All of lore.kernel.org
 help / color / mirror / Atom feed
From: Clemens Ladisch <clemens@ladisch.de>
To: lm-sensors@vger.kernel.org
Subject: [lm-sensors] [PATCH] sensors-detect: DDR3 SPD EEPROM support
Date: Fri, 11 Feb 2011 09:06:08 +0000	[thread overview]
Message-ID: <4D54FC00.1010600@ladisch.de> (raw)

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) {
+		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

             reply	other threads:[~2011-02-11  9:06 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-02-11  9:06 Clemens Ladisch [this message]
2011-02-15  1:23 ` [lm-sensors] [PATCH] sensors-detect: DDR3 SPD EEPROM support Guenter Roeck
2011-02-16 15:11 ` Jean Delvare
2011-02-16 15:25 ` Clemens Ladisch

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=4D54FC00.1010600@ladisch.de \
    --to=clemens@ladisch.de \
    --cc=lm-sensors@vger.kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.