1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * pps_parport.c -- kernel parallel port PPS client
4 *
5 * Copyright (C) 2009 Alexander Gordeev <lasaine@lvk.cs.msu.su>
6 */
7
8
9 /*
10 * TODO:
11 * implement echo over SEL pin
12 */
13
14 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
15
16 #include <linux/kernel.h>
17 #include <linux/module.h>
18 #include <linux/init.h>
19 #include <linux/irqnr.h>
20 #include <linux/time.h>
21 #include <linux/slab.h>
22 #include <linux/parport.h>
23 #include <linux/pps_kernel.h>
24
25 #define DRVDESC "parallel port PPS client"
26
27 /* module parameters */
28
29 #define CLEAR_WAIT_MAX 100
30 #define CLEAR_WAIT_MAX_ERRORS 5
31
32 static unsigned int clear_wait = 100;
33 MODULE_PARM_DESC(clear_wait,
34 "Maximum number of port reads when polling for signal clear,"
35 " zero turns clear edge capture off entirely");
36 module_param(clear_wait, uint, 0);
37
38 static DEFINE_IDA(pps_client_index);
39
40 /* internal per port structure */
41 struct pps_client_pp {
42 struct pardevice *pardev; /* parport device */
43 struct pps_device *pps; /* PPS device */
44 unsigned int cw; /* port clear timeout */
45 unsigned int cw_err; /* number of timeouts */
46 int index; /* device number */
47 };
48
signal_is_set(struct parport * port)49 static inline int signal_is_set(struct parport *port)
50 {
51 return (port->ops->read_status(port) & PARPORT_STATUS_ACK) != 0;
52 }
53
54 /* parport interrupt handler */
parport_irq(void * handle)55 static void parport_irq(void *handle)
56 {
57 struct pps_event_time ts_assert, ts_clear;
58 struct pps_client_pp *dev = handle;
59 struct parport *port = dev->pardev->port;
60 unsigned int i;
61 unsigned long flags;
62
63 /* first of all we get the time stamp... */
64 pps_get_ts(&ts_assert);
65
66 if (dev->cw == 0)
67 /* clear edge capture disabled */
68 goto out_assert;
69
70 /* try capture the clear edge */
71
72 /* We have to disable interrupts here. The idea is to prevent
73 * other interrupts on the same processor to introduce random
74 * lags while polling the port. Reading from IO port is known
75 * to take approximately 1us while other interrupt handlers can
76 * take much more potentially.
77 *
78 * Interrupts won't be disabled for a long time because the
79 * number of polls is limited by clear_wait parameter which is
80 * kept rather low. So it should never be an issue.
81 */
82 local_irq_save(flags);
83 /* check the signal (no signal means the pulse is lost this time) */
84 if (!signal_is_set(port)) {
85 local_irq_restore(flags);
86 dev_err(dev->pps->dev, "lost the signal\n");
87 goto out_assert;
88 }
89
90 /* poll the port until the signal is unset */
91 for (i = dev->cw; i; i--)
92 if (!signal_is_set(port)) {
93 pps_get_ts(&ts_clear);
94 local_irq_restore(flags);
95 dev->cw_err = 0;
96 goto out_both;
97 }
98 local_irq_restore(flags);
99
100 /* timeout */
101 dev->cw_err++;
102 if (dev->cw_err >= CLEAR_WAIT_MAX_ERRORS) {
103 dev_err(dev->pps->dev, "disabled clear edge capture after %d"
104 " timeouts\n", dev->cw_err);
105 dev->cw = 0;
106 dev->cw_err = 0;
107 }
108
109 out_assert:
110 /* fire assert event */
111 pps_event(dev->pps, &ts_assert,
112 PPS_CAPTUREASSERT, NULL);
113 return;
114
115 out_both:
116 /* fire assert event */
117 pps_event(dev->pps, &ts_assert,
118 PPS_CAPTUREASSERT, NULL);
119 /* fire clear event */
120 pps_event(dev->pps, &ts_clear,
121 PPS_CAPTURECLEAR, NULL);
