Release 4.7 drivers/pps/generators/pps_gen_parport.c
/*
* pps_gen_parport.c -- kernel parallel port PPS signal generator
*
*
* 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:
* fix issues when realtime clock is adjusted in a leap
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/time.h>
#include <linux/hrtimer.h>
#include <linux/parport.h>
#define DRVDESC "parallel port PPS signal generator"
#define SIGNAL 0
#define NO_SIGNAL PARPORT_CONTROL_STROBE
/* module parameters */
#define SEND_DELAY_MAX 100000
static unsigned int send_delay = 30000;
MODULE_PARM_DESC(delay,
"Delay between setting and dropping the signal (ns)");
module_param_named(delay, send_delay, uint, 0);
#define SAFETY_INTERVAL 3000
/* set the hrtimer earlier for safety (ns) */
/* internal per port structure */
struct pps_generator_pp {
struct pardevice *pardev; /* parport device */
struct hrtimer timer;
long port_write_time; /* calibrated port write time (ns) */
};
static struct pps_generator_pp device = {
.pardev = NULL,
};
static int attached;
/* calibrated time between a hrtimer event and the reaction */
static long hrtimer_error = SAFETY_INTERVAL;
/* the kernel hrtimer event */
static enum hrtimer_restart hrtimer_event(struct hrtimer *timer)
{
struct timespec expire_time, ts1, ts2, ts3, dts;
struct pps_generator_pp *dev;
struct parport *port;
long lim, delta;
unsigned long flags;
/* We have to disable interrupts here. The idea is to prevent
* other interrupts on the same processor to introduce random
* lags while polling the clock. getnstimeofday() takes <1us on
* most machines while other interrupt handlers can take much
* more potentially.
*
* NB: approx time with blocked interrupts =
* send_delay + 3 * SAFETY_INTERVAL
*/
local_irq_save(flags);
/* first of all we get the time stamp... */
getnstimeofday(&ts1);
expire_time = ktime_to_timespec(hrtimer_get_softexpires(timer));
dev = container_of(timer, struct pps_generator_pp, timer);
lim = NSEC_PER_SEC - send_delay - dev->port_write_time;
/* check if we are late */
if (expire_time.tv_sec != ts1.tv_sec || ts1.tv_nsec > lim) {
local_irq_restore(flags);
pr_err("we are late this time %ld.%09ld\n",
ts1.tv_sec, ts1.tv_nsec);
goto done;
}
/* busy loop until the time is right for an assert edge */
do {
getnstimeofday(&ts2);
} while (expire_time.tv_sec == ts2.tv_sec && ts2.tv_nsec < lim);
/* set the signal */
port = dev->pardev->port;
port->ops->write_control(port, SIGNAL);
/* busy loop until the time is right for a clear edge */
lim = NSEC_PER_SEC - dev->port_write_time;
do {
getnstimeofday(&ts2);
} while (expire_time.tv_sec == ts2.tv_sec && ts2.tv_nsec < lim);
/* unset the signal */
port->ops->write_control(port, NO_SIGNAL);
getnstimeofday(&ts3);
local_irq_restore(flags);
/* update calibrated port write time */
dts = timespec_sub(ts3, ts2);
dev->port_write_time =
(dev->port_write_time + timespec_to_ns(&dts)) >> 1;
done:
/* update calibrated hrtimer error */
dts = timespec_sub(ts1, expire_time);
delta = timespec_to_ns(&dts);
/* If the new error value is bigger then the old, use the new
* value, if not then slowly move towards the new value. This
* way it should be safe in bad conditions and efficient in
* good conditions.
