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.X or less supported by this code
  22          */
  23         if (spd_rev >= 0x20) {
  24                 printf("SPD revision %02X not supported by this code\n",
  25                        spd_rev);
  26                 return 1;
  27         }
  28         if (spd_rev > 0x13) {
  29                 printf("SPD revision %02X not verified by this code\n",
  30                        spd_rev);
  31         }
  32
  33         /*
  34          * Calculate checksum
  35          */
  36         for (i = 0; i < 63; i++) {
  37                 cksum += *buf++;
  38         }
  39         cksum &= 0xFF;
  40
  41         if (cksum != spd_cksum) {
  42                 printf("SPD checksum unexpected. "
  43                         "Checksum in SPD = %02X, computed SPD = %02X\n",
  44                         spd_cksum, cksum);
  45                 return 1;
  46         }
  47
  48         return 0;
  49 }
  50
  51 unsigned int
  52 ddr1_spd_check(const ddr1_spd_eeprom_t *spd)
  53 {
  54         const u8 *p = (const u8 *)spd;
  55
  56         return spd_check(p, spd->spd_rev, spd->cksum);
  57 }
  58
  59 unsigned int
  60 ddr2_spd_check(const ddr2_spd_eeprom_t *spd)
  61 {
  62         const u8 *p = (const u8 *)spd;
  63
  64         return spd_check(p, spd->spd_rev, spd->cksum);
  65 }
  66
  67 /*
  68  * CRC16 compute for DDR3 SPD
  69  * Copied from DDR3 SPD spec.
  70  */
  71 static int
  72 crc16(char *ptr, int count)
  73 {
  74         int crc, i;
  75
  76         crc = 0;
  77         while (--count >= 0) {
  78                 crc = crc ^ (int)*ptr++ << 8;
  79                 for (i = 0; i < 8; ++i)
  80                         if (crc & 0x8000)
  81                                 crc = crc << 1 ^ 0x1021;
  82                         else
  83                                 crc = crc << 1;
  84         }
  85         return crc & 0xffff;
  86 }
  87
  88 unsigned int
  89 ddr3_spd_check(const ddr3_spd_eeprom_t *spd)
  90 {
  91         char *p = (char *)spd;
  92         int csum16;
  93         int len;
  94         char crc_lsb;   /* byte 126 */
  95         char crc_msb;   /* byte 127 */
  96
  97         /*
  98          * SPD byte0[7] - CRC coverage
  99          * 0 = CRC covers bytes 0~125
 100          * 1 = CRC covers bytes 0~116
 101          */
 102
 103         len = !(spd->info_size_crc & 0x80) ? 126 : 117;
 104         csum16 = crc16(p, len);
 105
 106         crc_lsb = (char) (csum16 & 0xff);
 107         crc_msb = (char) (csum16 >> 8);
 108
 109         if (spd->crc[0] == crc_lsb && spd->crc[1] == crc_msb) {
 110                 return 0;
 111         } else {
 112                 printf("SPD checksum unexpected.\n"
 113                         "Checksum lsb in SPD = %02X, computed SPD = %02X\n"
 114                         "Checksum msb in SPD = %02X, computed SPD = %02X\n",
 115                         spd->crc[0], crc_lsb, spd->crc[1], crc_msb);
 116                 return 1;
 117         }
 118 }