hw/eeprom93xx.c

   1 /*
   2  * QEMU EEPROM 93xx emulation
   3  *
   4  * Copyright (c) 2006-2007 Stefan Weil
   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, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 /* Emulation for serial EEPROMs:
  21  * NMC93C06 256-Bit (16 x 16)
  22  * NMC93C46 1024-Bit (64 x 16)
  23  * NMC93C56 2028 Bit (128 x 16)
  24  * NMC93C66 4096 Bit (256 x 16)
  25  * Compatible devices include FM93C46 and others.
  26  *
  27  * Other drivers use these interface functions:
  28  * eeprom93xx_new   - add a new EEPROM (with 16, 64 or 256 words)
  29  * eeprom93xx_free  - destroy EEPROM
  30  * eeprom93xx_read  - read data from the EEPROM
  31  * eeprom93xx_write - write data to the EEPROM
  32  * eeprom93xx_data  - get EEPROM data array for external manipulation
  33  *
  34  * Todo list:
  35  * - No emulation of EEPROM timings.
  36  */
  37
  38 #include "hw.h"
  39 #include "eeprom93xx.h"
  40
  41 /* Debug EEPROM emulation. */
  42 //~ #define DEBUG_EEPROM
  43
  44 #ifdef DEBUG_EEPROM
  45 #define logout(fmt, ...) fprintf(stderr, "EEPROM\t%-24s" fmt, __func__, ## __VA_ARGS__)
  46 #else
  47 #define logout(fmt, ...) ((void)0)
  48 #endif
  49
  50 #define EEPROM_INSTANCE  0
  51 #define OLD_EEPROM_VERSION 20061112
  52 #define EEPROM_VERSION (OLD_EEPROM_VERSION + 1)
  53
  54 #if 0
  55 typedef enum {
  56   eeprom_read  = 0x80,   /* read register xx */
  57   eeprom_write = 0x40,   /* write register xx */
  58   eeprom_erase = 0xc0,   /* erase register xx */
  59   eeprom_ewen  = 0x30,   /* erase / write enable */
  60   eeprom_ewds  = 0x00,   /* erase / write disable */
  61   eeprom_eral  = 0x20,   /* erase all registers */
  62   eeprom_wral  = 0x10,   /* write all registers */
  63   eeprom_amask = 0x0f,
  64   eeprom_imask = 0xf0
  65 } eeprom_instruction_t;
  66 #endif
  67
  68 #ifdef DEBUG_EEPROM
  69 static const char *opstring[] = {
  70   "extended", "write", "read", "erase"
  71 };
  72 #endif
  73
  74 struct _eeprom_t {
  75     uint8_t  tick;
  76     uint8_t  address;
  77     uint8_t  command;
  78     uint8_t  writeable;
  79
  80     uint8_t eecs;
  81     uint8_t eesk;
  82     uint8_t eedo;
  83
  84     uint8_t  addrbits;
  85     uint16_t size;
  86     uint16_t data;
  87     uint16_t contents[0];
  88 };
