common/ddr_spd.c

   1 /*
   2  * Copyright 2008 Freescale Semiconductor, Inc.
   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  * Version 2 as published by the Free Software Foundation.
   7  */
   8
   9 #include <common.h>
  10 #include <ddr_spd.h>
  11
  12 /* used for ddr1 and ddr2 spd */
  13 static int
  14 spd_check(const u8 *buf, u8 spd_rev, u8 spd_cksum)
  15 {
  16         unsigned int cksum = 0;
  17         unsigned int i;
  18
  19         /*
  20          * Check SPD revision supported
  21          * Rev 1.2 or less supported by this code
  22          */
  23         if (spd_rev > 0x12) {
  24                 printf("SPD revision %02X not supported by this code\n",
  25                        spd_rev);
  26                 return 1;
  27         }
  28
  29         /*
  30          * Calculate checksum
  31          */
  32         for (i = 0; i < 63; i++) {
  33                 cksum += *buf++;
  34         }
  35         cksum &= 0xFF;
  36
  37         if (cksum != spd_cksum) {
  38                 printf("SPD checksum unexpected. "
  39                         "Checksum in SPD = %02X, computed SPD = %02X\n",
  40                         spd_cksum, cksum);
  41                 return 1;
  42         }
  43
  44         return 0;
  45 }
  46
  47 unsigned int
  48 ddr1_spd_check(const ddr1_spd_eeprom_t *spd)
  49 {
  50         const u8 *p = (const u8 *)spd;
  51
  52         return spd_check(p, spd->spd_rev, spd->cksum);
  53 }
  54
  55 unsigned int
  56 ddr2_spd_check(const ddr2_spd_eeprom_t *spd)
  57 {
  58         const u8 *p = (const u8 *)spd;
  59
  60         return spd_check(p, spd->spd_rev, spd->cksum);
  61 }
  62
  63 /*
  64  * CRC16 compute for DDR3 SPD
  65  * Copied from DDR3 SPD spec.
  66  */
  67 static int
  68 crc16(char *ptr, int count)
  69 {
  70         int crc, i;
  71
  72         crc = 0;
  73         while (--count >= 0) {
  74                 crc = crc ^ (int)*ptr++ << 8;
  75                 for (i = 0; i < 8; ++i)
  76                         if (crc & 0x8000)
  77                                 crc = crc << 1 ^ 0x1021;
  78                         else
  79                                 crc = crc << 1;
  80         }
  81         return crc & 0xffff;
  82 }
  83
  84 unsigned int
  85 ddr3_spd_check(const ddr3_spd_eeprom_t *spd)
  86 {
  87         char *p = (char *)spd;
  88         int csum16;
  89         int len;
  90         char crc_lsb;   /* byte 126 */
  91         char crc_msb;   /* byte 127 */
  92
  93         /*
  94          * SPD byte0[7] - CRC coverage
  95          * 0 = CRC covers bytes 0~125
  96          * 1 = CRC covers bytes 0~116
  97          */
  98
  99         len = !(spd->info_size_crc & 0x80) ? 126 : 117;
 100         csum16 = crc16(p, len);
 101
 102         crc_lsb = (char) (csum16 & 0xff);
 103         crc_msb = (char) (csum16 >> 8);
 104
 105         if (spd->crc[0] == crc_lsb && spd->crc[1] == crc_msb) {
 106                 return 0;
 107         } else {
 108                 printf("SPD checksum unexpected.\n"
 109                         "Checksum lsb in SPD = %02X, computed SPD = %02X\n"
 110                         "Checksum msb in SPD = %02X, computed SPD = %02X\n",
 111                         spd->crc[0], crc_lsb, spd->crc[1], crc_msb);
 112                 return 1;
 113         }
 114 }