Documentation/arm64/acpi_object_usage.txt

   1 ACPI Tables
   2 -----------
   3 The expectations of individual ACPI tables are discussed in the list that
   4 follows.
   5
   6 If a section number is used, it refers to a section number in the ACPI
   7 specification where the object is defined.  If "Signature Reserved" is used,
   8 the table signature (the first four bytes of the table) is the only portion
   9 of the table recognized by the specification, and the actual table is defined
  10 outside of the UEFI Forum (see Section 5.2.6 of the specification).
  11
  12 For ACPI on arm64, tables also fall into the following categories:
  13
  14        -- Required: DSDT, FADT, GTDT, MADT, MCFG, RSDP, SPCR, XSDT
  15
  16        -- Recommended: BERT, EINJ, ERST, HEST, SSDT
  17
  18        -- Optional: BGRT, CPEP, CSRT, DRTM, ECDT, FACS, FPDT, MCHI, MPST,
  19           MSCT, RASF, SBST, SLIT, SPMI, SRAT, TCPA, TPM2, UEFI
  20
  21        -- Not supported: BOOT, DBG2, DBGP, DMAR, ETDT, HPET, IBFT, IVRS,
  22           LPIT, MSDM, RSDT, SLIC, WAET, WDAT, WDRT, WPBT
  23
  24
  25 Table  Usage for ARMv8 Linux
  26 -----  ----------------------------------------------------------------
  27 BERT   Section 18.3 (signature == "BERT")
  28        == Boot Error Record Table ==
  29        Must be supplied if RAS support is provided by the platform.  It
  30        is recommended this table be supplied.
  31
  32 BOOT   Signature Reserved (signature == "BOOT")
  33        == simple BOOT flag table ==
  34        Microsoft only table, will not be supported.
  35
  36 BGRT   Section 5.2.22 (signature == "BGRT")
  37        == Boot Graphics Resource Table ==
  38        Optional, not currently supported, with no real use-case for an
  39        ARM server.
  40
  41 CPEP   Section 5.2.18 (signature == "CPEP")
  42        == Corrected Platform Error Polling table ==
  43        Optional, not currently supported, and not recommended until such
  44        time as ARM-compatible hardware is available, and the specification
  45        suitably modified.
  46
  47 CSRT   Signature Reserved (signature == "CSRT")
  48        == Core System Resources Table ==
  49        Optional, not currently supported.
  50
  51 DBG2   Signature Reserved (signature == "DBG2")
  52        == DeBuG port table 2 ==
  53        Microsoft only table, will not be supported.
  54
  55 DBGP   Signature Reserved (signature == "DBGP")
  56        == DeBuG Port table ==
  57        Microsoft only table, will not be supported.
  58
  59 DSDT   Section 5.2.11.1 (signature == "DSDT")
  60        == Differentiated System Description Table ==
  61        A DSDT is required; see also SSDT.
  62
  63        ACPI tables contain only one DSDT but can contain one or more SSDTs,
  64        which are optional.  Each SSDT can only add to the ACPI namespace,
  65        but cannot modify or replace anything in the DSDT.
  66
  67 DMAR   Signature Reserved (signature == "DMAR")
  68        == DMA Remapping table ==
  69        x86 only table, will not be supported.
  70
  71 DRTM   Signature Reserved (signature == "DRTM")
  72        == Dynamic Root of Trust for Measurement table ==
  73        Optional, not currently supported.
  74
  75 ECDT   Section 5.2.16 (signature == "ECDT")
  76        == Embedded Controller Description Table ==
  77        Optional, not currently supported, but could be used on ARM if and
  78        only if one uses the GPE_BIT field to represent an IRQ number, since
  79        there are no GPE blocks defined in hardware reduced mode.  This would
  80        need to be modified in the ACPI specification.
  81
  82 EINJ   Section 18.6 (signature == "EINJ")
  83        == Error Injection table ==
  84        This table is very useful for testing platform response to error
  85        conditions; it allows one to inject an error into the system as
  86        if it had actually occurred.  However, this table should not be
  87        shipped with a production system; it should be dynamically loaded
  88        and executed with the ACPICA tools only during testing.
