spi_tty.c

   1 /*
   2  * spi_butterfly.c - parport-to-butterfly adapter
   3  *
   4  * Copyright (C) 2005 David Brownell
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  19  */
  20 #include <linux/kernel.h>
  21 #include <linux/init.h>
  22 #include <linux/delay.h>
  23 #include <linux/device.h>
  24 #include <linux/parport.h>
  25
  26 #include <linux/sched.h>
  27 #include <linux/spi/spi.h>
  28 #include <linux/spi/spi_bitbang.h>
  29
  30
  31
  32 /*
  33  * This uses SPI to talk with an "AVR Butterfly", which is a $US20 card
  34  * with a battery powered AVR microcontroller and lots of goodies.  You
  35  * can use GCC to develop firmware for this.
  36  *
  37  * See Documentation/spi/butterfly for information about how to build
  38  * and use this custom parallel port cable.
  39  */
  40
  41 /*
  42  * spi_device
  43  * todo:
  44  * - implement SPI mode 1,2,3 is yet missing
  45  * - prevent ugly handling of global butterfly structure
  46  * - use serial subsystem
  47  * - make stuff module configurable during runtime
  48  */
  49
  50 /* DATA output bits (pins 2..9 == D0..D7) */
  51 #define butterfly_nreset (1 << 1)               /* pin 3 */
  52
  53 #define spi_sck_bit     (1 << 0)                /* pin 2 */
  54 #define spi_mosi_bit    (1 << 7)                /* pin 9 */
  55
  56 #define vcc_bits        ((1 << 6) | (1 << 5))   /* pins 7, 8 */
  57
  58 /* STATUS input bits */
  59 #define spi_miso_bit    PARPORT_STATUS_BUSY     /* pin 11 */
  60
  61 /* CONTROL output bits */
  62 #define spi_cs_bit      PARPORT_CONTROL_SELECT  /* pin 17 */
  63
  64
  65
  66 static inline struct butterfly *spidev_to_pp(struct spi_device *spi)
  67 {
  68         return spi->controller_data;
  69 }
  70
  71
  72 struct butterfly {
  73         /* REVISIT ... for now, this must be first */
  74         struct spi_bitbang      bitbang;
  75
  76         struct parport          *port;
  77         struct pardevice        *pd;
  78
  79         u8                      lastbyte;
  80
  81         struct spi_message      *msg;
  82         struct spi_device       *butterfly;
  83         struct spi_board_info   info[2];
  84
  85 };
  86
  87 /*----------------------------------------------------------------------*/
  88
  89 static inline void
  90 setsck(struct spi_device *spi, int is_on)
  91 {
  92         struct butterfly        *pp = spidev_to_pp(spi);
  93         u8                      bit, byte = pp->lastbyte;
  94
  95         bit = spi_sck_bit;
  96
  97         if (is_on)
  98                 byte |= bit;
  99         else
 100                 byte &= ~bit;
 101         parport_write_data(pp->port, byte);
 102         pp->lastbyte = byte;
 103 }
 104
 105 static inline void
 106 setmosi(struct spi_device *spi, int is_on)
 107 {
 108         struct butterfly        *pp = spidev_to_pp(spi);
 109         u8                      bit, byte = pp->lastbyte;
 110
 111         bit = spi_mosi_bit;
 112
 113         if (is_on)
 114                 byte |= bit;
 115         else
 116                 byte &= ~bit;
 117         parport_write_data(pp->port, byte);
 118         pp->lastbyte = byte;
 119 }
 120
 121 static inline int getmiso(struct spi_device *spi)
 122 {
 123         struct butterfly        *pp = spidev_to_pp(spi);
 124         int                     value;
 125         u8                      bit;
 126
 127         bit = spi_miso_bit;
 128
 129         /* only STATUS_BUSY is NOT negated */
 130         value = !(parport_read_status(pp->port) & bit);
 131         return (bit == PARPORT_STATUS_BUSY) ? value : !value;
 132 }
 133
 134 static void butterfly_chipselect(struct spi_device *spi, int value)
 135 {
 136         struct butterfly        *pp = spidev_to_pp(spi);
 137
 138         /* set default clock polarity */
 139         if (value != BITBANG_CS_INACTIVE)
 140                 setsck(spi, spi->mode & SPI_CPOL);
 141
 142         /* here, value == "activate or not";
 143          * most PARPORT_CONTROL_* bits are negated, so we must
