drivers/pwm/pwm-omap-dmtimer.c - kernel/quantenna - Git at Google

 /*
  * Copyright (c) 2015 Neil Armstrong <narmstrong@baylibre.com>
  * Copyright (c) 2014 Joachim Eastwood <manabian@gmail.com>
  * Copyright (c) 2012 NeilBrown <neilb@suse.de>
  * Heavily based on earlier code which is:
  * Copyright (c) 2010 Grant Erickson <marathon96@gmail.com>
  *
  * Also based on pwm-samsung.c
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License
  * version 2 as published by the Free Software Foundation.
  *
  * Description:
  *   This file is the core OMAP support for the generic, Linux
  *   PWM driver / controller, using the OMAP's dual-mode timers.
  */

 #include <linux/clk.h>
 #include <linux/err.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
 #include <linux/of.h>
 #include <linux/of_platform.h>
 #include <linux/platform_data/pwm_omap_dmtimer.h>
 #include <linux/platform_device.h>
 #include <linux/pm_runtime.h>
 #include <linux/pwm.h>
 #include <linux/slab.h>
 #include <linux/time.h>

 #define DM_TIMER_LOAD_MIN 0xfffffffe
 #define DM_TIMER_MAX      0xffffffff

 struct pwm_omap_dmtimer_chip {
 	struct pwm_chip chip;
 	struct mutex mutex;
 	pwm_omap_dmtimer *dm_timer;
 	struct pwm_omap_dmtimer_pdata *pdata;
 	struct platform_device *dm_timer_pdev;
 };

 static inline struct pwm_omap_dmtimer_chip *
 to_pwm_omap_dmtimer_chip(struct pwm_chip *chip)
 {
 	return container_of(chip, struct pwm_omap_dmtimer_chip, chip);
 }

 static u32 pwm_omap_dmtimer_get_clock_cycles(unsigned long clk_rate, int ns)
 {
 	return DIV_ROUND_CLOSEST_ULL((u64)clk_rate * ns, NSEC_PER_SEC);
 }

 static void pwm_omap_dmtimer_start(struct pwm_omap_dmtimer_chip *omap)
 {
 	/*
 	 * According to OMAP 4 TRM section 22.2.4.10 the counter should be
 	 * started at 0xFFFFFFFE when overflow and match is used to ensure
 	 * that the PWM line is toggled on the first event.
 	 *
 	 * Note that omap_dm_timer_enable/disable is for register access and
 	 * not the timer counter itself.
 	 */
 	omap->pdata->enable(omap->dm_timer);
 	omap->pdata->write_counter(omap->dm_timer, DM_TIMER_LOAD_MIN);
 	omap->pdata->disable(omap->dm_timer);

 	omap->pdata->start(omap->dm_timer);
 }

 static int pwm_omap_dmtimer_enable(struct pwm_chip *chip,
 				   struct pwm_device *pwm)
 {
 	struct pwm_omap_dmtimer_chip *omap = to_pwm_omap_dmtimer_chip(chip);

 	mutex_lock(&omap->mutex);
 	pwm_omap_dmtimer_start(omap);
 	mutex_unlock(&omap->mutex);

 	return 0;
 }

 static void pwm_omap_dmtimer_disable(struct pwm_chip *chip,
 				     struct pwm_device *pwm)
 {
 	struct pwm_omap_dmtimer_chip *omap = to_pwm_omap_dmtimer_chip(chip);

 	mutex_lock(&omap->mutex);
 	omap->pdata->stop(omap->dm_timer);
 	mutex_unlock(&omap->mutex);
 }

 static int pwm_omap_dmtimer_config(struct pwm_chip *chip,
 				   struct pwm_device *pwm,
 				   int duty_ns, int period_ns)
 {
 	struct pwm_omap_dmtimer_chip *omap = to_pwm_omap_dmtimer_chip(chip);
 	u32 period_cycles, duty_cycles;
 	u32 load_value, match_value;
 	struct clk *fclk;
 	unsigned long clk_rate;
 	bool timer_active;

 	dev_dbg(chip->dev, "requested duty cycle: %d ns, period: %d ns\n",
 		duty_ns, period_ns);