  89
  90 ERST   Section 18.5 (signature == "ERST")
  91        == Error Record Serialization Table ==
  92        On a platform supports RAS, this table must be supplied if it is not
  93        UEFI-based; if it is UEFI-based, this table may be supplied. When this
  94        table is not present, UEFI run time service will be utilized to save
  95        and retrieve hardware error information to and from a persistent store.
  96
  97 ETDT   Signature Reserved (signature == "ETDT")
  98        == Event Timer Description Table ==
  99        Obsolete table, will not be supported.
 100
 101 FACS   Section 5.2.10 (signature == "FACS")
 102        == Firmware ACPI Control Structure ==
 103        It is unlikely that this table will be terribly useful.  If it is
 104        provided, the Global Lock will NOT be used since it is not part of
 105        the hardware reduced profile, and only 64-bit address fields will
 106        be considered valid.
 107
 108 FADT   Section 5.2.9 (signature == "FACP")
 109        == Fixed ACPI Description Table ==
 110        Required for arm64.
 111
 112        The HW_REDUCED_ACPI flag must be set.  All of the fields that are
 113        to be ignored when HW_REDUCED_ACPI is set are expected to be set to
 114        zero.
 115
 116        If an FACS table is provided, the X_FIRMWARE_CTRL field is to be
 117        used, not FIRMWARE_CTRL.
 118
 119        If PSCI is used (as is recommended), make sure that ARM_BOOT_ARCH is
 120        filled in properly -- that the PSCI_COMPLIANT flag is set and that
 121        PSCI_USE_HVC is set or unset as needed (see table 5-37).
 122
 123        For the DSDT that is also required, the X_DSDT field is to be used,
 124        not the DSDT field.
 125
 126 FPDT   Section 5.2.23 (signature == "FPDT")
 127        == Firmware Performance Data Table ==
 128        Optional, not currently supported.
 129
 130 GTDT   Section 5.2.24 (signature == "GTDT")
 131        == Generic Timer Description Table ==
 132        Required for arm64.
 133
 134 HEST   Section 18.3.2 (signature == "HEST")
 135        == Hardware Error Source Table ==
 136        Until further error source types are defined, use only types 6 (AER
 137        Root Port), 7 (AER Endpoint), 8 (AER Bridge), or 9 (Generic Hardware
 138        Error Source).  Firmware first error handling is possible if and only
 139        if Trusted Firmware is being used on arm64.
 140
 141        Must be supplied if RAS support is provided by the platform.  It
 142        is recommended this table be supplied.
 143
 144 HPET   Signature Reserved (signature == "HPET")
 145        == High Precision Event timer Table ==
 146        x86 only table, will not be supported.
 147
 148 IBFT   Signature Reserved (signature == "IBFT")
 149        == iSCSI Boot Firmware Table ==
 150        Microsoft defined table, support TBD.
 151
 152 IVRS   Signature Reserved (signature == "IVRS")
 153        == I/O Virtualization Reporting Structure ==
 154        x86_64 (AMD) only table, will not be supported.
 155
 156 LPIT   Signature Reserved (signature == "LPIT")
 157        == Low Power Idle Table ==
 158        x86 only table as of ACPI 5.1; future versions have been adapted for
 159        use with ARM and will be recommended in order to support ACPI power
 160        management.
 161
 162 MADT   Section 5.2.12 (signature == "APIC")
 163        == Multiple APIC Description Table ==
 164        Required for arm64.  Only the GIC interrupt controller structures
 165        should be used (types 0xA - 0xE).
