1ACPI Tables 2----------- 3The expectations of individual ACPI tables are discussed in the list that 4follows. 5 6If a section number is used, it refers to a section number in the ACPI 7specification where the object is defined. If "Signature Reserved" is used, 8the table signature (the first four bytes of the table) is the only portion 9of the table recognized by the specification, and the actual table is defined 10outside of the UEFI Forum (see Section 5.2.6 of the specification). 11 12For 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 25Table Usage for ARMv8 Linux 26----- ---------------------------------------------------------------- 27BERT 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 32BOOT Signature Reserved (signature == "BOOT") 33 == simple BOOT flag table == 34 Microsoft only table, will not be supported. 35 36BGRT 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 41CPEP 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 47CSRT Signature Reserved (signature == "CSRT") 48 == Core System Resources Table == 49 Optional, not currently supported. 50 51DBG2 Signature Reserved (signature == "DBG2") 52 == DeBuG port table 2 == 53 Microsoft only table, will not be supported. 54 55DBGP Signature Reserved (signature == "DBGP") 56 == DeBuG Port table == 57 Microsoft only table, will not be supported. 58 59DSDT 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 67DMAR Signature Reserved (signature == "DMAR") 68 == DMA Remapping table == 69 x86 only table, will not be supported. 70 71DRTM Signature Reserved (signature == "DRTM") 72 == Dynamic Root of Trust for Measurement table == 73 Optional, not currently supported. 74 75ECDT 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 82EINJ 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 90ERST 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 97ETDT Signature Reserved (signature == "ETDT") 98 == Event Timer Description Table == 99 Obsolete table, will not be supported. 100 101FACS 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 108FADT 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 126FPDT Section 5.2.23 (signature == "FPDT") 127 == Firmware Performance Data Table == 128 Optional, not currently supported. 129 130GTDT Section 5.2.24 (signature == "GTDT") 131 == Generic Timer Description Table == 132 Required for arm64. 133 134HEST 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 144HPET Signature Reserved (signature == "HPET") 145 == High Precision Event timer Table == 146 x86 only table, will not be supported. 147 148IBFT Signature Reserved (signature == "IBFT") 149 == iSCSI Boot Firmware Table == 150 Microsoft defined table, support TBD. 151 152IVRS Signature Reserved (signature == "IVRS") 153 == I/O Virtualization Reporting Structure == 154 x86_64 (AMD) only table, will not be supported. 155 156LPIT 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 162MADT 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 167MCFG Signature Reserved (signature == "MCFG") 168 == Memory-mapped ConFiGuration space == 169 If the platform supports PCI/PCIe, an MCFG table is required. 170 171MCHI Signature Reserved (signature == "MCHI") 172 == Management Controller Host Interface table == 173 Optional, not currently supported. 174 175MPST Section 5.2.21 (signature == "MPST") 176 == Memory Power State Table == 177 Optional, not currently supported. 178 179MSDM Signature Reserved (signature == "MSDM") 180 == Microsoft Data Management table == 181 Microsoft only table, will not be supported. 182 183MSCT Section 5.2.19 (signature == "MSCT") 184 == Maximum System Characteristic Table == 185 Optional, not currently supported. 186 187RASF Section 5.2.20 (signature == "RASF") 188 == RAS Feature table == 189 Optional, not currently supported. 190 191RSDP Section 5.2.5 (signature == "RSD PTR") 192 == Root System Description PoinTeR == 193 Required for arm64. 194 195RSDT 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 200SBST Section 5.2.14 (signature == "SBST") 201 == Smart Battery Subsystem Table == 202 Optional, not currently supported. 203 204SLIC Signature Reserved (signature == "SLIC") 205 == Software LIcensing table == 206 Microsoft only table, will not be supported. 207 208SLIT Section 5.2.17 (signature == "SLIT") 209 == System Locality distance Information Table == 210 Optional in general, but required for NUMA systems. 211 212SPCR Signature Reserved (signature == "SPCR") 213 == Serial Port Console Redirection table == 214 Required for arm64. 215 216SPMI Signature Reserved (signature == "SPMI") 217 == Server Platform Management Interface table == 218 Optional, not currently supported. 