 	mutex_lock(&omap->mutex);
 	if (duty_ns == pwm_get_duty_cycle(pwm) &&
 	    period_ns == pwm_get_period(pwm)) {
 		/* No change - don't cause any transients. */
 		mutex_unlock(&omap->mutex);
 		return 0;
 	}

 	fclk = omap->pdata->get_fclk(omap->dm_timer);
 	if (!fclk) {
 		dev_err(chip->dev, "invalid pmtimer fclk\n");
 		goto err_einval;
 	}

 	clk_rate = clk_get_rate(fclk);
 	if (!clk_rate) {
 		dev_err(chip->dev, "invalid pmtimer fclk rate\n");
 		goto err_einval;
 	}

 	dev_dbg(chip->dev, "clk rate: %luHz\n", clk_rate);

 	/*
 	 * Calculate the appropriate load and match values based on the
 	 * specified period and duty cycle. The load value determines the
 	 * period time and the match value determines the duty time.
 	 *
 	 * The period lasts for (DM_TIMER_MAX-load_value+1) clock cycles.
 	 * Similarly, the active time lasts (match_value-load_value+1) cycles.
 	 * The non-active time is the remainder: (DM_TIMER_MAX-match_value)
 	 * clock cycles.
 	 *
 	 * NOTE: It is required that: load_value <= match_value < DM_TIMER_MAX
 	 *
 	 * References:
 	 *   OMAP4430/60/70 TRM sections 22.2.4.10 and 22.2.4.11
 	 *   AM335x Sitara TRM sections 20.1.3.5 and 20.1.3.6
 	 */
 	period_cycles = pwm_omap_dmtimer_get_clock_cycles(clk_rate, period_ns);
 	duty_cycles = pwm_omap_dmtimer_get_clock_cycles(clk_rate, duty_ns);

 	if (period_cycles < 2) {
 		dev_info(chip->dev,
 			 "period %d ns too short for clock rate %lu Hz\n",
 			 period_ns, clk_rate);
 		goto err_einval;
 	}

 	if (duty_cycles < 1) {
 		dev_dbg(chip->dev,
 			"duty cycle %d ns is too short for clock rate %lu Hz\n",
 			duty_ns, clk_rate);
 		dev_dbg(chip->dev, "using minimum of 1 clock cycle\n");
 		duty_cycles = 1;
 	} else if (duty_cycles >= period_cycles) {
 		dev_dbg(chip->dev,
 			"duty cycle %d ns is too long for period %d ns at clock rate %lu Hz\n",
 			duty_ns, period_ns, clk_rate);
 		dev_dbg(chip->dev, "using maximum of 1 clock cycle less than period\n");
 		duty_cycles = period_cycles - 1;
 	}

 	dev_dbg(chip->dev, "effective duty cycle: %lld ns, period: %lld ns\n",
 		DIV_ROUND_CLOSEST_ULL((u64)NSEC_PER_SEC * duty_cycles,
 				      clk_rate),
 		DIV_ROUND_CLOSEST_ULL((u64)NSEC_PER_SEC * period_cycles,
 				      clk_rate));

 	load_value = (DM_TIMER_MAX - period_cycles) + 1;
 	match_value = load_value + duty_cycles - 1;

 	/*
 	 * We MUST stop the associated dual-mode timer before attempting to
 	 * write its registers, but calls to omap_dm_timer_start/stop must
 	 * be balanced so check if timer is active before calling timer_stop.
 	 */
 	timer_active = pm_runtime_active(&omap->dm_timer_pdev->dev);
 	if (timer_active)
 		omap->pdata->stop(omap->dm_timer);

 	omap->pdata->set_load(omap->dm_timer, true, load_value);
 	omap->pdata->set_match(omap->dm_timer, true, match_value);

 	dev_dbg(chip->dev, "load value: %#08x (%d), match value: %#08x (%d)\n",
 		load_value, load_value,	match_value, match_value);

 	omap->pdata->set_pwm(omap->dm_timer,
 			      pwm_get_polarity(pwm) == PWM_POLARITY_INVERSED,
 			      true,
 			      PWM_OMAP_DMTIMER_TRIGGER_OVERFLOW_AND_COMPARE);

