reactos/drivers/bus/acpi/acpica/hardware/hwregs.c

   1 /*******************************************************************************
   2  *
   3  * Module Name: hwregs - Read/write access functions for the various ACPI
   4  *                       control and status registers.
   5  *
   6  ******************************************************************************/
   7
   8 /*
   9  * Copyright (C) 2000 - 2015, Intel Corp.
  10  * All rights reserved.
  11  *
  12  * Redistribution and use in source and binary forms, with or without
  13  * modification, are permitted provided that the following conditions
  14  * are met:
  15  * 1. Redistributions of source code must retain the above copyright
  16  *    notice, this list of conditions, and the following disclaimer,
  17  *    without modification.
  18  * 2. Redistributions in binary form must reproduce at minimum a disclaimer
  19  *    substantially similar to the "NO WARRANTY" disclaimer below
  20  *    ("Disclaimer") and any redistribution must be conditioned upon
  21  *    including a substantially similar Disclaimer requirement for further
  22  *    binary redistribution.
  23  * 3. Neither the names of the above-listed copyright holders nor the names
  24  *    of any contributors may be used to endorse or promote products derived
  25  *    from this software without specific prior written permission.
  26  *
  27  * Alternatively, this software may be distributed under the terms of the
  28  * GNU General Public License ("GPL") version 2 as published by the Free
  29  * Software Foundation.
  30  *
  31  * NO WARRANTY
  32  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  33  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  34  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR
  35  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  36  * HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  37  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  38  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  39  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  40  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
  41  * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  42  * POSSIBILITY OF SUCH DAMAGES.
  43  */
  44
  45 #include "acpi.h"
  46 #include "accommon.h"
  47 #include "acevents.h"
  48
  49 #define _COMPONENT          ACPI_HARDWARE
  50         ACPI_MODULE_NAME    ("hwregs")
  51
  52
  53 #if (!ACPI_REDUCED_HARDWARE)
  54
  55 /* Local Prototypes */
  56
  57 static ACPI_STATUS
  58 AcpiHwReadMultiple (
  59     UINT32                  *Value,
  60     ACPI_GENERIC_ADDRESS    *RegisterA,
  61     ACPI_GENERIC_ADDRESS    *RegisterB);
  62
  63 static ACPI_STATUS
  64 AcpiHwWriteMultiple (
  65     UINT32                  Value,
  66     ACPI_GENERIC_ADDRESS    *RegisterA,
  67     ACPI_GENERIC_ADDRESS    *RegisterB);
  68
  69 #endif /* !ACPI_REDUCED_HARDWARE */
  70
  71
  72 /******************************************************************************
  73  *
  74  * FUNCTION:    AcpiHwValidateRegister
  75  *
  76  * PARAMETERS:  Reg                 - GAS register structure
  77  *              MaxBitWidth         - Max BitWidth supported (32 or 64)
  78  *              Address             - Pointer to where the gas->address
  79  *                                    is returned
  80  *
  81  * RETURN:      Status
  82  *
  83  * DESCRIPTION: Validate the contents of a GAS register. Checks the GAS
  84  *              pointer, Address, SpaceId, BitWidth, and BitOffset.
  85  *
  86  ******************************************************************************/
  87
  88 ACPI_STATUS
  89 AcpiHwValidateRegister (
  90     ACPI_GENERIC_ADDRESS    *Reg,
  91     UINT8                   MaxBitWidth,
  92     UINT64                  *Address)
  93 {
  94
  95     /* Must have a valid pointer to a GAS structure */
  96
  97     if (!Reg)
  98     {
  99         return (AE_BAD_PARAMETER);
 100     }
 101
 102     /*
 103      * Copy the target address. This handles possible alignment issues.
 104      * Address must not be null. A null address also indicates an optional
 105      * ACPI register that is not supported, so no error message.
