On DDR4 modules there is a separate CRC for the second block of 128
bytes. Check it.
---
eeprom/decode-dimms | 32 +++++++++++++++++++++++++-------
1 file changed, 25 insertions(+), 7 deletions(-)
--- i2c-tools.orig/eeprom/decode-dimms 2017-11-17 11:28:32.262363769 +0100
+++ i2c-tools/eeprom/decode-dimms 2017-11-17 11:29:23.760989692 +0100
@@ -1728,7 +1728,7 @@ use constant DDR4_UNBUFFERED => 1;
use constant DDR4_REGISTERED => 2;
use constant DDR4_LOAD_REDUCED => 4;
-# Parameter: EEPROM bytes 0-383 (using 1-130)
+# Parameter: EEPROM bytes 0-383 (using 1-255)
sub decode_ddr4_sdram($)
{
my $bytes = shift;
@@ -1761,6 +1761,15 @@ sub decode_ddr4_sdram($)
printl("Module Type", $module_types[$bytes->[3] & 0x0f]->{type});
+# CRC of block 1
+ my $crc_calc = calculate_crc($bytes, 128, 126);
+ my $crc_spd = ($bytes->[255] << 8) | $bytes->[254];
+ my $crc_block_1_ok = $crc_calc == $crc_spd;
+ printl("EEPROM CRC of bytes 128-253", $crc_block_1_ok ?
+ sprintf("OK (0x\%04X)", $crc_calc) :
+ sprintf("Bad\n(found 0x\%04X, calculated 0x\%04X)",
+ $crc_spd, $crc_calc));
+
# time bases
if (($bytes->[17] & 0x03) != 0x00 || ($bytes->[17] & 0xc0) != 0x00) {
print STDERR "Unknown time base values, can't decode\n";
@@ -1918,6 +1927,8 @@ sub decode_ddr4_sdram($)
$bytes->[14] & 0x80 ? "TSE2004 compliant" : "No");
# type-specific settings
+ return unless $crc_block_1_ok || $opt_igncheck;
+
if ($module_types[$bytes->[3] & 0x0f]->{family} == DDR4_UNBUFFERED ||
$module_types[$bytes->[3] & 0x0f]->{family} == DDR4_REGISTERED ||
$module_types[$bytes->[3] & 0x0f]->{family} == DDR4_LOAD_REDUCED) {
@@ -2288,15 +2299,14 @@ sub checksum($)
}
# Calculate and verify CRC
-sub check_crc($)
+sub calculate_crc($$$)
{
- my $bytes = shift;
+ my ($bytes, $start, $len) = @_;
my $crc = 0;
- my $crc_cover = $bytes->[0] & 0x80 ? 116 : 125;
- my $crc_ptr = 0;
+ my $crc_ptr = $start;
my $crc_bit;
- while ($crc_ptr <= $crc_cover) {
+ while ($crc_ptr < $start + $len) {
$crc = $crc ^ ($bytes->[$crc_ptr] << 8);
for ($crc_bit = 0; $crc_bit < 8; $crc_bit++) {
if ($crc & 0x8000) {
@@ -2307,7 +2317,15 @@ sub check_crc($)
}
$crc_ptr++;
}
- $crc &= 0xffff;
+
+ return $crc & 0xffff;
+}
+
+sub check_crc($)
+{
+ my $bytes = shift;
+ my $crc_cover = $bytes->[0] & 0x80 ? 116 : 125;
+ my $crc = calculate_crc($bytes, 0, $crc_cover + 1);
my $dimm_crc = ($bytes->[127] << 8) | $bytes->[126];
return ("EEPROM CRC of bytes 0-$crc_cover",
--
Jean Delvare
SUSE L3 Support
