pwm-lpss.c 4.96 KB
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/*
 * Intel Low Power Subsystem PWM controller driver
 *
 * Copyright (C) 2014, Intel Corporation
 * Author: Mika Westerberg <mika.westerberg@linux.intel.com>
 * Author: Chew Kean Ho <kean.ho.chew@intel.com>
 * Author: Chang Rebecca Swee Fun <rebecca.swee.fun.chang@intel.com>
 * Author: Chew Chiau Ee <chiau.ee.chew@intel.com>
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 * Author: Alan Cox <alan@linux.intel.com>
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 *
 * 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.
 */

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#include <linux/delay.h>
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#include <linux/io.h>
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#include <linux/kernel.h>
#include <linux/module.h>
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#include <linux/pm_runtime.h>
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#include <linux/time.h>
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#include "pwm-lpss.h"
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#define PWM				0x00000000
#define PWM_ENABLE			BIT(31)
#define PWM_SW_UPDATE			BIT(30)
#define PWM_BASE_UNIT_SHIFT		8
#define PWM_ON_TIME_DIV_MASK		0x000000ff

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/* Size of each PWM register space if multiple */
#define PWM_SIZE			0x400

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struct pwm_lpss_chip {
	struct pwm_chip chip;
	void __iomem *regs;
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	const struct pwm_lpss_boardinfo *info;
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};

/* BayTrail */
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const struct pwm_lpss_boardinfo pwm_lpss_byt_info = {
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	.clk_rate = 25000000,
	.npwm = 1,
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	.base_unit_bits = 16,
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};
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EXPORT_SYMBOL_GPL(pwm_lpss_byt_info);
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/* Braswell */
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const struct pwm_lpss_boardinfo pwm_lpss_bsw_info = {
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	.clk_rate = 19200000,
	.npwm = 1,
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	.base_unit_bits = 16,
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};
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EXPORT_SYMBOL_GPL(pwm_lpss_bsw_info);
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/* Broxton */
const struct pwm_lpss_boardinfo pwm_lpss_bxt_info = {
	.clk_rate = 19200000,
	.npwm = 4,
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	.base_unit_bits = 22,
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};
EXPORT_SYMBOL_GPL(pwm_lpss_bxt_info);

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static inline struct pwm_lpss_chip *to_lpwm(struct pwm_chip *chip)
{
	return container_of(chip, struct pwm_lpss_chip, chip);
}

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static inline u32 pwm_lpss_read(const struct pwm_device *pwm)
{
	struct pwm_lpss_chip *lpwm = to_lpwm(pwm->chip);

	return readl(lpwm->regs + pwm->hwpwm * PWM_SIZE + PWM);
}

static inline void pwm_lpss_write(const struct pwm_device *pwm, u32 value)
{
	struct pwm_lpss_chip *lpwm = to_lpwm(pwm->chip);

	writel(value, lpwm->regs + pwm->hwpwm * PWM_SIZE + PWM);
}

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static void pwm_lpss_update(struct pwm_device *pwm)
{
	pwm_lpss_write(pwm, pwm_lpss_read(pwm) | PWM_SW_UPDATE);
	/* Give it some time to propagate */
	usleep_range(10, 50);
}

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static int pwm_lpss_config(struct pwm_chip *chip, struct pwm_device *pwm,
			   int duty_ns, int period_ns)
{
	struct pwm_lpss_chip *lpwm = to_lpwm(chip);
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	unsigned long long on_time_div;
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	unsigned long c = lpwm->info->clk_rate, base_unit_range;
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	unsigned long long base_unit, freq = NSEC_PER_SEC;
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	u32 ctrl;

	do_div(freq, period_ns);

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	/*
	 * The equation is:
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	 * base_unit = round(base_unit_range * freq / c)
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	 */
	base_unit_range = BIT(lpwm->info->base_unit_bits);
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	freq *= base_unit_range;
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	base_unit = DIV_ROUND_CLOSEST_ULL(freq, c);
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	if (duty_ns <= 0)
		duty_ns = 1;
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	on_time_div = 255ULL * duty_ns;
	do_div(on_time_div, period_ns);
	on_time_div = 255ULL - on_time_div;
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	pm_runtime_get_sync(chip->dev);

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	ctrl = pwm_lpss_read(pwm);
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	ctrl &= ~PWM_ON_TIME_DIV_MASK;
	ctrl &= ~((base_unit_range - 1) << PWM_BASE_UNIT_SHIFT);
	base_unit &= (base_unit_range - 1);
	ctrl |= (u32) base_unit << PWM_BASE_UNIT_SHIFT;
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	ctrl |= on_time_div;
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	pwm_lpss_write(pwm, ctrl);
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	/*
	 * If the PWM is already enabled we need to notify the hardware
	 * about the change by setting PWM_SW_UPDATE.
	 */
	if (pwm_is_enabled(pwm))
		pwm_lpss_update(pwm);

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	pm_runtime_put(chip->dev);

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	return 0;
}

static int pwm_lpss_enable(struct pwm_chip *chip, struct pwm_device *pwm)
{
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	pm_runtime_get_sync(chip->dev);
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	/*
	 * Hardware must first see PWM_SW_UPDATE before the PWM can be
	 * enabled.
	 */
	pwm_lpss_update(pwm);
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	pwm_lpss_write(pwm, pwm_lpss_read(pwm) | PWM_ENABLE);
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	return 0;
}

static void pwm_lpss_disable(struct pwm_chip *chip, struct pwm_device *pwm)
{
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	pwm_lpss_write(pwm, pwm_lpss_read(pwm) & ~PWM_ENABLE);
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	pm_runtime_put(chip->dev);
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}

static const struct pwm_ops pwm_lpss_ops = {
	.config = pwm_lpss_config,
	.enable = pwm_lpss_enable,
	.disable = pwm_lpss_disable,
	.owner = THIS_MODULE,
};

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struct pwm_lpss_chip *pwm_lpss_probe(struct device *dev, struct resource *r,
				     const struct pwm_lpss_boardinfo *info)
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{
	struct pwm_lpss_chip *lpwm;
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	unsigned long c;
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	int ret;

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	lpwm = devm_kzalloc(dev, sizeof(*lpwm), GFP_KERNEL);
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	if (!lpwm)
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		return ERR_PTR(-ENOMEM);
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	lpwm->regs = devm_ioremap_resource(dev, r);
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	if (IS_ERR(lpwm->regs))
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		return ERR_CAST(lpwm->regs);
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	lpwm->info = info;
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	c = lpwm->info->clk_rate;
	if (!c)
		return ERR_PTR(-EINVAL);

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	lpwm->chip.dev = dev;
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	lpwm->chip.ops = &pwm_lpss_ops;
	lpwm->chip.base = -1;
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	lpwm->chip.npwm = info->npwm;
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	ret = pwmchip_add(&lpwm->chip);
	if (ret) {
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		dev_err(dev, "failed to add PWM chip: %d\n", ret);
		return ERR_PTR(ret);
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	}

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	return lpwm;
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}
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EXPORT_SYMBOL_GPL(pwm_lpss_probe);
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int pwm_lpss_remove(struct pwm_lpss_chip *lpwm)
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{
	return pwmchip_remove(&lpwm->chip);
}
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EXPORT_SYMBOL_GPL(pwm_lpss_remove);
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MODULE_DESCRIPTION("PWM driver for Intel LPSS");
MODULE_AUTHOR("Mika Westerberg <mika.westerberg@linux.intel.com>");
MODULE_LICENSE("GPL v2");