arch/powerpc/platforms/powermac/nvram.c

   1 /*
   2  *  Copyright (C) 2002 Benjamin Herrenschmidt (benh@kernel.crashing.org)
   3  *
   4  *  This program is free software; you can redistribute it and/or
   5  *  modify it under the terms of the GNU General Public License
   6  *  as published by the Free Software Foundation; either version
   7  *  2 of the License, or (at your option) any later version.
   8  *
   9  *  Todo: - add support for the OF persistent properties
  10  */
  11 #include <linux/module.h>
  12 #include <linux/kernel.h>
  13 #include <linux/stddef.h>
  14 #include <linux/string.h>
  15 #include <linux/nvram.h>
  16 #include <linux/init.h>
  17 #include <linux/slab.h>
  18 #include <linux/delay.h>
  19 #include <linux/errno.h>
  20 #include <linux/adb.h>
  21 #include <linux/pmu.h>
  22 #include <linux/bootmem.h>
  23 #include <linux/completion.h>
  24 #include <linux/spinlock.h>
  25 #include <asm/sections.h>
  26 #include <asm/io.h>
  27 #include <asm/system.h>
  28 #include <asm/prom.h>
  29 #include <asm/machdep.h>
  30 #include <asm/nvram.h>
  31
  32 #include "pmac.h"
  33
  34 #define DEBUG
  35
  36 #ifdef DEBUG
  37 #define DBG(x...) printk(x)
  38 #else
  39 #define DBG(x...)
  40 #endif
  41
  42 #define NVRAM_SIZE              0x2000  /* 8kB of non-volatile RAM */
  43
  44 #define CORE99_SIGNATURE        0x5a
  45 #define CORE99_ADLER_START      0x14
  46
  47 /* On Core99, nvram is either a sharp, a micron or an AMD flash */
  48 #define SM_FLASH_STATUS_DONE    0x80
  49 #define SM_FLASH_STATUS_ERR     0x38
  50
  51 #define SM_FLASH_CMD_ERASE_CONFIRM      0xd0
  52 #define SM_FLASH_CMD_ERASE_SETUP        0x20
  53 #define SM_FLASH_CMD_RESET              0xff
  54 #define SM_FLASH_CMD_WRITE_SETUP        0x40
  55 #define SM_FLASH_CMD_CLEAR_STATUS       0x50
  56 #define SM_FLASH_CMD_READ_STATUS        0x70
  57
  58 /* CHRP NVRAM header */
  59 struct chrp_header {
  60   u8            signature;
  61   u8            cksum;
  62   u16           len;
  63   char          name[12];
  64   u8            data[0];
  65 };
  66
  67 struct core99_header {
  68   struct chrp_header    hdr;
  69   u32                   adler;
  70   u32                   generation;
  71   u32                   reserved[2];
  72 };
  73
  74 /*
  75  * Read and write the non-volatile RAM on PowerMacs and CHRP machines.
  76  */
  77 static int nvram_naddrs;
  78 static volatile unsigned char __iomem *nvram_data;
  79 static int is_core_99;
  80 static int core99_bank = 0;
  81 static int nvram_partitions[3];
  82 // XXX Turn that into a sem
  83 static DEFINE_SPINLOCK(nv_lock);
  84
  85 static int (*core99_write_bank)(int bank, u8* datas);
  86 static int (*core99_erase_bank)(int bank);
  87
  88 static char *nvram_image;
  89
  90
  91 static unsigned char core99_nvram_read_byte(int addr)
  92 {
  93         if (nvram_image == NULL)
  94                 return 0xff;
  95         return nvram_image[addr];
  96 }
  97
  98 static void core99_nvram_write_byte(int addr, unsigned char val)
  99 {
 100         if (nvram_image == NULL)
 101                 return;
 102         nvram_image[addr] = val;
 103 }
 104
 105 static ssize_t core99_nvram_read(char *buf, size_t count, loff_t *index)
 106 {
 107         int i;
 108
 109         if (nvram_image == NULL)
 110                 return -ENODEV;
 111         if (*index > NVRAM_SIZE)
 112                 return 0;
 113
 114         i = *index;
 115         if (i + count > NVRAM_SIZE)
 116                 count = NVRAM_SIZE - i;
 117
 118         memcpy(buf, &nvram_image[i], count);
 119         *index = i + count;
 120         return count;
 121 }
 122
 123 static ssize_t core99_nvram_write(char *buf, size_t count, loff_t *index)
 124 {
 125         int i;
 126
 127         if (nvram_image == NULL)
