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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* pps_parport.c -- kernel parallel port PPS client
*
* Copyright (C) 2009 Alexander Gordeev <lasaine@lvk.cs.msu.su>
*/
/*
* 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/slab.h>
#include <linux/parport.h>
#include <linux/pps_kernel.h>
/* 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);
static DEFINE_IDA(pps_client_index);
/* 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 */
int index; /* device number */
};
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;
}
static void parport_attach(struct parport *port)
{
struct pardev_cb pps_client_cb;
int index;
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,
.owner = THIS_MODULE,
.dev = NULL
};
if (clear_wait > CLEAR_WAIT_MAX) {
pr_err("clear_wait value should be not greater then %d\n",
CLEAR_WAIT_MAX);
return;
}
device = kzalloc(sizeof(struct pps_client_pp), GFP_KERNEL);
if (!device) {
pr_err("memory allocation failed, not attaching\n");
return;
}
index = ida_simple_get(&pps_client_index, 0, 0, GFP_KERNEL);
memset(&pps_client_cb, 0, sizeof(pps_client_cb));
pps_client_cb.private = device;
pps_client_cb.irq_func = parport_irq;
pps_client_cb.flags = PARPORT_FLAG_EXCL;
device->pardev = parport_register_dev_model(port,
KBUILD_MODNAME,
&pps_client_cb,
index);
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 (IS_ERR(device->pps)) {
pr_err("couldn't register PPS source\n");
goto err_release_dev;
}
device->cw = clear_wait;
port->ops->enable_irq(port);
device->index = index;
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:
ida_simple_remove(&pps_client_index, index);
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 (!pardev || 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);
ida_simple_remove(&pps_client_index, device->index);
kfree(device);
}
static struct parport_driver pps_parport_driver = {
.name = KBUILD_MODNAME,
.match_port = parport_attach,
.detach = parport_detach,
.devmodel = true,
};
module_parport_driver(pps_parport_driver);
MODULE_AUTHOR("Alexander Gordeev <lasaine@lvk.cs.msu.su>");
MODULE_DESCRIPTION("parallel port PPS client");
MODULE_LICENSE("GPL");
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