/*
* pps_parport.c -- kernel parallel port PPS client
*
*
* 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:
* implement echo over SEL pin
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/irqnr.h>
#include <linux/time.h>
#include <linux/parport.h>
#include <linux/pps_kernel.h>
#define DRVDESC "parallel port PPS client"
/* module parameters */
#define CLEAR_WAIT_MAX 100
#define CLEAR_WAIT_MAX_ERRORS 5
static unsigned int clear_wait = 100;
MODULE_PARM_DESC(clear_wait,
"Maximum number of port reads when polling for signal clear,"
" zero turns clear edge capture off entirely");
module_param(clear_wait, uint, 0);
/* internal per port structure */
struct pps_client_pp {
struct pardevice *pardev; /* parport device */
struct pps_device *pps; /* PPS device */
unsigned int cw; /* port clear timeout */
unsigned int cw_err; /* number of timeouts */
};
static inline int signal_is_set(struct parport *port)
{
return (port->ops->read_status(port) & PARPORT_STATUS_ACK) != 0;
}
/* parport interrupt handler */
static void parport_irq(void *handle)
{
struct pps_event_time ts_assert, ts_clear;
struct pps_client_pp *dev = handle;
struct parport *port = dev->pardev->port;
unsigned int i;
unsigned long flags;
/* first of all we get the time stamp... */
pps_get_ts(&ts_assert);
if (dev->cw == 0)
/* clear edge capture disabled */
goto out_assert;
/* try capture the clear edge */
/* We have to disable interrupts here. The idea is to prevent
* other interrupts on the same processor to introduce random
* lags while polling the port. Reading from IO port is known
* to take approximately 1us while other interrupt handlers can
* take much more potentially.
*
* Interrupts won't be disabled for a long time because the
* number of polls is limited by clear_wait parameter which is
* kept rather low. So it should never be an issue.
*/
local_irq_save(flags);
/* check the signal (no signal means the pulse is lost this time) */
if (!signal_is_set(port)) {
local_irq_restore(flags);
dev_err(dev->pps->dev, "lost the signal\n");
goto out_assert;
}
/* poll the port until the signal is unset */
for (i = dev->cw; i; i--)
if (!signal_is_set(port)) {
pps_get_ts(&ts_clear);
local_irq_restore(flags);
dev->cw_err = 0;
goto out_both;
}
local_irq_restore(flags);
/* timeout */
dev->cw_err++;
if (dev->cw_err >= CLEAR_WAIT_MAX_ERRORS) {
dev_err(dev->pps->dev, "disabled clear edge capture after %d"
" timeouts\n", dev->cw_err);
dev->cw = 0;
dev->cw_err = 0;
}
out_assert:
/* fire assert event */
pps_event(dev->pps, &ts_assert,
PPS_CAPTUREASSERT, NULL);
return;
out_both:
/* fire assert event */
pps_event(dev->pps, &ts_assert,
PPS_CAPTUREASSERT, NULL);
/* fire clear event */
pps_event(dev->pps, &ts_clear,
PPS_CAPTURECLEAR, NULL);
return;
}
/* the PPS echo function */
static void pps_echo(struct pps_device *pps, int event, void *data)
{
dev_info(pps->dev, "echo %s %s\n",
event & PPS_CAPTUREASSERT ? "assert" : "",
event & PPS_CAPTURECLEAR ? "clear" : "");
}
static void parport_attach(struct parport *port)
{
struct pps_client_pp *device;
struct pps_source_info info = {
.name = KBUILD_MODNAME,
.path = "",
.mode = PPS_CAPTUREBOTH | \
PPS_OFFSETASSERT | PPS_OFFSETCLEAR | \
PPS_ECHOASSERT | PPS_ECHOCLEAR | \
PPS_CANWAIT | PPS_TSFMT_TSPEC,
.echo = pps_echo,
.owner = THIS_MODULE,
.dev = NULL
};
device = kzalloc(sizeof(struct pps_client_pp), GFP_KERNEL);
if (!device) {
pr_err("memory allocation failed, not attaching\n");
return;
}
device->pardev = parport_register_device(port, KBUILD_MODNAME,
NULL, NULL, parport_irq, PARPORT_FLAG_EXCL, device);
if (!device->pardev) {
pr_err("couldn't register with %s\n", port->name);
goto err_free;
}
if (parport_claim_or_block(device->pardev) < 0) {
pr_err("couldn't claim %s\n", port->name);
goto err_unregister_dev;
}
device->pps = pps_register_source(&info,
PPS_CAPTUREBOTH | PPS_OFFSETASSERT | PPS_OFFSETCLEAR);
if (device->pps == NULL) {
pr_err("couldn't register PPS source\n");
goto err_release_dev;
}
device->cw = clear_wait;
port->ops->enable_irq(port);
pr_info("attached to %s\n", port->name);
return;
err_release_dev:
parport_release(device->pardev);
err_unregister_dev:
parport_unregister_device(device->pardev);
err_free:
kfree(device);
}
static void parport_detach(struct parport *port)
{
struct pardevice *pardev = port->cad;
struct pps_client_pp *device;
/* FIXME: oooh, this is ugly! */
if (strcmp(pardev->name, KBUILD_MODNAME))
/* not our port */
return;
device = pardev->private;
port->ops->disable_irq(port);
pps_unregister_source(device->pps);
parport_release(pardev);
parport_unregister_device(pardev);
kfree(device);
}
static struct parport_driver pps_parport_driver = {
.name = KBUILD_MODNAME,
.attach = parport_attach,
.detach = parport_detach,
};
/* module staff */
static int __init pps_parport_init(void)
{
int ret;
pr_info(DRVDESC "\n");
if (clear_wait > CLEAR_WAIT_MAX) {
pr_err("clear_wait value should be not greater"
" then %d\n", CLEAR_WAIT_MAX);
return -EINVAL;
}
ret = parport_register_driver(&pps_parport_driver);
if (ret) {
pr_err("unable to register with parport\n");
return ret;
}
return 0;
}
static void __exit pps_parport_exit(void)
{
parport_unregister_driver(&pps_parport_driver);
}
module_init(pps_parport_init);
module_exit(pps_parport_exit);
MODULE_AUTHOR("Alexander Gordeev <lasaine@lvk.cs.msu.su>");
MODULE_DESCRIPTION(DRVDESC);
MODULE_LICENSE("GPL");