summaryrefslogtreecommitdiff
path: root/drivers/pps/clients/pps_parport.c
blob: 32221efd9ca979d9518d2e130d2e4ebe3cba777c (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
/*
 * pps_parport.c -- kernel parallel port PPS client
 *
 *
 * Copyright (C) 2009   Alexander Gordeev <lasaine@lvk.cs.msu.su>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */


/*
 * TODO:
 * implement echo over SEL pin
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/irqnr.h>
#include <linux/time.h>
#include <linux/parport.h>
#include <linux/pps_kernel.h>

#define DRVDESC "parallel port PPS client"

/* module parameters */

#define CLEAR_WAIT_MAX		100
#define CLEAR_WAIT_MAX_ERRORS	5

static unsigned int clear_wait = 100;
MODULE_PARM_DESC(clear_wait,
	"Maximum number of port reads when polling for signal clear,"
	" zero turns clear edge capture off entirely");
module_param(clear_wait, uint, 0);


/* internal per port structure */
struct pps_client_pp {
	struct pardevice *pardev;	/* parport device */
	struct pps_device *pps;		/* PPS device */
	unsigned int cw;		/* port clear timeout */
	unsigned int cw_err;		/* number of timeouts */
};

static inline int signal_is_set(struct parport *port)
{
	return (port->ops->read_status(port) & PARPORT_STATUS_ACK) != 0;
}

/* parport interrupt handler */
static void parport_irq(void *handle)
{
	struct pps_event_time ts_assert, ts_clear;
	struct pps_client_pp *dev = handle;
	struct parport *port = dev->pardev->port;
	unsigned int i;
	unsigned long flags;

	/* first of all we get the time stamp... */
	pps_get_ts(&ts_assert);

	if (dev->cw == 0)
		/* clear edge capture disabled */
		goto out_assert;

	/* try capture the clear edge */

	/* We have to disable interrupts here. The idea is to prevent
	 * other interrupts on the same processor to introduce random
	 * lags while polling the port. Reading from IO port is known
	 * to take approximately 1us while other interrupt handlers can
	 * take much more potentially.
	 *
	 * Interrupts won't be disabled for a long time because the
	 * number of polls is limited by clear_wait parameter which is
	 * kept rather low. So it should never be an issue.
	 */
	local_irq_save(flags);
	/* check the signal (no signal means the pulse is lost this time) */
	if (!signal_is_set(port)) {
		local_irq_restore(flags);
		dev_err(dev->pps->dev, "lost the signal\n");
		goto out_assert;
	}

	/* poll the port until the signal is unset */
	for (i = dev->cw; i; i--)
		if (!signal_is_set(port)) {
			pps_get_ts(&ts_clear);
			local_irq_restore(flags);
			dev->cw_err = 0;
			goto out_both;
		}
	local_irq_restore(flags);

	/* timeout */
	dev->cw_err++;
	if (dev->cw_err >= CLEAR_WAIT_MAX_ERRORS) {
		dev_err(dev->pps->dev, "disabled clear edge capture after %d"
				" timeouts\n", dev->cw_err);
		dev->cw = 0;
		dev->cw_err = 0;
	}

out_assert:
	/* fire assert event */
	pps_event(dev->pps, &ts_assert,
			PPS_CAPTUREASSERT, NULL);
	return;

out_both:
	/* fire assert event */
	pps_event(dev->pps, &ts_assert,
			PPS_CAPTUREASSERT, NULL);
	/* fire clear event */
	pps_event(dev->pps, &ts_clear,
			PPS_CAPTURECLEAR, NULL);
	return;
}

/* the PPS echo function */
static void pps_echo(struct pps_device *pps, int event, void *data)
{
	dev_info(pps->dev, "echo %s %s\n",
		event & PPS_CAPTUREASSERT ? "assert" : "",
		event & PPS_CAPTURECLEAR ? "clear" : "");
}

static void parport_attach(struct parport *port)
{
	struct pps_client_pp *device;
	struct pps_source_info info = {
		.name		= KBUILD_MODNAME,
		.path		= "",
		.mode		= PPS_CAPTUREBOTH | \
				  PPS_OFFSETASSERT | PPS_OFFSETCLEAR | \
				  PPS_ECHOASSERT | PPS_ECHOCLEAR | \
				  PPS_CANWAIT | PPS_TSFMT_TSPEC,
		.echo		= pps_echo,
		.owner		= THIS_MODULE,
		.dev		= NULL
	};

	device = kzalloc(sizeof(struct pps_client_pp), GFP_KERNEL);
	if (!device) {
		pr_err("memory allocation failed, not attaching\n");
		return;
	}

	device->pardev = parport_register_device(port, KBUILD_MODNAME,
			NULL, NULL, parport_irq, 0, device);
	if (!device->pardev) {
		pr_err("couldn't register with %s\n", port->name);
		goto err_free;
	}

	if (parport_claim_or_block(device->pardev) < 0) {
		pr_err("couldn't claim %s\n", port->name);
		goto err_unregister_dev;
	}

	device->pps = pps_register_source(&info,
			PPS_CAPTUREBOTH | PPS_OFFSETASSERT | PPS_OFFSETCLEAR);
	if (device->pps == NULL) {
		pr_err("couldn't register PPS source\n");
		goto err_release_dev;
	}

	device->cw = clear_wait;

	port->ops->enable_irq(port);

	pr_info("attached to %s\n", port->name);

	return;

err_release_dev:
	parport_release(device->pardev);
err_unregister_dev:
	parport_unregister_device(device->pardev);
err_free:
	kfree(device);
}

static void parport_detach(struct parport *port)
{
	struct pardevice *pardev = port->cad;
	struct pps_client_pp *device;

	/* FIXME: oooh, this is ugly! */
	if (strcmp(pardev->name, KBUILD_MODNAME))
		/* not our port */
		return;

	device = pardev->private;

	port->ops->disable_irq(port);
	pps_unregister_source(device->pps);
	parport_release(pardev);
	parport_unregister_device(pardev);
	kfree(device);
}

static struct parport_driver pps_parport_driver = {
	.name = KBUILD_MODNAME,
	.attach = parport_attach,
	.detach = parport_detach,
};

/* module staff */

static int __init pps_parport_init(void)
{
	int ret;

	pr_info(DRVDESC "\n");

	if (clear_wait > CLEAR_WAIT_MAX) {
		pr_err("clear_wait value should be not greater"
				" then %d\n", CLEAR_WAIT_MAX);
		return -EINVAL;
	}

	ret = parport_register_driver(&pps_parport_driver);
	if (ret) {
		pr_err("unable to register with parport\n");
		return ret;
	}

	return  0;
}

static void __exit pps_parport_exit(void)
{
	parport_unregister_driver(&pps_parport_driver);
}

module_init(pps_parport_init);
module_exit(pps_parport_exit);

MODULE_AUTHOR("Alexander Gordeev <lasaine@lvk.cs.msu.su>");
MODULE_DESCRIPTION(DRVDESC);
MODULE_LICENSE("GPL");