219 220SRAT 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 225SSDT 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 238TCPA 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 243TPM2 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 248UEFI Signature Reserved (signature == "UEFI") 249 == UEFI ACPI data table == 250 Optional, not currently supported. No known use case for arm64, 251 at present. 252 253WAET Signature Reserved (signature == "WAET") 254 == Windows ACPI Emulated devices Table == 255 Microsoft only table, will not be supported. 256 257WDAT Signature Reserved (signature == "WDAT") 258 == Watch Dog Action Table == 259 Microsoft only table, will not be supported. 260 261WDRT Signature Reserved (signature == "WDRT") 262 == Watch Dog Resource Table == 263 Microsoft only table, will not be supported. 264 265WPBT Signature Reserved (signature == "WPBT") 266 == Windows Platform Binary Table == 267 Microsoft only table, will not be supported. 268 269XSDT Section 5.2.8 (signature == "XSDT") 270 == eXtended System Description Table == 271 Required for arm64. 272 273 274ACPI Objects 275------------ 276The expectations on individual ACPI objects are discussed in the list that 277follows: 278 279Name 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 492ACPI Event Model 493---------------- 494Do not use GPE block devices; these are not supported in the hardware reduced 495profile used by arm64. Since there are no GPE blocks defined for use on ARM 496platforms, GPIO-signaled interrupts should be used for creating system events. 497 498 499ACPI Processor Control 500---------------------- 501Section 8 of the ACPI specification is currently undergoing change that 502should be completed in the 6.0 version of the specification. Processor 503performance control will be handled differently for arm64 at that point 504in time. Processor aggregator devices (section 8.5) will not be used, 505for example, but another similar mechanism instead. 506 507While UEFI constrains what we can say until the release of 6.0, it is 508recommended that CPPC (8.4.5) be used as the primary model. This will 509still be useful into the future. C-states and P-states will still be 510provided, but most of the current design work appears to favor CPPC. 511 512Further, it is essential that the ARMv8 SoC provide a fully functional 513implementation of PSCI; this will be the only mechanism supported by ACPI 514to control CPU power state (including secondary CPU booting). 515 516More details will be provided on the release of the ACPI 6.0 specification. 517 518 519ACPI System Address Map Interfaces 520---------------------------------- 521In Section 15 of the ACPI specification, several methods are mentioned as 522possible mechanisms for conveying memory resource information to the kernel. 523For arm64, we will only support UEFI for booting with ACPI, hence the UEFI 524GetMemoryMap() boot service is the only mechanism that will be used. 525 526 527ACPI Platform Error Interfaces (APEI) 528------------------------------------- 529The APEI tables supported are described above. 530 531APEI requires the equivalent of an SCI and an NMI on ARMv8. The SCI is used 532to notify the OSPM of errors that have occurred but can be corrected and the 533system can continue correct operation, even if possibly degraded. The NMI is 534used to indicate fatal errors that cannot be corrected, and require immediate 535attention. 536 537Since there is no direct equivalent of the x86 SCI or NMI, arm64 handles 538these slightly differently. The SCI is handled as a normal GPIO-signaled 539interrupt; given that these are corrected (or correctable) errors being 540reported, this is sufficient. The NMI is emulated as the highest priority 541GPIO-signaled interrupt possible. This implies some caution must be used 542since there could be interrupts at higher privilege levels or even interrupts 543at the same priority as the emulated NMI. In Linux, this should not be the 544case but one should be aware it could happen. 545 546 547ACPI Objects Not Supported on ARM64 548----------------------------------- 549While this may change in the future, there are several classes of objects 550that can be defined, but are not currently of general interest to ARM servers. 551 552These 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 575ACPI Objects Not Yet Implemented 576-------------------------------- 577While these objects have x86 equivalents, and they do make some sense in ARM 578servers, there is either no hardware available at present, or in some cases 579there may not yet be a non-ARM implementation. Hence, they are currently not 580implemented though that may change in the future. 581 582Not 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) 594