+++ /dev/null
-// SPDX-License-Identifier: GPL-2.0-or-later
-/*
- * pps_gen_parport.c -- kernel parallel port PPS signal generator
- *
- * Copyright (C) 2009 Alexander Gordeev <lasaine@lvk.cs.msu.su>
- */
-
-
-/*
- * 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 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 timespec64 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. ktime_get_real_ts64() 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... */
- ktime_get_real_ts64(&ts1);
- expire_time = ktime_to_timespec64(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 %ptSp\n", &ts1);
- goto done;
- }
-
- /* busy loop until the time is right for an assert edge */
- do {
- ktime_get_real_ts64(&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 {
- ktime_get_real_ts64(&ts2);
- } while (expire_time.tv_sec == ts2.tv_sec && ts2.tv_nsec < lim);
-
- /* unset the signal */
- port->ops->write_control(port, NO_SIGNAL);
-
- ktime_get_real_ts64(&ts3);
-
- local_irq_restore(flags);
-
- /* update calibrated port write time */
- dts = timespec64_sub(ts3, ts2);
- dev->port_write_time =
- (dev->port_write_time + timespec64_to_ns(&dts)) >> 1;
-
-done:
- /* update calibrated hrtimer error */
- dts = timespec64_sub(ts1, expire_time);
- delta = timespec64_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;
-}
-
-/* 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 timespec64 a, b;
- unsigned long irq_flags;
-
- local_irq_save(irq_flags);
- ktime_get_real_ts64(&a);
- port->ops->write_control(port, NO_SIGNAL);
- ktime_get_real_ts64(&b);
- local_irq_restore(irq_flags);
-
- b = timespec64_sub(b, a);
- acc += timespec64_to_ns(&b);
- }
-
- dev->port_write_time = acc >> PORT_NTESTS_SHIFT;
- pr_info("port write takes %ldns\n", dev->port_write_time);
-}
-
-static inline ktime_t next_intr_time(struct pps_generator_pp *dev)
-{
- struct timespec64 ts;
-
- ktime_get_real_ts64(&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));
-}
-
-static void parport_attach(struct parport *port)
-{
- struct pardev_cb pps_cb;
-
- if (send_delay > SEND_DELAY_MAX) {
- pr_err("delay value should be not greater then %d\n", SEND_DELAY_MAX);
- return;
- }
-
- if (attached) {
- /* we already have a port */
- return;
- }
-
- memset(&pps_cb, 0, sizeof(pps_cb));
- pps_cb.private = &device;
- pps_cb.flags = PARPORT_FLAG_EXCL;
- device.pardev = parport_register_dev_model(port, KBUILD_MODNAME,
- &pps_cb, 0);
- 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_setup(&device.timer, hrtimer_event, CLOCK_REALTIME, HRTIMER_MODE_ABS);
- hrtimer_start(&device.timer, next_intr_time(&device), HRTIMER_MODE_ABS);
-
- return;
-
-err_unregister_dev:
- parport_unregister_device(device.pardev);
-}
-
-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);
-}
-
-static struct parport_driver pps_gen_parport_driver = {
- .name = KBUILD_MODNAME,
- .match_port = parport_attach,
- .detach = parport_detach,
-};
-module_parport_driver(pps_gen_parport_driver);
-
-MODULE_AUTHOR("Alexander Gordeev <lasaine@lvk.cs.msu.su>");
-MODULE_DESCRIPTION("parallel port PPS signal generator");
-MODULE_LICENSE("GPL");
projects / thirdparty / linux.git / commitdiff
