xref: /linux/drivers/pps/clients/pps_parport.c (revision 0d456bad36d42d16022be045c8a53ddbb59ee478)
1 /*
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 
45 static unsigned int clear_wait = 100;
46 MODULE_PARM_DESC(clear_wait,
47 	"Maximum number of port reads when polling for signal clear,"
48 	" zero turns clear edge capture off entirely");
49 module_param(clear_wait, uint, 0);
50 
51 
52 /* internal per port structure */
53 struct 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 
60 static 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 */
66 static 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 
120 out_assert:
121 	/* fire assert event */
122 	pps_event(dev->pps, &ts_assert,
123 			PPS_CAPTUREASSERT, NULL);
124 	return;
125 
126 out_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 
136 static 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,
146 		.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,
157 			NULL, NULL, parport_irq, PARPORT_FLAG_EXCL, device);
158 	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 
183 err_release_dev:
184 	parport_release(device->pardev);
185 err_unregister_dev:
186 	parport_unregister_device(device->pardev);
187 err_free:
188 	kfree(device);
189 }
190 
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 (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 
210 static struct parport_driver pps_parport_driver = {
211 	.name = KBUILD_MODNAME,
212 	.attach = parport_attach,
213 	.detach = parport_detach,
214 };
215 
216 /* module staff */
217 
218 static 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 
239 static void __exit pps_parport_exit(void)
240 {
241 	parport_unregister_driver(&pps_parport_driver);
242 }
243 
244 module_init(pps_parport_init);
245 module_exit(pps_parport_exit);
246 
247 MODULE_AUTHOR("Alexander Gordeev <lasaine@lvk.cs.msu.su>");
248 MODULE_DESCRIPTION(DRVDESC);
249 MODULE_LICENSE("GPL");
250