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Alexander Gordeeva10203c2011-01-12 17:00:58 -08001/*
2 * pps_parport.c -- kernel parallel port PPS client
3 *
4 *
5 * Copyright (C) 2009 Alexander Gordeev <lasaine@lvk.cs.msu.su>
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation; either version 2 of the License, or
10 * (at your option) any later version.
11 *
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
16 *
17 * You should have received a copy of the GNU General Public License
18 * along with this program; if not, write to the Free Software
19 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
20 */
21
22
23/*
24 * TODO:
25 * implement echo over SEL pin
26 */
27
28#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
29
30#include <linux/kernel.h>
31#include <linux/module.h>
32#include <linux/init.h>
33#include <linux/irqnr.h>
34#include <linux/time.h>
35#include <linux/parport.h>
36#include <linux/pps_kernel.h>
37
38#define DRVDESC "parallel port PPS client"
39
40/* module parameters */
41
42#define CLEAR_WAIT_MAX 100
43#define CLEAR_WAIT_MAX_ERRORS 5
44
45static unsigned int clear_wait = 100;
46MODULE_PARM_DESC(clear_wait,
47 "Maximum number of port reads when polling for signal clear,"
48 " zero turns clear edge capture off entirely");
49module_param(clear_wait, uint, 0);
50
51
52/* internal per port structure */
53struct pps_client_pp {
54 struct pardevice *pardev; /* parport device */
55 struct pps_device *pps; /* PPS device */
56 unsigned int cw; /* port clear timeout */
57 unsigned int cw_err; /* number of timeouts */
58};
59
60static inline int signal_is_set(struct parport *port)
61{
62 return (port->ops->read_status(port) & PARPORT_STATUS_ACK) != 0;
63}
64
65/* parport interrupt handler */
66static void parport_irq(void *handle)
67{
68 struct pps_event_time ts_assert, ts_clear;
69 struct pps_client_pp *dev = handle;
70 struct parport *port = dev->pardev->port;
71 unsigned int i;
72 unsigned long flags;
73
74 /* first of all we get the time stamp... */
75 pps_get_ts(&ts_assert);
76
77 if (dev->cw == 0)
78 /* clear edge capture disabled */
79 goto out_assert;
80
81 /* try capture the clear edge */
82
83 /* We have to disable interrupts here. The idea is to prevent
84 * other interrupts on the same processor to introduce random
85 * lags while polling the port. Reading from IO port is known
86 * to take approximately 1us while other interrupt handlers can
87 * take much more potentially.
88 *
89 * Interrupts won't be disabled for a long time because the
90 * number of polls is limited by clear_wait parameter which is
91 * kept rather low. So it should never be an issue.
92 */
93 local_irq_save(flags);
94 /* check the signal (no signal means the pulse is lost this time) */
95 if (!signal_is_set(port)) {
96 local_irq_restore(flags);
97 dev_err(dev->pps->dev, "lost the signal\n");
98 goto out_assert;
99 }
100
101 /* poll the port until the signal is unset */
102 for (i = dev->cw; i; i--)
103 if (!signal_is_set(port)) {
104 pps_get_ts(&ts_clear);
105 local_irq_restore(flags);
106 dev->cw_err = 0;
107 goto out_both;
108 }
109 local_irq_restore(flags);
110
111 /* timeout */
112 dev->cw_err++;
113 if (dev->cw_err >= CLEAR_WAIT_MAX_ERRORS) {
114 dev_err(dev->pps->dev, "disabled clear edge capture after %d"
115 " timeouts\n", dev->cw_err);
116 dev->cw = 0;
117 dev->cw_err = 0;
118 }
119
120out_assert:
121 /* fire assert event */
122 pps_event(dev->pps, &ts_assert,
123 PPS_CAPTUREASSERT, NULL);
124 return;
125
126out_both:
127 /* fire assert event */
128 pps_event(dev->pps, &ts_assert,
129 PPS_CAPTUREASSERT, NULL);
130 /* fire clear event */
131 pps_event(dev->pps, &ts_clear,
132 PPS_CAPTURECLEAR, NULL);
133 return;
134}
135
Alexander Gordeeva10203c2011-01-12 17:00:58 -0800136static void parport_attach(struct parport *port)
137{
138 struct pps_client_pp *device;
139 struct pps_source_info info = {
140 .name = KBUILD_MODNAME,
141 .path = "",
142 .mode = PPS_CAPTUREBOTH | \
143 PPS_OFFSETASSERT | PPS_OFFSETCLEAR | \
144 PPS_ECHOASSERT | PPS_ECHOCLEAR | \
145 PPS_CANWAIT | PPS_TSFMT_TSPEC,
Alexander Gordeeva10203c2011-01-12 17:00:58 -0800146 .owner = THIS_MODULE,
147 .dev = NULL
148 };
149
150 device = kzalloc(sizeof(struct pps_client_pp), GFP_KERNEL);
151 if (!device) {
152 pr_err("memory allocation failed, not attaching\n");
153 return;
154 }
155
156 device->pardev = parport_register_device(port, KBUILD_MODNAME,
Alexander Gordeev4f542e32011-01-25 15:07:19 -0800157 NULL, NULL, parport_irq, PARPORT_FLAG_EXCL, device);
Alexander Gordeeva10203c2011-01-12 17:00:58 -0800158 if (!device->pardev) {
159 pr_err("couldn't register with %s\n", port->name);
160 goto err_free;
161 }
162
163 if (parport_claim_or_block(device->pardev) < 0) {
164 pr_err("couldn't claim %s\n", port->name);
165 goto err_unregister_dev;
166 }
167
168 device->pps = pps_register_source(&info,
169 PPS_CAPTUREBOTH | PPS_OFFSETASSERT | PPS_OFFSETCLEAR);
170 if (device->pps == NULL) {
171 pr_err("couldn't register PPS source\n");
172 goto err_release_dev;
173 }
174
175 device->cw = clear_wait;
176
177 port->ops->enable_irq(port);
178
179 pr_info("attached to %s\n", port->name);
180
181 return;
182
183err_release_dev:
184 parport_release(device->pardev);
185err_unregister_dev:
186 parport_unregister_device(device->pardev);
187err_free:
188 kfree(device);
189}
190
191static 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 (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 kfree(device);
208}
209
210static struct parport_driver pps_parport_driver = {
211 .name = KBUILD_MODNAME,
212 .attach = parport_attach,
213 .detach = parport_detach,
214};
215
216/* module staff */
217
218static int __init pps_parport_init(void)
219{
220 int ret;
221
222 pr_info(DRVDESC "\n");
223
224 if (clear_wait > CLEAR_WAIT_MAX) {
225 pr_err("clear_wait value should be not greater"
226 " then %d\n", CLEAR_WAIT_MAX);
227 return -EINVAL;
228 }
229
230 ret = parport_register_driver(&pps_parport_driver);
231 if (ret) {
232 pr_err("unable to register with parport\n");
233 return ret;
234 }
235
236 return 0;
237}
238
239static void __exit pps_parport_exit(void)
240{
241 parport_unregister_driver(&pps_parport_driver);
242}
243
244module_init(pps_parport_init);
245module_exit(pps_parport_exit);
246
247MODULE_AUTHOR("Alexander Gordeev <lasaine@lvk.cs.msu.su>");
248MODULE_DESCRIPTION(DRVDESC);
249MODULE_LICENSE("GPL");