 128                 return -ENODEV;
 129         if (*index > NVRAM_SIZE)
 130                 return 0;
 131
 132         i = *index;
 133         if (i + count > NVRAM_SIZE)
 134                 count = NVRAM_SIZE - i;
 135
 136         memcpy(&nvram_image[i], buf, count);
 137         *index = i + count;
 138         return count;
 139 }
 140
 141 static ssize_t core99_nvram_size(void)
 142 {
 143         if (nvram_image == NULL)
 144                 return -ENODEV;
 145         return NVRAM_SIZE;
 146 }
 147
 148 #ifdef CONFIG_PPC32
 149 static volatile unsigned char __iomem *nvram_addr;
 150 static int nvram_mult;
 151
 152 static unsigned char direct_nvram_read_byte(int addr)
 153 {
 154         return in_8(&nvram_data[(addr & (NVRAM_SIZE - 1)) * nvram_mult]);
 155 }
 156
 157 static void direct_nvram_write_byte(int addr, unsigned char val)
 158 {
 159         out_8(&nvram_data[(addr & (NVRAM_SIZE - 1)) * nvram_mult], val);
 160 }
 161
 162
 163 static unsigned char indirect_nvram_read_byte(int addr)
 164 {
 165         unsigned char val;
 166         unsigned long flags;
 167
 168         spin_lock_irqsave(&nv_lock, flags);
 169         out_8(nvram_addr, addr >> 5);
 170         val = in_8(&nvram_data[(addr & 0x1f) << 4]);
 171         spin_unlock_irqrestore(&nv_lock, flags);
 172
 173         return val;
 174 }
 175
 176 static void indirect_nvram_write_byte(int addr, unsigned char val)
 177 {
 178         unsigned long flags;
 179
 180         spin_lock_irqsave(&nv_lock, flags);
 181         out_8(nvram_addr, addr >> 5);
 182         out_8(&nvram_data[(addr & 0x1f) << 4], val);
 183         spin_unlock_irqrestore(&nv_lock, flags);
 184 }
 185
 186
 187 #ifdef CONFIG_ADB_PMU
 188
 189 static void pmu_nvram_complete(struct adb_request *req)
 190 {
 191         if (req->arg)
 192                 complete((struct completion *)req->arg);
 193 }
 194
 195 static unsigned char pmu_nvram_read_byte(int addr)
 196 {
 197         struct adb_request req;
 198         DECLARE_COMPLETION_ONSTACK(req_complete);
 199
 200         req.arg = system_state == SYSTEM_RUNNING ? &req_complete : NULL;
 201         if (pmu_request(&req, pmu_nvram_complete, 3, PMU_READ_NVRAM,
 202                         (addr >> 8) & 0xff, addr & 0xff))
 203                 return 0xff;
 204         if (system_state == SYSTEM_RUNNING)
 205                 wait_for_completion(&req_complete);
 206         while (!req.complete)
 207                 pmu_poll();
 208         return req.reply[0];
 209 }
 210
 211 static void pmu_nvram_write_byte(int addr, unsigned char val)
 212 {
 213         struct adb_request req;
 214         DECLARE_COMPLETION_ONSTACK(req_complete);
 215
 216         req.arg = system_state == SYSTEM_RUNNING ? &req_complete : NULL;
 217         if (pmu_request(&req, pmu_nvram_complete, 4, PMU_WRITE_NVRAM,
 218                         (addr >> 8) & 0xff, addr & 0xff, val))
 219                 return;
 220         if (system_state == SYSTEM_RUNNING)
 221                 wait_for_completion(&req_complete);
 222         while (!req.complete)
 223                 pmu_poll();
 224 }
 225
 226 #endif /* CONFIG_ADB_PMU */
 227 #endif /* CONFIG_PPC32 */
 228
 229 static u8 chrp_checksum(struct chrp_header* hdr)
 230 {
 231         u8 *ptr;
 232         u16 sum = hdr->signature;
 233         for (ptr = (u8 *)&hdr->len; ptr < hdr->data; ptr++)
 234                 sum += *ptr;
 235         while (sum > 0xFF)
 236                 sum = (sum & 0xFF) + (sum>>8);
 237         return sum;
 238 }
 239
 240 static u32 core99_calc_adler(u8 *buffer)
 241 {
 242         int cnt;
 243         u32 low, high;
 244
 245         buffer += CORE99_ADLER_START;
 246         low = 1;
 247         high = 0;
 248         for (cnt=0; cnt<(NVRAM_SIZE-CORE99_ADLER_START); cnt++) {
 249                 if ((cnt % 5000) == 0) {