 	/* If config was called while timer was running it must be reenabled. */
 	if (timer_active)
 		pwm_omap_dmtimer_start(omap);

 	mutex_unlock(&omap->mutex);

 	return 0;

 err_einval:
 	mutex_unlock(&omap->mutex);

 	return -EINVAL;
 }

 static int pwm_omap_dmtimer_set_polarity(struct pwm_chip *chip,
 					 struct pwm_device *pwm,
 					 enum pwm_polarity polarity)
 {
 	struct pwm_omap_dmtimer_chip *omap = to_pwm_omap_dmtimer_chip(chip);

 	/*
 	 * PWM core will not call set_polarity while PWM is enabled so it's
 	 * safe to reconfigure the timer here without stopping it first.
 	 */
 	mutex_lock(&omap->mutex);
 	omap->pdata->set_pwm(omap->dm_timer,
 			      polarity == PWM_POLARITY_INVERSED,
 			      true,
 			      PWM_OMAP_DMTIMER_TRIGGER_OVERFLOW_AND_COMPARE);
 	mutex_unlock(&omap->mutex);

 	return 0;
 }

 static const struct pwm_ops pwm_omap_dmtimer_ops = {
 	.enable	= pwm_omap_dmtimer_enable,
 	.disable = pwm_omap_dmtimer_disable,
 	.config	= pwm_omap_dmtimer_config,
 	.set_polarity = pwm_omap_dmtimer_set_polarity,
 	.owner = THIS_MODULE,
 };

 static int pwm_omap_dmtimer_probe(struct platform_device *pdev)
 {
 	struct device_node *np = pdev->dev.of_node;
 	struct device_node *timer;
 	struct pwm_omap_dmtimer_chip *omap;
 	struct pwm_omap_dmtimer_pdata *pdata;
 	pwm_omap_dmtimer *dm_timer;
 	u32 prescaler;
 	int status;

 	pdata = dev_get_platdata(&pdev->dev);
 	if (!pdata) {
 		dev_err(&pdev->dev, "Missing dmtimer platform data\n");
 		return -EINVAL;
 	}

 	if (!pdata->request_by_node ||
 	    !pdata->free ||
 	    !pdata->enable ||
 	    !pdata->disable ||
 	    !pdata->get_fclk ||
 	    !pdata->start ||
 	    !pdata->stop ||
 	    !pdata->set_load ||
 	    !pdata->set_match ||
 	    !pdata->set_pwm ||
 	    !pdata->set_prescaler ||
 	    !pdata->write_counter) {
 		dev_err(&pdev->dev, "Incomplete dmtimer pdata structure\n");
 		return -EINVAL;
 	}

 	timer = of_parse_phandle(np, "ti,timers", 0);
 	if (!timer)
 		return -ENODEV;

 	if (!of_get_property(timer, "ti,timer-pwm", NULL)) {
 		dev_err(&pdev->dev, "Missing ti,timer-pwm capability\n");
 		return -ENODEV;
 	}

 	dm_timer = pdata->request_by_node(timer);
 	if (!dm_timer)
 		return -EPROBE_DEFER;

 	omap = devm_kzalloc(&pdev->dev, sizeof(*omap), GFP_KERNEL);
 	if (!omap) {
 		pdata->free(dm_timer);
 		return -ENOMEM;
 	}

 	omap->pdata = pdata;
 	omap->dm_timer = dm_timer;

 	omap->dm_timer_pdev = of_find_device_by_node(timer);
 	if (!omap->dm_timer_pdev) {
 		dev_err(&pdev->dev, "Unable to find timer pdev\n");
 		omap->pdata->free(dm_timer);
 		return -EINVAL;
 	}

 	/*
 	 * Ensure that the timer is stopped before we allow PWM core to call
 	 * pwm_enable.
 	 */
 	if (pm_runtime_active(&omap->dm_timer_pdev->dev))
 		omap->pdata->stop(omap->dm_timer);

