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Diffstat (limited to 'Documentation/drivers/edac/edac.txt')
| -rw-r--r-- | Documentation/drivers/edac/edac.txt | 192 |
1 files changed, 165 insertions, 27 deletions
diff --git a/Documentation/drivers/edac/edac.txt b/Documentation/drivers/edac/edac.txt index 3c5a9e4297b4..a5c36842ecef 100644 --- a/Documentation/drivers/edac/edac.txt +++ b/Documentation/drivers/edac/edac.txt @@ -2,22 +2,42 @@ EDAC - Error Detection And Correction -Written by Doug Thompson <norsk5@xmission.com> +Written by Doug Thompson <dougthompson@xmission.com> 7 Dec 2005 +17 Jul 2007 Updated -EDAC was written by: - Thayne Harbaugh, - modified by Dave Peterson, Doug Thompson, et al, - from the bluesmoke.sourceforge.net project. +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. In the initial release, memory Correctable Errors -(CE) and Uncorrectable Errors (UE) are the primary errors being harvested. +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 @@ -25,9 +45,27 @@ 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 @@ -35,11 +73,17 @@ 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. -[There are patches in the kernel queue which will allow for storage of -quirks of PCI devices reporting false parity positives. The 2.6.18 -kernel should have those patches included. When that becomes available, -then EDAC will be patched to utilize that information to "skip" such -devices.] +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: @@ -57,13 +101,14 @@ and the like. ============================================================================ EDAC VERSIONING -EDAC is composed of a "core" module (edac_mc.ko) and several Memory +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 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. +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 @@ -88,8 +133,9 @@ 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: +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 @@ -188,7 +234,7 @@ In directory 'mc' are EDAC system overall control and attribute files: Panic on UE control file: - 'panic_on_ue' + '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 @@ -199,12 +245,12 @@ Panic on UE control file: LOAD TIME: module/kernel parameter: panic_on_ue=[0|1] - RUN TIME: echo "1" >/sys/devices/system/edac/mc/panic_on_ue + RUN TIME: echo "1" >/sys/devices/system/edac/mc/edac_mc_panic_on_ue Log UE control file: - 'log_ue' + 'edac_mc_log_ue' Generate kernel messages describing uncorrectable errors. These errors are reported through the system message log system. UE statistics @@ -212,12 +258,12 @@ Log UE control file: LOAD TIME: module/kernel parameter: log_ue=[0|1] - RUN TIME: echo "1" >/sys/devices/system/edac/mc/log_ue + RUN TIME: echo "1" >/sys/devices/system/edac/mc/edac_mc_log_ue Log CE control file: - 'log_ce' + 'edac_mc_log_ce' Generate kernel messages describing correctable errors. These errors are reported through the system message log system. @@ -225,12 +271,12 @@ Log CE control file: LOAD TIME: module/kernel parameter: log_ce=[0|1] - RUN TIME: echo "1" >/sys/devices/system/edac/mc/log_ce + RUN TIME: echo "1" >/sys/devices/system/edac/mc/edac_mc_log_ce Polling period control file: - 'poll_msec' + '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 @@ -241,7 +287,7 @@ Polling period control file: LOAD TIME: module/kernel parameter: poll_msec=[0|1] - RUN TIME: echo "1000" >/sys/devices/system/edac/mc/poll_msec + RUN TIME: echo "1000" >/sys/devices/system/edac/mc/edac_mc_poll_msec ============================================================================ @@ -587,3 +633,95 @@ Parity Count: ======================================================================= + + +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. + |