 166
 167 MCFG   Signature Reserved (signature == "MCFG")
 168        == Memory-mapped ConFiGuration space ==
 169        If the platform supports PCI/PCIe, an MCFG table is required.
 170
 171 MCHI   Signature Reserved (signature == "MCHI")
 172        == Management Controller Host Interface table ==
 173        Optional, not currently supported.
 174
 175 MPST   Section 5.2.21 (signature == "MPST")
 176        == Memory Power State Table ==
 177        Optional, not currently supported.
 178
 179 MSDM   Signature Reserved (signature == "MSDM")
 180        == Microsoft Data Management table ==
 181        Microsoft only table, will not be supported.
 182
 183 MSCT   Section 5.2.19 (signature == "MSCT")
 184        == Maximum System Characteristic Table ==
 185        Optional, not currently supported.
 186
 187 RASF   Section 5.2.20 (signature == "RASF")
 188        == RAS Feature table ==
 189        Optional, not currently supported.
 190
 191 RSDP   Section 5.2.5 (signature == "RSD PTR")
 192        == Root System Description PoinTeR ==
 193        Required for arm64.
 194
 195 RSDT   Section 5.2.7 (signature == "RSDT")
 196        == Root System Description Table ==
 197        Since this table can only provide 32-bit addresses, it is deprecated
 198        on arm64, and will not be used.
 199
 200 SBST   Section 5.2.14 (signature == "SBST")
 201        == Smart Battery Subsystem Table ==
 202        Optional, not currently supported.
 203
 204 SLIC   Signature Reserved (signature == "SLIC")
 205        == Software LIcensing table ==
 206        Microsoft only table, will not be supported.
 207
 208 SLIT   Section 5.2.17 (signature == "SLIT")
 209        == System Locality distance Information Table ==
 210        Optional in general, but required for NUMA systems.
 211
 212 SPCR   Signature Reserved (signature == "SPCR")
 213        == Serial Port Console Redirection table ==
 214        Required for arm64.
 215
 216 SPMI   Signature Reserved (signature == "SPMI")
 217        == Server Platform Management Interface table ==
 218        Optional, not currently supported.
 219
 220 SRAT   Section 5.2.16 (signature == "SRAT")
 221        == System Resource Affinity Table ==
 222        Optional, but if used, only the GICC Affinity structures are read.
 223        To support NUMA, this table is required.
 224
 225 SSDT   Section 5.2.11.2 (signature == "SSDT")
 226        == Secondary System Description Table ==
 227        These tables are a continuation of the DSDT; these are recommended
 228        for use with devices that can be added to a running system, but can
 229        also serve the purpose of dividing up device descriptions into more
 230        manageable pieces.
 231
 232        An SSDT can only ADD to the ACPI namespace.  It cannot modify or
 233        replace existing device descriptions already in the namespace.
 234
 235        These tables are optional, however.  ACPI tables should contain only
 236        one DSDT but can contain many SSDTs.
 237
 238 TCPA   Signature Reserved (signature == "TCPA")
 239        == Trusted Computing Platform Alliance table ==
 240        Optional, not currently supported, and may need changes to fully
 241        interoperate with arm64.
 242
 243 TPM2   Signature Reserved (signature == "TPM2")
 244        == Trusted Platform Module 2 table ==
 245        Optional, not currently supported, and may need changes to fully
 246        interoperate with arm64.
 247
 248 UEFI   Signature Reserved (signature == "UEFI")
 249        == UEFI ACPI data table ==
 250        Optional, not currently supported.  No known use case for arm64,
 251        at present.
 252
 253 WAET   Signature Reserved (signature == "WAET")
 254        == Windows ACPI Emulated devices Table ==
 255        Microsoft only table, will not be supported.
 256
 257 WDAT   Signature Reserved (signature == "WDAT")
 258        == Watch Dog Action Table ==
 259        Microsoft only table, will not be supported.
 260
 261 WDRT   Signature Reserved (signature == "WDRT")
 262        == Watch Dog Resource Table ==
 263        Microsoft only table, will not be supported.
 264
 265 WPBT   Signature Reserved (signature == "WPBT")
 266        == Windows Platform Binary Table ==
 267        Microsoft only table, will not be supported.
 268
 269 XSDT   Section 5.2.8 (signature == "XSDT")
 270        == eXtended System Description Table ==
 271        Required for arm64.
 272
 273
 274 ACPI Objects
 275 ------------
 276 The expectations on individual ACPI objects are discussed in the list that
 277 follows:
 278
 279 Name   Section         Usage for ARMv8 Linux
 280 ----   ------------    -------------------------------------------------
 281 _ADR   6.1.1           Use as needed.
 282
 283 _BBN   6.5.5           Use as needed; PCI-specific.
