PageRenderTime 77ms CodeModel.GetById 59ms app.highlight 10ms RepoModel.GetById 1ms app.codeStats 0ms

/drivers/pps/clients/pps_parport.c

https://bitbucket.org/cyanogenmod/android_kernel_asus_tf300t
C | 258 lines | 163 code | 45 blank | 50 comment | 15 complexity | e4ed92d22890c586e3299e95aa594df7 MD5 | raw file
Possible License(s): LGPL-2.0, AGPL-1.0, GPL-2.0
  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
136/* the PPS echo function */
137static void pps_echo(struct pps_device *pps, int event, void *data)
138{
139	dev_info(pps->dev, "echo %s %s\n",
140		event & PPS_CAPTUREASSERT ? "assert" : "",
141		event & PPS_CAPTURECLEAR ? "clear" : "");
142}
143
144static void parport_attach(struct parport *port)
145{
146	struct pps_client_pp *device;
147	struct pps_source_info info = {
148		.name		= KBUILD_MODNAME,
149		.path		= "",
150		.mode		= PPS_CAPTUREBOTH | \
151				  PPS_OFFSETASSERT | PPS_OFFSETCLEAR | \
152				  PPS_ECHOASSERT | PPS_ECHOCLEAR | \
153				  PPS_CANWAIT | PPS_TSFMT_TSPEC,
154		.echo		= pps_echo,
155		.owner		= THIS_MODULE,
156		.dev		= NULL
157	};
158
159	device = kzalloc(sizeof(struct pps_client_pp), GFP_KERNEL);
160	if (!device) {
161		pr_err("memory allocation failed, not attaching\n");
162		return;
163	}
164
165	device->pardev = parport_register_device(port, KBUILD_MODNAME,
166			NULL, NULL, parport_irq, PARPORT_FLAG_EXCL, device);
167	if (!device->pardev) {
168		pr_err("couldn't register with %s\n", port->name);
169		goto err_free;
170	}
171
172	if (parport_claim_or_block(device->pardev) < 0) {
173		pr_err("couldn't claim %s\n", port->name);
174		goto err_unregister_dev;
175	}
176
177	device->pps = pps_register_source(&info,
178			PPS_CAPTUREBOTH | PPS_OFFSETASSERT | PPS_OFFSETCLEAR);
179	if (device->pps == NULL) {
180		pr_err("couldn't register PPS source\n");
181		goto err_release_dev;
182	}
183
184	device->cw = clear_wait;
185
186	port->ops->enable_irq(port);
187
188	pr_info("attached to %s\n", port->name);
189
190	return;
191
192err_release_dev:
193	parport_release(device->pardev);
194err_unregister_dev:
195	parport_unregister_device(device->pardev);
196err_free:
197	kfree(device);
198}
199
200static void parport_detach(struct parport *port)
201{
202	struct pardevice *pardev = port->cad;
203	struct pps_client_pp *device;
204
205	/* FIXME: oooh, this is ugly! */
206	if (strcmp(pardev->name, KBUILD_MODNAME))
207		/* not our port */
208		return;
209
210	device = pardev->private;
211
212	port->ops->disable_irq(port);
213	pps_unregister_source(device->pps);
214	parport_release(pardev);
215	parport_unregister_device(pardev);
216	kfree(device);
217}
218
219static struct parport_driver pps_parport_driver = {
220	.name = KBUILD_MODNAME,
221	.attach = parport_attach,
222	.detach = parport_detach,
223};
224
225/* module staff */
226
227static int __init pps_parport_init(void)
228{
229	int ret;
230
231	pr_info(DRVDESC "\n");
232
233	if (clear_wait > CLEAR_WAIT_MAX) {
234		pr_err("clear_wait value should be not greater"
235				" then %d\n", CLEAR_WAIT_MAX);
236		return -EINVAL;
237	}
238
239	ret = parport_register_driver(&pps_parport_driver);
240	if (ret) {
241		pr_err("unable to register with parport\n");
242		return ret;
243	}
244
245	return  0;
246}
247
248static void __exit pps_parport_exit(void)
249{
250	parport_unregister_driver(&pps_parport_driver);
251}
252
253module_init(pps_parport_init);
254module_exit(pps_parport_exit);
255
256MODULE_AUTHOR("Alexander Gordeev <lasaine@lvk.cs.msu.su>");
257MODULE_DESCRIPTION(DRVDESC);
258MODULE_LICENSE("GPL");