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/module.h>
16#include <linux/platform_device.h>
17#include <linux/slab.h>
18#include <linux/pps_kernel.h>
19#include <linux/pps-gpio.h>
20#include <linux/gpio/consumer.h>
21#include <linux/list.h>
22#include <linux/of_device.h>
23#include <linux/of_gpio.h>
24#include <linux/timer.h>
25#include <linux/jiffies.h>
26
27/* Info for each registered platform device */
28struct pps_gpio_device_data {
29	int irq;			/* IRQ used as PPS source */
30	struct pps_device *pps;		/* PPS source device */
31	struct pps_source_info info;	/* PPS source information */
32	struct gpio_desc *gpio_pin;	/* GPIO port descriptors */
33	struct gpio_desc *echo_pin;
34	struct timer_list echo_timer;	/* timer to reset echo active state */
35	bool assert_falling_edge;
36	bool capture_clear;
37	unsigned int echo_active_ms;	/* PPS echo active duration */
38	unsigned long echo_timeout;	/* timer timeout value in jiffies */
39};
40
41/*
42 * Report the PPS event
43 */
44
45static irqreturn_t pps_gpio_irq_handler(int irq, void *data)
46{
47	const struct pps_gpio_device_data *info;
48	struct pps_event_time ts;
49	int rising_edge;
50
51	/* Get the time stamp first */
52	pps_get_ts(&ts);
53
54	info = data;
55
56	rising_edge = gpiod_get_value(info->gpio_pin);
57	if ((rising_edge && !info->assert_falling_edge) ||
58			(!rising_edge && info->assert_falling_edge))
59		pps_event(info->pps, &ts, PPS_CAPTUREASSERT, data);
60	else if (info->capture_clear &&
61			((rising_edge && info->assert_falling_edge) ||
62			(!rising_edge && !info->assert_falling_edge)))
63		pps_event(info->pps, &ts, PPS_CAPTURECLEAR, data);
64
65	return IRQ_HANDLED;
66}
67
68/* This function will only be called when an ECHO GPIO is defined */
69static void pps_gpio_echo(struct pps_device *pps, int event, void *data)
70{
71	/* add_timer() needs to write into info->echo_timer */
72	struct pps_gpio_device_data *info = data;
73
74	switch (event) {
75	case PPS_CAPTUREASSERT:
76		if (pps->params.mode & PPS_ECHOASSERT)
77			gpiod_set_value(info->echo_pin, 1);
78		break;
79
80	case PPS_CAPTURECLEAR:
81		if (pps->params.mode & PPS_ECHOCLEAR)
82			gpiod_set_value(info->echo_pin, 1);
83		break;
84	}
85
86	/* fire the timer */
87	if (info->pps->params.mode & (PPS_ECHOASSERT | PPS_ECHOCLEAR)) {
88		info->echo_timer.expires = jiffies + info->echo_timeout;
89		add_timer(&info->echo_timer);
90	}
91}
92
93/* Timer callback to reset the echo pin to the inactive state */
94static void pps_gpio_echo_timer_callback(struct timer_list *t)
95{
96	const struct pps_gpio_device_data *info;
97
98	info = from_timer(info, t, echo_timer);
99
100	gpiod_set_value(info->echo_pin, 0);
101}
102
103static int pps_gpio_setup(struct platform_device *pdev)
104{
105	struct pps_gpio_device_data *data = platform_get_drvdata(pdev);
106	struct device_node *np = pdev->dev.of_node;
107	int ret;
108	u32 value;
109
110	data->gpio_pin = devm_gpiod_get(&pdev->dev,
111		NULL,	/* request "gpios" */
112		GPIOD_IN);
113	if (IS_ERR(data->gpio_pin)) {
114		dev_err(&pdev->dev,
115			"failed to request PPS GPIO\n");
116		return PTR_ERR(data->gpio_pin);
117	}
118
119	data->echo_pin = devm_gpiod_get_optional(&pdev->dev,
120			"echo",
121			GPIOD_OUT_LOW);
122	if (data->echo_pin) {
123		if (IS_ERR(data->echo_pin)) {
124			dev_err(&pdev->dev, "failed to request ECHO GPIO\n");
125			return PTR_ERR(data->echo_pin);
126		}
127
128		ret = of_property_read_u32(np,
129			"echo-active-ms",
130			&value);
131		if (ret) {
132			dev_err(&pdev->dev,
133				"failed to get echo-active-ms from OF\n");
134			return ret;
135		}
136		data->echo_active_ms = value;
137		/* sanity check on echo_active_ms */
138		if (!data->echo_active_ms || data->echo_active_ms > 999) {
139			dev_err(&pdev->dev,
140				"echo-active-ms: %u - bad value from OF\n",
141				data->echo_active_ms);
142			return -EINVAL;
143		}
144	}
145
146	if (of_property_read_bool(np, "assert-falling-edge"))
147		data->assert_falling_edge = true;
148	return 0;
149}
150
151static unsigned long
152get_irqf_trigger_flags(const struct pps_gpio_device_data *data)
153{
154	unsigned long flags = data->assert_falling_edge ?