 250                         high  %= 65521UL;
 251                         high %= 65521UL;
 252                 }
 253                 low += buffer[cnt];
 254                 high += low;
 255         }
 256         low  %= 65521UL;
 257         high %= 65521UL;
 258
 259         return (high << 16) | low;
 260 }
 261
 262 static u32 core99_check(u8* datas)
 263 {
 264         struct core99_header* hdr99 = (struct core99_header*)datas;
 265
 266         if (hdr99->hdr.signature != CORE99_SIGNATURE) {
 267                 DBG("Invalid signature\n");
 268                 return 0;
 269         }
 270         if (hdr99->hdr.cksum != chrp_checksum(&hdr99->hdr)) {
 271                 DBG("Invalid checksum\n");
 272                 return 0;
 273         }
 274         if (hdr99->adler != core99_calc_adler(datas)) {
 275                 DBG("Invalid adler\n");
 276                 return 0;
 277         }
 278         return hdr99->generation;
 279 }
 280
 281 static int sm_erase_bank(int bank)
 282 {
 283         int stat, i;
 284         unsigned long timeout;
 285
 286         u8 __iomem *base = (u8 __iomem *)nvram_data + core99_bank*NVRAM_SIZE;
 287
 288         DBG("nvram: Sharp/Micron Erasing bank %d...\n", bank);
 289
 290         out_8(base, SM_FLASH_CMD_ERASE_SETUP);
 291         out_8(base, SM_FLASH_CMD_ERASE_CONFIRM);
 292         timeout = 0;
 293         do {
 294                 if (++timeout > 1000000) {
 295                         printk(KERN_ERR "nvram: Sharp/Micron flash erase timeout !\n");
 296                         break;
 297                 }
 298                 out_8(base, SM_FLASH_CMD_READ_STATUS);
 299                 stat = in_8(base);
 300         } while (!(stat & SM_FLASH_STATUS_DONE));
 301
 302         out_8(base, SM_FLASH_CMD_CLEAR_STATUS);
 303         out_8(base, SM_FLASH_CMD_RESET);
 304
 305         for (i=0; i<NVRAM_SIZE; i++)
 306                 if (base[i] != 0xff) {
 307                         printk(KERN_ERR "nvram: Sharp/Micron flash erase failed !\n");
 308                         return -ENXIO;
 309                 }
 310         return 0;
 311 }
 312
 313 static int sm_write_bank(int bank, u8* datas)
 314 {
 315         int i, stat = 0;
 316         unsigned long timeout;
 317
 318         u8 __iomem *base = (u8 __iomem *)nvram_data + core99_bank*NVRAM_SIZE;
 319
 320         DBG("nvram: Sharp/Micron Writing bank %d...\n", bank);
 321
 322         for (i=0; i<NVRAM_SIZE; i++) {
 323                 out_8(base+i, SM_FLASH_CMD_WRITE_SETUP);
 324                 udelay(1);
 325                 out_8(base+i, datas[i]);
 326                 timeout = 0;
 327                 do {
 328                         if (++timeout > 1000000) {
 329                                 printk(KERN_ERR "nvram: Sharp/Micron flash write timeout !\n");
 330                                 break;
 331                         }
 332                         out_8(base, SM_FLASH_CMD_READ_STATUS);
 333                         stat = in_8(base);
 334                 } while (!(stat & SM_FLASH_STATUS_DONE));
 335                 if (!(stat & SM_FLASH_STATUS_DONE))
 336                         break;
 337         }
 338         out_8(base, SM_FLASH_CMD_CLEAR_STATUS);
 339         out_8(base, SM_FLASH_CMD_RESET);
 340         for (i=0; i<NVRAM_SIZE; i++)
 341                 if (base[i] != datas[i]) {
 342                         printk(KERN_ERR "nvram: Sharp/Micron flash write failed !\n");
 343                         return -ENXIO;
 344                 }
 345         return 0;
 346 }
 347
 348 static int amd_erase_bank(int bank)
 349 {
 350         int i, stat = 0;
 351         unsigned long timeout;
 352
 353         u8 __iomem *base = (u8 __iomem *)nvram_data + core99_bank*NVRAM_SIZE;
 354
 355         DBG("nvram: AMD Erasing bank %d...\n", bank);
 356
