Documentation/edac.txt: Add Nehalem specific EDAC characteristics
As Nehalem has a different binding to EDAC API, and its own different
error injection code, documents it.
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
diff --git a/Documentation/edac.txt b/Documentation/edac.txt
index 79c5332..8bc3204 100644
--- a/Documentation/edac.txt
+++ b/Documentation/edac.txt
@@ -6,6 +6,8 @@
7 Dec 2005
17 Jul 2007 Updated
+(c) Mauro Carvalho Chehab <mchehab@redhat.com>
+05 Aug 2009 Nehalem interface
EDAC is maintained and written by:
@@ -717,3 +719,111 @@
The 'test_device_edac' sample driver is located at the
bluesmoke.sourceforge.net project site for EDAC.
+=======================================================================
+NEHALEM USAGE OF EDAC APIs
+
+This chapter documents some EXPERIMENTAL mappings for EDAC API to handle
+Nehalem EDAC driver. They will likely be changed on future versions
+of the driver.
+
+Due to the way Nehalem exports Memory Controller data, some adjustments
+were done at i7core_edac driver. This chapter will cover those differences
+
+1) On Nehalem, there are one Memory Controller per Quick Patch Interconnect
+ (QPI). At the driver, the term "socket" means one QPI. It should also be
+ associated with the CPU physical socket.
+
+ Each MC have 3 physical read channels, 3 physical write channels and
+ 3 logic channels. The driver currenty sees it as just 3 channels.
+ Each channel can have up to 3 DIMMs.
+
+ The minimum known unity is DIMMs. There are no information about csrows.
+ As EDAC API maps the minimum unity is csrows, the driver exports one
+ DIMM per csrow.
+
+ Currently, it also exports the several memory controllers as just one. This
+ limit will be removed on future versions of the driver.
+
+2) Nehalem MC has the hability to generate errors. The driver implements this
+ functionality via some error injection nodes:
+
+ For injecting a memory error, there are some sysfs nodes, under
+ /sys/devices/system/edac/mc/mc0/:
+
+ inject_addrmatch:
+ Controls the error injection mask register. It is possible to specify
+ several characteristics of the address to match an error code:
+ dimm = the affected dimm. Numbers are relative to a channel;
+ rank = the memory rank;
+ channel = the channel that will generate an error;
+ bank = the affected bank;
+ page = the page address;
+ column (or col) = the address column.
+ each of the above values can be set to "any" to match any valid value.
+
+ At driver init, all values are set to any.
+
+ For example, to generate an error at rank 1 of dimm 2, for any channel,
+ any bank, any page, any column:
+ echo "dimm:2 rank:1" >/sys/devices/system/edac/mc/mc0/inject_addrmatch
+
+ To return to the default behaviour of matching any, you can do:
+ echo "dimm:any rank:any" >/sys/devices/system/edac/mc/mc0/inject_addrmatch
+
+ inject_eccmask:
+ specifies what bits will have troubles,
+
+ inject_section:
+ specifies what ECC cache section will get the error:
+ 3 for both
+ 2 for the highest
+ 1 for the lowest
+
+ inject_socket:
+ specifies what QPI (or processor socket) will generate the error.
+ on Xeon 35xx, it should be 0.
+ on Xeon 55xx, it should be 0 or 1.
+
+ inject_type:
+ specifies the type of error, being a combination of the following bits:
+ bit 0 - repeat
+ bit 1 - ecc
+ bit 2 - parity
+
+ inject_enable starts the error generation when something different
+ than 0 is written.
+
+ All inject vars can be read. root permission is needed for write.
+
+ Datasheet states that the error will only be generated after a write on an
+ address that matches inject_addrmatch. It seems, however, that reading will
+ also produce an error.
+
+ For example, the following code will generate an error for any write access
+ at socket 0, on any DIMM/address on channel 2:
+
+ echo "channel:2" > /sys/devices/system/edac/mc/mc0/inject_addrmatch
+ echo 2 >/sys/devices/system/edac/mc/mc0/inject_type
+ echo 64 >/sys/devices/system/edac/mc/mc0/inject_eccmask
+ echo 3 >/sys/devices/system/edac/mc/mc0/inject_section
+ echo 0 >/sys/devices/system/edac/mc/mc0/inject_socket
+ echo 1 >/sys/devices/system/edac/mc/mc0/inject_enable
+ dd if=/dev/mem of=/dev/null seek=16k bs=4k count=1 >& /dev/null
+
+ The generated error message will look like:
+
+ EDAC MC0: UE row 0, channel-a= 0 channel-b= 0 labels "-": NON_FATAL (addr = 0x0075b980, socket=0, Dimm=0, Channel=2, syndrome=0x00000040, count=1, Err=8c0000400001009f:4000080482 (read error: read ECC error))
+
+3) Nehalem specific Corrected Error memory counters
+
+ Nehalem have some registers to count memory errors, reporting it on a
+ way that it is different from what EDAC API allows. Due to that, a
+ separate sysfs note were created to handle such counters.
+
+ They can be read by looking at the contents of "corrected_error_counts"
+ counter:
+
+ $ cat /sys/devices/system/edac/mc/mc0/corrected_error_counts
+ dimm0: 15866
+ dimm1: 0
+ dimm2: 27285