hw/nvram/eeprom93xx.c

   1 /*
   2  * QEMU EEPROM 93xx emulation
   3  *
   4  * Copyright (c) 2006-2009 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 3 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  * Hint: This driver always uses host endianness!
  35  *
  36  * Todo list:
  37  * - No emulation of EEPROM timings.
  38  */
  39
  40 #include "qemu/osdep.h"
  41 #include "hw/nvram/eeprom93xx.h"
  42 #include "migration/qemu-file-types.h"
  43 #include "migration/vmstate.h"
  44
  45 /* Debug EEPROM emulation. */
  46 //~ #define DEBUG_EEPROM
  47
  48 #ifdef DEBUG_EEPROM
  49 #define logout(fmt, ...) fprintf(stderr, "EEPROM\t%-24s" fmt, __func__, ## __VA_ARGS__)
  50 #else
  51 #define logout(fmt, ...) ((void)0)
  52 #endif
  53
  54 #define EEPROM_INSTANCE  0
  55 #define OLD_EEPROM_VERSION 20061112
  56 #define EEPROM_VERSION (OLD_EEPROM_VERSION + 1)
  57
  58 #if 0
  59 typedef enum {
  60   eeprom_read  = 0x80,   /* read register xx */
  61   eeprom_write = 0x40,   /* write register xx */
  62   eeprom_erase = 0xc0,   /* erase register xx */
  63   eeprom_ewen  = 0x30,   /* erase / write enable */
  64   eeprom_ewds  = 0x00,   /* erase / write disable */
  65   eeprom_eral  = 0x20,   /* erase all registers */
  66   eeprom_wral  = 0x10,   /* write all registers */
  67   eeprom_amask = 0x0f,
  68   eeprom_imask = 0xf0
  69 } eeprom_instruction_t;
  70 #endif
  71
  72 #ifdef DEBUG_EEPROM
  73 static const char *opstring[] = {
  74   "extended", "write", "read", "erase"
  75 };
  76 #endif
  77
  78 struct _eeprom_t {
  79     uint8_t  tick;
  80     uint8_t  address;
  81     uint8_t  command;
  82     uint8_t  writable;
  83
  84     uint8_t eecs;
  85     uint8_t eesk;
  86     uint8_t eedo;
  87
  88     uint8_t  addrbits;
  89     uint16_t size;
  90     uint16_t data;
  91     uint16_t contents[];
  92 };
  93
  94 /* Code for saving and restoring of EEPROM state. */
  95
  96 /* Restore an uint16_t from an uint8_t
  97    This is a Big hack, but it is how the old state did it.
  98  */
  99
 100 static int get_uint16_from_uint8(QEMUFile *f, void *pv, size_t size,
 101                                  const VMStateField *field)
 102 {
 103     uint16_t *v = pv;
 104     *v = qemu_get_ubyte(f);
 105     return 0;
 106 }
 107
 108 static int put_unused(QEMUFile *f, void *pv, size_t size,
 109                       const VMStateField *field, QJSON *vmdesc)
 110 {
 111     fprintf(stderr, "uint16_from_uint8 is used only for backwards compatibility.\n");
 112     fprintf(stderr, "Never should be used to write a new state.\n");
 113     exit(0);
 114
 115     return 0;
 116 }
 117
 118 static const VMStateInfo vmstate_hack_uint16_from_uint8 = {
 119     .name = "uint16_from_uint8",
 120     .get  = get_uint16_from_uint8,
 121     .put  = put_unused,
 122 };
 123
 124 #define VMSTATE_UINT16_HACK_TEST(_f, _s, _t)                           \
 125     VMSTATE_SINGLE_TEST(_f, _s, _t, 0, vmstate_hack_uint16_from_uint8, uint16_t)
 126
 127 static bool is_old_eeprom_version(void *opaque, int version_id)
 128 {
 129     return version_id == OLD_EEPROM_VERSION;
 130 }
 131
 132 static const VMStateDescription vmstate_eeprom = {
 133     .name = "eeprom",
 134     .version_id = EEPROM_VERSION,
 135     .minimum_version_id = OLD_EEPROM_VERSION,
 136     .fields = (VMStateField[]) {
 137         VMSTATE_UINT8(tick, eeprom_t),
 138         VMSTATE_UINT8(address, eeprom_t),
 139         VMSTATE_UINT8(command, eeprom_t),
 140         VMSTATE_UINT8(writable, eeprom_t),
 141
 142         VMSTATE_UINT8(eecs, eeprom_t),
 143         VMSTATE_UINT8(eesk, eeprom_t),
