remarkable-linux/drivers/pwm/pwm-lpss.c

/*
 * 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>
 * Author: Alan Cox <alan@linux.intel.com>
 *
 * 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.
 */

#include <linux/delay.h>
#include <linux/io.h>
#include <linux/iopoll.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/pm_runtime.h>
#include <linux/time.h>

#include "pwm-lpss.h"

#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

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

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

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

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);
}

static int pwm_lpss_wait_for_update(struct pwm_device *pwm)
{
	struct pwm_lpss_chip *lpwm = to_lpwm(pwm->chip);
	const void __iomem *addr = lpwm->regs + pwm->hwpwm * PWM_SIZE + PWM;
	const unsigned int ms = 500 * USEC_PER_MSEC;
	u32 val;
	int err;

	/*
	 * PWM Configuration register has SW_UPDATE bit that is set when a new
	 * configuration is written to the register. The bit is automatically
	 * cleared at the start of the next output cycle by the IP block.
	 *
	 * If one writes a new configuration to the register while it still has
	 * the bit enabled, PWM may freeze. That is, while one can still write
	 * to the register, it won't have an effect. Thus, we try to sleep long
	 * enough that the bit gets cleared and make sure the bit is not
	 * enabled while we update the configuration.
	 */
	err = readl_poll_timeout(addr, val, !(val & PWM_SW_UPDATE), 40, ms);
	if (err)
		dev_err(pwm->chip->dev, "PWM_SW_UPDATE was not cleared\n");

	return err;
}

static inline int pwm_lpss_is_updating(struct pwm_device *pwm)
{
	return (pwm_lpss_read(pwm) & PWM_SW_UPDATE) ? -EBUSY : 0;
}

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

	do_div(freq, period_ns);

	/*
	 * The equation is:
	 * base_unit = round(base_unit_range * freq / c)
	 */
	base_unit_range = BIT(lpwm->info->base_unit_bits) - 1;
	freq *= base_unit_range;

	base_unit = DIV_ROUND_CLOSEST_ULL(freq, c);

	on_time_div = 255ULL * duty_ns;
	do_div(on_time_div, period_ns);
	on_time_div = 255ULL - on_time_div;

	ctrl = pwm_lpss_read(pwm);
	ctrl &= ~PWM_ON_TIME_DIV_MASK;
	ctrl &= ~(base_unit_range << PWM_BASE_UNIT_SHIFT);
	base_unit &= base_unit_range;
	ctrl |= (u32) base_unit << PWM_BASE_UNIT_SHIFT;
	ctrl |= on_time_div;
	pwm_lpss_write(pwm, ctrl);
}

static inline void pwm_lpss_cond_enable(struct pwm_device *pwm, bool cond)
{
	if (cond)
		pwm_lpss_write(pwm, pwm_lpss_read(pwm) | PWM_ENABLE);
}

static int pwm_lpss_apply(struct pwm_chip *chip, struct pwm_device *pwm,
			  struct pwm_state *state)
{
	struct pwm_lpss_chip *lpwm = to_lpwm(chip);
	int ret;

	if (state->enabled) {
		if (!pwm_is_enabled(pwm)) {
			pm_runtime_get_sync(chip->dev);
			ret = pwm_lpss_is_updating(pwm);
			if (ret) {
				pm_runtime_put(chip->dev);
				return ret;
			}
			pwm_lpss_prepare(lpwm, pwm, state->duty_cycle, state->period);
			pwm_lpss_write(pwm, pwm_lpss_read(pwm) | PWM_SW_UPDATE);
			pwm_lpss_cond_enable(pwm, lpwm->info->bypass == false);
			ret = pwm_lpss_wait_for_update(pwm);
			if (ret) {
				pm_runtime_put(chip->dev);
				return ret;
			}
			pwm_lpss_cond_enable(pwm, lpwm->info->bypass == true);
		} else {
			ret = pwm_lpss_is_updating(pwm);
			if (ret)
				return ret;
			pwm_lpss_prepare(lpwm, pwm, state->duty_cycle, state->period);
			pwm_lpss_write(pwm, pwm_lpss_read(pwm) | PWM_SW_UPDATE);
			return pwm_lpss_wait_for_update(pwm);
		}
	} else if (pwm_is_enabled(pwm)) {
		pwm_lpss_write(pwm, pwm_lpss_read(pwm) & ~PWM_ENABLE);
		pm_runtime_put(chip->dev);
	}

	return 0;
}

static const struct pwm_ops pwm_lpss_ops = {
	.apply = pwm_lpss_apply,
	.owner = THIS_MODULE,
};

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

	lpwm = devm_kzalloc(dev, sizeof(*lpwm), GFP_KERNEL);
	if (!lpwm)
		return ERR_PTR(-ENOMEM);

	lpwm->regs = devm_ioremap_resource(dev, r);
	if (IS_ERR(lpwm->regs))
		return ERR_CAST(lpwm->regs);

	lpwm->info = info;

	c = lpwm->info->clk_rate;
	if (!c)
		return ERR_PTR(-EINVAL);

	lpwm->chip.dev = dev;
	lpwm->chip.ops = &pwm_lpss_ops;
	lpwm->chip.base = -1;
	lpwm->chip.npwm = info->npwm;

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

	return lpwm;
}
EXPORT_SYMBOL_GPL(pwm_lpss_probe);

int pwm_lpss_remove(struct pwm_lpss_chip *lpwm)
{
	return pwmchip_remove(&lpwm->chip);
}
EXPORT_SYMBOL_GPL(pwm_lpss_remove);

MODULE_DESCRIPTION("PWM driver for Intel LPSS");
MODULE_AUTHOR("Mika Westerberg <mika.westerberg@linux.intel.com>");
MODULE_LICENSE("GPL v2");