--- /dev/null
+/*
+ * 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");
projects / mv-sheeva.git / blobdiff