Changeset 5930

Timestamp:

02/16/11 16:08:25 (2 years ago)

Author:

khali

Message:

Fix detection of SPD EEPROM on DDR3 memory modules. DDR3 uses CRC16 over
128 bytes instead of basic checksum over 64 bytes. Contributed by
Clemens Ladisch.

Location:

lm-sensors/trunk

Files:

• CHANGES (modified) (1 diff)
• prog/detect/sensors-detect (modified) (1 diff)

lm-sensors/trunk/CHANGES

@@ -27 +27 @@
                         EMC1072, EMC1073, EMC1074, EMC1402, and EMC1424
                   Fixed address ranges checked for SMSC EMC1403 and EMC1404.
+                  Fix detection of SPD EEPROM on DDR3 memory modules
 
 3.2.0 (2010-10-10)

lm-sensors/trunk/prog/detect/sensors-detect

@@ -5265 +5265 @@
 
 # Registers used:
-#   0-63: SPD Data and Checksum
+#   0-63: SPD Data and Checksum (up to DDR2)
+#   0-127: SPD data and CRC (DDR3)
 sub eeprom_detect
 {
         my ($file, $addr) = @_;
+        my $device_type = i2c_smbus_read_byte_data($file, 2);
         my $checksum = 0;
 
-        # Check the checksum for validity (works for most DIMMs and RIMMs)
-        for (my $i = 0; $i <= 62; $i++) {
-                $checksum += i2c_smbus_read_byte_data($file, $i);
-        }
-        $checksum &= 255;
-
-        return 8 if $checksum == i2c_smbus_read_byte_data($file, 63);
+        # Check the checksum or CRC16 for validity
+        if ($device_type >= 1 and $device_type <= 8) {
+                for (my $i = 0; $i < 63; $i++) {
+                        $checksum += i2c_smbus_read_byte_data($file, $i);
+                }
+                $checksum &= 0xff;
+
+                return 8 if $checksum == i2c_smbus_read_byte_data($file, 63);
+        } elsif ($device_type => 9 && $device_type <= 11) {
+                # see JEDEC 21-C 4.1.2.11 2.4
+                my $crc_coverage = i2c_smbus_read_byte_data($file, 0);
+                $crc_coverage = ($crc_coverage & 0x80) ? 117 : 126;
+                for (my $i = 0; $i < $crc_coverage; $i++) {
+                        $checksum ^= i2c_smbus_read_byte_data($file, $i) << 8;
+                        for (my $bit = 0; $bit < 8; $bit++) {
+                                if ($checksum & 0x8000) {
+                                        $checksum = ($checksum << 1) ^ 0x1021;
+                                } else {
+                                        $checksum <<= 1;
+                                }
+                        }
+                }
+                $checksum &= 0xffff;
+
+                return 8 if ($checksum & 0xff) == i2c_smbus_read_byte_data($file, 126) and
+                            ($checksum >> 8) == i2c_smbus_read_byte_data($file, 127);
+
+                # note: if bit 7 of byte 32 is set, a jc42 sensor is at $addr-0x38
+        }
+
         return;
 }