_SCALE_WIDTH)
 		return -EINVAL;

 	val |= rate << PWM_SCALE_SHIFT;

 	/*
 	 * If the PWM channel is disabled, make sure to turn on the clock
 	 * before writing the register. Otherwise, keep it enabled.
 	 */
 	if (!pwm_is_enabled(pwm)) {
 		err = pm_runtime_resume_and_get(pc->dev);
 		if (err)
 			return err;
 	} else
 		val |= PWM_ENABLE;

 	pwm_writel(pc, pwm->hwpwm, val);

 	/*
 	 * If the PWM is not enabled, turn the clock off again to save power.
 	 */
 	if (!pwm_is_enabled(pwm))
 		pm_runtime_put(pc->dev);

 	return 0;
 }

 static int tegra_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
 {
 	struct tegra_pwm_chip *pc = to_tegra_pwm_chip(chip);
 	int rc = 0;
 	u32 val;

 	rc = pm_runtime_resume_and_get(pc->dev);
 	if (rc)
 		return rc;

 	val = pwm_readl(pc, pwm->hwpwm);
 	val |= PWM_ENABLE;
 	pwm_writel(pc, pwm->hwpwm, val);

 	return 0;
 }

 static void tegra_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
 {
 	struct tegra_pwm_chip *pc = to_tegra_pwm_chip(chip);
 	u32 val;

 	val = pwm_readl(pc, pwm->hwpwm);
 	val &= ~PWM_ENABLE;
 	pwm_writel(pc, pwm->hwpwm, val);

 	pm_runtime_put_sync(pc->dev);
 }

 static int tegra_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_POLARITY_NORMAL)
 		return -EINVAL;

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

 		return 0;
 	}

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

 	if (!enabled)
 		err = tegra_pwm_enable(chip, pwm);

 	return err;
 }

 static const struct pwm_ops tegra_pwm_ops = {
 	.apply = tegra_pwm_apply,
 	.owner = THIS_MODULE,
 };

 static int tegra_pwm_probe(struct platform_device *pdev)
 {
 	struct tegra_pwm_chip *pc;
 	int ret;

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

 	pc->soc = of_device_get_match_data(&pdev->dev);
 	pc->dev = &pdev->dev;

 	pc->regs = devm_platform_ioremap_resource(pdev, 0);
 	if (IS_ERR(pc->regs))
 		return PTR_ERR(pc->regs);

 	platform_set_drvdata(pdev, pc);

 	pc->clk = devm_clk_get(&pdev->dev, NULL);
 	if (IS_ERR(pc->clk))
 		return PTR_ERR(pc->clk);

 	ret = devm_tegra_core_dev_init_opp_table_common(&pdev->dev);
 	if (ret)
 		return ret;

 	pm_runtime_enable(&pdev->dev);
 	ret = pm_runtime_resume_and_get(&pdev->dev);
 	if (ret)
 		return ret;

 	/* Set maximum frequency of the IP */
 	ret = dev_pm_opp_set_rate(pc->dev, pc->soc->max_frequency);
 	if (ret < 0) {
 		dev_err(&pdev->dev, "Failed to set max frequency: %d\n", ret);
 		goto put_pm;
 	}

 	/*
 	 * The requested and configured frequency may differ due to
 	 * clock register resolutions. Get the configured frequency
 	 * so that PWM period can be calculated more accurately.
 	 */
 	pc->clk_rate = clk_get_rate(pc->clk);

 	/* Set minimum limit of PWM period for the IP */
 	pc->min_period_ns =
 	    (NSEC_PER_SEC / (pc->soc->max_frequency >> PWM_DUTY_WIDTH)) + 1;

 	pc->rst = devm_reset_control_get_exclusive(&pdev->dev, "pwm");
 	if (IS_ERR(pc->rst)) {
 		ret = PTR_ERR(pc->rst);
 		dev_err(&pdev->dev, "Reset control is not found: %d\n", ret);
 		goto put_pm;
 	}

 	reset_control_deassert(pc->rst);

 	pc->chip.dev = &pdev->dev;
 	pc->chip.ops = &tegra_pwm_ops;
 	pc->chip.npwm = pc->soc->num_channels;

 	ret = pwmchip_add(&pc->chip);
 	if (ret < 0) {
 		dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret);
 		reset_control_assert(pc->rst);
 		goto put_pm;
 	}