 144         VMSTATE_UINT8(eedo, eeprom_t),
 145
 146         VMSTATE_UINT8(addrbits, eeprom_t),
 147         VMSTATE_UINT16_HACK_TEST(size, eeprom_t, is_old_eeprom_version),
 148         VMSTATE_UNUSED_TEST(is_old_eeprom_version, 1),
 149         VMSTATE_UINT16_EQUAL_V(size, eeprom_t, EEPROM_VERSION, NULL),
 150         VMSTATE_UINT16(data, eeprom_t),
 151         VMSTATE_VARRAY_UINT16_UNSAFE(contents, eeprom_t, size, 0,
 152                                      vmstate_info_uint16, uint16_t),
 153         VMSTATE_END_OF_LIST()
 154     }
 155 };
 156
 157 void eeprom93xx_write(eeprom_t *eeprom, int eecs, int eesk, int eedi)
 158 {
 159     uint8_t tick = eeprom->tick;
 160     uint8_t eedo = eeprom->eedo;
 161     uint16_t address = eeprom->address;
 162     uint8_t command = eeprom->command;
 163
 164     logout("CS=%u SK=%u DI=%u DO=%u, tick = %u\n",
 165            eecs, eesk, eedi, eedo, tick);
 166
 167     if (!eeprom->eecs && eecs) {
 168         /* Start chip select cycle. */
 169         logout("Cycle start, waiting for 1st start bit (0)\n");
 170         tick = 0;
 171         command = 0x0;
 172         address = 0x0;
 173     } else if (eeprom->eecs && !eecs) {
 174         /* End chip select cycle. This triggers write / erase. */
 175         if (eeprom->writable) {
 176             uint8_t subcommand = address >> (eeprom->addrbits - 2);
 177             if (command == 0 && subcommand == 2) {
 178                 /* Erase all. */
 179                 for (address = 0; address < eeprom->size; address++) {
 180                     eeprom->contents[address] = 0xffff;
 181                 }
 182             } else if (command == 3) {
 183                 /* Erase word. */
 184                 eeprom->contents[address] = 0xffff;
 185             } else if (tick >= 2 + 2 + eeprom->addrbits + 16) {
 186                 if (command == 1) {
 187                     /* Write word. */
 188                     eeprom->contents[address] &= eeprom->data;
 189                 } else if (command == 0 && subcommand == 1) {
 190                     /* Write all. */
 191                     for (address = 0; address < eeprom->size; address++) {
 192                         eeprom->contents[address] &= eeprom->data;
 193                     }
 194                 }
 195             }
 196         }
 197         /* Output DO is tristate, read results in 1. */
 198         eedo = 1;
 199     } else if (eecs && !eeprom->eesk && eesk) {
 200         /* Raising edge of clock shifts data in. */
 201         if (tick == 0) {
 202             /* Wait for 1st start bit. */
 203             if (eedi == 0) {
 204                 logout("Got redundant bit (0), waiting for start bit (1)\n");
 205             } else {
 206                 logout("Got start bit (1), getting command + address\n");
 207                 tick++;
 208             }
 209         } else if (tick < 1 + 2) {
 210             /* Got 1 start bit, transfer 2 opcode bits. */
 211             tick++;
 212             command <<= 1;
 213             if (eedi) {
 214                 command += 1;
 215             }
 216         } else if (tick < 1 + 2 + eeprom->addrbits) {
 217             /* Got 2 start bits and 2 opcode bits, transfer all address bits. */
 218             tick++;
 219             address = ((address << 1) | eedi);
 220             if (tick == 1 + 2 + eeprom->addrbits) {
 221                 logout("%s command, address = 0x%02x (value 0x%04x)\n",
 222                        opstring[command], address, eeprom->contents[address]);
 223                 if (command == 2) {
 224                     eedo = 0;
