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Mark D. Studebaker
49754b948f
software write-protect registers.
prevent Vaio detection from running more than once.
update eeprom driver documentation.
git-svn-id: http://lm-sensors.org/svn/lm-sensors/trunk@2448 7894878c-1315-0410-8ee3-d5d059ff63e0
221 lines
9.0 KiB
Plaintext
221 lines
9.0 KiB
Plaintext
Kernel driver `eeprom.o'
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========================
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Status: Complete and well-tested
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Supported chips:
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* Any EEPROM chip in the designated address range
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Prefix `eeprom'
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Addresses scanned: I2C 0x50 - 0x57 (inclusive)
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Datasheets: Publicly available from:
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Atmel (www.atmel.com),
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Catalyst (www.catsemi.com),
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Fairchild (www.fairchildsemi.com),
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Microchip (www.microchip.com),
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Philips (www.semiconductor.philips.com),
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Rohm (www.rohm.com),
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ST (www.st.com),
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Xicor (www.xicor.com)
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Chip Size (bits) Address
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24C01 1K 0x50 (shadows at 0x51 - 0x57)
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24C01A 1K 0x50 - 0x57 (Typical device on DIMMs)
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24C02 2K 0x50 - 0x57
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24C04 4K 0x50, 0x52, 0x54, 0x56
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(additional data at 0x51, 0x53, 0x55, 0x57)
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24C08 8K 0x50, 0x54 (additional data at 0x51, 0x52,
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0x53, 0x55, 0x56, 0x57)
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24C16 16K 0x50 (additional data at 0x51 - 0x57)
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Sony 2K 0x57
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Microchip 24AA52 2K 0x50 - 0x57, SW write protect at 0x30-37
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ST M34C02 2K 0x50 - 0x57, SW write protect at 0x30-37
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Author: Frodo Looijaard <frodol@dds.nl> and Philip Edelbrock
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<phil@netroedge.com>
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Module Parameters
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-----------------
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* checksum: int
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Only accept eeproms whose checksum is correct
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* force: short array (min = 1, max = 48)
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List of adapter,address pairs to boldly assume to be present
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* force_eeprom: short array (min = 1, max = 48)
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List of adapter,address pairs which are unquestionably assumed to contain
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a `eeprom' chip
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* ignore: short array (min = 1, max = 48)
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List of adapter,address pairs not to scan
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* ignore_range: short array (min = 1, max = 48)
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List of adapter,start-addr,end-addr triples not to scan
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* probe: short array (min = 1, max = 48)
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List of adapter,address pairs to scan additionally
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* probe_range: short array (min = 1, max = 48)
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List of adapter,start-addr,end-addr triples to scan additionally
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Description
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-----------
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This is a simple EEPROM module meant to enable reading the first 256 bytes
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of an EEPROM (on a SDRAM DIMM for example). However, it will access serial
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EEPROMs on any I2C adapter. This module will probably need to be
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expanded. A /dev file interface would probably be more effective.
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This module was a programming exercise to get used to the new project
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organization laid out by Frodo, but it should be at least completely
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effective for decoding the contents of EEPROMs on DIMMs.
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DIMMS will typically contain a 24C01A or 24C02. The other devices
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will not be found on a DIMM because they respond to more than one
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address.
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DDC Monitors may contain any device. Often a 24C01, which responds
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to all 8 addresses, is found. See the 'ddcmon' driver which has
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specialized /proc entries for DDC monitors. If the eeprom driver is
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loaded before the ddcmon driver and there is no 'ignore' line in the
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/etc/sensors.conf file, the eeprom driver will latch onto the DDC monitor
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eeprom.
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Recent Sony Vaio laptops have an EEPROM at 0x57. We couldn't get the
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specification, so it is guess work and far from being complete.
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The Microchip 24AA52/24LCS52 and the ST M34C02 support an additional
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software write protect register at 0x30 - 0x37 (0x20 less than the
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memory location). The chip responds to "write quick" detection at this
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address but does not respond to byte reads.
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If this register is present, the lower 128 bytes of the memory
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array are not write protected. Any byte data write to this address
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will write protect the memory array permanently, and the device
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will no longer respond at the 0x30-37 address.
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The eeprom driver does not support this register.
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Lacking functionality:
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* Full support for larger devices (24C04, 24C08, 24C16). These are
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not typically found on a PC. These devices will appear as separate
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devices at multiple addresses.
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* Support for really large devices (24C32, 24C64, 24C128, 24C256, 24C512).
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These devices require two-byte address fields and are not supported.