 357         /* Unlock 1 */
 358         out_8(base+0x555, 0xaa);
 359         udelay(1);
 360         /* Unlock 2 */
 361         out_8(base+0x2aa, 0x55);
 362         udelay(1);
 363
 364         /* Sector-Erase */
 365         out_8(base+0x555, 0x80);
 366         udelay(1);
 367         out_8(base+0x555, 0xaa);
 368         udelay(1);
 369         out_8(base+0x2aa, 0x55);
 370         udelay(1);
 371         out_8(base, 0x30);
 372         udelay(1);
 373
 374         timeout = 0;
 375         do {
 376                 if (++timeout > 1000000) {
 377                         printk(KERN_ERR "nvram: AMD flash erase timeout !\n");
 378                         break;
 379                 }
 380                 stat = in_8(base) ^ in_8(base);
 381         } while (stat != 0);
 382
 383         /* Reset */
 384         out_8(base, 0xf0);
 385         udelay(1);
 386
 387         for (i=0; i<NVRAM_SIZE; i++)
 388                 if (base[i] != 0xff) {
 389                         printk(KERN_ERR "nvram: AMD flash erase failed !\n");
 390                         return -ENXIO;
 391                 }
 392         return 0;
 393 }
 394
 395 static int amd_write_bank(int bank, u8* datas)
 396 {
 397         int i, stat = 0;
 398         unsigned long timeout;
 399
 400         u8 __iomem *base = (u8 __iomem *)nvram_data + core99_bank*NVRAM_SIZE;
 401
 402         DBG("nvram: AMD Writing bank %d...\n", bank);
 403
 404         for (i=0; i<NVRAM_SIZE; i++) {
 405                 /* Unlock 1 */
 406                 out_8(base+0x555, 0xaa);
 407                 udelay(1);
 408                 /* Unlock 2 */
 409                 out_8(base+0x2aa, 0x55);
 410                 udelay(1);
 411
 412                 /* Write single word */
 413                 out_8(base+0x555, 0xa0);
 414                 udelay(1);
 415                 out_8(base+i, datas[i]);
 416
 417                 timeout = 0;
 418                 do {
 419                         if (++timeout > 1000000) {
 420                                 printk(KERN_ERR "nvram: AMD flash write timeout !\n");
 421                                 break;
 422                         }
 423                         stat = in_8(base) ^ in_8(base);
 424                 } while (stat != 0);
 425                 if (stat != 0)
 426                         break;
 427         }
 428
 429         /* Reset */
 430         out_8(base, 0xf0);
 431         udelay(1);
 432
 433         for (i=0; i<NVRAM_SIZE; i++)
 434                 if (base[i] != datas[i]) {
 435                         printk(KERN_ERR "nvram: AMD flash write failed !\n");
 436                         return -ENXIO;
 437                 }
 438         return 0;
 439 }
 440
 441 static void __init lookup_partitions(void)
 442 {
 443         u8 buffer[17];
 444         int i, offset;
 445         struct chrp_header* hdr;
 446
 447         if (pmac_newworld) {
 448                 nvram_partitions[pmac_nvram_OF] = -1;
 449                 nvram_partitions[pmac_nvram_XPRAM] = -1;
 450                 nvram_partitions[pmac_nvram_NR] = -1;
 451                 hdr = (struct chrp_header *)buffer;
 452
 453                 offset = 0;
 454                 buffer[16] = 0;
 455                 do {
 456                         for (i=0;i<16;i++)
 457                                 buffer[i] = ppc_md.nvram_read_val(offset+i);
 458                         if (!strcmp(hdr->name, "common"))
 459                                 nvram_partitions[pmac_nvram_OF] = offset + 0x10;
 460                         if (!strcmp(hdr->name, "APL,MacOS75")) {
 461                                 nvram_partitions[pmac_nvram_XPRAM] = offset + 0x10;
 462                                 nvram_partitions[pmac_nvram_NR] = offset + 0x110;
 463                         }
 464                         offset += (hdr->len * 0x10);