 106      */
 107     ACPI_MOVE_64_TO_64 (Address, &Reg->Address);
 108     if (!(*Address))
 109     {
 110         return (AE_BAD_ADDRESS);
 111     }
 112
 113     /* Validate the SpaceID */
 114
 115     if ((Reg->SpaceId != ACPI_ADR_SPACE_SYSTEM_MEMORY) &&
 116         (Reg->SpaceId != ACPI_ADR_SPACE_SYSTEM_IO))
 117     {
 118         ACPI_ERROR ((AE_INFO,
 119             "Unsupported address space: 0x%X", Reg->SpaceId));
 120         return (AE_SUPPORT);
 121     }
 122
 123     /* Validate the BitWidth */
 124
 125     if ((Reg->BitWidth != 8) &&
 126         (Reg->BitWidth != 16) &&
 127         (Reg->BitWidth != 32) &&
 128         (Reg->BitWidth != MaxBitWidth))
 129     {
 130         ACPI_ERROR ((AE_INFO,
 131             "Unsupported register bit width: 0x%X", Reg->BitWidth));
 132         return (AE_SUPPORT);
 133     }
 134
 135     /* Validate the BitOffset. Just a warning for now. */
 136
 137     if (Reg->BitOffset != 0)
 138     {
 139         ACPI_WARNING ((AE_INFO,
 140             "Unsupported register bit offset: 0x%X", Reg->BitOffset));
 141     }
 142
 143     return (AE_OK);
 144 }
 145
 146
 147 /******************************************************************************
 148  *
 149  * FUNCTION:    AcpiHwRead
 150  *
 151  * PARAMETERS:  Value               - Where the value is returned
 152  *              Reg                 - GAS register structure
 153  *
 154  * RETURN:      Status
 155  *
 156  * DESCRIPTION: Read from either memory or IO space. This is a 32-bit max
 157  *              version of AcpiRead, used internally since the overhead of
 158  *              64-bit values is not needed.
 159  *
 160  * LIMITATIONS: <These limitations also apply to AcpiHwWrite>
 161  *      BitWidth must be exactly 8, 16, or 32.
 162  *      SpaceID must be SystemMemory or SystemIO.
 163  *      BitOffset and AccessWidth are currently ignored, as there has
 164  *          not been a need to implement these.
 165  *
 166  ******************************************************************************/
 167
 168 ACPI_STATUS
 169 AcpiHwRead (
 170     UINT32                  *Value,
 171     ACPI_GENERIC_ADDRESS    *Reg)
 172 {
 173     UINT64                  Address;
 174     UINT64                  Value64;
 175     ACPI_STATUS             Status;
 176
 177
 178     ACPI_FUNCTION_NAME (HwRead);
 179
 180
 181     /* Validate contents of the GAS register */
 182
 183     Status = AcpiHwValidateRegister (Reg, 32, &Address);
 184     if (ACPI_FAILURE (Status))
 185     {
 186         return (Status);
 187     }
 188
 189     /* Initialize entire 32-bit return value to zero */
 190
 191     *Value = 0;
 192
 193     /*
 194      * Two address spaces supported: Memory or IO. PCI_Config is
 195      * not supported here because the GAS structure is insufficient
 196      */
 197     if (Reg->SpaceId == ACPI_ADR_SPACE_SYSTEM_MEMORY)
 198     {
 199         Status = AcpiOsReadMemory ((ACPI_PHYSICAL_ADDRESS)
 200             Address, &Value64, Reg->BitWidth);
 201
 202         *Value = (UINT32) Value64;
 203     }
 204     else /* ACPI_ADR_SPACE_SYSTEM_IO, validated earlier */
 205     {
 206         Status = AcpiHwReadPort ((ACPI_IO_ADDRESS)
 207             Address, Value, Reg->BitWidth);
 208     }
 209
 210     ACPI_DEBUG_PRINT ((ACPI_DB_IO,
 211         "Read:  %8.8X width %2d from %8.8X%8.8X (%s)\n",
 212         *Value, Reg->BitWidth, ACPI_FORMAT_UINT64 (Address),
 213         AcpiUtGetRegionName (Reg->SpaceId)));
 214
 215     return (Status);
 216 }
 217
 218
 219 /******************************************************************************
 220  *
 221  * FUNCTION:    AcpiHwWrite
 222  *
 223  * PARAMETERS:  Value               - Value to be written
 224  *              Reg                 - GAS register structure
 225  *
 226  * RETURN:      Status
 227  *
 228  * DESCRIPTION: Write to either memory or IO space. This is a 32-bit max
 229  *              version of AcpiWrite, used internally since the overhead of
 230  *              64-bit values is not needed.
