Message-ID: <20071105170608.GV12045@stusta.de>
Date:	Mon, 5 Nov 2007 18:06:08 +0100
From:	Adrian Bunk <bunk@...nel.org>
To:	dougthompson@...ssion.com
Cc:	bluesmoke-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: [2.6 patch] move edac.txt two levels up

There's no reason for edac.txt for being at this unusual place.

Signed-off-by: Adrian Bunk <bunk@...nel.org>

---

 Documentation/00-INDEX                    |    4 ++--
 Documentation/{drivers/edac => }/edac.txt |    0 
 2 files changed, 2 insertions(+), 2 deletions(-)

86283ddd49f39c01cbc4ddf65818f9ddc9de4a22 
diff --git a/Documentation/00-INDEX b/Documentation/00-INDEX
index 299615d..a877629 100644
--- a/Documentation/00-INDEX
+++ b/Documentation/00-INDEX
@@ -132,12 +132,12 @@ dontdiff
 	- file containing a list of files that should never be diff'ed.
 driver-model/
 	- directory with info about Linux driver model.
-drivers/
-	- directory with driver documentation (currently only EDAC).
 dvb/
 	- info on Linux Digital Video Broadcast (DVB) subsystem.
 early-userspace/
 	- info about initramfs, klibc, and userspace early during boot.
+edac.txt
+	- information on EDAC - Error Detection And Correction
 eisa.txt
 	- info on EISA bus support.
 exception.txt
diff --git a/Documentation/drivers/edac/edac.txt b/Documentation/drivers/edac/edac.txt
deleted file mode 100644
index a5c3684..0000000
--- a/Documentation/drivers/edac/edac.txt
+++ /dev/null
@@ -1,727 +0,0 @@
-
-
-EDAC - Error Detection And Correction
-
-Written by Doug Thompson <dougthompson@...ssion.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@...ts.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.
-
diff --git a/Documentation/edac.txt b/Documentation/edac.txt
new file mode 100644
index 0000000..a5c3684
--- /dev/null
+++ b/Documentation/edac.txt
@@ -0,0 +1,727 @@
+
+
+EDAC - Error Detection And Correction
+
+Written by Doug Thompson <dougthompson@...ssion.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@...ts.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.
+

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