 465                 } while(offset < NVRAM_SIZE);
 466         } else {
 467                 nvram_partitions[pmac_nvram_OF] = 0x1800;
 468                 nvram_partitions[pmac_nvram_XPRAM] = 0x1300;
 469                 nvram_partitions[pmac_nvram_NR] = 0x1400;
 470         }
 471         DBG("nvram: OF partition at 0x%x\n", nvram_partitions[pmac_nvram_OF]);
 472         DBG("nvram: XP partition at 0x%x\n", nvram_partitions[pmac_nvram_XPRAM]);
 473         DBG("nvram: NR partition at 0x%x\n", nvram_partitions[pmac_nvram_NR]);
 474 }
 475
 476 static void core99_nvram_sync(void)
 477 {
 478         struct core99_header* hdr99;
 479         unsigned long flags;
 480
 481         if (!is_core_99 || !nvram_data || !nvram_image)
 482                 return;
 483
 484         spin_lock_irqsave(&nv_lock, flags);
 485         if (!memcmp(nvram_image, (u8*)nvram_data + core99_bank*NVRAM_SIZE,
 486                 NVRAM_SIZE))
 487                 goto bail;
 488
 489         DBG("Updating nvram...\n");
 490
 491         hdr99 = (struct core99_header*)nvram_image;
 492         hdr99->generation++;
 493         hdr99->hdr.signature = CORE99_SIGNATURE;
 494         hdr99->hdr.cksum = chrp_checksum(&hdr99->hdr);
 495         hdr99->adler = core99_calc_adler(nvram_image);
 496         core99_bank = core99_bank ? 0 : 1;
 497         if (core99_erase_bank)
 498                 if (core99_erase_bank(core99_bank)) {
 499                         printk("nvram: Error erasing bank %d\n", core99_bank);
 500                         goto bail;
 501                 }
 502         if (core99_write_bank)
 503                 if (core99_write_bank(core99_bank, nvram_image))
 504                         printk("nvram: Error writing bank %d\n", core99_bank);
 505  bail:
 506         spin_unlock_irqrestore(&nv_lock, flags);
 507
 508 #ifdef DEBUG
 509         mdelay(2000);
 510 #endif
 511 }
 512
 513 static int __init core99_nvram_setup(struct device_node *dp, unsigned long addr)
 514 {
 515         int i;
 516         u32 gen_bank0, gen_bank1;
 517
 518         if (nvram_naddrs < 1) {
 519                 printk(KERN_ERR "nvram: no address\n");
 520                 return -EINVAL;
 521         }
 522         nvram_image = alloc_bootmem(NVRAM_SIZE);
 523         if (nvram_image == NULL) {
 524                 printk(KERN_ERR "nvram: can't allocate ram image\n");
 525                 return -ENOMEM;
 526         }
 527         nvram_data = ioremap(addr, NVRAM_SIZE*2);
 528         nvram_naddrs = 1; /* Make sure we get the correct case */
 529
 530         DBG("nvram: Checking bank 0...\n");
 531
 532         gen_bank0 = core99_check((u8 *)nvram_data);
 533         gen_bank1 = core99_check((u8 *)nvram_data + NVRAM_SIZE);
 534         core99_bank = (gen_bank0 < gen_bank1) ? 1 : 0;
 535
 536         DBG("nvram: gen0=%d, gen1=%d\n", gen_bank0, gen_bank1);
 537         DBG("nvram: Active bank is: %d\n", core99_bank);
 538
 539         for (i=0; i<NVRAM_SIZE; i++)
 540                 nvram_image[i] = nvram_data[i + core99_bank*NVRAM_SIZE];
 541
 542         ppc_md.nvram_read_val   = core99_nvram_read_byte;
 543         ppc_md.nvram_write_val  = core99_nvram_write_byte;
 544         ppc_md.nvram_read       = core99_nvram_read;
 545         ppc_md.nvram_write      = core99_nvram_write;
 546         ppc_md.nvram_size       = core99_nvram_size;
 547         ppc_md.nvram_sync       = core99_nvram_sync;
 548         ppc_md.machine_shutdown = core99_nvram_sync;
 549         /*
 550          * Maybe we could be smarter here though making an exclusive list
 551          * of known flash chips is a bit nasty as older OF didn't provide us
 552          * with a useful "compatible" entry. A solution would be to really
 553          * identify the chip using flash id commands and base ourselves on