 144          * morph it to value == "bit value to write in control register"
 145          */
 146         if (spi_cs_bit == PARPORT_CONTROL_INIT)
 147                 value = !value;
 148
 149         parport_frob_control(pp->port, spi_cs_bit, value ? spi_cs_bit : 0);
 150 }
 151
 152
 153 /* we only needed to implement one mode here, and choose SPI_MODE_0 */
 154
 155 #define spidelay(X)     do{}while(0)
 156 //#define       spidelay        ndelay
 157
 158 #define EXPAND_BITBANG_TXRX
 159 #include <linux/spi/spi_bitbang.h>
 160
 161 static u32
 162 butterfly_txrx_word_mode0(struct spi_device *spi,
 163                 unsigned nsecs,
 164                 u32 word, u8 bits)
 165 {
 166         return bitbang_txrx_be_cpha0(spi, nsecs, 0, word, bits);
 167 }
 168
 169 /*----------------------------------------------------------------------*/
 170
 171 /* REVISIT remove this ugly global and its "only one" limitation */
 172 static struct butterfly *butterfly;
 173
 174 static void butterfly_attach(struct parport *p)
 175 {
 176         struct pardevice        *pd;
 177         int                     status;
 178         struct butterfly        *pp;
 179         struct spi_master       *master;
 180         struct device           *dev = p->physport->dev;
 181
 182         if (butterfly || !dev)
 183                 return;
 184
 185         /* REVISIT:  this just _assumes_ a butterfly is there ... no probe,
 186          * and no way to be selective about what it binds to.
 187          */
 188
 189         master = spi_alloc_master(dev, sizeof *pp);
 190         if (!master) {
 191                 status = -ENOMEM;
 192                 goto done;
 193         }
 194         pp = spi_master_get_devdata(master);
 195
 196         /*
 197          * SPI and bitbang hookup
 198          *
 199          * use default setup(), cleanup(), and transfer() methods; and
 200          * only bother implementing mode 0.  Start it later.
 201          */
 202         master->bus_num = 42;                                       // hard coded?!?
 203         master->num_chipselect = 2;                                 // hard coded?!?
 204
 205         pp->bitbang.master = spi_master_get(master);
 206         pp->bitbang.chipselect = butterfly_chipselect;
 207         pp->bitbang.txrx_word[SPI_MODE_0] = butterfly_txrx_word_mode0;
 208
 209         /*
 210          * parport hookup
 211          */
 212         pp->port = p;
 213         pd = parport_register_device(p, "spi_butterfly",
 214                         NULL, NULL, NULL,
 215                         0 /* FLAGS */, pp);
 216         if (!pd) {
 217                 status = -ENOMEM;
 218                 goto clean0;
 219         }
 220         pp->pd = pd;
 221
 222         status = parport_claim(pd);
 223         if (status < 0)
 224                 goto clean1;
 225
 226         /*
 227          * Butterfly reset, powerup, run firmware
 228          */
 229         pr_debug("%s: powerup/reset Butterfly\n", p->name);
 230
 231         /* nCS for dataflash (this bit is inverted on output) */
 232         parport_frob_control(pp->port, spi_cs_bit, 0);
 233
 234         /* stabilize power with chip in reset (nRESET), and
 235          * spi_sck_bit clear (CPOL=0)
 236          */
 237         pp->lastbyte |= vcc_bits;
 238         parport_write_data(pp->port, pp->lastbyte);
 239         msleep(5);
 240
 241         /* take it out of reset; assume long reset delay */
 242         pp->lastbyte |= butterfly_nreset;
 243         parport_write_data(pp->port, pp->lastbyte);
 244         msleep(100);
 245
 246
 247         /*
 248          * Start SPI ... for now, hide that we're two physical busses.
 249          */
 250         status = spi_bitbang_start(&pp->bitbang);
 251         if (status < 0)
 252                 goto clean2;
 253
 254         /* Bus 1 lets us talk to at45db041b (firmware disables AVR SPI), AVR
 255          * (firmware resets at45, acts as spi slave) or neither (we ignore
 256          * both, AVR uses AT45).  Here we expect firmware for the first option.