*/
if (delta >= hrtimer_error)
hrtimer_error = delta;
else
hrtimer_error = (3 * hrtimer_error + delta) >> 2;
/* update the hrtimer expire time */
hrtimer_set_expires(timer,
ktime_set(expire_time.tv_sec + 1,
NSEC_PER_SEC - (send_delay +
dev->port_write_time + SAFETY_INTERVAL +
2 * hrtimer_error)));
return HRTIMER_RESTART;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| alexander gordeev | alexander gordeev | 339 | 100.00% | 2 | 100.00% |
| Total | 339 | 100.00% | 2 | 100.00% |
/* calibrate port write time */
#define PORT_NTESTS_SHIFT 5
static void calibrate_port(struct pps_generator_pp *dev)
{
struct parport *port = dev->pardev->port;
int i;
long acc = 0;
for (i = 0; i < (1 << PORT_NTESTS_SHIFT); i++) {
struct timespec a, b;
unsigned long irq_flags;
local_irq_save(irq_flags);
getnstimeofday(&a);
port->ops->write_control(port, NO_SIGNAL);
getnstimeofday(&b);
local_irq_restore(irq_flags);
b = timespec_sub(b, a);
acc += timespec_to_ns(&b);
}
dev->port_write_time = acc >> PORT_NTESTS_SHIFT;
pr_info("port write takes %ldns\n", dev->port_write_time);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| alexander gordeev | alexander gordeev | 126 | 100.00% | 1 | 100.00% |
| Total | 126 | 100.00% | 1 | 100.00% |
static inline ktime_t next_intr_time(struct pps_generator_pp *dev)
{
struct timespec ts;
getnstimeofday(&ts);
return ktime_set(ts.tv_sec +
((ts.tv_nsec > 990 * NSEC_PER_MSEC) ? 1 : 0),
NSEC_PER_SEC - (send_delay +
dev->port_write_time + 3 * SAFETY_INTERVAL));
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| alexander gordeev | alexander gordeev | 60 | 100.00% | 1 | 100.00% |
| Total | 60 | 100.00% | 1 | 100.00% |
static void parport_attach(struct parport *port)
{
if (attached) {
/* we already have a port */
return;
}
device.pardev = parport_register_device(port, KBUILD_MODNAME,
NULL, NULL, NULL, PARPORT_FLAG_EXCL, &device);
if (!device.pardev) {
pr_err("couldn't register with %s\n", port->name);
return;
}
if (parport_claim_or_block(device.pardev) < 0) {
pr_err("couldn't claim %s\n", port->name);
goto err_unregister_dev;
}
pr_info("attached to %s\n", port->name);
attached = 1;
calibrate_port(&device);
hrtimer_init(&device.timer, CLOCK_REALTIME, HRTIMER_MODE_ABS);
device.timer.function = hrtimer_event;
hrtimer_start(&device.timer, next_intr_time(&device), HRTIMER_MODE_ABS);
return;
err_unregister_dev:
parport_unregister_device(device.pardev);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| alexander gordeev | alexander gordeev | 150 | 100.00% | 2 | 100.00% |
| Total | 150 | 100.00% | 2 | 100.00% |
static void parport_detach(struct parport *port)
{
if (port->cad != device.pardev)
return; /* not our port */
hrtimer_cancel(&device.timer);
parport_release(device.pardev);
parport_unregister_device(device.pardev);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| alexander gordeev | alexander gordeev | 45 | 100.00% | 1 | 100.00% |
| Total | 45 | 100.00% | 1 | 100.00% |
static struct parport_driver pps_gen_parport_driver = {
.name = KBUILD_MODNAME,
.attach = parport_attach,
.detach = parport_detach,
};
/* module staff */
static int __init pps_gen_parport_init(void)
{
int ret;
pr_info(DRVDESC "\n");
if (send_delay > SEND_DELAY_MAX) {
pr_err("delay value should be not greater"
" then %d\n", SEND_DELAY_MAX);
return -EINVAL;
}
ret = parport_register_driver(&pps_gen_parport_driver);
if (ret) {
pr_err("unable to register with parport\n");
return ret;
}
return 0;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| alexander gordeev | alexander gordeev | 63 | 100.00% | 1 | 100.00% |
| Total | 63 | 100.00% | 1 | 100.00% |
static void __exit pps_gen_parport_exit(void)
{
parport_unregister_driver(&pps_gen_parport_driver);
pr_info("hrtimer avg error is %ldns\n", hrtimer_error);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| alexander gordeev | alexander gordeev | 22 | 100.00% | 1 | 100.00% |
| Total | 22 | 100.00% | 1 | 100.00% |
module_init(pps_gen_parport_init);
module_exit(pps_gen_parport_exit);
MODULE_AUTHOR("Alexander Gordeev <lasaine@lvk.cs.msu.su>");
MODULE_DESCRIPTION(DRVDESC);
MODULE_LICENSE("GPL");
Overall Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| alexander gordeev | alexander gordeev | 976 | 100.00% | 3 | 100.00% |
| Total | 976 | 100.00% | 3 | 100.00% |
Information contained on this website is for historical information purposes only and does not indicate or represent copyright ownership.