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: &ts);
52
53 info = data;
54
55 /* Small trick to bypass the check on edge's direction when capture_clear is unset */
56 rising_edge = info->capture_clear ?
57 gpiod_get_value(desc: info->gpio_pin) : !info->assert_falling_edge;
58 if ((rising_edge && !info->assert_falling_edge) ||
59 (!rising_edge && info->assert_falling_edge))
60 pps_event(pps: info->pps, ts: &ts, PPS_CAPTUREASSERT, data);
61 else if (info->capture_clear &&
62 ((rising_edge && info->assert_falling_edge) ||
63 (!rising_edge && !info->assert_falling_edge)))
64 pps_event(pps: info->pps, ts: &ts, PPS_CAPTURECLEAR, data);
65 else
66 dev_warn_ratelimited(&info->pps->dev, "IRQ did not trigger any PPS event\n");
67
68 return IRQ_HANDLED;
69}
70
71/* This function will only be called when an ECHO GPIO is defined */
72static void pps_gpio_echo(struct pps_device *pps, int event, void *data)
73{
74 /* add_timer() needs to write into info->echo_timer */
75 struct pps_gpio_device_data *info = data;
76
77 switch (event) {
78 case PPS_CAPTUREASSERT:
79 if (pps->params.mode & PPS_ECHOASSERT)
80 gpiod_set_value(desc: info->echo_pin, value: 1);
81 break;
82
83 case PPS_CAPTURECLEAR:
84 if (pps->params.mode & PPS_ECHOCLEAR)
85 gpiod_set_value(desc: info->echo_pin, value: 1);
86 break;
87 }
88
89 /* fire the timer */
90 if (info->pps->params.mode & (PPS_ECHOASSERT | PPS_ECHOCLEAR)) {
91 info->echo_timer.expires = jiffies + info->echo_timeout;
92 add_timer(timer: &info->echo_timer);
93 }
94}
95
96/* Timer callback to reset the echo pin to the inactive state */
97static void pps_gpio_echo_timer_callback(struct timer_list *t)
98{
99 const struct pps_gpio_device_data *info;
100
101 info = timer_container_of(info, t, echo_timer);
102
103 gpiod_set_value(desc: info->echo_pin, value: 0);
104}
105
106static int pps_gpio_setup(struct device *dev)
107{
108 struct pps_gpio_device_data *data = dev_get_drvdata(dev);
109 int ret;
110 u32 value;
111
112 data->gpio_pin = devm_gpiod_get(dev, NULL, flags: GPIOD_IN);
113 if (IS_ERR(ptr: data->gpio_pin))
114 return dev_err_probe(dev, err: PTR_ERR(ptr: data->gpio_pin),
115 fmt: "failed to request PPS GPIO\n");
116
117 data->assert_falling_edge =
118 device_property_read_bool(dev, propname: "assert-falling-edge");
119
120 data->echo_pin = devm_gpiod_get_optional(dev, con_id: "echo", flags: GPIOD_OUT_LOW);
121 if (IS_ERR(ptr: data->echo_pin))
122 return dev_err_probe(dev, err: PTR_ERR(ptr: data->echo_pin),
123 fmt: "failed to request ECHO GPIO\n");
124
125 if (!data->echo_pin)
126 return 0;
127
128 ret = device_property_read_u32(dev, propname: "echo-active-ms", val: &value);
129 if (ret) {
130 dev_err(dev, "failed to get echo-active-ms from FW\n");
131 return ret;
132 }
133
134 /* sanity check on echo_active_ms */
135 if (!value || value > 999) {
136 dev_err(dev, "echo-active-ms: %u - bad value from FW\n", value);
137 return -EINVAL;
138 }
139
140 data->echo_active_ms = value;
141
142 return 0;
143}
144
145static unsigned long
146get_irqf_trigger_flags(const struct pps_gpio_device_data *data)
147{
148 unsigned long flags = data->assert_falling_edge ?
149 IRQF_TRIGGER_FALLING : IRQF_TRIGGER_RISING;
150
151 if (data->capture_clear) {
152 flags |= ((flags & IRQF_TRIGGER_RISING) ?