 231  *
 232  ******************************************************************************/
 233
 234 ACPI_STATUS
 235 AcpiHwWrite (
 236     UINT32                  Value,
 237     ACPI_GENERIC_ADDRESS    *Reg)
 238 {
 239     UINT64                  Address;
 240     ACPI_STATUS             Status;
 241
 242
 243     ACPI_FUNCTION_NAME (HwWrite);
 244
 245
 246     /* Validate contents of the GAS register */
 247
 248     Status = AcpiHwValidateRegister (Reg, 32, &Address);
 249     if (ACPI_FAILURE (Status))
 250     {
 251         return (Status);
 252     }
 253
 254     /*
 255      * Two address spaces supported: Memory or IO. PCI_Config is
 256      * not supported here because the GAS structure is insufficient
 257      */
 258     if (Reg->SpaceId == ACPI_ADR_SPACE_SYSTEM_MEMORY)
 259     {
 260         Status = AcpiOsWriteMemory ((ACPI_PHYSICAL_ADDRESS)
 261             Address, (UINT64) Value, Reg->BitWidth);
 262     }
 263     else /* ACPI_ADR_SPACE_SYSTEM_IO, validated earlier */
 264     {
 265         Status = AcpiHwWritePort ((ACPI_IO_ADDRESS)
 266             Address, Value, Reg->BitWidth);
 267     }
 268
 269     ACPI_DEBUG_PRINT ((ACPI_DB_IO,
 270         "Wrote: %8.8X width %2d   to %8.8X%8.8X (%s)\n",
 271         Value, Reg->BitWidth, ACPI_FORMAT_UINT64 (Address),
 272         AcpiUtGetRegionName (Reg->SpaceId)));
 273
 274     return (Status);
 275 }
 276
 277
 278 #if (!ACPI_REDUCED_HARDWARE)
 279 /*******************************************************************************
 280  *
 281  * FUNCTION:    AcpiHwClearAcpiStatus
 282  *
 283  * PARAMETERS:  None
 284  *
 285  * RETURN:      Status
 286  *
 287  * DESCRIPTION: Clears all fixed and general purpose status bits
 288  *
 289  ******************************************************************************/
 290
 291 ACPI_STATUS
 292 AcpiHwClearAcpiStatus (
 293     void)
 294 {
 295     ACPI_STATUS             Status;
 296     ACPI_CPU_FLAGS          LockFlags = 0;
 297
 298
 299     ACPI_FUNCTION_TRACE (HwClearAcpiStatus);
 300
 301
 302     ACPI_DEBUG_PRINT ((ACPI_DB_IO, "About to write %04X to %8.8X%8.8X\n",
 303         ACPI_BITMASK_ALL_FIXED_STATUS,
 304         ACPI_FORMAT_UINT64 (AcpiGbl_XPm1aStatus.Address)));
 305
 306     LockFlags = AcpiOsAcquireLock (AcpiGbl_HardwareLock);
 307
 308     /* Clear the fixed events in PM1 A/B */
 309
 310     Status = AcpiHwRegisterWrite (ACPI_REGISTER_PM1_STATUS,
 311         ACPI_BITMASK_ALL_FIXED_STATUS);
 312
 313     AcpiOsReleaseLock (AcpiGbl_HardwareLock, LockFlags);
 314
 315     if (ACPI_FAILURE (Status))
 316     {
 317         goto Exit;
 318     }
 319
 320     /* Clear the GPE Bits in all GPE registers in all GPE blocks */
 321
 322     Status = AcpiEvWalkGpeList (AcpiHwClearGpeBlock, NULL);
 323
 324 Exit:
 325     return_ACPI_STATUS (Status);
 326 }
 327
 328
 329 /*******************************************************************************
 330  *
 331  * FUNCTION:    AcpiHwGetBitRegisterInfo
 332  *
 333  * PARAMETERS:  RegisterId          - Index of ACPI Register to access
 334  *
 335  * RETURN:      The bitmask to be used when accessing the register
 336  *
 337  * DESCRIPTION: Map RegisterId into a register bitmask.
