drivers/spi/spi-butterfly.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * parport-to-butterfly adapter
   4  *
   5  * Copyright (C) 2005 David Brownell
   6  */
   7 #include <linux/kernel.h>
   8 #include <linux/init.h>
   9 #include <linux/delay.h>
  10 #include <linux/module.h>
  11 #include <linux/device.h>
  12 #include <linux/parport.h>
  13
  14 #include <linux/sched.h>
  15 #include <linux/spi/spi.h>
  16 #include <linux/spi/spi_bitbang.h>
  17 #include <linux/spi/flash.h>
  18
  19 #include <linux/mtd/partitions.h>
  20
  21 /*
  22  * This uses SPI to talk with an "AVR Butterfly", which is a $US20 card
  23  * with a battery powered AVR microcontroller and lots of goodies.  You
  24  * can use GCC to develop firmware for this.
  25  *
  26  * See Documentation/spi/butterfly.rst for information about how to build
  27  * and use this custom parallel port cable.
  28  */
  29
  30 /* DATA output bits (pins 2..9 == D0..D7) */
  31 #define butterfly_nreset (1 << 1)               /* pin 3 */
  32
  33 #define spi_sck_bit     (1 << 0)                /* pin 2 */
  34 #define spi_mosi_bit    (1 << 7)                /* pin 9 */
  35
  36 #define vcc_bits        ((1 << 6) | (1 << 5))   /* pins 7, 8 */
  37
  38 /* STATUS input bits */
  39 #define spi_miso_bit    PARPORT_STATUS_BUSY     /* pin 11 */
  40
  41 /* CONTROL output bits */
  42 #define spi_cs_bit      PARPORT_CONTROL_SELECT  /* pin 17 */
  43
  44 static inline struct butterfly *spidev_to_pp(struct spi_device *spi)
  45 {
  46         return spi->controller_data;
  47 }
  48
  49 struct butterfly {
  50         /* REVISIT ... for now, this must be first */
  51         struct spi_bitbang      bitbang;
  52
  53         struct parport          *port;
  54         struct pardevice        *pd;
  55
  56         u8                      lastbyte;
  57
  58         struct spi_device       *dataflash;
  59         struct spi_device       *butterfly;
  60         struct spi_board_info   info[2];
  61
  62 };
  63
  64 /*----------------------------------------------------------------------*/
  65
  66 static inline void
  67 setsck(struct spi_device *spi, int is_on)
  68 {
  69         struct butterfly        *pp = spidev_to_pp(spi);
  70         u8                      bit, byte = pp->lastbyte;
  71
  72         bit = spi_sck_bit;
  73
  74         if (is_on)
  75                 byte |= bit;
  76         else
  77                 byte &= ~bit;
  78         parport_write_data(pp->port, byte);
  79         pp->lastbyte = byte;
  80 }
  81
  82 static inline void
  83 setmosi(struct spi_device *spi, int is_on)
  84 {
  85         struct butterfly        *pp = spidev_to_pp(spi);
  86         u8                      bit, byte = pp->lastbyte;
  87
  88         bit = spi_mosi_bit;
  89
  90         if (is_on)
  91                 byte |= bit;
  92         else
  93                 byte &= ~bit;
  94         parport_write_data(pp->port, byte);
  95         pp->lastbyte = byte;
  96 }
  97
  98 static inline int getmiso(struct spi_device *spi)
  99 {
 100         struct butterfly        *pp = spidev_to_pp(spi);
 101         int                     value;
 102         u8                      bit;
 103
 104         bit = spi_miso_bit;
 105
 106         /* only STATUS_BUSY is NOT negated */
 107         value = !(parport_read_status(pp->port) & bit);
 108         return (bit == PARPORT_STATUS_BUSY) ? value : !value;
 109 }
 110
 111 static void butterfly_chipselect(struct spi_device *spi, int value)