 225                 }
 226                 address = address % eeprom->size;
 227                 if (command == 0) {
 228                     /* Command code in upper 2 bits of address. */
 229                     switch (address >> (eeprom->addrbits - 2)) {
 230                     case 0:
 231                         logout("write disable command\n");
 232                         eeprom->writable = 0;
 233                         break;
 234                     case 1:
 235                         logout("write all command\n");
 236                         break;
 237                     case 2:
 238                         logout("erase all command\n");
 239                         break;
 240                     case 3:
 241                         logout("write enable command\n");
 242                         eeprom->writable = 1;
 243                         break;
 244                     }
 245                 } else {
 246                     /* Read, write or erase word. */
 247                     eeprom->data = eeprom->contents[address];
 248                 }
 249             }
 250         } else if (tick < 1 + 2 + eeprom->addrbits + 16) {
 251             /* Transfer 16 data bits. */
 252             tick++;
 253             if (command == 2) {
 254                 /* Read word. */
 255                 eedo = ((eeprom->data & 0x8000) != 0);
 256             }
 257             eeprom->data <<= 1;
 258             eeprom->data += eedi;
 259         } else {
 260             logout("additional unneeded tick, not processed\n");
 261         }
 262     }
 263     /* Save status of EEPROM. */
 264     eeprom->tick = tick;
 265     eeprom->eecs = eecs;
 266     eeprom->eesk = eesk;
 267     eeprom->eedo = eedo;
 268     eeprom->address = address;
 269     eeprom->command = command;
 270 }
 271
 272 uint16_t eeprom93xx_read(eeprom_t *eeprom)
 273 {
 274     /* Return status of pin DO (0 or 1). */
 275     logout("CS=%u DO=%u\n", eeprom->eecs, eeprom->eedo);
 276     return eeprom->eedo;
 277 }
 278
 279 #if 0
 280 void eeprom93xx_reset(eeprom_t *eeprom)
 281 {
 282     /* prepare eeprom */
 283     logout("eeprom = 0x%p\n", eeprom);
 284     eeprom->tick = 0;
 285     eeprom->command = 0;
 286 }
 287 #endif
 288
 289 eeprom_t *eeprom93xx_new(DeviceState *dev, uint16_t nwords)
 290 {
 291     /* Add a new EEPROM (with 16, 64 or 256 words). */
 292     eeprom_t *eeprom;
 293     uint8_t addrbits;
 294
 295     switch (nwords) {
 296     case 16:
 297     case 64:
 298         addrbits = 6;
 299         break;
 300     case 128:
 301     case 256:
 302         addrbits = 8;
 303         break;
 304     default:
 305         assert(!"Unsupported EEPROM size, fallback to 64 words!");
 306         nwords = 64;
 307         addrbits = 6;
 308     }
 309
 310     eeprom = (eeprom_t *)g_malloc0(sizeof(*eeprom) + nwords * 2);
 311     eeprom->size = nwords;
 312     eeprom->addrbits = addrbits;
 313     /* Output DO is tristate, read results in 1. */
 314     eeprom->eedo = 1;
 315     logout("eeprom = 0x%p, nwords = %u\n", eeprom, nwords);
 316     vmstate_register(VMSTATE_IF(dev), 0, &vmstate_eeprom, eeprom);
 317     return eeprom;
 318 }
 319
 320 void eeprom93xx_free(DeviceState *dev, eeprom_t *eeprom)
 321 {
 322     /* Destroy EEPROM. */
 323     logout("eeprom = 0x%p\n", eeprom);
 324     vmstate_unregister(VMSTATE_IF(dev), &vmstate_eeprom, eeprom);
 325     g_free(eeprom);
 326 }
 327
 328 uint16_t *eeprom93xx_data(eeprom_t *eeprom)
 329 {
 330     /* Get EEPROM data array. */
 331     return &eeprom->contents[0];
 332 }
 333
 334 /* eof */