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