/*
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* Copyright (c) 2015 Olliver Schinagl <oliver@schinagl.nl>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* This driver adds a high-resolution timer based PWM driver. Since this is a
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* bit-banged driver, accuracy will always depend on a lot of factors, such as
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* GPIO toggle speed and system load.
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*/
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#include <linux/device.h>
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#include <linux/errno.h>
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#include <linux/err.h>
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#include <linux/gpio/consumer.h>
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#include <linux/hrtimer.h>
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#include <linux/ktime.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/mod_devicetable.h>
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#include <linux/of.h>
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#include <linux/of_gpio.h>
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#include <linux/platform_device.h>
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#include <linux/property.h>
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#include <linux/pwm.h>
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struct gpio_pwm_chip {
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struct pwm_chip chip;
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struct hrtimer timer;
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struct gpio_desc *gpiod;
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unsigned int on_time;
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unsigned int off_time;
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bool pin_on;
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};
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static inline struct gpio_pwm_chip *to_gpio_pwm_chip(struct pwm_chip *c)
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{
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return container_of(c, struct gpio_pwm_chip, chip);
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}
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static void gpio_pwm_off(struct gpio_pwm_chip *pc)
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{
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enum pwm_polarity polarity = pwm_get_polarity(pc->chip.pwms);
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gpiod_set_value(pc->gpiod, polarity ? 1 : 0);
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}
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static void gpio_pwm_on(struct gpio_pwm_chip *pc)
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{
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enum pwm_polarity polarity = pwm_get_polarity(pc->chip.pwms);
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gpiod_set_value(pc->gpiod, polarity ? 0 : 1);
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}
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static enum hrtimer_restart gpio_pwm_timer(struct hrtimer *timer)
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{
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struct gpio_pwm_chip *pc = container_of(timer,
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struct gpio_pwm_chip,
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timer);
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if (!pwm_is_enabled(pc->chip.pwms)) {
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gpio_pwm_off(pc);
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pc->pin_on = false;
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return HRTIMER_NORESTART;
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}
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if (!pc->pin_on) {
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hrtimer_forward_now(&pc->timer, ns_to_ktime(pc->on_time));
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if (pc->on_time) {
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gpio_pwm_on(pc);
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pc->pin_on = true;
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}
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} else {
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hrtimer_forward_now(&pc->timer, ns_to_ktime(pc->off_time));
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if (pc->off_time) {
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gpio_pwm_off(pc);
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pc->pin_on = false;
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}
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}
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return HRTIMER_RESTART;
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}
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static int gpio_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
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int duty_ns, int period_ns)
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{
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struct gpio_pwm_chip *pc = to_gpio_pwm_chip(chip);
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pc->on_time = duty_ns;
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pc->off_time = period_ns - duty_ns;
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return 0;
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}
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static int gpio_pwm_set_polarity(struct pwm_chip *chip, struct pwm_device *pwm,
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enum pwm_polarity polarity)
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{
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return 0;
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}
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static int gpio_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
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{
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struct gpio_pwm_chip *pc = to_gpio_pwm_chip(chip);
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if (pwm_is_enabled(pc->chip.pwms))
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return -EBUSY;
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if (pc->off_time) {
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hrtimer_start(&pc->timer, ktime_set(0, 0), HRTIMER_MODE_REL);
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} else {
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if (pc->on_time)
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gpio_pwm_on(pc);
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else
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gpio_pwm_off(pc);
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}
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return 0;
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}
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static void gpio_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
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{
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struct gpio_pwm_chip *pc = to_gpio_pwm_chip(chip);
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if (!pc->off_time)
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gpio_pwm_off(pc);
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}
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static const struct pwm_ops gpio_pwm_ops = {
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.config = gpio_pwm_config,
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.set_polarity = gpio_pwm_set_polarity,
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.enable = gpio_pwm_enable,
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.disable = gpio_pwm_disable,
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.owner = THIS_MODULE,
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};
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static int gpio_pwm_probe(struct platform_device *pdev)
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{
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int ret;
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struct gpio_pwm_chip *pc;
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pc = devm_kzalloc(&pdev->dev, sizeof(*pc), GFP_KERNEL);
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if (!pc)
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return -ENOMEM;
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pc->chip.dev = &pdev->dev;
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pc->chip.ops = &gpio_pwm_ops;
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pc->chip.base = -1;
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pc->chip.npwm = 1;
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pc->chip.of_xlate = of_pwm_xlate_with_flags;
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pc->chip.of_pwm_n_cells = 3;
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pc->gpiod = devm_gpiod_get(&pdev->dev, "pwm", GPIOD_OUT_LOW);
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if (IS_ERR(pc->gpiod))
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return PTR_ERR(pc->gpiod);
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hrtimer_init(&pc->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
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pc->timer.function = &gpio_pwm_timer;
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pc->pin_on = false;
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if (!hrtimer_is_hres_active(&pc->timer))
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dev_warn(&pdev->dev, "HR timer unavailable, restricting to "
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"low resolution\n");
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ret = pwmchip_add(&pc->chip);
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if (ret < 0) {
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dev_err(&pdev->dev, "failed to add PWM chip: %d\n", ret);
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return ret;
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}
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platform_set_drvdata(pdev, pc);
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return 0;
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}
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static int gpio_pwm_remove(struct platform_device *pdev)
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{
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struct gpio_pwm_chip *pc = platform_get_drvdata(pdev);
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hrtimer_cancel(&pc->timer);
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return pwmchip_remove(&pc->chip);
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}
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#ifdef CONFIG_OF
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static const struct of_device_id gpio_pwm_of_match[] = {
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{ .compatible = "pwm-gpio", },
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{ }
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};
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MODULE_DEVICE_TABLE(of, gpio_pwm_of_match);
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#endif
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static struct platform_driver gpio_pwm_driver = {
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.probe = gpio_pwm_probe,
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.remove = gpio_pwm_remove,
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.driver = {
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.name = "pwm-gpio",
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.of_match_table = of_match_ptr(gpio_pwm_of_match),
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},
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};
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module_platform_driver(gpio_pwm_driver);
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MODULE_AUTHOR("Olliver Schinagl <oliver@schinagl.nl>");
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MODULE_DESCRIPTION("Generic GPIO bit-banged PWM driver");
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MODULE_LICENSE("GPL");
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