xref: /openbmc/u-boot/common/ddr_spd.c (revision b8d41dda)
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 }
119