 	pm_runtime_put(&pdev->dev);

 	return 0;
 put_pm:
 	pm_runtime_put_sync_suspend(&pdev->dev);
 	pm_runtime_force_suspend(&pdev->dev);
 	return ret;
 }

 static void tegra_pwm_remove(struct platform_device *pdev)
 {
 	struct tegra_pwm_chip *pc = platform_get_drvdata(pdev);

 	pwmchip_remove(&pc->chip);

 	reset_control_assert(pc->rst);

 	pm_runtime_force_suspend(&pdev->dev);
 }

 static int __maybe_unused tegra_pwm_runtime_suspend(struct device *dev)
 {
 	struct tegra_pwm_chip *pc = dev_get_drvdata(dev);
 	int err;

 	clk_disable_unprepare(pc->clk);

 	err = pinctrl_pm_select_sleep_state(dev);
 	if (err) {
 		clk_prepare_enable(pc->clk);
 		return err;
 	}

 	return 0;
 }

 static int __maybe_unused tegra_pwm_runtime_resume(struct device *dev)
 {
 	struct tegra_pwm_chip *pc = dev_get_drvdata(dev);
 	int err;

 	err = pinctrl_pm_select_default_state(dev);
 	if (err)
 		return err;

 	err = clk_prepare_enable(pc->clk);
 	if (err) {
 		pinctrl_pm_select_sleep_state(dev);
 		return err;
 	}

 	return 0;
 }

 static const struct tegra_pwm_soc tegra20_pwm_soc = {
 	.num_channels = 4,
 	.max_frequency = 48000000UL,
 };

 static const struct tegra_pwm_soc tegra186_pwm_soc = {
 	.num_channels = 1,
 	.max_frequency = 102000000UL,
 };

 static const struct tegra_pwm_soc tegra194_pwm_soc = {
 	.num_channels = 1,
 	.max_frequency = 408000000UL,
 };

 static const struct of_device_id tegra_pwm_of_match[] = {
 	{ .compatible = "nvidia,tegra20-pwm", .data = &tegra20_pwm_soc },
 	{ .compatible = "nvidia,tegra186-pwm", .data = &tegra186_pwm_soc },
 	{ .compatible = "nvidia,tegra194-pwm", .data = &tegra194_pwm_soc },
 	{ }
 };
 MODULE_DEVICE_TABLE(of, tegra_pwm_of_match);

 static const struct dev_pm_ops tegra_pwm_pm_ops = {
 	SET_RUNTIME_PM_OPS(tegra_pwm_runtime_suspend, tegra_pwm_runtime_resume,
 			   NULL)
 	SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
 				pm_runtime_force_resume)
 };

 static struct platform_driver tegra_pwm_driver = {
 	.driver = {
 		.name = "tegra-pwm",
 		.of_match_table = tegra_pwm_of_match,
 		.pm = &tegra_pwm_pm_ops,
 	},
 	.probe = tegra_pwm_probe,
 	.remove_new = tegra_pwm_remove,
 };

 module_platform_driver(tegra_pwm_driver);

 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Sandipan Patra <spatra@nvidia.com>");
 MODULE_DESCRIPTION("Tegra PWM controller driver");
 MODULE_ALIAS("platform:tegra-pwm");
	// SPDX-License-Identifier: GPL-2.0-or-later
	/*
	* drivers/pwm/pwm-tegra.c
	*
	* Tegra pulse-width-modulation controller driver
	*
	* Copyright (c) 2010-2020, NVIDIA Corporation.
	* Based on arch/arm/plat-mxc/pwm.c by Sascha Hauer <s.hauer@pengutronix.de>
	*
	* Overview of Tegra Pulse Width Modulator Register:
	* 1. 13-bit: Frequency division (SCALE)
	* 2. 8-bit : Pulse division (DUTY)
	* 3. 1-bit : Enable bit
	*
	* The PWM clock frequency is divided by 256 before subdividing it based
	* on the programmable frequency division value to generate the required
	* frequency for PWM output. The maximum output frequency that can be
	* achieved is (max rate of source clock) / 256.
	* e.g. if source clock rate is 408 MHz, maximum output frequency can be:
	* 408 MHz/256 = 1.6 MHz.
	* This 1.6 MHz frequency can further be divided using SCALE value in PWM.
	*
	* PWM pulse width: 8 bits are usable [23:16] for varying pulse width.
	* To achieve 100% duty cycle, program Bit [24] of this register to
	* 1’b1. In which case the other bits [23:16] are set to don't care.
	*
	* Limitations:
	* - When PWM is disabled, the output is driven to inactive.
	* - It does not allow the current PWM period to complete and
	* stops abruptly.
	*
	* - If the register is reconfigured while PWM is running,
	* it does not complete the currently running period.
	*
	* - If the user input duty is beyond acceptible limits,
	* -EINVAL is returned.
	*/

