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diff --git a/Documentation/drivers/edac/edac.txt b/Documentation/drivers/edac/edac.txt deleted file mode 100644 index a5c36842ece..00000000000 --- a/Documentation/drivers/edac/edac.txt +++ /dev/null @@ -1,727 +0,0 @@ - - -EDAC - Error Detection And Correction - -Written by Doug Thompson <dougthompson@xmission.com> -7 Dec 2005 -17 Jul 2007 Updated - - -EDAC is maintained and written by: - - Doug Thompson, Dave Jiang, Dave Peterson et al, - original author: Thayne Harbaugh, - -Contact: - website: bluesmoke.sourceforge.net - mailing list: bluesmoke-devel@lists.sourceforge.net - -"bluesmoke" was the name for this device driver when it was "out-of-tree" -and maintained at sourceforge.net. When it was pushed into 2.6.16 for the -first time, it was renamed to 'EDAC'. - -The bluesmoke project at sourceforge.net is now utilized as a 'staging area' -for EDAC development, before it is sent upstream to kernel.org - -At the bluesmoke/EDAC project site, is a series of quilt patches against -recent kernels, stored in a SVN respository. For easier downloading, there -is also a tarball snapshot available. - -============================================================================ -EDAC PURPOSE - -The 'edac' kernel module goal is to detect and report errors that occur -within the computer system running under linux. - -MEMORY - -In the initial release, memory Correctable Errors (CE) and Uncorrectable -Errors (UE) are the primary errors being harvested. These types of errors -are harvested by the 'edac_mc' class of device. - -Detecting CE events, then harvesting those events and reporting them, -CAN be a predictor of future UE events. With CE events, the system can -continue to operate, but with less safety. Preventive maintenance and -proactive part replacement of memory DIMMs exhibiting CEs can reduce -the likelihood of the dreaded UE events and system 'panics'. - -NON-MEMORY - -A new feature for EDAC, the edac_device class of device, was added in -the 2.6.23 version of the kernel. - -This new device type allows for non-memory type of ECC hardware detectors -to have their states harvested and presented to userspace via the sysfs -interface. - -Some architectures have ECC detectors for L1, L2 and L3 caches, along with DMA -engines, fabric switches, main data path switches, interconnections, -and various other hardware data paths. If the hardware reports it, then -a edac_device device probably can be constructed to harvest and present -that to userspace. - - -PCI BUS SCANNING - -In addition, PCI Bus Parity and SERR Errors are scanned for on PCI devices -in order to determine if errors are occurring on data transfers. - -The presence of PCI Parity errors must be examined with a grain of salt. -There are several add-in adapters that do NOT follow the PCI specification -with regards to Parity generation and reporting. The specification says -the vendor should tie the parity status bits to 0 if they do not intend -to generate parity. Some vendors do not do this, and thus the parity bit -can "float" giving false positives. - -In the kernel there is a pci device attribute located in sysfs that is -checked by the EDAC PCI scanning code. If that attribute is set, -PCI parity/error scannining is skipped for that device. The attribute -is: - - broken_parity_status - -as is located in /sys/devices/pci<XXX>/0000:XX:YY.Z directorys for -PCI devices. - -FUTURE HARDWARE SCANNING - -EDAC will have future error detectors that will be integrated with -EDAC or added to it, in the following list: - - MCE Machine Check Exception - MCA Machine Check Architecture - NMI NMI notification of ECC errors - MSRs Machine Specific Register error cases - and other mechanisms. - -These errors are usually bus errors, ECC errors, thermal throttling -and the like. - - -============================================================================ -EDAC VERSIONING - -EDAC is composed of a "core" module (edac_core.ko) and several Memory -Controller (MC) driver modules. On a given system, the CORE -is loaded and one MC driver will be loaded. Both the CORE and -the MC driver (or edac_device driver) have individual versions that reflect -current release level of their respective modules. - -Thus, to "report" on what version a system is running, one must report both -the CORE's and the MC driver's versions. - - -LOADING - -If 'edac' was statically linked with the