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