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