 284
 285 _BDN   6.5.3           Optional; not likely to be used on arm64.
 286
 287 _CCA   6.2.17          This method should be defined for all bus masters
 288                        on arm64.  While cache coherency is assumed, making
 289                        it explicit ensures the kernel will set up DMA as
 290                        it should.
 291
 292 _CDM   6.2.1           Optional, to be used only for processor devices.
 293
 294 _CID   6.1.2           Use as needed.
 295
 296 _CLS   6.1.3           Use as needed.
 297
 298 _CRS   6.2.2           Required on arm64.
 299
 300 _DCK   6.5.2           Optional; not likely to be used on arm64.
 301
 302 _DDN   6.1.4           This field can be used for a device name.  However,
 303                        it is meant for DOS device names (e.g., COM1), so be
 304                        careful of its use across OSes.
 305
 306 _DEP   6.5.8           Use as needed.
 307
 308 _DIS   6.2.3           Optional, for power management use.
 309
 310 _DLM   5.7.5           Optional.
 311
 312 _DMA   6.2.4           Optional.
 313
 314 _DSD   6.2.5           To be used with caution.  If this object is used, try
 315                        to use it within the constraints already defined by the
 316                        Device Properties UUID.  Only in rare circumstances
 317                        should it be necessary to create a new _DSD UUID.
 318
 319                        In either case, submit the _DSD definition along with
 320                        any driver patches for discussion, especially when
 321                        device properties are used.  A driver will not be
 322                        considered complete without a corresponding _DSD
 323                        description.  Once approved by kernel maintainers,
 324                        the UUID or device properties must then be registered
 325                        with the UEFI Forum; this may cause some iteration as
 326                        more than one OS will be registering entries.
 327
 328 _DSM                   Do not use this method.  It is not standardized, the
 329                        return values are not well documented, and it is
 330                        currently a frequent source of error.
 331
 332 _DSW   7.2.1           Use as needed; power management specific.
 333
 334 _EDL   6.3.1           Optional.
 335
 336 _EJD   6.3.2           Optional.
 337
 338 _EJx   6.3.3           Optional.
 339
 340 _FIX   6.2.7           x86 specific, not used on arm64.
 341
 342 \_GL   5.7.1           This object is not to be used in hardware reduced
 343                        mode, and therefore should not be used on arm64.
 344
 345 _GLK   6.5.7           This object requires a global lock be defined; there
 346                        is no global lock on arm64 since it runs in hardware
 347                        reduced mode.  Hence, do not use this object on arm64.
 348
 349 \_GPE  5.3.1           This namespace is for x86 use only.  Do not use it
 350                        on arm64.
 351
 352 _GSB   6.2.7           Optional.
 353
 354 _HID   6.1.5           Use as needed.  This is the primary object to use in
 355                        device probing, though _CID and _CLS may also be used.
 356
 357 _HPP   6.2.8           Optional, PCI specific.
 358
 359 _HPX   6.2.9           Optional, PCI specific.
 360
 361 _HRV   6.1.6           Optional, use as needed to clarify device behavior; in
 362                        some cases, this may be easier to use than _DSD.
 363
 364 _INI   6.5.1           Not required, but can be useful in setting up devices
 365                        when UEFI leaves them in a state that may not be what
 366                        the driver expects before it starts probing.
 367
 368 _IRC   7.2.15          Use as needed; power management specific.
 369
 370 _LCK   6.3.4           Optional.
 371
 372 _MAT   6.2.10          Optional; see also the MADT.
 373
 374 _MLS   6.1.7           Optional, but highly recommended for use in
 375                        internationalization.
 376
 377 _OFF   7.1.2           It is recommended to define this method for any device
 378                        that can be turned on or off.
 379
 380 _ON    7.1.3           It is recommended to define this method for any device
 381                        that can be turned on or off.
 382
 383 \_OS   5.7.3           This method will return "Linux" by default (this is
 384                        the value of the macro ACPI_OS_NAME on Linux).  The
 385                        command line parameter acpi_os=<string> can be used
 386                        to set it to some other value.
