drivers/pps/clients/pps_parport.c

   1 /*
   2  * pps_parport.c -- kernel parallel port PPS client
   3  *
   4  *
   5  * Copyright (C) 2009   Alexander Gordeev <lasaine@lvk.cs.msu.su>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  20  */
  21
  22
  23 /*
  24  * TODO:
  25  * implement echo over SEL pin
  26  */
  27
  28 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  29
  30 #include <linux/kernel.h>
  31 #include <linux/module.h>
  32 #include <linux/init.h>
  33 #include <linux/irqnr.h>
  34 #include <linux/time.h>
  35 #include <linux/slab.h>
  36 #include <linux/parport.h>
  37 #include <linux/pps_kernel.h>
  38
  39 #define DRVDESC "parallel port PPS client"
  40
  41 /* module parameters */
  42
  43 #define CLEAR_WAIT_MAX          100
  44 #define CLEAR_WAIT_MAX_ERRORS   5
  45
  46 static unsigned int clear_wait = 100;
  47 MODULE_PARM_DESC(clear_wait,
  48         "Maximum number of port reads when polling for signal clear,"
  49         " zero turns clear edge capture off entirely");
  50 module_param(clear_wait, uint, 0);
  51
  52
  53 /* internal per port structure */
  54 struct pps_client_pp {
  55         struct pardevice *pardev;       /* parport device */
  56         struct pps_device *pps;         /* PPS device */
  57         unsigned int cw;                /* port clear timeout */
  58         unsigned int cw_err;            /* number of timeouts */
  59 };
  60
  61 static inline int signal_is_set(struct parport *port)
  62 {
  63         return (port->ops->read_status(port) & PARPORT_STATUS_ACK) != 0;
  64 }
  65
  66 /* parport interrupt handler */
  67 static void parport_irq(void *handle)
  68 {
  69         struct pps_event_time ts_assert, ts_clear;
  70         struct pps_client_pp *dev = handle;
  71         struct parport *port = dev->pardev->port;
  72         unsigned int i;
  73         unsigned long flags;
  74
  75         /* first of all we get the time stamp... */
  76         pps_get_ts(&ts_assert);
  77
  78         if (dev->cw == 0)
  79                 /* clear edge capture disabled */
  80                 goto out_assert;
  81
  82         /* try capture the clear edge */
  83
  84         /* We have to disable interrupts here. The idea is to prevent
  85          * other interrupts on the same processor to introduce random
  86          * lags while polling the port. Reading from IO port is known
  87          * to take approximately 1us while other interrupt handlers can
  88          * take much more potentially.
  89          *
  90          * Interrupts won't be disabled for a long time because the
  91          * number of polls is limited by clear_wait parameter which is
  92          * kept rather low. So it should never be an issue.
  93          */
  94         local_irq_save(flags);
  95         /* check the signal (no signal means the pulse is lost this time) */
  96         if (!signal_is_set(port)) {
  97                 local_irq_restore(flags);
  98                 dev_err(dev->pps->dev, "lost the signal\n");
  99                 goto out_assert;
 100         }
 101
 102         /* poll the port until the signal is unset */
 103         for (i = dev->cw; i; i--)
 104                 if (!signal_is_set(port)) {
 105                         pps_get_ts(&ts_clear);
 106                         local_irq_restore(flags);
 107                         dev->cw_err = 0;
 108                         goto out_both;
 109                 }
 110         local_irq_restore(flags);
 111
 112         /* timeout */
 113         dev->cw_err++;
 114         if (dev->cw_err >= CLEAR_WAIT_MAX_ERRORS) {
 115                 dev_err(dev->pps->dev, "disabled clear edge capture after %d"
 116                                 " timeouts\n", dev->cw_err);
 117                 dev->cw = 0;
 118                 dev->cw_err = 0;
 119         }
 120
 121 out_assert:
 122         /* fire assert event */
 123         pps_event(dev->pps, &ts_assert,
 124                         PPS_CAPTUREASSERT, NULL);
 125         return;
 126
 127 out_both:
 128         /* fire assert event */