kernel then no loading is -necessary. If 'edac' was built as modules then simply modprobe the -'edac' pieces that you need. You should be able to modprobe -hardware-specific modules and have the dependencies load the necessary core -modules. - -Example: - -$> modprobe amd76x_edac - -loads both the amd76x_edac.ko memory controller module and the edac_mc.ko -core module. - - -============================================================================ -EDAC sysfs INTERFACE - -EDAC presents a 'sysfs' interface for control, reporting and attribute -reporting purposes. - -EDAC lives in the /sys/devices/system/edac directory. - -Within this directory there currently reside 2 'edac' components: - - mc memory controller(s) system - pci PCI control and status system - - -============================================================================ -Memory Controller (mc) Model - -First a background on the memory controller's model abstracted in EDAC. -Each 'mc' device controls a set of DIMM memory modules. These modules are -laid out in a Chip-Select Row (csrowX) and Channel table (chX). There can -be multiple csrows and multiple channels. - -Memory controllers allow for several csrows, with 8 csrows being a typical value. -Yet, the actual number of csrows depends on the electrical "loading" -of a given motherboard, memory controller and DIMM characteristics. - -Dual channels allows for 128 bit data transfers to the CPU from memory. -Some newer chipsets allow for more than 2 channels, like Fully Buffered DIMMs -(FB-DIMMs). The following example will assume 2 channels: - - - Channel 0 Channel 1 - =================================== - csrow0 | DIMM_A0 | DIMM_B0 | - csrow1 | DIMM_A0 | DIMM_B0 | - =================================== - - =================================== - csrow2 | DIMM_A1 | DIMM_B1 | - csrow3 | DIMM_A1 | DIMM_B1 | - =================================== - -In the above example table there are 4 physical slots on the motherboard -for memory DIMMs: - - DIMM_A0 - DIMM_B0 - DIMM_A1 - DIMM_B1 - -Labels for these slots are usually silk screened on the motherboard. Slots -labeled 'A' are channel 0 in this example. Slots labeled 'B' -are channel 1. Notice that there are two csrows possible on a -physical DIMM. These csrows are allocated their csrow assignment -based on the slot into which the memory DIMM is placed. Thus, when 1 DIMM -is placed in each Channel, the csrows cross both DIMMs. - -Memory DIMMs come single or dual "ranked". A rank is a populated csrow. -Thus, 2 single ranked DIMMs, placed in slots DIMM_A0 and DIMM_B0 above -will have 1 csrow, csrow0. csrow1 will be empty. On the other hand, -when 2 dual ranked DIMMs are similarly placed, then both csrow0 and -csrow1 will be populated. The pattern repeats itself for csrow2 and -csrow3. - -The representation of the above is reflected in the directory tree -in EDAC's sysfs interface. Starting in directory -/sys/devices/system/edac/mc each memory controller will be represented -by its own 'mcX' directory, where 'X" is the index of the MC. - - - ..../edac/mc/ - | - |->mc0 - |->mc1 - |->mc2 - .... - -Under each 'mcX' directory each 'csrowX' is again represented by a -'csrowX', where 'X" is the csrow index: - - - .../mc/mc0/ - | - |->csrow0 - |->csrow2 - |->csrow3 - .... - -Notice that there is no csrow1, which indicates that csrow0 is -composed of a single ranked DIMMs. This should also apply in both -Channels, in order to have dual-channel mode be operational. Since -both csrow2 and csrow3 are populated, this indicates a dual ranked -set of DIMMs for channels 0 and 1. - - -Within each of the 'mc','mcX' and 'csrowX' directories are several -EDAC control and attribute files. - - -============================================================================ -DIRECTORY 'mc' - -In directory 'mc' are EDAC system overall control and attribute files: - - -Panic on UE control file: - - 'edac_mc_panic_on_ue' - - An uncorrectable error will cause a machine panic. This is usually - desirable. It is a bad idea to continue when an uncorrectable error - occurs - it is indeterminate what was uncorrected and the operating - system context might be so mangled that continuing will lead to further - corruption. If the kernel has MCE configured, then EDAC will never - notice the UE. - - LOAD TIME: module/kernel parameter: panic_on_ue=[0|1] - - RUN TIME: echo "1" >/sys/devices/system/edac/mc/edac_mc_panic_on_ue - - -Log UE control file: - - 'edac_mc_log_ue' - - Generate kernel messages describing uncorrectable errors. These errors - are reported through the system message log system. UE statistics - will be accumulated even when UE logging is disabled. - - LOAD TIME: module/kernel parameter: log_ue=[0|1] - - RUN TIME: echo "1" >/sys/devices/system/edac/mc/edac_mc_log_ue - - -Log CE control file: - - 'edac_mc_log_ce' - - Generate kernel messages describing correctable errors. These - errors are reported through the system message log system. - CE statistics will be accumulated even when CE logging is disabled. - - LOAD TIME: module/kernel parameter: log_ce=[0|1] - - RUN TIME: echo "1" >/sys/devices/system/edac/mc/edac_mc_log_ce - - -Polling period control file: - - 'edac_mc_poll_msec' - - The time period, in milliseconds, for polling for error information. - Too small a value wastes resources. Too large a value might delay - necessary handling of errors and might loose valuable information for - locating the error. 1000 milliseconds (once each second) is the current - default. Systems which require all the bandwidth they can get, may - increase this. - - LOAD TIME: module/kernel parameter: poll_msec=[0|1] - - RUN TIME: echo "1000" >/sys/devices/system/edac/mc/edac_mc_poll_msec - - -============================================================================ -'mcX' DIRECTORIES - - -In 'mcX' directories are EDAC control and attribute files for -this 'X" instance of the memory controllers: - - -Counter reset control file: - - 'reset_counters' - - This write-only control file will zero all the statistical counters - for UE and CE errors. Zeroing the counters will also reset the timer - indicating how long since the last counter zero. This is useful - for computing errors/time. Since the counters are always reset at - driver initialization time, no module/kernel parameter is available. - - RUN TIME: echo "anything" >/sys/devices/system/edac/mc/mc0/counter_reset - - This resets the counters on memory controller 0 - - -Seconds since last counter reset control file: - - 'seconds_since_reset' - - This attribute file displays how many seconds have elapsed since the - last counter reset. This can be used with the error counters to - measure error rates. - - - -Memory Controller name attribute file: - - 'mc_name' - - This attribute file displays the type of memory controller - that is being utilized. - - -Total memory managed by this memory controller attribute file: - - 'size_mb' - - This attribute file displays, in count of megabytes, of memory - that this instance of memory controller manages. - - -Total Uncorrectable Errors count attribute file: - - 'ue_count' - - This attribute file displays the total count of uncorrectable - errors that have occurred on this memory controller. If panic_on_ue - is set this counter will not have a chance to increment, - since EDAC will panic the system. - - -Total UE count that had no information attribute fileY: - - 'ue_noinfo_count' - - This attribute file displays the number of UEs that - have occurred have occurred with no informations as to which DIMM - slot is having errors. - - -Total Correctable Errors count attribute file: - - 'ce_count' - - This attribute file displays the total count of correctable - errors that have occurred on this memory controller. This - count is very important to examine. CEs provide early - indications that a DIMM is beginning to fail. This count - field should be monitored for non-zero values and report - such information to the system administrator. - - -Total Correctable Errors count attribute file: - - 'ce_noinfo_count' - - This attribute file displays the number of CEs that - have occurred wherewith no informations as to which DIMM slot - is having errors. Memory is handicapped, but operational, - yet no information is available to indicate which slot - the failing memory is in. This count field should be also - be monitored for non-zero values. - -Device Symlink: - - 'device' - - Symlink to the memory controller device. - -Sdram memory scrubbing rate: - - 'sdram_scrub_rate' - - Read/Write attribute file that controls memory scrubbing. The scrubbing - rate is set by writing a minimum bandwith in bytes/sec to the attribute - file. The rate will be translated to an internal value that gives at - least the specified rate. - - Reading the file will return the actual scrubbing rate employed. - - If configuration fails or memory