Hi Clemens,
On Fri, 11 Feb 2011 10:06:08 +0100, Clemens Ladisch wrote:
> This adds CRC-16 calculation, needed to correctly detect DDR3 SPD EEPROMs.
>
> --- a/prog/detect/sensors-detect
> +++ b/prog/detect/sensors-detect
> @@ -5265,18 +5265,43 @@
>
> # Registers used:
> # 0-63: SPD Data and Checksum
> +# 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, $i);
> + if ($device_type >= 1 and $device_type <= 10) {
Device type 9 (FB-DIMM) also uses the CRC16, so this test is not
correct. Not sure about type 10 (what the hell is "FB-DIMM Probe"?)
> + 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);
> + } elsif ($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
> }
> - $checksum &= 255;
>
> - return 8 if $checksum == i2c_smbus_read_byte_data($file, 63);
> return;
> }
Other than this, your patch looks good and works for me. So I've
applied it with just the device type checks changed. Thanks for your
contribution!
--
Jean Delvare
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