1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * pps-gpio.c -- PPS client driver using GPIO
4 *
5 * Copyright (C) 2010 Ricardo Martins <rasm@fe.up.pt>
6 * Copyright (C) 2011 James Nuss <jamesnuss@nanometrics.ca>
7 */
8
9#define PPS_GPIO_NAME "pps-gpio"
10#define pr_fmt(fmt) PPS_GPIO_NAME ": " fmt
11
12#include <linux/init.h>
13#include <linux/kernel.h>
14#include <linux/interrupt.h>
15#include <linux/mod_devicetable.h>
16#include <linux/module.h>
17#include <linux/platform_device.h>
18#include <linux/slab.h>
19#include <linux/pps_kernel.h>
20#include <linux/gpio/consumer.h>
21#include <linux/list.h>
22#include <linux/property.h>
23#include <linux/timer.h>
24#include <linux/jiffies.h>
25
26/* Info for each registered platform device */
27struct pps_gpio_device_data {
28	int irq;			/* IRQ used as PPS source */
29	struct pps_device *pps;		/* PPS source device */
30	struct pps_source_info info;	/* PPS source information */
31	struct gpio_desc *gpio_pin;	/* GPIO port descriptors */
32	struct gpio_desc *echo_pin;
33	struct timer_list echo_timer;	/* timer to reset echo active state */
34	bool assert_falling_edge;
35	bool capture_clear;
36	unsigned int echo_active_ms;	/* PPS echo active duration */
37	unsigned long echo_timeout;	/* timer timeout value in jiffies */
38};
39
40/*
41 * Report the PPS event
42 */
43
44static irqreturn_t pps_gpio_irq_handler(int irq, void *data)
45{
46	const struct pps_gpio_device_data *info;
47	struct pps_event_time ts;
48	int rising_edge;
49
50	/* Get the time stamp first */
51	pps_get_ts(&ts);
52
53	info = data;
54
55	rising_edge = gpiod_get_value(info->gpio_pin);
56	if ((rising_edge && !info->assert_falling_edge) ||
57			(!rising_edge && info->assert_falling_edge))
58		pps_event(info->pps, &ts, PPS_CAPTUREASSERT, data);
59	else if (info->capture_clear &&
60			((rising_edge && info->assert_falling_edge) ||
61			(!rising_edge && !info->assert_falling_edge)))
62		pps_event(info->pps, &ts, PPS_CAPTURECLEAR, data);
63
64	return IRQ_HANDLED;
65}
66
67/* This function will only be called when an ECHO GPIO is defined */
68static void pps_gpio_echo(struct pps_device *pps, int event, void *data)
69{
70	/* add_timer() needs to write into info->echo_timer */
71	struct pps_gpio_device_data *info = data;
72
73	switch (event) {
74	case PPS_CAPTUREASSERT:
75		if (pps->params.mode & PPS_ECHOASSERT)
76			gpiod_set_value(info->echo_pin, 1);
77		break;
78
79	case PPS_CAPTURECLEAR:
80		if (pps->params.mode & PPS_ECHOCLEAR)
81			gpiod_set_value(info->echo_pin, 1);
82		break;
83	}
84
85	/* fire the timer */
86	if (info->pps->params.mode & (PPS_ECHOASSERT | PPS_ECHOCLEAR)) {
87		info->echo_timer.expires = jiffies + info->echo_timeout;
88		add_timer(&info->echo_timer);
89	}
90}
91
92/* Timer callback to reset the echo pin to the inactive state */
93static void pps_gpio_echo_timer_callback(struct timer_list *t)
94{
95	const struct pps_gpio_device_data *info;
96
97	info = from_timer(info, t, echo_timer);
98
99	gpiod_set_value(info->echo_pin, 0);
100}
101
102static int pps_gpio_setup(struct device *dev)
103{
104	struct pps_gpio_device_data *data = dev_get_drvdata(dev);
105	int ret;
106	u32 value;
107
108	data->gpio_pin = devm_gpiod_get(dev, NULL, GPIOD_IN);
109	if (IS_ERR(data->gpio_pin))
110		return dev_err_probe(dev, PTR_ERR(data->gpio_pin),
111				     "failed to request PPS GPIO\n");
112
113	data->assert_falling_edge =
114		device_property_read_bool(dev, "assert-falling-edge");
115
116	data->echo_pin = devm_gpiod_get_optional(dev, "echo", GPIOD_OUT_LOW);
117	if (IS_ERR(data->echo_pin))
118		return dev_err_probe(dev, PTR_ERR(data->echo_pin),
119				     "failed to request ECHO GPIO\n");
120
121	if (!data->echo_pin)
122		return 0;
123
124	ret = device_property_read_u32(dev, "echo-active-ms", &value);
125	if (ret) {
126		dev_err(dev, "failed to get echo-active-ms from FW\n");
127		return ret;
128	}
129
130	/* sanity check on echo_active_ms */
131	if (!value || value > 999) {
132		dev_err(dev, "echo-active-ms: %u - bad value from FW\n", value);
133		return -EINVAL;
134	}
135
136	data->echo_active_ms = value;
137
138	return 0;
139}
140
141static unsigned long
142get_irqf_trigger_flags(const struct pps_gpio_device_data *data)
143{
144	unsigned long flags = data->assert_falling_edge ?