	#include <linux/clk.h>
	#include <linux/err.h>
	#include <linux/io.h>
	#include <linux/module.h>
	#include <linux/of.h>
	#include <linux/pm_opp.h>
	#include <linux/pwm.h>
	#include <linux/platform_device.h>
	#include <linux/pinctrl/consumer.h>
	#include <linux/pm_runtime.h>
	#include <linux/slab.h>
	#include <linux/reset.h>

	#include <soc/tegra/common.h>

	#define PWM_ENABLE (1 << 31)
	#define PWM_DUTY_WIDTH 8
	#define PWM_DUTY_SHIFT 16
	#define PWM_SCALE_WIDTH 13
	#define PWM_SCALE_SHIFT 0

	struct tegra_pwm_soc {
	unsigned int num_channels;

	/* Maximum IP frequency for given SoCs */
	unsigned long max_frequency;
	};

	struct tegra_pwm_chip {
	struct pwm_chip chip;
	struct device *dev;

	struct clk *clk;
	struct reset_control*rst;

	unsigned long clk_rate;
	unsigned long min_period_ns;

	void __iomem *regs;

	const struct tegra_pwm_soc *soc;
	};

	static inline struct tegra_pwm_chip to_tegra_pwm_chip(struct pwm_chip chip)
	{
	return container_of(chip, struct tegra_pwm_chip, chip);
	}

	static inline u32 pwm_readl(struct tegra_pwm_chip *pc, unsigned int offset)
	{
	return readl(pc->regs + (offset << 4));
	}

	static inline void pwm_writel(struct tegra_pwm_chip *pc, unsigned int offset, u32 value)
	{
	writel(value, pc->regs + (offset << 4));
	}

	static int tegra_pwm_config(struct pwm_chip chip, struct pwm_device pwm,
	int duty_ns, int period_ns)
	{
	struct tegra_pwm_chip *pc = to_tegra_pwm_chip(chip);
	unsigned long long c = duty_ns;
	unsigned long rate, required_clk_rate;
	u32 val = 0;
	int err;

	/*
	* Convert from duty_ns / period_ns to a fixed number of duty ticks
	* per (1 << PWM_DUTY_WIDTH) cycles and make sure to round to the
	* nearest integer during division.
	*/
	c *= (1 << PWM_DUTY_WIDTH);
	c = DIV_ROUND_CLOSEST_ULL(c, period_ns);

	val = (u32)c << PWM_DUTY_SHIFT;

	/*
	* min period = max clock limit >> PWM_DUTY_WIDTH
	*/
	if (period_ns < pc->min_period_ns)
	return -EINVAL;

	/*
	* Compute the prescaler value for which (1 << PWM_DUTY_WIDTH)
	* cycles at the PWM clock rate will take period_ns nanoseconds.
	*
	* num_channels: If single instance of PWM controller has multiple
	* channels (e.g. Tegra210 or older) then it is not possible to
	* configure separate clock rates to each of the channels, in such
	* case the value stored during probe will be referred.
	*
	* If every PWM controller instance has one channel respectively, i.e.
	* nums_channels == 1 then only the clock rate can be modified
	* dynamically (e.g. Tegra186 or Tegra194).
	*/
	if (pc->soc->num_channels == 1) {
	/*
	* Rate is multiplied with 2^PWM_DUTY_WIDTH so that it matches
	* with the maximum possible rate that the controller can
	* provide. Any further lower value can be derived by setting
	* PFM bits[0:12].
	*
	* required_clk_rate is a reference rate for source clock and
	* it is derived based on user requested period. By setting the
	* source clock rate as required_clk_rate, PWM controller will
	* be able to configure the requested period.
	*/
	required_clk_rate = DIV_ROUND_UP_ULL((u64)NSEC_PER_SEC << PWM_DUTY_WIDTH,
	period_ns);

	if (required_clk_rate > clk_round_rate(pc->clk, required_clk_rate))
	/*
	* required_clk_rate is a lower bound for the input
	* rate; for lower rates there is no value for PWM_SCALE
	* that yields a period less than or equal to the
	* requested period. Hence, for lower rates, double the
	* required_clk_rate to get a clock rate that can meet
	* the requested period.
	*/
	required_clk_rate *= 2;

	err = dev_pm_opp_set_rate(pc->dev, required_clk_rate);
	if (err < 0)
	return -EINVAL;