scrubbing is not implemented, the value - of the attribute file will be -1. - - - -============================================================================ -'csrowX' DIRECTORIES - -In the 'csrowX' directories are EDAC control and attribute files for -this 'X" instance of csrow: - - -Total Uncorrectable Errors count attribute file: - - 'ue_count' - - This attribute file displays the total count of uncorrectable - errors that have occurred on this csrow. If panic_on_ue is set - this counter will not have a chance to increment, since EDAC - will panic the system. - - -Total Correctable Errors count attribute file: - - 'ce_count' - - This attribute file displays the total count of correctable - errors that have occurred on this csrow. This - count is very important to examine. CEs provide early - indications that a DIMM is beginning to fail. This count - field should be monitored for non-zero values and report - such information to the system administrator. - - -Total memory managed by this csrow attribute file: - - 'size_mb' - - This attribute file displays, in count of megabytes, of memory - that this csrow contains. - - -Memory Type attribute file: - - 'mem_type' - - This attribute file will display what type of memory is currently - on this csrow. Normally, either buffered or unbuffered memory. - Examples: - Registered-DDR - Unbuffered-DDR - - -EDAC Mode of operation attribute file: - - 'edac_mode' - - This attribute file will display what type of Error detection - and correction is being utilized. - - -Device type attribute file: - - 'dev_type' - - This attribute file will display what type of DRAM device is - being utilized on this DIMM. - Examples: - x1 - x2 - x4 - x8 - - -Channel 0 CE Count attribute file: - - 'ch0_ce_count' - - This attribute file will display the count of CEs on this - DIMM located in channel 0. - - -Channel 0 UE Count attribute file: - - 'ch0_ue_count' - - This attribute file will display the count of UEs on this - DIMM located in channel 0. - - -Channel 0 DIMM Label control file: - - 'ch0_dimm_label' - - This control file allows this DIMM to have a label assigned - to it. With this label in the module, when errors occur - the output can provide the DIMM label in the system log. - This becomes vital for panic events to isolate the - cause of the UE event. - - DIMM Labels must be assigned after booting, with information - that correctly identifies the physical slot with its - silk screen label. This information is currently very - motherboard specific and determination of this information - must occur in userland at this time. - - -Channel 1 CE Count attribute file: - - 'ch1_ce_count' - - This attribute file will display the count of CEs on this - DIMM located in channel 1. - - -Channel 1 UE Count attribute file: - - 'ch1_ue_count' - - This attribute file will display the count of UEs on this - DIMM located in channel 0. - - -Channel 1 DIMM Label control file: - - 'ch1_dimm_label' - - This control file allows this DIMM to have a label assigned - to it. With this label in the module, when errors occur - the output can provide the DIMM label in the system log. - This becomes vital for panic events to isolate the - cause of the UE event. - - DIMM Labels must be assigned after booting, with information - that correctly identifies the physical slot with its - silk screen label. This information is currently very - motherboard specific and determination of this information - must occur in userland at this time. - - -============================================================================ -SYSTEM LOGGING - -If logging for UEs and CEs are enabled then system logs will have -error notices indicating errors that have been detected: - -EDAC MC0: CE page 0x283, offset 0xce0, grain 8, syndrome 0x6ec3, row 0, -channel 1 "DIMM_B1": amd76x_edac - -EDAC MC0: CE page 0x1e5, offset 0xfb0, grain 8, syndrome 0xb741, row 0, -channel 1 "DIMM_B1": amd76x_edac - - -The structure of the message is: - the memory controller (MC0) - Error type (CE) - memory page (0x283) - offset in the page (0xce0) - the byte granularity (grain 8) - or resolution of the error - the error syndrome (0xb741) - memory row (row 0) - memory channel (channel 1) - DIMM label, if set prior (DIMM B1 - and then an optional, driver-specific message that may - have additional information. - -Both UEs and CEs with no info will lack all but memory controller, -error type, a notice of "no