 112 {
 113         struct butterfly        *pp = spidev_to_pp(spi);
 114
 115         /* set default clock polarity */
 116         if (value != BITBANG_CS_INACTIVE)
 117                 setsck(spi, spi->mode & SPI_CPOL);
 118
 119         /* here, value == "activate or not";
 120          * most PARPORT_CONTROL_* bits are negated, so we must
 121          * morph it to value == "bit value to write in control register"
 122          */
 123         if (spi_cs_bit == PARPORT_CONTROL_INIT)
 124                 value = !value;
 125
 126         parport_frob_control(pp->port, spi_cs_bit, value ? spi_cs_bit : 0);
 127 }
 128
 129 /* we only needed to implement one mode here, and choose SPI_MODE_0 */
 130
 131 #define spidelay(X)     do { } while (0)
 132 /* #define spidelay     ndelay */
 133
 134 #include "spi-bitbang-txrx.h"
 135
 136 static u32
 137 butterfly_txrx_word_mode0(struct spi_device *spi, unsigned nsecs, u32 word,
 138                           u8 bits, unsigned flags)
 139 {
 140         return bitbang_txrx_be_cpha0(spi, nsecs, 0, flags, word, bits);
 141 }
 142
 143 /*----------------------------------------------------------------------*/
 144
 145 /* override default partitioning with cmdlinepart */
 146 static struct mtd_partition partitions[] = { {
 147         /* JFFS2 wants partitions of 4*N blocks for this device,
 148          * so sectors 0 and 1 can't be partitions by themselves.
 149          */
 150
 151         /* sector 0 = 8 pages * 264 bytes/page (1 block)
 152          * sector 1 = 248 pages * 264 bytes/page
 153          */
 154         .name           = "bookkeeping",        /* 66 KB */
 155         .offset         = 0,
 156         .size           = (8 + 248) * 264,
 157         /* .mask_flags  = MTD_WRITEABLE, */
 158 }, {
 159         /* sector 2 = 256 pages * 264 bytes/page
 160          * sectors 3-5 = 512 pages * 264 bytes/page
 161          */
 162         .name           = "filesystem",         /* 462 KB */
 163         .offset         = MTDPART_OFS_APPEND,
 164         .size           = MTDPART_SIZ_FULL,
 165 } };
 166
 167 static struct flash_platform_data flash = {
 168         .name           = "butterflash",
 169         .parts          = partitions,
 170         .nr_parts       = ARRAY_SIZE(partitions),
 171 };
 172
 173 /* REVISIT remove this ugly global and its "only one" limitation */
 174 static struct butterfly *butterfly;
 175
 176 static void butterfly_attach(struct parport *p)
 177 {
 178         struct pardevice        *pd;
 179         int                     status;
 180         struct butterfly        *pp;
 181         struct spi_master       *master;
 182         struct device           *dev = p->physport->dev;
 183         struct pardev_cb        butterfly_cb;
 184
 185         if (butterfly || !dev)
 186                 return;
 187
 188         /* REVISIT:  this just _assumes_ a butterfly is there ... no probe,
 189          * and no way to be selective about what it binds to.
 190          */
 191
 192         master = spi_alloc_master(dev, sizeof(*pp));
 193         if (!master) {
 194                 status = -ENOMEM;
 195                 goto done;
 196         }
 197         pp = spi_master_get_devdata(master);
 198
 199         /*
 200          * SPI and bitbang hookup
 201          *
 202          * use default setup(), cleanup(), and transfer() methods; and
 203          * only bother implementing mode 0.  Start it later.
