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    SubjectRe: [PATCHv2 5/6] pps: add parallel port PPS signal generator
    On Wed, Feb 24, 2010 at 03:28:16PM +0300, Alexander Gordeev wrote:
    > Add PPS signal generator which utilizes STROBE pin of a parallel port to
    > send PPS signals. It uses parport abstraction layer and hrtimers to
    > precisely control the signal.
    >
    > Signed-off-by: Alexander Gordeev <lasaine@lvk.cs.msu.su>
    > ---
    > drivers/pps/Kconfig | 2 +
    > drivers/pps/Makefile | 1 +
    > drivers/pps/generators/Kconfig | 17 ++
    > drivers/pps/generators/Makefile | 9 +
    > drivers/pps/generators/pps_gen_parport.c | 264 ++++++++++++++++++++++++++++++
    > 5 files changed, 293 insertions(+), 0 deletions(-)
    > create mode 100644 drivers/pps/generators/Kconfig
    > create mode 100644 drivers/pps/generators/Makefile
    > create mode 100644 drivers/pps/generators/pps_gen_parport.c
    >
    > diff --git a/drivers/pps/Kconfig b/drivers/pps/Kconfig
    > index 2bd4f65..f3b14cd 100644
    > --- a/drivers/pps/Kconfig
    > +++ b/drivers/pps/Kconfig
    > @@ -31,4 +31,6 @@ config PPS_DEBUG
    > messages to the system log. Select this if you are having a
    > problem with PPS support and want to see more of what is going on.
    >
    > +source drivers/pps/generators/Kconfig
    > +
    > endmenu
    > diff --git a/drivers/pps/Makefile b/drivers/pps/Makefile
    > index 19ea582..b299814 100644
    > --- a/drivers/pps/Makefile
    > +++ b/drivers/pps/Makefile
    > @@ -4,5 +4,6 @@
    >
    > pps_core-y := pps.o kapi.o sysfs.o
    > obj-$(CONFIG_PPS) := pps_core.o
    > +obj-y += generators/

    I suppose this patch doesn't apply on top of my latest PPS patchset,
    does it?

    http://permalink.gmane.org/gmane.linux.kernel/954152

    Generators support should be added after PPS clients one.

    >
    > ccflags-$(CONFIG_PPS_DEBUG) := -DDEBUG
    > diff --git a/drivers/pps/generators/Kconfig b/drivers/pps/generators/Kconfig
    > new file mode 100644
    > index 0000000..9cc1118
    > --- /dev/null
    > +++ b/drivers/pps/generators/Kconfig
    > @@ -0,0 +1,17 @@
    > +#
    > +# PPS clients configuration
    > +#

    s/clients/generators

    > +
    > +if PPS
    > +
    > +comment "PPS generators support"
    > +
    > +config PPS_GENERATOR_PARPORT
    > + tristate "Parallel port PPS signal generator"
    > + depends on PARPORT != n && GENERIC_TIME
    > + help
    > + If you say yes here you get support for a PPS signal generator which
    > + utilizes STROBE pin of a parallel port to send PPS signals. It uses
    > + parport abstraction layer and hrtimers to precisely control the signal.
    > +
    > +endif
    > diff --git a/drivers/pps/generators/Makefile b/drivers/pps/generators/Makefile
    > new file mode 100644
    > index 0000000..303304a
    > --- /dev/null
    > +++ b/drivers/pps/generators/Makefile
    > @@ -0,0 +1,9 @@
    > +#
    > +# Makefile for PPS generators.
    > +#
    > +
    > +obj-$(CONFIG_PPS_GENERATOR_PARPORT) += pps_gen_parport.o
    > +
    > +ifeq ($(CONFIG_PPS_DEBUG),y)
    > +EXTRA_CFLAGS += -DDEBUG
    > +endif
    > diff --git a/drivers/pps/generators/pps_gen_parport.c b/drivers/pps/generators/pps_gen_parport.c
    > new file mode 100644
    > index 0000000..e7cce30
    > --- /dev/null
    > +++ b/drivers/pps/generators/pps_gen_parport.c
    > @@ -0,0 +1,264 @@
    > +/*
    > + * 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:
    > + * 1. module parameters
    > + * 2. check that local interrupts are blocked in hrtimer handler
    > + * 3. fix issues when realtime clock is adjusted in a leap
    > + * 4. test under heavy load
    > + */
    > +
    > +#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 DRVNAME "pps_gen_parport"
    > +#define DRVDESC "parallel port PPS signal generator"
    > +
    > +#define SIGNAL 0
    > +#define NO_SIGNAL PARPORT_CONTROL_STROBE
    > +
    > +#define SEND_DELAY 30000 /* delay between setting and
    > + dropping the signal (ns) */
    > +#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;
    > +
    > + /* 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(timer->_expires);
    > + 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(DRVNAME ": 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;
    > +}
    > +
    > +/* 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(DRVNAME ": port write takes %ldns\n", dev->port_write_time);
    > +}
    > +
    > +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));
    > +}
    > +
    > +static void parport_attach(struct parport *port)
    > +{
    > + if (attached) {
    > + /* we already have a port */
    > + return;
    > + }
    > +
    > + device.pardev = parport_register_device(port, DRVNAME,
    > + NULL, NULL, NULL, 0, &device);
    > + if (!device.pardev) {
    > + pr_err(DRVNAME ": couldn't register with %s\n", port->name);
    > + return;
    > + }
    > +
    > + if (parport_claim_or_block(device.pardev) < 0) {
    > + pr_err(DRVNAME ": couldn't claim %s\n", port->name);
    > + goto err_unregister_dev;
    > + }
    > +
    > + pr_info(DRVNAME ": 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;
    > +#ifdef CONFIG_PREEMPT_RT
    > + /* hrtimer interrupt will run in the interrupt context with this */
    > + device.timer.irqsafe = 1;
    > +#endif
    > +
    > + 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)
    > + /* not our port */
    > + return;

    Please use:

    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 = DRVNAME,
    > + .attach = parport_attach,
    > + .detach = parport_detach,
    > +};
    > +
    > +/* module staff */
    > +
    > +static int __init pps_gen_parport_init(void)
    > +{
    > + int ret;
    > +
    > + pr_info(DRVNAME ": " DRVDESC "\n");
    > +
    > + ret = parport_register_driver(&pps_gen_parport_driver);
    > + if (ret) {
    > + pr_err(DRVNAME ": unable to register with parport\n");
    > + return ret;
    > + }
    > +
    > + return 0;
    > +}
    > +
    > +static void __exit pps_gen_parport_exit(void)
    > +{
    > + parport_unregister_driver(&pps_gen_parport_driver);
    > + pr_info(DRVNAME ": hrtimer avg error is %ldns\n", hrtimer_error);
    > +}
    > +
    > +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");
    > --
    > 1.6.6.1
    >

    --

    GNU/Linux Solutions e-mail: giometti@enneenne.com
    Linux Device Driver giometti@linux.it
    Embedded Systems phone: +39 349 2432127
    UNIX programming skype: rodolfo.giometti
    Freelance ICT Italia - Consulente ICT Italia - www.consulenti-ict.it


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