Documentation/edac/scrub.rst

1 .. SPDX-License-Identifier: GPL-2.0 OR GFDL-1.2-no-invariants-or-later
7 Copyright (c) 2024-2025 HiSilicon Limited.
11            Invariant Sections, Front-Cover Texts nor Back-Cover Texts.
14 - Written for: 6.15
17 ------------
24 Memory scrubbing is a feature where an ECC (Error-Correcting Code) engine
49 2. On-demand scrubbing for a specific address range or region of memory.
52 identified, such as CXL memory device patrol scrub, CXL DDR5 ECS, ACPI
53 RAS2 memory scrubbing, and ACPI NVDIMM ARS (Address Range Scrub).
65 -----------------------------------------
69    ACPI RAS2 memory scrubbing features, ACPI NVDIMM ARS (Address Range Scrub),
70    and software-based memory scrubbers.
73    control over patrol (background) scrubbing (e.g., ACPI RAS2, CXL) and/or
74    on-demand scrubbing (e.g., ACPI RAS2, ACPI ARS). However, the scrub control
79 2. User-space scrub controls allow users to disable scrubbing if necessary,
81    rate for performance-aware operations where background activities need to
84 3. User-space tools enable on-demand scrubbing for specific address ranges,
87 4. User-space tools can also control memory DIMM scrubbing at a configurable
97    be a system-wide BIOS or similar control to manage scrub settings for a CXL
105 ------------------
123 with performance-aware operations which require the background operations to
130 - a feature defined in the JEDEC DDR5 SDRAM Specification (JESD79-5) and
131 allowing DRAM to internally read, correct single-bit errors, and write back
139 ACPI RAS2 Hardware-based Memory Scrubbing
142 ACPI spec 6.5 [2]_ section 5.2.21 ACPI RAS2 describes an ACPI RAS2 table
148 are specific to memory. RAS2 PCC sub-spaces for memory-specific RAS features
151 The platform can use the hardware-based memory scrubbing feature to expose
152 controls and capabilities associated with hardware-based memory scrub
159    as well as on-demand scrubbing for a specific region of memory.
161 ACPI Address Range Scrubbing (ARS)
164 ACPI spec 6.5 [2]_ section 9.19.7.2 describes Address Range Scrubbing (ARS).
173    supports the ACPI NVDIMM Root Device Unconsumed Error Notification.
190 .. [1] https://computeexpresslink.org/cxl-specification/
192 .. [2] https://uefi.org/specs/ACPI/6.5/
197  +--------------+-----------+-----------+-----------+-----------+
198  |              |   ACPI    | CXL patrol|  CXL ECS  |  ARS      |
200  +--------------+-----------+-----------+-----------+-----------+
202  | On-demand    | Supported | No        | No        | Supported |
205  +--------------+-----------+-----------+-----------+-----------+
210  +--------------+-----------+-----------+-----------+-----------+
215  +--------------+-----------+-----------+-----------+-----------+
220  +--------------+-----------+-----------+-----------+-----------+
225  +--------------+-----------+-----------+-----------+-----------+
230  +--------------+-----------+-----------+-----------+-----------+
235  +--------------+-----------+-----------+-----------+-----------+
237  | Scrub        | on-demand | No        | No        | Supported |
240  +--------------+-----------+-----------+-----------+-----------+
241  | UC error     |           |CXL general|CXL general| ACPI UCE  |
245  +--------------+-----------+-----------+-----------+-----------+
250  +--------------+-----------+-----------+-----------+-----------+
253 ---------------
258 /sys/bus/edac/devices/<dev-name>/scrubX/
261 -----
264 `Documentation/ABI/testing/sysfs-edac-scrub`
266 `Documentation/ABI/testing/sysfs-edac-ecs`