text: // SPDX-License-Identifier: GPL-2.0-or-later
  /*
   * pps-gpio.c -- PPS client driver using GPIO
   *
   * Copyright (C) 2010 Ricardo Martins <rasm@fe.up.pt>
   * Copyright (C) 2011 James Nuss <jamesnuss@nanometrics.ca>
   */
  
  #define PPS_GPIO_NAME "pps-gpio"
  #define pr_fmt(fmt) PPS_GPIO_NAME ": " fmt
  
  #include <linux/init.h>
  #include <linux/kernel.h>
  #include <linux/interrupt.h>
  #include <linux/mod_devicetable.h>
  #include <linux/module.h>
  #include <linux/platform_device.h>
  #include <linux/slab.h>
  #include <linux/pps_kernel.h>
  #include <linux/gpio/consumer.h>
  #include <linux/list.h>
  #include <linux/property.h>
  #include <linux/timer.h>
  #include <linux/jiffies.h>
  
  /* Info for each registered platform device */
  struct pps_gpio_device_data {
  	int irq;			/* IRQ used as PPS source */
  	struct pps_device *pps;		/* PPS source device */
  	struct pps_source_info info;	/* PPS source information */
  	struct gpio_desc *gpio_pin;	/* GPIO port descriptors */
  	struct gpio_desc *echo_pin;
  	struct timer_list echo_timer;	/* timer to reset echo active state */
  	bool assert_falling_edge;
  	bool capture_clear;
  	unsigned int echo_active_ms;	/* PPS echo active duration */
  	unsigned long echo_timeout;	/* timer timeout value in jiffies */
  };
  
  /*
   * Report the PPS event
   */
  
  static irqreturn_t pps_gpio_irq_handler(int irq, void *data)
  {
  	const struct pps_gpio_device_data *info;
  	struct pps_event_time ts;
  	int rising_edge;
  
  	/* Get the time stamp first */
  	pps_get_ts(&ts);
  
  	info = data;
  
  	rising_edge = gpiod_get_value(info->gpio_pin);
  	if ((rising_edge && !info->assert_falling_edge) ||
  			(!rising_edge && info->assert_falling_edge))
  		pps_event(info->pps, &ts, PPS_CAPTUREASSERT, data);
  	else if (info->capture_clear &&
  			((rising_edge && info->assert_falling_edge) ||
  			(!rising_edge && !info->assert_falling_edge)))
  		pps_event(info->pps, &ts, PPS_CAPTURECLEAR, data);
  
  	return IRQ_HANDLED;
  }
  
  /* This function will only be called when an ECHO GPIO is defined */
  static void pps_gpio_echo(struct pps_device *pps, int event, void *data)
  {
  	/* add_timer() needs to write into info->echo_timer */
  	struct pps_gpio_device_data *info = data;
  
  	switch (event) {
  	case PPS_CAPTUREASSERT:
  		if (pps->params.mode & PPS_ECHOASSERT)
  			gpiod_set_value(info->echo_pin, 1);
  		break;
  
  	case PPS_CAPTURECLEAR:
  		if (pps->params.mode & PPS_ECHOCLEAR)
  			gpiod_set_value(info->echo_pin, 1);
  		break;
  	}
  
  	/* fire the timer */
  	if (info->pps->params.mode & (PPS_ECHOASSERT | PPS_ECHOCLEAR)) {
  		info->echo_timer.expires = jiffies + info->echo_timeout;
  		add_timer(&info->echo_timer);
  	}
  }
  
  /* Timer callback to reset the echo pin to the inactive state */
  static void pps_gpio_echo_timer_callback(struct timer_list *t)
  {
  	const struct pps_gpio_device_data *info;
  
  	info = from_timer(info, t, echo_timer);
  
  	gpiod_set_value(info->echo_pin, 0);
  }
  
  static int pps_gpio_setup(struct device *dev)
  {
  	struct pps_gpio_device_data *data = dev_get_drvdata(dev);
  	int ret;
  	u32 value;
  
  	data->gpio_pin = devm_gpiod_get(dev, NULL, GPIOD_IN);
  	if (IS_ERR(data->gpio_pin))
  		return dev_err_probe(dev, PTR_ERR(data->gpio_pin),
  				     "failed to request PPS GPIO\n");
  
  	data->assert_falling_edge =
  		device_property_read_bool(dev, "assert-falling-edge");
  
  	data->echo_pin = devm_gpiod_get_optional(dev, "echo", GPIOD_OUT_LOW);
  	if (IS_ERR(data->echo_pin))
  		return dev_err_probe(dev, PTR_ERR(data->echo_pin),
  				     "failed to request ECHO GPIO\n");
  
  	if (!data->echo_pin)
  		return 0;
  
  	ret = device_property_read_u32(dev, "echo-active-ms", &value);
  	if (ret) {
  		dev_err(dev, "failed to get echo-active-ms from FW\n");
  		return ret;
  	}
  