 	/* setup dmtimer prescaler */
 	if (!of_property_read_u32(pdev->dev.of_node, "ti,prescaler",
 				&prescaler))
 		omap->pdata->set_prescaler(omap->dm_timer, prescaler);

 	omap->chip.dev = &pdev->dev;
 	omap->chip.ops = &pwm_omap_dmtimer_ops;
 	omap->chip.base = -1;
 	omap->chip.npwm = 1;
 	omap->chip.of_xlate = of_pwm_xlate_with_flags;
 	omap->chip.of_pwm_n_cells = 3;

 	mutex_init(&omap->mutex);

 	status = pwmchip_add(&omap->chip);
 	if (status < 0) {
 		dev_err(&pdev->dev, "failed to register PWM\n");
 		omap->pdata->free(omap->dm_timer);
 		return status;
 	}

 	platform_set_drvdata(pdev, omap);

 	return 0;
 }

 static int pwm_omap_dmtimer_remove(struct platform_device *pdev)
 {
 	struct pwm_omap_dmtimer_chip *omap = platform_get_drvdata(pdev);

 	if (pm_runtime_active(&omap->dm_timer_pdev->dev))
 		omap->pdata->stop(omap->dm_timer);

 	omap->pdata->free(omap->dm_timer);

 	mutex_destroy(&omap->mutex);

 	return pwmchip_remove(&omap->chip);
 }

 static const struct of_device_id pwm_omap_dmtimer_of_match[] = {
 	{.compatible = "ti,omap-dmtimer-pwm"},
 	{}
 };
 MODULE_DEVICE_TABLE(of, pwm_omap_dmtimer_of_match);

 static struct platform_driver pwm_omap_dmtimer_driver = {
 	.driver = {
 		.name = "omap-dmtimer-pwm",
 		.of_match_table = of_match_ptr(pwm_omap_dmtimer_of_match),
 	},
 	.probe = pwm_omap_dmtimer_probe,
 	.remove	= pwm_omap_dmtimer_remove,
 };
 module_platform_driver(pwm_omap_dmtimer_driver);

 MODULE_AUTHOR("Grant Erickson <marathon96@gmail.com>");
 MODULE_AUTHOR("NeilBrown <neilb@suse.de>");
 MODULE_AUTHOR("Neil Armstrong <narmstrong@baylibre.com>");
 MODULE_LICENSE("GPL v2");
 MODULE_DESCRIPTION("OMAP PWM Driver using Dual-mode Timers");
	/*
	* Copyright (c) 2015 Neil Armstrong <narmstrong@baylibre.com>
	* Copyright (c) 2014 Joachim Eastwood <manabian@gmail.com>
	* Copyright (c) 2012 NeilBrown <neilb@suse.de>
	* Heavily based on earlier code which is:
	* Copyright (c) 2010 Grant Erickson <marathon96@gmail.com>
	*
	* Also based on pwm-samsung.c
	*
	* This program is free software; you can redistribute it and/or
	* modify it under the terms of the GNU General Public License
	* version 2 as published by the Free Software Foundation.
	*
	* Description:
	* This file is the core OMAP support for the generic, Linux
	* PWM driver / controller, using the OMAP's dual-mode timers.
	*/

	#include <linux/clk.h>
	#include <linux/err.h>
	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/mutex.h>
	#include <linux/of.h>
	#include <linux/of_platform.h>
	#include <linux/platform_data/pwm_omap_dmtimer.h>
	#include <linux/platform_device.h>
	#include <linux/pm_runtime.h>
	#include <linux/pwm.h>
	#include <linux/slab.h>
	#include <linux/time.h>