 129         pps_event(dev->pps, &ts_assert,
 130                         PPS_CAPTUREASSERT, NULL);
 131         /* fire clear event */
 132         pps_event(dev->pps, &ts_clear,
 133                         PPS_CAPTURECLEAR, NULL);
 134         return;
 135 }
 136
 137 static void parport_attach(struct parport *port)
 138 {
 139         struct pps_client_pp *device;
 140         struct pps_source_info info = {
 141                 .name           = KBUILD_MODNAME,
 142                 .path           = "",
 143                 .mode           = PPS_CAPTUREBOTH | \
 144                                   PPS_OFFSETASSERT | PPS_OFFSETCLEAR | \
 145                                   PPS_ECHOASSERT | PPS_ECHOCLEAR | \
 146                                   PPS_CANWAIT | PPS_TSFMT_TSPEC,
 147                 .owner          = THIS_MODULE,
 148                 .dev            = NULL
 149         };
 150
 151         device = kzalloc(sizeof(struct pps_client_pp), GFP_KERNEL);
 152         if (!device) {
 153                 pr_err("memory allocation failed, not attaching\n");
 154                 return;
 155         }
 156
 157         device->pardev = parport_register_device(port, KBUILD_MODNAME,
 158                         NULL, NULL, parport_irq, PARPORT_FLAG_EXCL, device);
 159         if (!device->pardev) {
 160                 pr_err("couldn't register with %s\n", port->name);
 161                 goto err_free;
 162         }
 163
 164         if (parport_claim_or_block(device->pardev) < 0) {
 165                 pr_err("couldn't claim %s\n", port->name);
 166                 goto err_unregister_dev;
 167         }
 168
 169         device->pps = pps_register_source(&info,
 170                         PPS_CAPTUREBOTH | PPS_OFFSETASSERT | PPS_OFFSETCLEAR);
 171         if (device->pps == NULL) {
 172                 pr_err("couldn't register PPS source\n");
 173                 goto err_release_dev;
 174         }
 175
 176         device->cw = clear_wait;
 177
 178         port->ops->enable_irq(port);
 179
 180         pr_info("attached to %s\n", port->name);
 181
 182         return;
 183
 184 err_release_dev:
 185         parport_release(device->pardev);
 186 err_unregister_dev:
 187         parport_unregister_device(device->pardev);
 188 err_free:
 189         kfree(device);
 190 }
 191
 192 static void parport_detach(struct parport *port)
 193 {
 194         struct pardevice *pardev = port->cad;
 195         struct pps_client_pp *device;
 196
 197         /* FIXME: oooh, this is ugly! */
 198         if (!pardev || strcmp(pardev->name, KBUILD_MODNAME))
 199                 /* not our port */
 200                 return;
 201
 202         device = pardev->private;
 203
 204         port->ops->disable_irq(port);
 205         pps_unregister_source(device->pps);
 206         parport_release(pardev);
 207         parport_unregister_device(pardev);
 208         kfree(device);
 209 }
 210
 211 static struct parport_driver pps_parport_driver = {
 212         .name = KBUILD_MODNAME,
 213         .attach = parport_attach,
 214         .detach = parport_detach,
 215 };
 216
 217 /* module staff */
 218
 219 static int __init pps_parport_init(void)
 220 {
 221         int ret;
 222
 223         pr_info(DRVDESC "\n");
 224
 225         if (clear_wait > CLEAR_WAIT_MAX) {
 226                 pr_err("clear_wait value should be not greater"
 227                                 " then %d\n", CLEAR_WAIT_MAX);
 228                 return -EINVAL;
 229         }
 230
 231         ret = parport_register_driver(&pps_parport_driver);
 232         if (ret) {
 233                 pr_err("unable to register with parport\n");
 234                 return ret;
 235         }
 236
 237         return  0;
 238 }
 239
 240 static void __exit pps_parport_exit(void)
 241 {
 242         parport_unregister_driver(&pps_parport_driver);
 243 }
 244
 245 module_init(pps_parport_init);
 246 module_exit(pps_parport_exit);
 247
 248 MODULE_AUTHOR("Alexander Gordeev <lasaine@lvk.cs.msu.su>");
 249 MODULE_DESCRIPTION(DRVDESC);
 250 MODULE_LICENSE("GPL");