  	/* sanity check on echo_active_ms */
  	if (!value || value > 999) {
  		dev_err(dev, "echo-active-ms: %u - bad value from FW\n", value);
  		return -EINVAL;
  	}
  
  	data->echo_active_ms = value;
  
  	return 0;
  }
  
  static unsigned long
  get_irqf_trigger_flags(const struct pps_gpio_device_data *data)
  {
  	unsigned long flags = data->assert_falling_edge ?
  		IRQF_TRIGGER_FALLING : IRQF_TRIGGER_RISING;
  
  	if (data->capture_clear) {
  		flags |= ((flags & IRQF_TRIGGER_RISING) ?
  				IRQF_TRIGGER_FALLING : IRQF_TRIGGER_RISING);
  	}
  
  	return flags;
  }
  
  static int pps_gpio_probe(struct platform_device *pdev)
  {
  	struct pps_gpio_device_data *data;
  	struct device *dev = &pdev->dev;
  	int ret;
  	int pps_default_params;
  
  	/* allocate space for device info */
  	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
  	if (!data)
  		return -ENOMEM;
  
  	dev_set_drvdata(dev, data);
  
  	/* GPIO setup */
  	ret = pps_gpio_setup(dev);
  	if (ret)
  		return -EINVAL;
  
  	/* IRQ setup */
  	ret = gpiod_to_irq(data->gpio_pin);
  	if (ret < 0) {
  		dev_err(dev, "failed to map GPIO to IRQ: %d\n", ret);
  		return -EINVAL;
  	}
  	data->irq = ret;
  
  	/* initialize PPS specific parts of the bookkeeping data structure. */
  	data->info.mode = PPS_CAPTUREASSERT | PPS_OFFSETASSERT |
  		PPS_ECHOASSERT | PPS_CANWAIT | PPS_TSFMT_TSPEC;
  	if (data->capture_clear)
  		data->info.mode |= PPS_CAPTURECLEAR | PPS_OFFSETCLEAR |
  			PPS_ECHOCLEAR;
  	data->info.owner = THIS_MODULE;
  	snprintf(data->info.name, PPS_MAX_NAME_LEN - 1, "%s.%d",
  		 pdev->name, pdev->id);
  	if (data->echo_pin) {
  		data->info.echo = pps_gpio_echo;
  		data->echo_timeout = msecs_to_jiffies(data->echo_active_ms);
  		timer_setup(&data->echo_timer, pps_gpio_echo_timer_callback, 0);
  	}
  
  	/* register PPS source */
  	pps_default_params = PPS_CAPTUREASSERT | PPS_OFFSETASSERT;
  	if (data->capture_clear)
  		pps_default_params |= PPS_CAPTURECLEAR | PPS_OFFSETCLEAR;
  	data->pps = pps_register_source(&data->info, pps_default_params);
  	if (IS_ERR(data->pps)) {
  		dev_err(dev, "failed to register IRQ %d as PPS source\n",
  			data->irq);
  		return PTR_ERR(data->pps);
  	}
  
  	/* register IRQ interrupt handler */
  	ret = devm_request_irq(dev, data->irq, pps_gpio_irq_handler,
  			get_irqf_trigger_flags(data), data->info.name, data);
  	if (ret) {
  		pps_unregister_source(data->pps);
  		dev_err(dev, "failed to acquire IRQ %d\n", data->irq);
  		return -EINVAL;
  	}
  
  	dev_info(data->pps->dev, "Registered IRQ %d as PPS source\n",
  		 data->irq);
  
  	return 0;
  }
  
  static int pps_gpio_remove(struct platform_device *pdev)
  {
  	struct pps_gpio_device_data *data = platform_get_drvdata(pdev);
  
  	pps_unregister_source(data->pps);
  	del_timer_sync(&data->echo_timer);
  	/* reset echo pin in any case */
  	gpiod_set_value(data->echo_pin, 0);
  	dev_info(&pdev->dev, "removed IRQ %d as PPS source\n", data->irq);
  	return 0;
  }
  
  static const struct of_device_id pps_gpio_dt_ids[] = {
  	{ .compatible = "pps-gpio", },
  	{ /* sentinel */ }
  };
  MODULE_DEVICE_TABLE(of, pps_gpio_dt_ids);
  
  static struct platform_driver pps_gpio_driver = {
  	.probe		= pps_gpio_probe,
  	.remove		= pps_gpio_remove,
  	.driver		= {
  		.name	= PPS_GPIO_NAME,
  		.of_match_table	= pps_gpio_dt_ids,
  	},
  };
  
  module_platform_driver(pps_gpio_driver);
  MODULE_AUTHOR("Ricardo Martins <rasm@fe.up.pt>");
  MODULE_AUTHOR("James Nuss <jamesnuss@nanometrics.ca>");
  MODULE_DESCRIPTION("Use GPIO pin as PPS source");
  MODULE_LICENSE("GPL");
  MODULE_VERSION("1.2.0");
  