  89
  90 /* Code for saving and restoring of EEPROM state. */
  91
  92 /* Restore an uint16_t from an uint8_t
  93    This is a Big hack, but it is how the old state did it.
  94  */
  95
  96 static int get_uint16_from_uint8(QEMUFile *f, void *pv, size_t size)
  97 {
  98     uint16_t *v = pv;
  99     *v = qemu_get_ubyte(f);
 100     return 0;
 101 }
 102
 103 static void put_unused(QEMUFile *f, void *pv, size_t size)
 104 {
 105     fprintf(stderr, "uint16_from_uint8 is used only for backwards compatibility.\n");
 106     fprintf(stderr, "Never should be used to write a new state.\n");
 107     exit(0);
 108 }
 109
 110 static const VMStateInfo vmstate_hack_uint16_from_uint8 = {
 111     .name = "uint16_from_uint8",
 112     .get  = get_uint16_from_uint8,
 113     .put  = put_unused,
 114 };
 115
 116 #define VMSTATE_UINT16_HACK_TEST(_f, _s, _t)                           \
 117     VMSTATE_SINGLE_TEST(_f, _s, _t, 0, vmstate_hack_uint16_from_uint8, uint16_t)
 118
 119 static bool is_old_eeprom_version(void *opaque, int version_id)
 120 {
 121     return version_id == OLD_EEPROM_VERSION;
 122 }
 123
 124 static const VMStateDescription vmstate_eeprom = {
 125     .name = "eeprom",
 126     .version_id = EEPROM_VERSION,
 127     .minimum_version_id = OLD_EEPROM_VERSION,
 128     .minimum_version_id_old = OLD_EEPROM_VERSION,
 129     .fields      = (VMStateField []) {
 130         VMSTATE_UINT8(tick, eeprom_t),
 131         VMSTATE_UINT8(address, eeprom_t),
 132         VMSTATE_UINT8(command, eeprom_t),
 133         VMSTATE_UINT8(writeable, eeprom_t),
 134
 135         VMSTATE_UINT8(eecs, eeprom_t),
 136         VMSTATE_UINT8(eesk, eeprom_t),
 137         VMSTATE_UINT8(eedo, eeprom_t),
 138
 139         VMSTATE_UINT8(addrbits, eeprom_t),
 140         VMSTATE_UINT16_HACK_TEST(size, eeprom_t, is_old_eeprom_version),
 141         VMSTATE_UNUSED_TEST(is_old_eeprom_version, 1),
 142         VMSTATE_UINT16_EQUAL_V(size, eeprom_t, EEPROM_VERSION),
 143         VMSTATE_UINT16(data, eeprom_t),
 144         VMSTATE_VARRAY_UINT16_UNSAFE(contents, eeprom_t, size, 0,
 145                                      vmstate_info_uint16, uint16_t),
 146         VMSTATE_END_OF_LIST()
 147     }
 148 };
 149
 150 void eeprom93xx_write(eeprom_t *eeprom, int eecs, int eesk, int eedi)
 151 {
 152     uint8_t tick = eeprom->tick;
 153     uint8_t eedo = eeprom->eedo;
 154     uint16_t address = eeprom->address;
 155     uint8_t command = eeprom->command;
 156
 157     logout("CS=%u SK=%u DI=%u DO=%u, tick = %u\n",
 158            eecs, eesk, eedi, eedo, tick);
 159
 160     if (! eeprom->eecs && eecs) {
 161         /* Start chip select cycle. */
 162         logout("Cycle start, waiting for 1st start bit (0)\n");
 163         tick = 0;
 164         command = 0x0;
 165         address = 0x0;
 166     } else if (eeprom->eecs && ! eecs) {
 167         /* End chip select cycle. This triggers write / erase. */
 168         if (eeprom->writeable) {
 169             uint8_t subcommand = address >> (eeprom->addrbits - 2);
 170             if (command == 0 && subcommand == 2) {
 171                 /* Erase all. */
 172                 for (address = 0; address < eeprom->size; address++) {
 173                     eeprom->contents[address] = 0xffff;
 174                 }
 175             } else if (command == 3) {
 176                 /* Erase word. */
 177                 eeprom->contents[address] = 0xffff;
 178             } else if (tick >= 2 + 2 + eeprom->addrbits + 16) {
 179                 if (command == 1) {
 180                     /* Write word. */
 181                     eeprom->contents[address] &= eeprom->data;
 182                 } else if (command == 0 && subcommand == 1) {
 183                     /* Write all. */
 184                     for (address = 0; address < eeprom->size; address++) {
 185                         eeprom->contents[address] &= eeprom->data;
 186                     }
 187                 }
 188             }
 189         }
 190         /* Output DO is tristate, read results in 1. */
 191         eedo = 1;
 192     } else if (eecs && ! eeprom->eesk && eesk) {
 193         /* Raising edge of clock shifts data in. */
 194         if (tick == 0) {
 195             /* Wait for 1st start bit. */
 196             if (eedi == 0) {
 197                 logout("Got correct 1st start bit, waiting for 2nd start bit (1)\n");
 198                 tick++;
 199             } else {
 200                 logout("wrong 1st start bit (is 1, should be 0)\n");
 201                 tick = 2;
 202                 //~ assert(!"wrong start bit");
 203             }
 204         } else if (tick == 1) {
 205             /* Wait for 2nd start bit. */