145		IRQF_TRIGGER_FALLING : IRQF_TRIGGER_RISING;
146
147	if (data->capture_clear) {
148		flags |= ((flags & IRQF_TRIGGER_RISING) ?
149				IRQF_TRIGGER_FALLING : IRQF_TRIGGER_RISING);
150	}
151
152	return flags;
153}
154
155static int pps_gpio_probe(struct platform_device *pdev)
156{
157	struct pps_gpio_device_data *data;
158	struct device *dev = &pdev->dev;
159	int ret;
160	int pps_default_params;
161
162	/* allocate space for device info */
163	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
164	if (!data)
165		return -ENOMEM;
166
167	dev_set_drvdata(dev, data);
168
169	/* GPIO setup */
170	ret = pps_gpio_setup(dev);
171	if (ret)
172		return ret;
173
174	/* IRQ setup */
175	ret = gpiod_to_irq(data->gpio_pin);
176	if (ret < 0) {
177		dev_err(dev, "failed to map GPIO to IRQ: %d\n", ret);
178		return -EINVAL;
179	}
180	data->irq = ret;
181
182	/* initialize PPS specific parts of the bookkeeping data structure. */
183	data->info.mode = PPS_CAPTUREASSERT | PPS_OFFSETASSERT |
184		PPS_ECHOASSERT | PPS_CANWAIT | PPS_TSFMT_TSPEC;
185	if (data->capture_clear)
186		data->info.mode |= PPS_CAPTURECLEAR | PPS_OFFSETCLEAR |
187			PPS_ECHOCLEAR;
188	data->info.owner = THIS_MODULE;
189	snprintf(data->info.name, PPS_MAX_NAME_LEN - 1, "%s.%d",
190		 pdev->name, pdev->id);
191	if (data->echo_pin) {
192		data->info.echo = pps_gpio_echo;
193		data->echo_timeout = msecs_to_jiffies(data->echo_active_ms);
194		timer_setup(&data->echo_timer, pps_gpio_echo_timer_callback, 0);
195	}
196
197	/* register PPS source */
198	pps_default_params = PPS_CAPTUREASSERT | PPS_OFFSETASSERT;
199	if (data->capture_clear)
200		pps_default_params |= PPS_CAPTURECLEAR | PPS_OFFSETCLEAR;
201	data->pps = pps_register_source(&data->info, pps_default_params);
202	if (IS_ERR(data->pps)) {
203		dev_err(dev, "failed to register IRQ %d as PPS source\n",
204			data->irq);
205		return PTR_ERR(data->pps);
206	}
207
208	/* register IRQ interrupt handler */
209	ret = devm_request_irq(dev, data->irq, pps_gpio_irq_handler,
210			get_irqf_trigger_flags(data), data->info.name, data);
211	if (ret) {
212		pps_unregister_source(data->pps);
213		dev_err(dev, "failed to acquire IRQ %d\n", data->irq);
214		return -EINVAL;
215	}
216
217	dev_info(data->pps->dev, "Registered IRQ %d as PPS source\n",
218		 data->irq);
219
220	return 0;
221}
222
223static int pps_gpio_remove(struct platform_device *pdev)
224{
225	struct pps_gpio_device_data *data = platform_get_drvdata(pdev);
226
227	pps_unregister_source(data->pps);
228	del_timer_sync(&data->echo_timer);
229	/* reset echo pin in any case */
230	gpiod_set_value(data->echo_pin, 0);
231	dev_info(&pdev->dev, "removed IRQ %d as PPS source\n", data->irq);
232	return 0;
233}
234
235static const struct of_device_id pps_gpio_dt_ids[] = {
236	{ .compatible = "pps-gpio", },
237	{ /* sentinel */ }
238};
239MODULE_DEVICE_TABLE(of, pps_gpio_dt_ids);
240
241static struct platform_driver pps_gpio_driver = {
242	.probe		= pps_gpio_probe,
243	.remove		= pps_gpio_remove,
244	.driver		= {
245		.name	= PPS_GPIO_NAME,
246		.of_match_table	= pps_gpio_dt_ids,
247	},
248};
249
250module_platform_driver(pps_gpio_driver);
251MODULE_AUTHOR("Ricardo Martins <rasm@fe.up.pt>");
252MODULE_AUTHOR("James Nuss <jamesnuss@nanometrics.ca>");
253MODULE_DESCRIPTION("Use GPIO pin as PPS source");
254MODULE_LICENSE("GPL");
255MODULE_VERSION("1.2.0");
256