From: Guenter Roeck <guenter.roeck@ericsson.com>
To: lm-sensors@vger.kernel.org
Subject: Re: [lm-sensors] [PATCH] sensors-detect: DDR3 SPD EEPROM support
Date: Tue, 15 Feb 2011 01:23:52 +0000 [thread overview]
Message-ID: <20110215012352.GA28194@ericsson.com> (raw)
In-Reply-To: <4D54FC00.1010600@ladisch.de>
On Fri, Feb 11, 2011 at 04:06:08AM -0500, Clemens Ladisch wrote:
> This adds CRC-16 calculation, needed to correctly detect DDR3 SPD EEPROMs.
>
For DDR3: Tested-by: Guenter Roeck <guenter.roeck@ericsson.com>
> --- 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) {
> + 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;
> }
>
>
> _______________________________________________
> lm-sensors mailing list
> lm-sensors@lm-sensors.org
> http://lists.lm-sensors.org/mailman/listinfo/lm-sensors
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next prev parent reply other threads:[~2011-02-15 1:23 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-02-11 9:06 [lm-sensors] [PATCH] sensors-detect: DDR3 SPD EEPROM support Clemens Ladisch
2011-02-15 1:23 ` Guenter Roeck [this message]
2011-02-16 15:11 ` Jean Delvare
2011-02-16 15:25 ` Clemens Ladisch
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