 338  *
 339  ******************************************************************************/
 340
 341 ACPI_BIT_REGISTER_INFO *
 342 AcpiHwGetBitRegisterInfo (
 343     UINT32                  RegisterId)
 344 {
 345     ACPI_FUNCTION_ENTRY ();
 346
 347
 348     if (RegisterId > ACPI_BITREG_MAX)
 349     {
 350         ACPI_ERROR ((AE_INFO, "Invalid BitRegister ID: 0x%X", RegisterId));
 351         return (NULL);
 352     }
 353
 354     return (&AcpiGbl_BitRegisterInfo[RegisterId]);
 355 }
 356
 357
 358 /******************************************************************************
 359  *
 360  * FUNCTION:    AcpiHwWritePm1Control
 361  *
 362  * PARAMETERS:  Pm1aControl         - Value to be written to PM1A control
 363  *              Pm1bControl         - Value to be written to PM1B control
 364  *
 365  * RETURN:      Status
 366  *
 367  * DESCRIPTION: Write the PM1 A/B control registers. These registers are
 368  *              different than than the PM1 A/B status and enable registers
 369  *              in that different values can be written to the A/B registers.
 370  *              Most notably, the SLP_TYP bits can be different, as per the
 371  *              values returned from the _Sx predefined methods.
 372  *
 373  ******************************************************************************/
 374
 375 ACPI_STATUS
 376 AcpiHwWritePm1Control (
 377     UINT32                  Pm1aControl,
 378     UINT32                  Pm1bControl)
 379 {
 380     ACPI_STATUS             Status;
 381
 382
 383     ACPI_FUNCTION_TRACE (HwWritePm1Control);
 384
 385
 386     Status = AcpiHwWrite (Pm1aControl, &AcpiGbl_FADT.XPm1aControlBlock);
 387     if (ACPI_FAILURE (Status))
 388     {
 389         return_ACPI_STATUS (Status);
 390     }
 391
 392     if (AcpiGbl_FADT.XPm1bControlBlock.Address)
 393     {
 394         Status = AcpiHwWrite (Pm1bControl, &AcpiGbl_FADT.XPm1bControlBlock);
 395     }
 396     return_ACPI_STATUS (Status);
 397 }
 398
 399
 400 /******************************************************************************
 401  *
 402  * FUNCTION:    AcpiHwRegisterRead
 403  *
 404  * PARAMETERS:  RegisterId          - ACPI Register ID
 405  *              ReturnValue         - Where the register value is returned
 406  *
 407  * RETURN:      Status and the value read.
 408  *
 409  * DESCRIPTION: Read from the specified ACPI register
 410  *
 411  ******************************************************************************/
 412
 413 ACPI_STATUS
 414 AcpiHwRegisterRead (
 415     UINT32                  RegisterId,
 416     UINT32                  *ReturnValue)
 417 {
 418     UINT32                  Value = 0;
 419     ACPI_STATUS             Status;
 420
 421
 422     ACPI_FUNCTION_TRACE (HwRegisterRead);
 423
 424
 425     switch (RegisterId)
 426     {
 427     case ACPI_REGISTER_PM1_STATUS:           /* PM1 A/B: 16-bit access each */
 428
 429         Status = AcpiHwReadMultiple (&Value,
 430             &AcpiGbl_XPm1aStatus,
 431             &AcpiGbl_XPm1bStatus);
 432         break;
 433
 434     case ACPI_REGISTER_PM1_ENABLE:           /* PM1 A/B: 16-bit access each */
 435
 436         Status = AcpiHwReadMultiple (&Value,
 437             &AcpiGbl_XPm1aEnable,
 438             &AcpiGbl_XPm1bEnable);
 439         break;
 440
 441     case ACPI_REGISTER_PM1_CONTROL:          /* PM1 A/B: 16-bit access each */
 442
 443         Status = AcpiHwReadMultiple (&Value,
 444             &AcpiGbl_FADT.XPm1aControlBlock,
 445             &AcpiGbl_FADT.XPm1bControlBlock);
 446
 447         /*
 448          * Zero the write-only bits. From the ACPI specification, "Hardware
 449          * Write-Only Bits": "Upon reads to registers with write-only bits,
 450          * software masks out all write-only bits."