info" and then an optional, -driver-specific error message. - - - -============================================================================ -PCI Bus Parity Detection - - -On Header Type 00 devices the primary status is looked at -for any parity error regardless of whether Parity is enabled on the -device. (The spec indicates parity is generated in some cases). -On Header Type 01 bridges, the secondary status register is also -looked at to see if parity occurred on the bus on the other side of -the bridge. - - -SYSFS CONFIGURATION - -Under /sys/devices/system/edac/pci are control and attribute files as follows: - - -Enable/Disable PCI Parity checking control file: - - 'check_pci_parity' - - - This control file enables or disables the PCI Bus Parity scanning - operation. Writing a 1 to this file enables the scanning. Writing - a 0 to this file disables the scanning. - - Enable: - echo "1" >/sys/devices/system/edac/pci/check_pci_parity - - Disable: - echo "0" >/sys/devices/system/edac/pci/check_pci_parity - - - -Panic on PCI PARITY Error: - - 'panic_on_pci_parity' - - - This control files enables or disables panicking when a parity - error has been detected. - - - module/kernel parameter: panic_on_pci_parity=[0|1] - - Enable: - echo "1" >/sys/devices/system/edac/pci/panic_on_pci_parity - - Disable: - echo "0" >/sys/devices/system/edac/pci/panic_on_pci_parity - - -Parity Count: - - 'pci_parity_count' - - This attribute file will display the number of parity errors that - have been detected. - - - -======================================================================= - - -EDAC_DEVICE type of device - -In the header file, edac_core.h, there is a series of edac_device structures -and APIs for the EDAC_DEVICE. - -User space access to an edac_device is through the sysfs interface. - -At the location /sys/devices/system/edac (sysfs) new edac_device devices will -appear. - -There is a three level tree beneath the above 'edac' directory. For example, -the 'test_device_edac' device (found at the bluesmoke.sourceforget.net website) -installs itself as: - - /sys/devices/systm/edac/test-instance - -in this directory are various controls, a symlink and one or more 'instance' -directorys. - -The standard default controls are: - - log_ce boolean to log CE events - log_ue boolean to log UE events - panic_on_ue boolean to 'panic' the system if an UE is encountered - (default off, can be set true via startup script) - poll_msec time period between POLL cycles for events - -The test_device_edac device adds at least one of its own custom control: - - test_bits which in the current test driver does nothing but - show how it is installed. A ported driver can - add one or more such controls and/or attributes - for specific uses. - One out-of-tree driver uses controls here to allow - for ERROR INJECTION operations to hardware - injection registers - -The symlink points to the 'struct dev' that is registered for this edac_device. - -INSTANCES - -One or more instance directories are present. For the 'test_device_edac' case: - - test-instance0 - - -In this directory there are two default counter attributes, which are totals of -counter in deeper subdirectories. - - ce_count total of CE events of subdirectories - ue_count total of UE events of subdirectories - -BLOCKS - -At the lowest directory level is the 'block' directory. There can be 0, 1 -or more blocks specified in each instance. - - test-block0 - - -In this directory the default attributes are: - - ce_count which is counter of CE events for this 'block' - of hardware being monitored - ue_count which is counter of UE events for this 'block' - of hardware being monitored - - -The 'test_device_edac' device adds 4 attributes and 1 control: - - test-block-bits-0 for every POLL cycle this counter - is incremented - test-block-bits-1 every 10 cycles, this counter is bumped once, - and test-block-bits-0 is set to 0 - test-block-bits-2 every 100 cycles, this counter is bumped once, - and test-block-bits-1 is set to 0 - test-block-bits-3 every 1000 cycles, this counter is bumped once, - and test-block-bits-2 is set to 0 - - - reset-counters writing ANY thing to this control will - reset all the above counters. - - -Use of the 'test_device_edac' driver should any others to create their own -unique drivers for their hardware systems. - -The 'test_device_edac' sample driver is located at the -bluesmoke.sourceforge.net project site for EDAC. - |