 554          * a list of known chips IDs
 555          */
 556         if (of_device_is_compatible(dp, "amd-0137")) {
 557                 core99_erase_bank = amd_erase_bank;
 558                 core99_write_bank = amd_write_bank;
 559         } else {
 560                 core99_erase_bank = sm_erase_bank;
 561                 core99_write_bank = sm_write_bank;
 562         }
 563         return 0;
 564 }
 565
 566 int __init pmac_nvram_init(void)
 567 {
 568         struct device_node *dp;
 569         struct resource r1, r2;
 570         unsigned int s1 = 0, s2 = 0;
 571         int err = 0;
 572
 573         nvram_naddrs = 0;
 574
 575         dp = of_find_node_by_name(NULL, "nvram");
 576         if (dp == NULL) {
 577                 printk(KERN_ERR "Can't find NVRAM device\n");
 578                 return -ENODEV;
 579         }
 580
 581         /* Try to obtain an address */
 582         if (of_address_to_resource(dp, 0, &r1) == 0) {
 583                 nvram_naddrs = 1;
 584                 s1 = (r1.end - r1.start) + 1;
 585                 if (of_address_to_resource(dp, 1, &r2) == 0) {
 586                         nvram_naddrs = 2;
 587                         s2 = (r2.end - r2.start) + 1;
 588                 }
 589         }
 590
 591         is_core_99 = of_device_is_compatible(dp, "nvram,flash");
 592         if (is_core_99) {
 593                 err = core99_nvram_setup(dp, r1.start);
 594                 goto bail;
 595         }
 596
 597 #ifdef CONFIG_PPC32
 598         if (machine_is(chrp) && nvram_naddrs == 1) {
 599                 nvram_data = ioremap(r1.start, s1);
 600                 nvram_mult = 1;
 601                 ppc_md.nvram_read_val   = direct_nvram_read_byte;
 602                 ppc_md.nvram_write_val  = direct_nvram_write_byte;
 603         } else if (nvram_naddrs == 1) {
 604                 nvram_data = ioremap(r1.start, s1);
 605                 nvram_mult = (s1 + NVRAM_SIZE - 1) / NVRAM_SIZE;
 606                 ppc_md.nvram_read_val   = direct_nvram_read_byte;
 607                 ppc_md.nvram_write_val  = direct_nvram_write_byte;
 608         } else if (nvram_naddrs == 2) {
 609                 nvram_addr = ioremap(r1.start, s1);
 610                 nvram_data = ioremap(r2.start, s2);
 611                 ppc_md.nvram_read_val   = indirect_nvram_read_byte;
 612                 ppc_md.nvram_write_val  = indirect_nvram_write_byte;
 613         } else if (nvram_naddrs == 0 && sys_ctrler == SYS_CTRLER_PMU) {
 614 #ifdef CONFIG_ADB_PMU
 615                 nvram_naddrs = -1;
 616                 ppc_md.nvram_read_val   = pmu_nvram_read_byte;
 617                 ppc_md.nvram_write_val  = pmu_nvram_write_byte;
 618 #endif /* CONFIG_ADB_PMU */
 619         } else {
 620                 printk(KERN_ERR "Incompatible type of NVRAM\n");
 621                 err = -ENXIO;
 622         }
 623 #endif /* CONFIG_PPC32 */
 624 bail:
 625         of_node_put(dp);
 626         if (err == 0)
 627                 lookup_partitions();
 628         return err;
 629 }
 630
 631 int pmac_get_partition(int partition)
 632 {
 633         return nvram_partitions[partition];
 634 }
 635
 636 u8 pmac_xpram_read(int xpaddr)
 637 {
 638         int offset = pmac_get_partition(pmac_nvram_XPRAM);
 639
 640         if (offset < 0 || xpaddr < 0 || xpaddr > 0x100)
 641                 return 0xff;
 642
 643         return ppc_md.nvram_read_val(xpaddr + offset);
 644 }
 645
 646 void pmac_xpram_write(int xpaddr, u8 data)
 647 {
 648         int offset = pmac_get_partition(pmac_nvram_XPRAM);
 649
 650         if (offset < 0 || xpaddr < 0 || xpaddr > 0x100)
 651                 return;
 652
 653         ppc_md.nvram_write_val(xpaddr + offset, data);
 654 }
 655
 656 EXPORT_SYMBOL(pmac_get_partition);
 657 EXPORT_SYMBOL(pmac_xpram_read);
 658 EXPORT_SYMBOL(pmac_xpram_write);