	/* Store the new rate for further references */
	pc->clk_rate = clk_get_rate(pc->clk);
	}

	/* Consider precision in PWM_SCALE_WIDTH rate calculation */
	rate = mul_u64_u64_div_u64(pc->clk_rate, period_ns,
	(u64)NSEC_PER_SEC << PWM_DUTY_WIDTH);

	/*
	* Since the actual PWM divider is the register's frequency divider
	* field plus 1, we need to decrement to get the correct value to
	* write to the register.
	*/
	if (rate > 0)
	rate--;
	else
	return -EINVAL;

	/*
	* Make sure that the rate will fit in the register's frequency
	* divider field.
	*/
	if (rate >> PWM_SCALE_WIDTH)
	return -EINVAL;

	val \|= rate << PWM_SCALE_SHIFT;

	/*
	* If the PWM channel is disabled, make sure to turn on the clock
	* before writing the register. Otherwise, keep it enabled.
	*/
	if (!pwm_is_enabled(pwm)) {
	err = pm_runtime_resume_and_get(pc->dev);
	if (err)
	return err;
	} else
	val \|= PWM_ENABLE;

	pwm_writel(pc, pwm->hwpwm, val);

	/*
	* If the PWM is not enabled, turn the clock off again to save power.
	*/
	if (!pwm_is_enabled(pwm))
	pm_runtime_put(pc->dev);

	return 0;
	}

	static int tegra_pwm_enable(struct pwm_chip chip, struct pwm_device pwm)
	{
	struct tegra_pwm_chip *pc = to_tegra_pwm_chip(chip);
	int rc = 0;
	u32 val;

	rc = pm_runtime_resume_and_get(pc->dev);
	if (rc)
	return rc;

	val = pwm_readl(pc, pwm->hwpwm);
	val \|= PWM_ENABLE;
	pwm_writel(pc, pwm->hwpwm, val);

	return 0;
	}

	static void tegra_pwm_disable(struct pwm_chip chip, struct pwm_device pwm)
	{
	struct tegra_pwm_chip *pc = to_tegra_pwm_chip(chip);
	u32 val;

	val = pwm_readl(pc, pwm->hwpwm);
	val &= ~PWM_ENABLE;
	pwm_writel(pc, pwm->hwpwm, val);

	pm_runtime_put_sync(pc->dev);
	}

	static int tegra_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_POLARITY_NORMAL)
	return -EINVAL;

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

	return 0;
	}

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

	if (!enabled)
	err = tegra_pwm_enable(chip, pwm);

	return err;
	}

	static const struct pwm_ops tegra_pwm_ops = {
	.apply = tegra_pwm_apply,
	.owner = THIS_MODULE,
	};

	static int tegra_pwm_probe(struct platform_device *pdev)
	{
	struct tegra_pwm_chip *pc;
	int ret;

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

	pc->soc = of_device_get_match_data(&pdev->dev);
	pc->dev = &pdev->dev;

	pc->regs = devm_platform_ioremap_resource(pdev, 0);
	if (IS_ERR(pc->regs))
	return PTR_ERR(pc->regs);

	platform_set_drvdata(pdev, pc);

	pc->clk = devm_clk_get(&pdev->dev, NULL);
	if (IS_ERR(pc->clk))
	return PTR_ERR(pc->clk);

	ret = devm_tegra_core_dev_init_opp_table_common(&pdev->dev);
	if (ret)
	return ret;

	pm_runtime_enable(&pdev->dev);
	ret = pm_runtime_resume_and_get(&pdev->dev);
	if (ret)
	return ret;

	/* Set maximum frequency of the IP */
	ret = dev_pm_opp_set_rate(pc->dev, pc->soc->max_frequency);
	if (ret < 0) {
	dev_err(&pdev->dev, "Failed to set max frequency: %d\n", ret);
	goto put_pm;
	}