	#define DM_TIMER_LOAD_MIN 0xfffffffe
	#define DM_TIMER_MAX 0xffffffff

	struct pwm_omap_dmtimer_chip {
	struct pwm_chip chip;
	struct mutex mutex;
	pwm_omap_dmtimer *dm_timer;
	struct pwm_omap_dmtimer_pdata *pdata;
	struct platform_device *dm_timer_pdev;
	};

	static inline struct pwm_omap_dmtimer_chip *
	to_pwm_omap_dmtimer_chip(struct pwm_chip *chip)
	{
	return container_of(chip, struct pwm_omap_dmtimer_chip, chip);
	}

	static u32 pwm_omap_dmtimer_get_clock_cycles(unsigned long clk_rate, int ns)
	{
	return DIV_ROUND_CLOSEST_ULL((u64)clk_rate * ns, NSEC_PER_SEC);
	}

	static void pwm_omap_dmtimer_start(struct pwm_omap_dmtimer_chip *omap)
	{
	/*
	* According to OMAP 4 TRM section 22.2.4.10 the counter should be
	* started at 0xFFFFFFFE when overflow and match is used to ensure
	* that the PWM line is toggled on the first event.
	*
	* Note that omap_dm_timer_enable/disable is for register access and
	* not the timer counter itself.
	*/
	omap->pdata->enable(omap->dm_timer);
	omap->pdata->write_counter(omap->dm_timer, DM_TIMER_LOAD_MIN);
	omap->pdata->disable(omap->dm_timer);

	omap->pdata->start(omap->dm_timer);
	}

	static int pwm_omap_dmtimer_enable(struct pwm_chip *chip,
	struct pwm_device *pwm)
	{
	struct pwm_omap_dmtimer_chip *omap = to_pwm_omap_dmtimer_chip(chip);

	mutex_lock(&omap->mutex);
	pwm_omap_dmtimer_start(omap);
	mutex_unlock(&omap->mutex);

	return 0;
	}

	static void pwm_omap_dmtimer_disable(struct pwm_chip *chip,
	struct pwm_device *pwm)
	{
	struct pwm_omap_dmtimer_chip *omap = to_pwm_omap_dmtimer_chip(chip);

	mutex_lock(&omap->mutex);
	omap->pdata->stop(omap->dm_timer);
	mutex_unlock(&omap->mutex);
	}

	static int pwm_omap_dmtimer_config(struct pwm_chip *chip,
	struct pwm_device *pwm,
	int duty_ns, int period_ns)
	{
	struct pwm_omap_dmtimer_chip *omap = to_pwm_omap_dmtimer_chip(chip);
	u32 period_cycles, duty_cycles;
	u32 load_value, match_value;
	struct clk *fclk;
	unsigned long clk_rate;
	bool timer_active;

	dev_dbg(chip->dev, "requested duty cycle: %d ns, period: %d ns\n",
	duty_ns, period_ns);

	mutex_lock(&omap->mutex);
	if (duty_ns == pwm_get_duty_cycle(pwm) &&
	period_ns == pwm_get_period(pwm)) {
	/* No change - don't cause any transients. */
	mutex_unlock(&omap->mutex);
	return 0;
	}

	fclk = omap->pdata->get_fclk(omap->dm_timer);
	if (!fclk) {
	dev_err(chip->dev, "invalid pmtimer fclk\n");
	goto err_einval;
	}

	clk_rate = clk_get_rate(fclk);
	if (!clk_rate) {
	dev_err(chip->dev, "invalid pmtimer fclk rate\n");
	goto err_einval;
	}

	dev_dbg(chip->dev, "clk rate: %luHz\n", clk_rate);

	/*
	* Calculate the appropriate load and match values based on the
	* specified period and duty cycle. The load value determines the
	* period time and the match value determines the duty time.
	*
	* The period lasts for (DM_TIMER_MAX-load_value+1) clock cycles.
	* Similarly, the active time lasts (match_value-load_value+1) cycles.
	* The non-active time is the remainder: (DM_TIMER_MAX-match_value)
	* clock cycles.
	*
	* NOTE: It is required that: load_value <= match_value < DM_TIMER_MAX
	*
	* References:
	* OMAP4430/60/70 TRM sections 22.2.4.10 and 22.2.4.11
	* AM335x Sitara TRM sections 20.1.3.5 and 20.1.3.6
	*/
	period_cycles = pwm_omap_dmtimer_get_clock_cycles(clk_rate, period_ns);
	duty_cycles = pwm_omap_dmtimer_get_clock_cycles(clk_rate, duty_ns);

	if (period_cycles < 2) {
	dev_info(chip->dev,
	"period %d ns too short for clock rate %lu Hz\n",
	period_ns, clk_rate);
	goto err_einval;
	}

