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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 }