features.rst

  1.. SPDX-License-Identifier: GPL-2.0 OR GFDL-1.2-no-invariants-or-later
  2
  3=================
  4EDAC/RAS features
  5=================
  6
  7Copyright (c) 2024-2025 HiSilicon Limited.
  8
  9:Author:   Shiju Jose <shiju.jose@huawei.com>
 10:License:  The GNU Free Documentation License, Version 1.2 without
 11           Invariant Sections, Front-Cover Texts nor Back-Cover Texts.
 12           (dual licensed under the GPL v2)
 13
 14- Written for: 6.15
 15
 16Introduction
 17------------
 18
 19EDAC/RAS components plugging and high-level design:
 20
 211. Scrub control
 22
 232. Error Check Scrub (ECS) control
 24
 253. ACPI RAS2 features
 26
 274. Post Package Repair (PPR) control
 28
 295. Memory Sparing Repair control
 30
 31High level design is illustrated in the following diagram::
 32
 33        +-----------------------------------------------+
 34        |   Userspace - Rasdaemon                       |
 35        | +-------------+                               |
 36        | | RAS CXL mem |     +---------------+         |
 37        | |error handler|---->|               |         |
 38        | +-------------+     | RAS dynamic   |         |
 39        | +-------------+     | scrub, memory |         |
 40        | | RAS memory  |---->| repair control|         |
 41        | |error handler|     +----|----------+         |
 42        | +-------------+          |                    |
 43        +--------------------------|--------------------+
 44                                   |
 45                                   |
 46   +-------------------------------|------------------------------+
 47   |     Kernel EDAC extension for | controlling RAS Features     |
 48   |+------------------------------|----------------------------+ |
 49   || EDAC Core          Sysfs EDAC| Bus                        | |
 50   ||   +--------------------------|---------------------------+| |
 51   ||   |/sys/bus/edac/devices/<dev>/scrubX/ |   | EDAC device || |
 52   ||   |/sys/bus/edac/devices/<dev>/ecsX/   |<->| EDAC MC     || |
 53   ||   |/sys/bus/edac/devices/<dev>/repairX |   | EDAC sysfs  || |
 54   ||   +---------------------------|--------------------------+| |
 55   ||                           EDAC|Bus                        | |
 56   ||                               |                           | |
 57   ||   +----------+ Get feature    |      Get feature          | |
 58   ||   |          | desc +---------|------+ desc +----------+  | |
 59   ||   |EDAC scrub|<-----| EDAC device    |      |          |  | |
 60   ||   +----------+      | driver- RAS    |----->| EDAC mem |  | |
 61   ||   +----------+      | feature control|      | repair   |  | |
 62   ||   |          |<-----|                |      +----------+  | |
 63   ||   |EDAC ECS  |      +---------|------+                    | |
 64   ||   +----------+    Register RAS|features                   | |
 65   ||         ______________________|_____________              | |
 66   |+---------|---------------|------------------|--------------+ |
 67   |  +-------|----+  +-------|-------+     +----|----------+     |
 68   |  |            |  | CXL mem driver|     | Client driver |     |
 69   |  | ACPI RAS2  |  | scrub, ECS,   |     | memory repair |     |
 70   |  | driver     |  | sparing, PPR  |     | features      |     |
 71   |  +-----|------+  +-------|-------+     +------|--------+     |
 72   |        |                 |                    |              |
 73   +--------|-----------------|--------------------|--------------+
 74            |                 |                    |
 75   +--------|-----------------|--------------------|--------------+
 76   |    +---|-----------------|--------------------|-------+      |
 77   |    |                                                  |      |
 78   |    |            Platform HW and Firmware              |      |
 79   |    +--------------------------------------------------+      |
 80   +--------------------------------------------------------------+
 81
 82
 831. EDAC Features components - Create feature-specific descriptors. For
 84   example: scrub, ECS, memory repair in the above diagram.
 85
 862. EDAC device driver for controlling RAS Features - Get feature's attribute
 87   descriptors from EDAC RAS feature component and registers device's RAS
 88   features with EDAC bus and expose the features control attributes via
 89   sysfs. For example, /sys/bus/edac/devices/<dev-name>/<feature>X/
 90
 913. RAS dynamic feature controller - Userspace sample modules in rasdaemon for
 92   dynamic scrub/repair control to issue scrubbing/repair when excess number
 93   of corrected memory errors are reported in a short span of time.
 94
 95RAS features
 96------------
 971. Memory Scrub
 98
 99Memory scrub features are documented in `Documentation/edac/scrub.rst`.
100
1012. Memory Repair
102
103Memory repair features are documented in `Documentation/edac/memory_repair.rst`.