122 return;
123 }
124
parport_attach(struct parport * port)125 static void parport_attach(struct parport *port)
126 {
127 struct pardev_cb pps_client_cb;
128 int index;
129 struct pps_client_pp *device;
130 struct pps_source_info info = {
131 .name = KBUILD_MODNAME,
132 .path = "",
133 .mode = PPS_CAPTUREBOTH | \
134 PPS_OFFSETASSERT | PPS_OFFSETCLEAR | \
135 PPS_ECHOASSERT | PPS_ECHOCLEAR | \
136 PPS_CANWAIT | PPS_TSFMT_TSPEC,
137 .owner = THIS_MODULE,
138 .dev = NULL
139 };
140
141 device = kzalloc(sizeof(struct pps_client_pp), GFP_KERNEL);
142 if (!device) {
143 pr_err("memory allocation failed, not attaching\n");
144 return;
145 }
146
147 index = ida_simple_get(&pps_client_index, 0, 0, GFP_KERNEL);
148 memset(&pps_client_cb, 0, sizeof(pps_client_cb));
149 pps_client_cb.private = device;
150 pps_client_cb.irq_func = parport_irq;
151 pps_client_cb.flags = PARPORT_FLAG_EXCL;
152 device->pardev = parport_register_dev_model(port,
153 KBUILD_MODNAME,
154 &pps_client_cb,
155 index);
156 if (!device->pardev) {
157 pr_err("couldn't register with %s\n", port->name);
158 goto err_free;
159 }
160
161 if (parport_claim_or_block(device->pardev) < 0) {
162 pr_err("couldn't claim %s\n", port->name);
163 goto err_unregister_dev;
164 }
165
166 device->pps = pps_register_source(&info,
167 PPS_CAPTUREBOTH | PPS_OFFSETASSERT | PPS_OFFSETCLEAR);
168 if (IS_ERR(device->pps)) {
169 pr_err("couldn't register PPS source\n");
170 goto err_release_dev;
171 }
172
173 device->cw = clear_wait;
174
175 port->ops->enable_irq(port);
176 device->index = index;
177
178 pr_info("attached to %s\n", port->name);
179
180 return;
181
182 err_release_dev:
183 parport_release(device->pardev);
184 err_unregister_dev:
185 parport_unregister_device(device->pardev);
186 err_free:
187 ida_simple_remove(&pps_client_index, index);
188 kfree(device);
189 }
190
parport_detach(struct parport * port)191 static void parport_detach(struct parport *port)
192 {
193 struct pardevice *pardev = port->cad;
194 struct pps_client_pp *device;
195
196 /* FIXME: oooh, this is ugly! */
197 if (!pardev || strcmp(pardev->name, KBUILD_MODNAME))
198 /* not our port */
199 return;
200
201 device = pardev->private;
202
203 port->ops->disable_irq(port);
204 pps_unregister_source(device->pps);
205 parport_release(pardev);
206 parport_unregister_device(pardev);
207 ida_simple_remove(&pps_client_index, device->index);
208 kfree(device);
209 }
210
211 static struct parport_driver pps_parport_driver = {
212 .name = KBUILD_MODNAME,
213 .match_port = parport_attach,
214 .detach = parport_detach,
215 .devmodel = true,
216 };
217
218 /* module staff */
219
pps_parport_init(void)220 static int __init pps_parport_init(void)
221 {
222 int ret;
223
224 pr_info(DRVDESC "\n");
225
226 if (clear_wait > CLEAR_WAIT_MAX) {
227 pr_err("clear_wait value should be not greater"
228 " then %d\n", CLEAR_WAIT_MAX);
229 return -EINVAL;
230 }
231
232 ret = parport_register_driver(&pps_parport_driver);
233 if (ret) {
234 pr_err("unable to register with parport\n");
235 return ret;
236 }
237
238 return 0;
239 }
240
pps_parport_exit(void)241 static void __exit pps_parport_exit(void)
242 {
243 parport_unregister_driver(&pps_parport_driver);
244 }
245
246 module_init(pps_parport_init);
247 module_exit(pps_parport_exit);
248
249 MODULE_AUTHOR("Alexander Gordeev <lasaine@lvk.cs.msu.su>");
250 MODULE_DESCRIPTION(DRVDESC);
251 MODULE_LICENSE("GPL");
252