 204          */
 205         master->bus_num = 42;
 206         master->num_chipselect = 2;
 207
 208         pp->bitbang.master = master;
 209         pp->bitbang.chipselect = butterfly_chipselect;
 210         pp->bitbang.txrx_word[SPI_MODE_0] = butterfly_txrx_word_mode0;
 211
 212         /*
 213          * parport hookup
 214          */
 215         pp->port = p;
 216         memset(&butterfly_cb, 0, sizeof(butterfly_cb));
 217         butterfly_cb.private = pp;
 218         pd = parport_register_dev_model(p, "spi_butterfly", &butterfly_cb, 0);
 219         if (!pd) {
 220                 status = -ENOMEM;
 221                 goto clean0;
 222         }
 223         pp->pd = pd;
 224
 225         status = parport_claim(pd);
 226         if (status < 0)
 227                 goto clean1;
 228
 229         /*
 230          * Butterfly reset, powerup, run firmware
 231          */
 232         pr_debug("%s: powerup/reset Butterfly\n", p->name);
 233
 234         /* nCS for dataflash (this bit is inverted on output) */
 235         parport_frob_control(pp->port, spi_cs_bit, 0);
 236
 237         /* stabilize power with chip in reset (nRESET), and
 238          * spi_sck_bit clear (CPOL=0)
 239          */
 240         pp->lastbyte |= vcc_bits;
 241         parport_write_data(pp->port, pp->lastbyte);
 242         msleep(5);
 243
 244         /* take it out of reset; assume long reset delay */
 245         pp->lastbyte |= butterfly_nreset;
 246         parport_write_data(pp->port, pp->lastbyte);
 247         msleep(100);
 248
 249         /*
 250          * Start SPI ... for now, hide that we're two physical busses.
 251          */
 252         status = spi_bitbang_start(&pp->bitbang);
 253         if (status < 0)
 254                 goto clean2;
 255
 256         /* Bus 1 lets us talk to at45db041b (firmware disables AVR SPI), AVR
 257          * (firmware resets at45, acts as spi slave) or neither (we ignore
 258          * both, AVR uses AT45).  Here we expect firmware for the first option.
 259          */
 260
 261         pp->info[0].max_speed_hz = 15 * 1000 * 1000;
 262         strcpy(pp->info[0].modalias, "mtd_dataflash");
 263         pp->info[0].platform_data = &flash;
 264         pp->info[0].chip_select = 1;
 265         pp->info[0].controller_data = pp;
 266         pp->dataflash = spi_new_device(pp->bitbang.master, &pp->info[0]);
 267         if (pp->dataflash)
 268                 pr_debug("%s: dataflash at %s\n", p->name,
 269                          dev_name(&pp->dataflash->dev));
 270
 271         pr_info("%s: AVR Butterfly\n", p->name);
 272         butterfly = pp;
 273         return;
 274
 275 clean2:
 276         /* turn off VCC */
 277         parport_write_data(pp->port, 0);
 278
 279         parport_release(pp->pd);
 280 clean1:
 281         parport_unregister_device(pd);
 282 clean0:
 283         spi_master_put(pp->bitbang.master);
 284 done:
 285         pr_debug("%s: butterfly probe, fail %d\n", p->name, status);
 286 }
 287
 288 static void butterfly_detach(struct parport *p)
 289 {
 290         struct butterfly        *pp;
 291
 292         /* FIXME this global is ugly ... but, how to quickly get from
 293          * the parport to the "struct butterfly" associated with it?
 294          * "old school" driver-internal device lists?
 295          */
 296         if (!butterfly || butterfly->port != p)
 297                 return;
 298         pp = butterfly;
 299         butterfly = NULL;
 300
 301         /* stop() unregisters child devices too */
 302         spi_bitbang_stop(&pp->bitbang);
 303
 304         /* turn off VCC */
 305         parport_write_data(pp->port, 0);
 306         msleep(10);
 307
 308         parport_release(pp->pd);
 309         parport_unregister_device(pp->pd);
 310
 311         spi_master_put(pp->bitbang.master);
 312 }
 313
 314 static struct parport_driver butterfly_driver = {
 315         .name =         "spi_butterfly",
 316         .match_port =   butterfly_attach,
 317         .detach =       butterfly_detach,
 318         .devmodel = true,
 319 };
 320
 321 static int __init butterfly_init(void)
 322 {
 323         return parport_register_driver(&butterfly_driver);
 324 }
 325 device_initcall(butterfly_init);
 326
 327 static void __exit butterfly_exit(void)
 328 {
 329         parport_unregister_driver(&butterfly_driver);
 330 }
 331 module_exit(butterfly_exit);
 332
 333 MODULE_DESCRIPTION("Parport Adapter driver for AVR Butterfly");
 334 MODULE_LICENSE("GPL");