 257          */
 258
 259         pp->info[0].max_speed_hz = 15 * 1000 * 1000;
 260
 261         strcpy(pp->info[0].modalias, "spi_tty");                       // name length check ! < KOBJ_NAME_LEN
 262         pp->info[0].platform_data = NULL;                              // here we should add data structures for subsystem driver ???
 263         pp->info[0].chip_select = 1;                                   // 0: .. 1:
 264         pp->info[0].controller_data = pp;        /* save my structure for later use */
 265         pp->butterfly = spi_new_device(pp->bitbang.master, &pp->info[0]);
 266         if (pp->butterfly)
 267                 pr_debug("%s: dataflash at %s\n", p->name,
 268                                 pp->butterfly->dev.bus_id);
 269
 270         // dev_info(_what?_, ...)
 271         pr_info("%s: AVR Butterfly\n", p->name);
 272
 273
 274         /* get spi_bitbang_transfer either via global Symbol, or better
 275          * ask it from the driver structure
 276          */
 277         pp->msg = spi_message_alloc(1, GFP_KERNEL);
 278         if (master) { /* the same address is also saved in pp->bitbang.master or pp->butterfly->master */
 279               struct spi_message *spi_msg;
 280               spi_msg = pp->msg;
 281               if (spi_msg) {
 282                       // spi_message_init(spi_msg);
 283                       pr_info("Alloc SPI message buffer\n");
 284                       spi_msg->spi = pp->butterfly;
 285                       spi_msg->actual_length = 1;
 286 #if 0
 287                       spi_msg->list_head ... Addresse der ersten SPI transfer struct
 288
 289
 290                       spi_msg->tx_buf = ;
 291                       spi_msg->len = 1;
 292                       spi_msg->cs_change = 1;
 293                       spi_msg->delay_usecs = 0;
 294
 295                       /* fill up message */
 296                       master->transfer(pp->butterfly, spi_msg);
 297 #endif
 298               }
 299         }
 300         butterfly = pp;
 301         return;
 302
 303 clean2:
 304         /* turn off VCC */
 305         parport_write_data(pp->port, 0);
 306
 307         parport_release(pp->pd);
 308 clean1:
 309         parport_unregister_device(pd);
 310 clean0:
 311         (void) spi_master_put(pp->bitbang.master);
 312 done:
 313         pr_debug("%s: butterfly probe, fail %d\n", p->name, status);
 314 }
 315
 316 static void butterfly_detach(struct parport *p)
 317 {
 318         struct butterfly        *pp;
 319         int                     status;
 320
 321         /* FIXME this global is ugly ... but, how to quickly get from
 322          * the parport to the "struct butterfly" associated with it?
 323          * "old school" driver-internal device lists?
 324          */
 325         if (!butterfly || butterfly->port != p)
 326                 return;
 327         pp = butterfly;
 328         if (pp->msg) {
 329                 spi_message_free(pp->msg);
 330                 pr_info("Dealloc SPI message buffer\n");
 331         }
 332         butterfly = NULL;
 333
 334         /* stop() unregisters child devices too */
 335         status = spi_bitbang_stop(&pp->bitbang);
 336
 337         /* turn off VCC */
 338         parport_write_data(pp->port, 0);
 339         msleep(10);
 340
 341         parport_release(pp->pd);
 342         parport_unregister_device(pp->pd);
 343
 344         (void) spi_master_put(pp->bitbang.master);
 345 }
 346
 347 static struct parport_driver butterfly_driver = {
 348         .name =         "spi_butterfly",
 349         .attach =       butterfly_attach,
 350         .detach =       butterfly_detach,
 351 };
 352
 353
 354 static int __init butterfly_init(void)
 355 {
 356         return parport_register_driver(&butterfly_driver);
 357 }
 358 device_initcall(butterfly_init);
 359
 360 static void __exit butterfly_exit(void)
 361 {
 362         parport_unregister_driver(&butterfly_driver);
 363 }
 364 module_exit(butterfly_exit);
 365
 366 MODULE_DESCRIPTION("Parport Adapter driver for SPI tty Butterfly");
 367 MODULE_LICENSE("GPL");