	/*
	* The requested and configured frequency may differ due to
	* clock register resolutions. Get the configured frequency
	* so that PWM period can be calculated more accurately.
	*/
	pc->clk_rate = clk_get_rate(pc->clk);

	/* Set minimum limit of PWM period for the IP */
	pc->min_period_ns =
	(NSEC_PER_SEC / (pc->soc->max_frequency >> PWM_DUTY_WIDTH)) + 1;

	pc->rst = devm_reset_control_get_exclusive(&pdev->dev, "pwm");
	if (IS_ERR(pc->rst)) {
	ret = PTR_ERR(pc->rst);
	dev_err(&pdev->dev, "Reset control is not found: %d\n", ret);
	goto put_pm;
	}

	reset_control_deassert(pc->rst);

	pc->chip.dev = &pdev->dev;
	pc->chip.ops = &tegra_pwm_ops;
	pc->chip.npwm = pc->soc->num_channels;

	ret = pwmchip_add(&pc->chip);
	if (ret < 0) {
	dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret);
	reset_control_assert(pc->rst);
	goto put_pm;
	}

	pm_runtime_put(&pdev->dev);

	return 0;
	put_pm:
	pm_runtime_put_sync_suspend(&pdev->dev);
	pm_runtime_force_suspend(&pdev->dev);
	return ret;
	}

	static void tegra_pwm_remove(struct platform_device *pdev)
	{
	struct tegra_pwm_chip *pc = platform_get_drvdata(pdev);

	pwmchip_remove(&pc->chip);

	reset_control_assert(pc->rst);

	pm_runtime_force_suspend(&pdev->dev);
	}

	static int __maybe_unused tegra_pwm_runtime_suspend(struct device *dev)
	{
	struct tegra_pwm_chip *pc = dev_get_drvdata(dev);
	int err;

	clk_disable_unprepare(pc->clk);

	err = pinctrl_pm_select_sleep_state(dev);
	if (err) {
	clk_prepare_enable(pc->clk);
	return err;
	}

	return 0;
	}

	static int __maybe_unused tegra_pwm_runtime_resume(struct device *dev)
	{
	struct tegra_pwm_chip *pc = dev_get_drvdata(dev);
	int err;

	err = pinctrl_pm_select_default_state(dev);
	if (err)
	return err;

	err = clk_prepare_enable(pc->clk);
	if (err) {
	pinctrl_pm_select_sleep_state(dev);
	return err;
	}

	return 0;
	}

	static const struct tegra_pwm_soc tegra20_pwm_soc = {
	.num_channels = 4,
	.max_frequency = 48000000UL,
	};

	static const struct tegra_pwm_soc tegra186_pwm_soc = {
	.num_channels = 1,
	.max_frequency = 102000000UL,
	};

	static const struct tegra_pwm_soc tegra194_pwm_soc = {
	.num_channels = 1,
	.max_frequency = 408000000UL,
	};

	static const struct of_device_id tegra_pwm_of_match[] = {
	{ .compatible = "nvidia,tegra20-pwm", .data = &tegra20_pwm_soc },
	{ .compatible = "nvidia,tegra186-pwm", .data = &tegra186_pwm_soc },
	{ .compatible = "nvidia,tegra194-pwm", .data = &tegra194_pwm_soc },
	{ }
	};
	MODULE_DEVICE_TABLE(of, tegra_pwm_of_match);

	static const struct dev_pm_ops tegra_pwm_pm_ops = {
	SET_RUNTIME_PM_OPS(tegra_pwm_runtime_suspend, tegra_pwm_runtime_resume,
	NULL)
	SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
	pm_runtime_force_resume)
	};

	static struct platform_driver tegra_pwm_driver = {
	.driver = {
	.name = "tegra-pwm",
	.of_match_table = tegra_pwm_of_match,
	.pm = &tegra_pwm_pm_ops,
	},
	.probe = tegra_pwm_probe,
	.remove_new = tegra_pwm_remove,
	};

	module_platform_driver(tegra_pwm_driver);

	MODULE_LICENSE("GPL");
	MODULE_AUTHOR("Sandipan Patra <spatra@nvidia.com>");
	MODULE_DESCRIPTION("Tegra PWM controller driver");
	MODULE_ALIAS("platform:tegra-pwm");