 451          */
 452         Value &= ~ACPI_PM1_CONTROL_WRITEONLY_BITS;
 453         break;
 454
 455     case ACPI_REGISTER_PM2_CONTROL:          /* 8-bit access */
 456
 457         Status = AcpiHwRead (&Value, &AcpiGbl_FADT.XPm2ControlBlock);
 458         break;
 459
 460     case ACPI_REGISTER_PM_TIMER:             /* 32-bit access */
 461
 462         Status = AcpiHwRead (&Value, &AcpiGbl_FADT.XPmTimerBlock);
 463         break;
 464
 465     case ACPI_REGISTER_SMI_COMMAND_BLOCK:    /* 8-bit access */
 466
 467         Status = AcpiHwReadPort (AcpiGbl_FADT.SmiCommand, &Value, 8);
 468         break;
 469
 470     default:
 471
 472         ACPI_ERROR ((AE_INFO, "Unknown Register ID: 0x%X",
 473             RegisterId));
 474         Status = AE_BAD_PARAMETER;
 475         break;
 476     }
 477
 478     if (ACPI_SUCCESS (Status))
 479     {
 480         *ReturnValue = Value;
 481     }
 482
 483     return_ACPI_STATUS (Status);
 484 }
 485
 486
 487 /******************************************************************************
 488  *
 489  * FUNCTION:    AcpiHwRegisterWrite
 490  *
 491  * PARAMETERS:  RegisterId          - ACPI Register ID
 492  *              Value               - The value to write
 493  *
 494  * RETURN:      Status
 495  *
 496  * DESCRIPTION: Write to the specified ACPI register
 497  *
 498  * NOTE: In accordance with the ACPI specification, this function automatically
 499  * preserves the value of the following bits, meaning that these bits cannot be
 500  * changed via this interface:
 501  *
 502  * PM1_CONTROL[0] = SCI_EN
 503  * PM1_CONTROL[9]
 504  * PM1_STATUS[11]
 505  *
 506  * ACPI References:
 507  * 1) Hardware Ignored Bits: When software writes to a register with ignored
 508  *      bit fields, it preserves the ignored bit fields
 509  * 2) SCI_EN: OSPM always preserves this bit position
 510  *
 511  ******************************************************************************/
 512
 513 ACPI_STATUS
 514 AcpiHwRegisterWrite (
 515     UINT32                  RegisterId,
 516     UINT32                  Value)
 517 {
 518     ACPI_STATUS             Status;
 519     UINT32                  ReadValue;
 520
 521
 522     ACPI_FUNCTION_TRACE (HwRegisterWrite);
 523
 524
 525     switch (RegisterId)
 526     {
 527     case ACPI_REGISTER_PM1_STATUS:           /* PM1 A/B: 16-bit access each */
 528         /*
 529          * Handle the "ignored" bit in PM1 Status. According to the ACPI
 530          * specification, ignored bits are to be preserved when writing.
 531          * Normally, this would mean a read/modify/write sequence. However,
 532          * preserving a bit in the status register is different. Writing a
 533          * one clears the status, and writing a zero preserves the status.
 534          * Therefore, we must always write zero to the ignored bit.
 535          *
 536          * This behavior is clarified in the ACPI 4.0 specification.
 537          */
 538         Value &= ~ACPI_PM1_STATUS_PRESERVED_BITS;
 539
 540         Status = AcpiHwWriteMultiple (Value,
 541             &AcpiGbl_XPm1aStatus,
 542             &AcpiGbl_XPm1bStatus);
 543         break;
 544
 545     case ACPI_REGISTER_PM1_ENABLE:           /* PM1 A/B: 16-bit access each */
 546
 547         Status = AcpiHwWriteMultiple (Value,
 548             &AcpiGbl_XPm1aEnable,
 549             &AcpiGbl_XPm1bEnable);
 550         break;
 551
 552     case ACPI_REGISTER_PM1_CONTROL:          /* PM1 A/B: 16-bit access each */
 553         /*
 554          * Perform a read first to preserve certain bits (per ACPI spec)
 555          * Note: This includes SCI_EN, we never want to change this bit
 556          */
 557         Status = AcpiHwReadMultiple (&ReadValue,
 558             &AcpiGbl_FADT.XPm1aControlBlock,
 559             &AcpiGbl_FADT.XPm1bControlBlock);
 560         if (ACPI_FAILURE (Status))
 561         {
 562             goto Exit;
 563         }
 564
 565         /* Insert the bits to be preserved */
 566
 567         ACPI_INSERT_BITS (Value, ACPI_PM1_CONTROL_PRESERVED_BITS, ReadValue);
 568
 569         /* Now we can write the data */
 570
 571         Status = AcpiHwWriteMultiple (Value,
 572             &AcpiGbl_FADT.XPm1aControlBlock,
 573             &AcpiGbl_FADT.XPm1bControlBlock);
 574         break;
 575
 576     case ACPI_REGISTER_PM2_CONTROL:          /* 8-bit access */
 577         /*
 578          * For control registers, all reserved bits must be preserved,
 579          * as per the ACPI spec.