 387
 388 _OSC   6.2.11          This method can be a global method in ACPI (i.e.,
 389                        \_SB._OSC), or it may be associated with a specific
 390                        device (e.g., \_SB.DEV0._OSC), or both.  When used
 391                        as a global method, only capabilities published in
 392                        the ACPI specification are allowed.  When used as
 393                        a device-specific method, the process described for
 394                        using _DSD MUST be used to create an _OSC definition;
 395                        out-of-process use of _OSC is not allowed.  That is,
 396                        submit the device-specific _OSC usage description as
 397                        part of the kernel driver submission, get it approved
 398                        by the kernel community, then register it with the
 399                        UEFI Forum.
 400
 401 \_OSI  5.7.2           Deprecated on ARM64.  Any invocation of this method
 402                        will print a warning on the console and return false.
 403                        That is, as far as ACPI firmware is concerned, _OSI
 404                        cannot be used to determine what sort of system is
 405                        being used or what functionality is provided.  The
 406                        _OSC method is to be used instead.
 407
 408 _OST   6.3.5           Optional.
 409
 410 _PDC   8.4.1           Deprecated, do not use on arm64.
 411
 412 \_PIC  5.8.1           The method should not be used.  On arm64, the only
 413                        interrupt model available is GIC.
 414
 415 _PLD   6.1.8           Optional.
 416
 417 \_PR   5.3.1           This namespace is for x86 use only on legacy systems.
 418                        Do not use it on arm64.
 419
 420 _PRS   6.2.12          Optional.
 421
 422 _PRT   6.2.13          Required as part of the definition of all PCI root
 423                        devices.
 424
 425 _PRW   7.2.13          Use as needed; power management specific.
 426
 427 _PRx   7.2.8-11        Use as needed; power management specific.  If _PR0 is
 428                        defined, _PR3 must also be defined.
 429
 430 _PSC   7.2.6           Use as needed; power management specific.
 431
 432 _PSE   7.2.7           Use as needed; power management specific.
 433
 434 _PSW   7.2.14          Use as needed; power management specific.
 435
 436 _PSx   7.2.2-5         Use as needed; power management specific.  If _PS0 is
 437                        defined, _PS3 must also be defined.  If clocks or
 438                        regulators need adjusting to be consistent with power
 439                        usage, change them in these methods.
 440
 441 \_PTS  7.3.1           Use as needed; power management specific.
 442
 443 _PXM   6.2.14          Optional.
 444
 445 _REG   6.5.4           Use as needed.
 446
 447 \_REV  5.7.4           Always returns the latest version of ACPI supported.
 448
 449 _RMV   6.3.6           Optional.
 450
 451 \_SB   5.3.1           Required on arm64; all devices must be defined in this
 452                        namespace.
 453
 454 _SEG   6.5.6           Use as needed; PCI-specific.
 455
 456 \_SI   5.3.1,          Optional.
 457        9.1
 458
 459 _SLI   6.2.15          Optional; recommended when SLIT table is in use.
 460
 461 _STA   6.3.7,          It is recommended to define this method for any device
 462        7.1.4           that can be turned on or off.
 463
 464 _SRS   6.2.16          Optional; see also _PRS.
 465
 466 _STR   6.1.10          Recommended for conveying device names to end users;
 467                        this is preferred over using _DDN.
 468
 469 _SUB   6.1.9           Use as needed; _HID or _CID are preferred.
 470
 471 _SUN   6.1.11          Optional.
 472
 473 \_Sx   7.3.2           Use as needed; power management specific.
 474
 475 _SxD   7.2.16-19       Use as needed; power management specific.
 476
 477 _SxW   7.2.20-24       Use as needed; power management specific.
 478
 479 _SWS   7.3.3           Use as needed; power management specific; this may
 480                        require specification changes for use on arm64.
 481
 482 \_TTS  7.3.4           Use as needed; power management specific.
 483
 484 \_TZ   5.3.1           Optional.
 485
 486 _UID   6.1.12          Recommended for distinguishing devices of the same
 487                        class; define it if at all possible.
 488
 489 \_WAK  7.3.5           Use as needed; power management specific.