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* Enable Writing. Again, no technical reason why not, but making it easy
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to change the contents of the EEPROMs (on DIMMs anyway) also makes it easy
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to disable the DIMMs (potentially preventing the computer from booting)
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until the values are restored somehow.
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Use:
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After inserting the module (and any other required smbus/i2c modules), you
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should have some EEPROM directories in /proc/sys/dev/sensors/ of names such
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as "eeprom-i2c-0-50". Inside each of these is a series of files which
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represent 16 bytes blocks from the EEPROM. The data is in decimal (base
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10) delimited by spaces.
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Note:
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EEPROMs reported are not nessesarily all from DIMMs. Xeon processors, for
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example, have serial EEPROMs in them connected to the SMBus which will be
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found by the module. Take care to ignore the output of decode-dimms.pl for
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these EEPROMs. There is decode-xeon.pl for them. Same applies to Vaio
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EEPROMs, which have decode-vaio.pl.
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The driver caches the data from the monitor and only rereads it
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from the eeprom if the cache is more than 5 minutes old.
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Decode-dimms.pl
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---------------
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This Perl script attempts to make sense of the first 128 bytes of a SDRAM
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PC-100 DIMM. Using the 'Serial Presence Detect (SPD)' Spec (Rev1.2a)** from
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Intel. When finished, it will decode and report all the values defined in
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the spec. Much of the information is technical timing and interfacing info
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(probably not all used by the BIOS or clocking IC).
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Note: During testing, we noticed that many DIMMs have trucated SPD records.
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I'm not sure if these conform to an old spec, or if the manufacturers are
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simply just taking shortcuts. But, many DIMMs have all zeros stored past
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byte 21. I asked an Intel SDRAM tester, Sat Kolli (skolli@smartm.com),
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about this and this is what he had to say:
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"[...] Now in terms of SPD contents, you are right that people do all kinds
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of things. The way to insure that any module works is to look for the most
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basic information, such as module bank density, number of banks, and device
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addresses. That will give you the module size and what devices are used. It
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is very difficult to verify if the module is PC-100, because of
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inconsistencies between spd data from different manufacturers. You could
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read the timing information or the special Intel bytes (126 & 127) but I do
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not know how many program that information. These inconsistencies may be
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minimized if you or your customers stay with some of the better known
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manufacturers." (Thanks goes to Sat Kolli for his comments and help.)
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Use:
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After inserting the necessary modules, run the script!
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Notes:
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The script assumes that Perl can be found at /usr/bin/perl. If different,
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you will need to adjust the first line of the file accordingly, or else
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you will get a strange "decode-dimms.pl: no such file or directory" error.
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Also note that the script assumes that _all_ the eeproms belong to DIMMs,
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which may not be the case.
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Decode-vaio.pl
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--------------
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This Perl script looks for a Sony Vaio EEPROM at 0x57. If your system is not
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a Sony Vaio laptop, you just don't care. If your system is an old Vaio, you
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probably don't have an EEPROM on it and this script will be useless to you
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as well.
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Use:
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After inserting the necessary modules, run the script!
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Notes:
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The script assumes that Perl can be found at /usr/bin/perl. If different,
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you will need to adjust the first line of the file accordingly, or else
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you will get a strange "decode-vaio.pl: no such file or directory" error.
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Decode-edid.pl
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This Perl script acts as an interface between the eeprom module and
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parse-edid, which is part of read-edid. Read-edid is a tool for gathering
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information on VESA PNP monitors. It is somewhat similar to what our
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ddcmon driver does, except that ddcmon outputs user-oriented data while
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read-edid generates a a computer oriented configuration file (primarily
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for XFree86).
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Read-edid is made of two components, get-edid which retrieves binary data
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from the monitor, and parse-edid which decodes the data into useful
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information. Get-edid uses low level functions, and relies on compliance
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of both the video card and the monitor to some standard (DCC as it is
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called). It may not work for everyone. On the other hand, some video
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cards make this information available on an I2C bus and we are able to
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get it using our eeprom module. That's why we wrote this script that
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converts the data as exported by our eeprom module into what parse-edid
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expects from get-edid. That way, users who can't get get-edid to work
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still have a chance to be able to retrieve the wanted information thanks
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to the lm_sensors modules and tools.
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Use:
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Unload the ddcmon if it was loaded, load the eeprom module instead. Then,
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run the script. The script will try to figure out on which I2C bus and at
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which address is the eeprom, but it may fail. In this case, you can pass
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the parameters to the script. Examples:
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decode-edid.pl 1
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decode-edid.pl 2 0x50
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You will find additional details in the script itself. Read-edid is avilable
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there:
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http://john.fremlin.de/programs/linux/read-edid/
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