	if (duty_cycles < 1) {
	dev_dbg(chip->dev,
	"duty cycle %d ns is too short for clock rate %lu Hz\n",
	duty_ns, clk_rate);
	dev_dbg(chip->dev, "using minimum of 1 clock cycle\n");
	duty_cycles = 1;
	} else if (duty_cycles >= period_cycles) {
	dev_dbg(chip->dev,
	"duty cycle %d ns is too long for period %d ns at clock rate %lu Hz\n",
	duty_ns, period_ns, clk_rate);
	dev_dbg(chip->dev, "using maximum of 1 clock cycle less than period\n");
	duty_cycles = period_cycles - 1;
	}

	dev_dbg(chip->dev, "effective duty cycle: %lld ns, period: %lld ns\n",
	DIV_ROUND_CLOSEST_ULL((u64)NSEC_PER_SEC * duty_cycles,
	clk_rate),
	DIV_ROUND_CLOSEST_ULL((u64)NSEC_PER_SEC * period_cycles,
	clk_rate));

	load_value = (DM_TIMER_MAX - period_cycles) + 1;
	match_value = load_value + duty_cycles - 1;

	/*
	* We MUST stop the associated dual-mode timer before attempting to
	* write its registers, but calls to omap_dm_timer_start/stop must
	* be balanced so check if timer is active before calling timer_stop.
	*/
	timer_active = pm_runtime_active(&omap->dm_timer_pdev->dev);
	if (timer_active)
	omap->pdata->stop(omap->dm_timer);

	omap->pdata->set_load(omap->dm_timer, true, load_value);
	omap->pdata->set_match(omap->dm_timer, true, match_value);

	dev_dbg(chip->dev, "load value: %#08x (%d), match value: %#08x (%d)\n",
	load_value, load_value, match_value, match_value);

	omap->pdata->set_pwm(omap->dm_timer,
	pwm_get_polarity(pwm) == PWM_POLARITY_INVERSED,
	true,
	PWM_OMAP_DMTIMER_TRIGGER_OVERFLOW_AND_COMPARE);

	/* If config was called while timer was running it must be reenabled. */
	if (timer_active)
	pwm_omap_dmtimer_start(omap);

	mutex_unlock(&omap->mutex);

	return 0;

	err_einval:
	mutex_unlock(&omap->mutex);

	return -EINVAL;
	}

	static int pwm_omap_dmtimer_set_polarity(struct pwm_chip *chip,
	struct pwm_device *pwm,
	enum pwm_polarity polarity)
	{
	struct pwm_omap_dmtimer_chip *omap = to_pwm_omap_dmtimer_chip(chip);

	/*
	* PWM core will not call set_polarity while PWM is enabled so it's
	* safe to reconfigure the timer here without stopping it first.
	*/
	mutex_lock(&omap->mutex);
	omap->pdata->set_pwm(omap->dm_timer,
	polarity == PWM_POLARITY_INVERSED,
	true,
	PWM_OMAP_DMTIMER_TRIGGER_OVERFLOW_AND_COMPARE);
	mutex_unlock(&omap->mutex);

	return 0;
	}

	static const struct pwm_ops pwm_omap_dmtimer_ops = {
	.enable = pwm_omap_dmtimer_enable,
	.disable = pwm_omap_dmtimer_disable,
	.config = pwm_omap_dmtimer_config,
	.set_polarity = pwm_omap_dmtimer_set_polarity,
	.owner = THIS_MODULE,
	};

	static int pwm_omap_dmtimer_probe(struct platform_device *pdev)
	{
	struct device_node *np = pdev->dev.of_node;
	struct device_node *timer;
	struct pwm_omap_dmtimer_chip *omap;
	struct pwm_omap_dmtimer_pdata *pdata;
	pwm_omap_dmtimer *dm_timer;
	u32 prescaler;
	int status;

	pdata = dev_get_platdata(&pdev->dev);
	if (!pdata) {
	dev_err(&pdev->dev, "Missing dmtimer platform data\n");
	return -EINVAL;
	}

