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
 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
136static 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
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");