diff options
Diffstat (limited to 'common/ddr_spd.c')
| -rw-r--r-- | common/ddr_spd.c | 53 |
1 files changed, 53 insertions, 0 deletions
diff --git a/common/ddr_spd.c b/common/ddr_spd.c index 78e3c5d..c058e4f 100644 --- a/common/ddr_spd.c +++ b/common/ddr_spd.c @@ -59,3 +59,56 @@ ddr2_spd_check(const ddr2_spd_eeprom_t *spd) return spd_check(p, spd->spd_rev, spd->cksum); } + +/* + * CRC16 compute for DDR3 SPD + * Copied from DDR3 SPD spec. + */ +static int +crc16(char *ptr, int count) +{ + int crc, i; + + crc = 0; + while (--count >= 0) { + crc = crc ^ (int)*ptr++ << 8; + for (i = 0; i < 8; ++i) + if (crc & 0x8000) + crc = crc << 1 ^ 0x1021; + else + crc = crc << 1; + } + return crc & 0xffff; +} + +unsigned int +ddr3_spd_check(const ddr3_spd_eeprom_t *spd) +{ + char *p = (char *)spd; + int csum16; + int len; + char crc_lsb; /* byte 126 */ + char crc_msb; /* byte 127 */ + + /* + * SPD byte0[7] - CRC coverage + * 0 = CRC covers bytes 0~125 + * 1 = CRC covers bytes 0~116 + */ + + len = !(spd->info_size_crc & 0x80) ? 126 : 117; + csum16 = crc16(p, len); + + crc_lsb = (char) (csum16 & 0xff); + crc_msb = (char) (csum16 >> 8); + + if (spd->crc[0] == crc_lsb && spd->crc[1] == crc_msb) { + return 0; + } else { + printf("SPD checksum unexpected.\n" + "Checksum lsb in SPD = %02X, computed SPD = %02X\n" + "Checksum msb in SPD = %02X, computed SPD = %02X\n", + spd->crc[0], crc_lsb, spd->crc[1], crc_msb); + return 1; + } +} |