diff options
Diffstat (limited to 'src/device/dram/ddr3.c')
| -rw-r--r-- | src/device/dram/ddr3.c | 62 |
1 files changed, 42 insertions, 20 deletions
diff --git a/src/device/dram/ddr3.c b/src/device/dram/ddr3.c index d98de91956..9b4f490630 100644 --- a/src/device/dram/ddr3.c +++ b/src/device/dram/ddr3.c @@ -49,6 +49,46 @@ int dimm_is_registered(enum spd_dimm_type type) } /** + * \brief Calculate the CRC of a DDR3 SPD + * + * @param spd pointer to raw SPD data + * @param len length of data in SPD + * + * @return the CRC of the SPD data, or 0 when spd data is truncated. + */ +u16 spd_ddr3_calc_crc(u8 *spd, int len) +{ + int n_crc, i; + u8 *ptr; + u16 crc; + + /* Find the number of bytes covered by CRC */ + if (spd[0] & 0x80) { + n_crc = 117; + } else { + n_crc = 126; + } + + if (len < n_crc) + /* Not enough bytes available to get the CRC */ + return 0; + + /* Compute the CRC */ + crc = 0; + ptr = spd; + while (--n_crc >= 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; +} + +/** * \brief Decode the raw SPD data * * Decodes a raw SPD data from a DDR3 DIMM, and organizes it into a @@ -68,9 +108,8 @@ int dimm_is_registered(enum spd_dimm_type type) */ int spd_decode_ddr3(dimm_attr * dimm, spd_raw_data spd) { - int nCRC, i, ret; + int ret; u16 crc, spd_crc; - u8 *ptr = spd; u8 ftb_divisor, ftb_dividend, capacity_shift, bus_width, sdram_width; u8 reg8; u32 mtb; /* medium time base */ @@ -88,24 +127,7 @@ int spd_decode_ddr3(dimm_attr * dimm, spd_raw_data spd) } dimm->dram_type = SPD_MEMORY_TYPE_SDRAM_DDR3; - /* Find the number of bytes covered by CRC */ - if (spd[0] & 0x80) { - nCRC = 117; - } else { - nCRC = 126; - } - - /* Compute the CRC */ - crc = 0; - while (--nCRC >= 0) { - crc = crc ^ (int)*ptr++ << 8; - for (i = 0; i < 8; ++i) - if (crc & 0x8000) { - crc = crc << 1 ^ 0x1021; - } else { - crc = crc << 1; - } - } + crc = spd_ddr3_calc_crc(spd, sizeof(spd)); /* Compare with the CRC in the SPD */ spd_crc = (spd[127] << 8) + spd[126]; /* Verify the CRC is correct */ |