	if (!pdata->request_by_node \|\|
	!pdata->free \|\|
	!pdata->enable \|\|
	!pdata->disable \|\|
	!pdata->get_fclk \|\|
	!pdata->start \|\|
	!pdata->stop \|\|
	!pdata->set_load \|\|
	!pdata->set_match \|\|
	!pdata->set_pwm \|\|
	!pdata->set_prescaler \|\|
	!pdata->write_counter) {
	dev_err(&pdev->dev, "Incomplete dmtimer pdata structure\n");
	return -EINVAL;
	}

	timer = of_parse_phandle(np, "ti,timers", 0);
	if (!timer)
	return -ENODEV;

	if (!of_get_property(timer, "ti,timer-pwm", NULL)) {
	dev_err(&pdev->dev, "Missing ti,timer-pwm capability\n");
	return -ENODEV;
	}

	dm_timer = pdata->request_by_node(timer);
	if (!dm_timer)
	return -EPROBE_DEFER;

	omap = devm_kzalloc(&pdev->dev, sizeof(*omap), GFP_KERNEL);
	if (!omap) {
	pdata->free(dm_timer);
	return -ENOMEM;
	}

	omap->pdata = pdata;
	omap->dm_timer = dm_timer;

	omap->dm_timer_pdev = of_find_device_by_node(timer);
	if (!omap->dm_timer_pdev) {
	dev_err(&pdev->dev, "Unable to find timer pdev\n");
	omap->pdata->free(dm_timer);
	return -EINVAL;
	}

	/*
	* Ensure that the timer is stopped before we allow PWM core to call
	* pwm_enable.
	*/
	if (pm_runtime_active(&omap->dm_timer_pdev->dev))
	omap->pdata->stop(omap->dm_timer);

	/* setup dmtimer prescaler */
	if (!of_property_read_u32(pdev->dev.of_node, "ti,prescaler",
	&prescaler))
	omap->pdata->set_prescaler(omap->dm_timer, prescaler);

	omap->chip.dev = &pdev->dev;
	omap->chip.ops = &pwm_omap_dmtimer_ops;
	omap->chip.base = -1;
	omap->chip.npwm = 1;
	omap->chip.of_xlate = of_pwm_xlate_with_flags;
	omap->chip.of_pwm_n_cells = 3;

	mutex_init(&omap->mutex);

	status = pwmchip_add(&omap->chip);
	if (status < 0) {
	dev_err(&pdev->dev, "failed to register PWM\n");
	omap->pdata->free(omap->dm_timer);
	return status;
	}

	platform_set_drvdata(pdev, omap);

	return 0;
	}

	static int pwm_omap_dmtimer_remove(struct platform_device *pdev)
	{
	struct pwm_omap_dmtimer_chip *omap = platform_get_drvdata(pdev);

	if (pm_runtime_active(&omap->dm_timer_pdev->dev))
	omap->pdata->stop(omap->dm_timer);

	omap->pdata->free(omap->dm_timer);

	mutex_destroy(&omap->mutex);

	return pwmchip_remove(&omap->chip);
	}

	static const struct of_device_id pwm_omap_dmtimer_of_match[] = {
	{.compatible = "ti,omap-dmtimer-pwm"},
	{}
	};
	MODULE_DEVICE_TABLE(of, pwm_omap_dmtimer_of_match);

	static struct platform_driver pwm_omap_dmtimer_driver = {
	.driver = {
	.name = "omap-dmtimer-pwm",
	.of_match_table = of_match_ptr(pwm_omap_dmtimer_of_match),
	},
	.probe = pwm_omap_dmtimer_probe,
	.remove = pwm_omap_dmtimer_remove,
	};
	module_platform_driver(pwm_omap_dmtimer_driver);

	MODULE_AUTHOR("Grant Erickson <marathon96@gmail.com>");
	MODULE_AUTHOR("NeilBrown <neilb@suse.de>");
	MODULE_AUTHOR("Neil Armstrong <narmstrong@baylibre.com>");
	MODULE_LICENSE("GPL v2");
	MODULE_DESCRIPTION("OMAP PWM Driver using Dual-mode Timers");