 206             if (eedi != 0) {
 207                 logout("Got correct 2nd start bit, getting command + address\n");
 208                 tick++;
 209             } else {
 210                 logout("1st start bit is longer than needed\n");
 211             }
 212         } else if (tick < 2 + 2) {
 213             /* Got 2 start bits, transfer 2 opcode bits. */
 214             tick++;
 215             command <<= 1;
 216             if (eedi) {
 217                 command += 1;
 218             }
 219         } else if (tick < 2 + 2 + eeprom->addrbits) {
 220             /* Got 2 start bits and 2 opcode bits, transfer all address bits. */
 221             tick++;
 222             address = ((address << 1) | eedi);
 223             if (tick == 2 + 2 + eeprom->addrbits) {
 224                 logout("%s command, address = 0x%02x (value 0x%04x)\n",
 225                        opstring[command], address, eeprom->contents[address]);
 226                 if (command == 2) {
 227                     eedo = 0;
 228                 }
 229                 address = address % eeprom->size;
 230                 if (command == 0) {
 231                     /* Command code in upper 2 bits of address. */
 232                     switch (address >> (eeprom->addrbits - 2)) {
 233                         case 0:
 234                             logout("write disable command\n");
 235                             eeprom->writeable = 0;
 236                             break;
 237                         case 1:
 238                             logout("write all command\n");
 239                             break;
 240                         case 2:
 241                             logout("erase all command\n");
 242                             break;
 243                         case 3:
 244                             logout("write enable command\n");
 245                             eeprom->writeable = 1;
 246                             break;
 247                     }
 248                 } else {
 249                     /* Read, write or erase word. */
 250                     eeprom->data = eeprom->contents[address];
 251                 }
 252             }
 253         } else if (tick < 2 + 2 + eeprom->addrbits + 16) {
 254             /* Transfer 16 data bits. */
 255             tick++;
 256             if (command == 2) {
 257                 /* Read word. */
 258                 eedo = ((eeprom->data & 0x8000) != 0);
 259             }
 260             eeprom->data <<= 1;
 261             eeprom->data += eedi;
 262         } else {
 263             logout("additional unneeded tick, not processed\n");
 264         }
 265     }
 266     /* Save status of EEPROM. */
 267     eeprom->tick = tick;
 268     eeprom->eecs = eecs;
 269     eeprom->eesk = eesk;
 270     eeprom->eedo = eedo;
 271     eeprom->address = address;
 272     eeprom->command = command;
 273 }
 274
 275 uint16_t eeprom93xx_read(eeprom_t *eeprom)
 276 {
 277     /* Return status of pin DO (0 or 1). */
 278     logout("CS=%u DO=%u\n", eeprom->eecs, eeprom->eedo);
 279     return (eeprom->eedo);
 280 }
 281
 282 #if 0
 283 void eeprom93xx_reset(eeprom_t *eeprom)
 284 {
 285     /* prepare eeprom */
 286     logout("eeprom = 0x%p\n", eeprom);
 287     eeprom->tick = 0;
 288     eeprom->command = 0;
 289 }
 290 #endif
 291
 292 eeprom_t *eeprom93xx_new(uint16_t nwords)
 293 {
 294     /* Add a new EEPROM (with 16, 64 or 256 words). */
 295     eeprom_t *eeprom;
 296     uint8_t addrbits;
 297
 298     switch (nwords) {
 299         case 16:
 300         case 64:
 301             addrbits = 6;
 302             break;
 303         case 128:
 304         case 256:
 305             addrbits = 8;
 306             break;
 307         default:
 308             assert(!"Unsupported EEPROM size, fallback to 64 words!");
 309             nwords = 64;
 310             addrbits = 6;
 311     }
 312
 313     eeprom = (eeprom_t *)qemu_mallocz(sizeof(*eeprom) + nwords * 2);
 314     eeprom->size = nwords;
 315     eeprom->addrbits = addrbits;
 316     /* Output DO is tristate, read results in 1. */
 317     eeprom->eedo = 1;
 318     logout("eeprom = 0x%p, nwords = %u\n", eeprom, nwords);
 319     vmstate_register(0, &vmstate_eeprom, eeprom);
 320     return eeprom;
 321 }
 322
 323 void eeprom93xx_free(eeprom_t *eeprom)
 324 {
 325     /* Destroy EEPROM. */
 326     logout("eeprom = 0x%p\n", eeprom);
 327     vmstate_unregister(&vmstate_eeprom, eeprom);
 328     qemu_free(eeprom);
 329 }
 330
 331 uint16_t *eeprom93xx_data(eeprom_t *eeprom)
 332 {
 333     /* Get EEPROM data array. */
 334     return &eeprom->contents[0];
 335 }
 336
 337 /* eof */