155		IRQF_TRIGGER_FALLING : IRQF_TRIGGER_RISING;
156
157	if (data->capture_clear) {
158		flags |= ((flags & IRQF_TRIGGER_RISING) ?
159				IRQF_TRIGGER_FALLING : IRQF_TRIGGER_RISING);
160	}
161
162	return flags;
163}
164
165static int pps_gpio_probe(struct platform_device *pdev)
166{
167	struct pps_gpio_device_data *data;
168	int ret;
169	int pps_default_params;
170	const struct pps_gpio_platform_data *pdata = pdev->dev.platform_data;
171
172	/* allocate space for device info */
173	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
174	if (!data)
175		return -ENOMEM;
176	platform_set_drvdata(pdev, data);
177
178	/* GPIO setup */
179	if (pdata) {
180		data->gpio_pin = pdata->gpio_pin;
181		data->echo_pin = pdata->echo_pin;
182
183		data->assert_falling_edge = pdata->assert_falling_edge;
184		data->capture_clear = pdata->capture_clear;
185		data->echo_active_ms = pdata->echo_active_ms;
186	} else {
187		ret = pps_gpio_setup(pdev);
188		if (ret)
189			return -EINVAL;
190	}
191
192	/* IRQ setup */
193	ret = gpiod_to_irq(data->gpio_pin);
194	if (ret < 0) {
195		dev_err(&pdev->dev, "failed to map GPIO to IRQ: %d\n", ret);
196		return -EINVAL;
197	}
198	data->irq = ret;
199
200	/* initialize PPS specific parts of the bookkeeping data structure. */
201	data->info.mode = PPS_CAPTUREASSERT | PPS_OFFSETASSERT |
202		PPS_ECHOASSERT | PPS_CANWAIT | PPS_TSFMT_TSPEC;
203	if (data->capture_clear)
204		data->info.mode |= PPS_CAPTURECLEAR | PPS_OFFSETCLEAR |
205			PPS_ECHOCLEAR;
206	data->info.owner = THIS_MODULE;
207	snprintf(data->info.name, PPS_MAX_NAME_LEN - 1, "%s.%d",
208		 pdev->name, pdev->id);
209	if (data->echo_pin) {
210		data->info.echo = pps_gpio_echo;
211		data->echo_timeout = msecs_to_jiffies(data->echo_active_ms);
212		timer_setup(&data->echo_timer, pps_gpio_echo_timer_callback, 0);
213	}
214
215	/* register PPS source */
216	pps_default_params = PPS_CAPTUREASSERT | PPS_OFFSETASSERT;
217	if (data->capture_clear)
218		pps_default_params |= PPS_CAPTURECLEAR | PPS_OFFSETCLEAR;
219	data->pps = pps_register_source(&data->info, pps_default_params);
220	if (IS_ERR(data->pps)) {
221		dev_err(&pdev->dev, "failed to register IRQ %d as PPS source\n",
222			data->irq);
223		return PTR_ERR(data->pps);
224	}
225
226	/* register IRQ interrupt handler */
227	ret = devm_request_irq(&pdev->dev, data->irq, pps_gpio_irq_handler,
228			get_irqf_trigger_flags(data), data->info.name, data);
229	if (ret) {
230		pps_unregister_source(data->pps);
231		dev_err(&pdev->dev, "failed to acquire IRQ %d\n", data->irq);
232		return -EINVAL;
233	}
234
235	dev_info(data->pps->dev, "Registered IRQ %d as PPS source\n",
236		 data->irq);
237
238	return 0;
239}
240
241static int pps_gpio_remove(struct platform_device *pdev)
242{
243	struct pps_gpio_device_data *data = platform_get_drvdata(pdev);
244
245	pps_unregister_source(data->pps);
246	if (data->echo_pin) {
247		del_timer_sync(&data->echo_timer);
248		/* reset echo pin in any case */
249		gpiod_set_value(data->echo_pin, 0);
250	}
251	dev_info(&pdev->dev, "removed IRQ %d as PPS source\n", data->irq);
252	return 0;
253}
254
255static const struct of_device_id pps_gpio_dt_ids[] = {
256	{ .compatible = "pps-gpio", },
257	{ /* sentinel */ }
258};
259MODULE_DEVICE_TABLE(of, pps_gpio_dt_ids);
260
261static struct platform_driver pps_gpio_driver = {
262	.probe		= pps_gpio_probe,
263	.remove		= pps_gpio_remove,
264	.driver		= {
265		.name	= PPS_GPIO_NAME,
266		.of_match_table	= pps_gpio_dt_ids,
267	},
268};
269
270module_platform_driver(pps_gpio_driver);
271MODULE_AUTHOR("Ricardo Martins <rasm@fe.up.pt>");
272MODULE_AUTHOR("James Nuss <jamesnuss@nanometrics.ca>");
273MODULE_DESCRIPTION("Use GPIO pin as PPS source");
274MODULE_LICENSE("GPL");
275MODULE_VERSION("1.2.0");
276