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/parport.h>
  36 #include <linux/pps_kernel.h>
  37
  38 #define DRVDESC "parallel port PPS client"
  39
  40 /* module parameters */
  41
  42 #define CLEAR_WAIT_MAX          100
  43 #define CLEAR_WAIT_MAX_ERRORS   5
  44
  45 static unsigned int clear_wait = 100;
  46 MODULE_PARM_DESC(clear_wait,
  47         "Maximum number of port reads when polling for signal clear,"
  48         " zero turns clear edge capture off entirely");
  49 module_param(clear_wait, uint, 0);
  50
  51
  52 /* internal per port structure */
  53 struct pps_client_pp {
  54         struct pardevice *pardev;       /* parport device */
  55         struct pps_device *pps;         /* PPS device */
  56         unsigned int cw;                /* port clear timeout */
  57         unsigned int cw_err;            /* number of timeouts */
  58 };
  59
  60 static inline int signal_is_set(struct parport *port)
  61 {
  62         return (port->ops->read_status(port) & PARPORT_STATUS_ACK) != 0;
  63 }
  64
  65 /* parport interrupt handler */
  66 static void parport_irq(void *handle)
  67 {
  68         struct pps_event_time ts_assert, ts_clear;
  69         struct pps_client_pp *dev = handle;
  70         struct parport *port = dev->pardev->port;
  71         unsigned int i;
  72         unsigned long flags;
  73
  74         /* first of all we get the time stamp... */
  75         pps_get_ts(&ts_assert);
  76
  77         if (dev->cw == 0)
  78                 /* clear edge capture disabled */
  79                 goto out_assert;
  80
  81         /* try capture the clear edge */
  82
  83         /* We have to disable interrupts here. The idea is to prevent
  84          * other interrupts on the same processor to introduce random
  85          * lags while polling the port. Reading from IO port is known
  86          * to take approximately 1us while other interrupt handlers can
  87          * take much more potentially.
  88          *
  89          * Interrupts won't be disabled for a long time because the
  90          * number of polls is limited by clear_wait parameter which is
  91          * kept rather low. So it should never be an issue.
  92          */
  93         local_irq_save(flags);
  94         /* check the signal (no signal means the pulse is lost this time) */
  95         if (!signal_is_set(port)) {
  96                 local_irq_restore(flags);
  97                 dev_err(dev->pps->dev, "lost the signal\n");
  98                 goto out_assert;
  99         }
 100
 101         /* poll the port until the signal is unset */
 102         for (i = dev->cw; i; i--)
 103                 if (!signal_is_set(port)) {
 104                         pps_get_ts(&ts_clear);
 105                         local_irq_restore(flags);
 106                         dev->cw_err = 0;
 107                         goto out_both;
 108                 }
 109         local_irq_restore(flags);
 110
 111         /* timeout */
 112         dev->cw_err++;
 113         if (dev->cw_err >= CLEAR_WAIT_MAX_ERRORS) {
 114                 dev_err(dev->pps->dev, "disabled clear edge capture after %d"
 115                                 " timeouts\n", dev->cw_err);
 116                 dev->cw = 0;
 117                 dev->cw_err = 0;
 118         }
 119
 120 out_assert:
 121         /* fire assert event */
 122         pps_event(dev->pps, &ts_assert,
 123                         PPS_CAPTUREASSERT, NULL);
 124         return;
 125
 126 out_both:
 127         /* fire assert event */
 128         pps_event(dev->pps, &ts_assert,
 129                         PPS_CAPTUREASSERT, NULL);
 130         /* fire clear event */
 131         pps_event(dev->pps, &ts_clear,
 132                         PPS_CAPTURECLEAR, NULL);
 133         return;
 134 }
 135
 136 static void parport_attach(struct parport *port)
 137 {
 138         struct pps_client_pp *device;
 139         struct pps_source_info info = {
 140                 .name           = KBUILD_MODNAME,
 141                 .path           = "",
 142                 .mode           = PPS_CAPTUREBOTH | \
 143                                   PPS_OFFSETASSERT | PPS_OFFSETCLEAR | \
 144                                   PPS_ECHOASSERT | PPS_ECHOCLEAR | \
 145                                   PPS_CANWAIT | PPS_TSFMT_TSPEC,
 146                 .owner          = THIS_MODULE,
 147                 .dev            = NULL
 148         };
 149
 150         device = kzalloc(sizeof(struct pps_client_pp), GFP_KERNEL);
 151         if (!device) {
 152                 pr_err("memory allocation failed, not attaching\n");
 153                 return;
 154         }
 155
 156         device->pardev = parport_register_device(port, KBUILD_MODNAME,
 157                         NULL, NULL, parport_irq, PARPORT_FLAG_EXCL, device);
 158         if (!device->pardev) {
 159                 pr_err("couldn't register with %s\n", port->name);
 160                 goto err_free;
 161         }
 162
 163         if (parport_claim_or_block(device->pardev) < 0) {
 164                 pr_err("couldn't claim %s\n", port->name);
 165                 goto err_unregister_dev;
 166         }
 167
 168         device->pps = pps_register_source(&info,
 169                         PPS_CAPTUREBOTH | PPS_OFFSETASSERT | PPS_OFFSETCLEAR);
 170         if (device->pps == NULL) {
 171                 pr_err("couldn't register PPS source\n");
 172                 goto err_release_dev;
 173         }
 174
 175         device->cw = clear_wait;
 176
 177         port->ops->enable_irq(port);
 178
 179         pr_info("attached to %s\n", port->name);
 180
 181         return;
 182
 183 err_release_dev:
 184         parport_release(device->pardev);
 185 err_unregister_dev:
 186         parport_unregister_device(device->pardev);
 187 err_free:
 188         kfree(device);
 189 }
 190
 191 static void parport_detach(struct parport *port)
 192 {
 193         struct pardevice *pardev = port->cad;
 194         struct pps_client_pp *device;
 195
 196         /* FIXME: oooh, this is ugly! */
 197         if (strcmp(pardev->name, KBUILD_MODNAME))
 198                 /* not our port */
 199                 return;
 200
 201         device = pardev->private;
 202
 203         port->ops->disable_irq(port);
 204         pps_unregister_source(device->pps);
 205         parport_release(pardev);
 206         parport_unregister_device(pardev);
 207         kfree(device);
 208 }
 209
 210 static struct parport_driver pps_parport_driver = {
 211         .name = KBUILD_MODNAME,
 212         .attach = parport_attach,
 213         .detach = parport_detach,
 214 };
 215
 216 /* module staff */
 217
 218 static int __init pps_parport_init(void)
 219 {
 220         int ret;
 221
 222         pr_info(DRVDESC "\n");
 223
 224         if (clear_wait > CLEAR_WAIT_MAX) {
 225                 pr_err("clear_wait value should be not greater"
 226                                 " then %d\n", CLEAR_WAIT_MAX);
 227                 return -EINVAL;
 228         }
 229
 230         ret = parport_register_driver(&pps_parport_driver);
 231         if (ret) {
 232                 pr_err("unable to register with parport\n");
 233                 return ret;
 234         }
 235
 236         return  0;
 237 }
 238
 239 static void __exit pps_parport_exit(void)
 240 {
 241         parport_unregister_driver(&pps_parport_driver);
 242 }
 243
 244 module_init(pps_parport_init);
 245 module_exit(pps_parport_exit);
 246
 247 MODULE_AUTHOR("Alexander Gordeev <lasaine@lvk.cs.msu.su>");
 248 MODULE_DESCRIPTION(DRVDESC);
 249 MODULE_LICENSE("GPL");