153 IRQF_TRIGGER_FALLING : IRQF_TRIGGER_RISING);
154 }
155
156 return flags;
157}
158
159static int pps_gpio_probe(struct platform_device *pdev)
160{
161 struct pps_gpio_device_data *data;
162 struct device *dev = &pdev->dev;
163 int ret;
164 int pps_default_params;
165
166 /* allocate space for device info */
167 data = devm_kzalloc(dev, size: sizeof(*data), GFP_KERNEL);
168 if (!data)
169 return -ENOMEM;
170
171 dev_set_drvdata(dev, data);
172
173 /* GPIO setup */
174 ret = pps_gpio_setup(dev);
175 if (ret)
176 return ret;
177
178 /* IRQ setup */
179 ret = gpiod_to_irq(desc: data->gpio_pin);
180 if (ret < 0) {
181 dev_err(dev, "failed to map GPIO to IRQ: %d\n", ret);
182 return -EINVAL;
183 }
184 data->irq = ret;
185
186 /* initialize PPS specific parts of the bookkeeping data structure. */
187 data->info.mode = PPS_CAPTUREASSERT | PPS_OFFSETASSERT |
188 PPS_ECHOASSERT | PPS_CANWAIT | PPS_TSFMT_TSPEC;
189 if (data->capture_clear)
190 data->info.mode |= PPS_CAPTURECLEAR | PPS_OFFSETCLEAR |
191 PPS_ECHOCLEAR;
192 data->info.owner = THIS_MODULE;
193 snprintf(buf: data->info.name, PPS_MAX_NAME_LEN - 1, fmt: "%s.%d",
194 pdev->name, pdev->id);
195 if (data->echo_pin) {
196 data->info.echo = pps_gpio_echo;
197 data->echo_timeout = msecs_to_jiffies(m: data->echo_active_ms);
198 timer_setup(&data->echo_timer, pps_gpio_echo_timer_callback, 0);
199 }
200
201 /* register PPS source */
202 pps_default_params = PPS_CAPTUREASSERT | PPS_OFFSETASSERT;
203 if (data->capture_clear)
204 pps_default_params |= PPS_CAPTURECLEAR | PPS_OFFSETCLEAR;
205 data->pps = pps_register_source(info: &data->info, default_params: pps_default_params);
206 if (IS_ERR(ptr: data->pps)) {
207 dev_err(dev, "failed to register IRQ %d as PPS source\n",
208 data->irq);
209 return PTR_ERR(ptr: data->pps);
210 }
211
212 /* register IRQ interrupt handler */
213 ret = devm_request_irq(dev, irq: data->irq, handler: pps_gpio_irq_handler,
214 irqflags: get_irqf_trigger_flags(data), devname: data->info.name, dev_id: data);
215 if (ret) {
216 pps_unregister_source(pps: data->pps);
217 dev_err(dev, "failed to acquire IRQ %d\n", data->irq);
218 return -EINVAL;
219 }
220
221 dev_dbg(&data->pps->dev, "Registered IRQ %d as PPS source\n",
222 data->irq);
223
224 return 0;
225}
226
227static void pps_gpio_remove(struct platform_device *pdev)
228{
229 struct pps_gpio_device_data *data = platform_get_drvdata(pdev);
230
231 pps_unregister_source(pps: data->pps);
232 timer_delete_sync(timer: &data->echo_timer);
233 /* reset echo pin in any case */
234 gpiod_set_value(desc: data->echo_pin, value: 0);
235 dev_info(&pdev->dev, "removed IRQ %d as PPS source\n", data->irq);
236}
237
238static const struct of_device_id pps_gpio_dt_ids[] = {
239 { .compatible = "pps-gpio", },
240 { /* sentinel */ }
241};
242MODULE_DEVICE_TABLE(of, pps_gpio_dt_ids);
243
244static struct platform_driver pps_gpio_driver = {
245 .probe = pps_gpio_probe,
246 .remove = pps_gpio_remove,
247 .driver = {
248 .name = PPS_GPIO_NAME,
249 .of_match_table = pps_gpio_dt_ids,
250 },
251};
252
253module_platform_driver(pps_gpio_driver);
254MODULE_AUTHOR("Ricardo Martins <rasm@fe.up.pt>");
255MODULE_AUTHOR("James Nuss <jamesnuss@nanometrics.ca>");
256MODULE_DESCRIPTION("Use GPIO pin as PPS source");
257MODULE_LICENSE("GPL");
258MODULE_VERSION("1.2.0");
259

source code of linux/drivers/pps/clients/pps-gpio.c