Documentation/driver-api/edac.rst

5 ----------------------------------------
7 There are several things to be aware of that aren't at all obvious, like
8 *sockets, *socket sets*, *banks*, *rows*, *chip-select rows*, *channels*,
16 * Memory devices
18 The individual DRAM chips on a memory stick.  These devices commonly
20 provides the number of bits that the memory controller expects:
21 typically 72 bits, in order to provide 64 bits + 8 bits of ECC data.
23 * Memory Stick
25 A printed circuit board that aggregates multiple memory devices in
28 called DIMM (Dual Inline Memory Module).
30 * Memory Socket
32 A physical connector on the motherboard that accepts a single memory
37 A memory controller channel, responsible to communicate with a group of
43 It is typically the highest hierarchy on a Fully-Buffered DIMM memory
47 some performance penalty. Also, it is generally not possible to point to
48 just one memory stick when an error occurs, as the error correction code
49 is calculated using two DIMMs instead of one. Due to that, it is capable
52 * Single-channel
54 The data accessed by the memory controller is contained into one dimm
55 only. E. g. if the data is 64 bits-wide, the data flows to the CPU using
57 memories. FB-DIMM and RAMBUS use a different concept for channel, so
60 * Double-channel
62 The data size accessed by the memory controller is interlaced into two
63 dimms, accessed at the same time. E. g. if the DIMM is 64 bits-wide (72
64 bits with ECC), the data flows to the CPU using a 128 bits parallel
67 * Chip-select row
69 This is the name of the DRAM signal used to select the DRAM ranks to be
70 accessed. Common chip-select rows for single channel are 64 bits, for
71 dual channel 128 bits. It may not be visible by the memory controller,
72 as some DIMM types have a memory buffer that can hide direct access to
73 it from the Memory Controller.
75 * Single-Ranked stick
77 A Single-ranked stick has 1 chip-select row of memory. Motherboards
78 commonly drive two chip-select pins to a memory stick. A single-ranked
83 * Double-Ranked stick
85 A double-ranked stick has two chip-select rows which access different
86 sets of memory devices.  The two rows cannot be accessed concurrently.
88 * Double-sided stick
90 **DEPRECATED TERM**, see :ref:`Double-Ranked stick <doubleranked>`.
92 A double-sided stick has two chip-select rows which access different sets
93 of memory devices. The two rows cannot be accessed concurrently.
94 "Double-sided" is irrespective of the memory devices being mounted on
95 both sides of the memory stick.
99 All of the memory sticks that are required for a single memory access or
100 all of the memory sticks spanned by a chip-select row.  A single socket
101 set has two chip-select rows and if double-sided sticks are used these
102 will occupy those chip-select rows.
106 This term is avoided because it is unclear when needing to distinguish
107 between chip-select rows and socket sets.
110 Memory Controllers
111 ------------------
113 Most of the EDAC core is focused on doing Memory Controller error detection.
115 to describe the memory controllers, with is an opaque struct for the EDAC
116 drivers. Only the EDAC core is allowed to touch it.
118 .. kernel-doc:: include/linux/edac.h
120 .. kernel-doc:: drivers/edac/edac_mc.h
123 ---------------
125 The EDAC subsystem provides a mechanism to handle PCI controllers by calling
127 :c:type:`edac_pci_ctl_info` to describe the PCI controllers.
129 .. kernel-doc:: drivers/edac/edac_pci.h
132 -----------
134 The EDAC subsystem also provides a generic mechanism to report errors on
142 …s the APIs for the same, provide for registering EDAC type devices which are NOT standard memory or
145 - CPU caches (L1 and L2)
146 - DMA engines
147 - Core CPU switches
148 - Fabric switch units
149 - PCIe interface controllers
150 - other EDAC/ECC type devices that can be monitored for
163 	mc/		<existing memory device directory>
165 		/L1-cache/ce_count
167 		/L2-cache/ce_count
170 		/L1-cache/ce_count
172 		/L2-cache/ce_count
178 .. kernel-doc:: drivers/edac/edac_device.h