 490
 491
 492 ACPI Event Model
 493 ----------------
 494 Do not use GPE block devices; these are not supported in the hardware reduced
 495 profile used by arm64.  Since there are no GPE blocks defined for use on ARM
 496 platforms, GPIO-signaled interrupts should be used for creating system events.
 497
 498
 499 ACPI Processor Control
 500 ----------------------
 501 Section 8 of the ACPI specification is currently undergoing change that
 502 should be completed in the 6.0 version of the specification.  Processor
 503 performance control will be handled differently for arm64 at that point
 504 in time.  Processor aggregator devices (section 8.5) will not be used,
 505 for example, but another similar mechanism instead.
 506
 507 While UEFI constrains what we can say until the release of 6.0, it is
 508 recommended that CPPC (8.4.5) be used as the primary model.  This will
 509 still be useful into the future.  C-states and P-states will still be
 510 provided, but most of the current design work appears to favor CPPC.
 511
 512 Further, it is essential that the ARMv8 SoC provide a fully functional
 513 implementation of PSCI; this will be the only mechanism supported by ACPI
 514 to control CPU power state (including secondary CPU booting).
 515
 516 More details will be provided on the release of the ACPI 6.0 specification.
 517
 518
 519 ACPI System Address Map Interfaces
 520 ----------------------------------
 521 In Section 15 of the ACPI specification, several methods are mentioned as
 522 possible mechanisms for conveying memory resource information to the kernel.
 523 For arm64, we will only support UEFI for booting with ACPI, hence the UEFI
 524 GetMemoryMap() boot service is the only mechanism that will be used.
 525
 526
 527 ACPI Platform Error Interfaces (APEI)
 528 -------------------------------------
 529 The APEI tables supported are described above.
 530
 531 APEI requires the equivalent of an SCI and an NMI on ARMv8.  The SCI is used
 532 to notify the OSPM of errors that have occurred but can be corrected and the
 533 system can continue correct operation, even if possibly degraded.  The NMI is
 534 used to indicate fatal errors that cannot be corrected, and require immediate
 535 attention.
 536
 537 Since there is no direct equivalent of the x86 SCI or NMI, arm64 handles
 538 these slightly differently.  The SCI is handled as a normal GPIO-signaled
 539 interrupt; given that these are corrected (or correctable) errors being
 540 reported, this is sufficient.  The NMI is emulated as the highest priority
 541 GPIO-signaled interrupt possible.  This implies some caution must be used
 542 since there could be interrupts at higher privilege levels or even interrupts
 543 at the same priority as the emulated NMI.  In Linux, this should not be the
 544 case but one should be aware it could happen.
 545
 546
 547 ACPI Objects Not Supported on ARM64
 548 -----------------------------------
 549 While this may change in the future, there are several classes of objects
 550 that can be defined, but are not currently of general interest to ARM servers.
 551
 552 These are not supported:
 553
 554        -- Section 9.2: ambient light sensor devices
 555
 556        -- Section 9.3: battery devices
 557
 558        -- Section 9.4: lids (e.g., laptop lids)
 559
 560        -- Section 9.8.2: IDE controllers
 561
 562        -- Section 9.9: floppy controllers
 563
 564        -- Section 9.10: GPE block devices
 565
 566        -- Section 9.15: PC/AT RTC/CMOS devices
 567
 568        -- Section 9.16: user presence detection devices
 569
 570        -- Section 9.17: I/O APIC devices; all GICs must be enumerable via MADT
 571
 572        -- Section 9.18: time and alarm devices (see 9.15)
 573
 574
 575 ACPI Objects Not Yet Implemented
 576 --------------------------------
 577 While these objects have x86 equivalents, and they do make some sense in ARM
 578 servers, there is either no hardware available at present, or in some cases
 579 there may not yet be a non-ARM implementation.  Hence, they are currently not
 580 implemented though that may change in the future.
 581
 582 Not yet implemented are:
 583
 584        -- Section 10: power source and power meter devices
 585
 586        -- Section 11: thermal management
 587
 588        -- Section 12: embedded controllers interface
 589
 590        -- Section 13: SMBus interfaces
 591
 592        -- Section 17: NUMA support (prototypes have been submitted for
 593           review)