 580          */
 581         Status = AcpiHwRead (&ReadValue, &AcpiGbl_FADT.XPm2ControlBlock);
 582         if (ACPI_FAILURE (Status))
 583         {
 584             goto Exit;
 585         }
 586
 587         /* Insert the bits to be preserved */
 588
 589         ACPI_INSERT_BITS (Value, ACPI_PM2_CONTROL_PRESERVED_BITS, ReadValue);
 590
 591         Status = AcpiHwWrite (Value, &AcpiGbl_FADT.XPm2ControlBlock);
 592         break;
 593
 594     case ACPI_REGISTER_PM_TIMER:             /* 32-bit access */
 595
 596         Status = AcpiHwWrite (Value, &AcpiGbl_FADT.XPmTimerBlock);
 597         break;
 598
 599     case ACPI_REGISTER_SMI_COMMAND_BLOCK:    /* 8-bit access */
 600
 601         /* SMI_CMD is currently always in IO space */
 602
 603         Status = AcpiHwWritePort (AcpiGbl_FADT.SmiCommand, Value, 8);
 604         break;
 605
 606     default:
 607
 608         ACPI_ERROR ((AE_INFO, "Unknown Register ID: 0x%X",
 609             RegisterId));
 610         Status = AE_BAD_PARAMETER;
 611         break;
 612     }
 613
 614 Exit:
 615     return_ACPI_STATUS (Status);
 616 }
 617
 618
 619 /******************************************************************************
 620  *
 621  * FUNCTION:    AcpiHwReadMultiple
 622  *
 623  * PARAMETERS:  Value               - Where the register value is returned
 624  *              RegisterA           - First ACPI register (required)
 625  *              RegisterB           - Second ACPI register (optional)
 626  *
 627  * RETURN:      Status
 628  *
 629  * DESCRIPTION: Read from the specified two-part ACPI register (such as PM1 A/B)
 630  *
 631  ******************************************************************************/
 632
 633 static ACPI_STATUS
 634 AcpiHwReadMultiple (
 635     UINT32                  *Value,
 636     ACPI_GENERIC_ADDRESS    *RegisterA,
 637     ACPI_GENERIC_ADDRESS    *RegisterB)
 638 {
 639     UINT32                  ValueA = 0;
 640     UINT32                  ValueB = 0;
 641     ACPI_STATUS             Status;
 642
 643
 644     /* The first register is always required */
 645
 646     Status = AcpiHwRead (&ValueA, RegisterA);
 647     if (ACPI_FAILURE (Status))
 648     {
 649         return (Status);
 650     }
 651
 652     /* Second register is optional */
 653
 654     if (RegisterB->Address)
 655     {
 656         Status = AcpiHwRead (&ValueB, RegisterB);
 657         if (ACPI_FAILURE (Status))
 658         {
 659             return (Status);
 660         }
 661     }
 662
 663     /*
 664      * OR the two return values together. No shifting or masking is necessary,
 665      * because of how the PM1 registers are defined in the ACPI specification:
 666      *
 667      * "Although the bits can be split between the two register blocks (each
 668      * register block has a unique pointer within the FADT), the bit positions
 669      * are maintained. The register block with unimplemented bits (that is,
 670      * those implemented in the other register block) always returns zeros,
 671      * and writes have no side effects"
 672      */
 673     *Value = (ValueA | ValueB);
 674     return (AE_OK);
 675 }
 676
 677
 678 /******************************************************************************
 679  *
 680  * FUNCTION:    AcpiHwWriteMultiple
 681  *
 682  * PARAMETERS:  Value               - The value to write
 683  *              RegisterA           - First ACPI register (required)
 684  *              RegisterB           - Second ACPI register (optional)
 685  *
 686  * RETURN:      Status
 687  *
 688  * DESCRIPTION: Write to the specified two-part ACPI register (such as PM1 A/B)
 689  *
 690  ******************************************************************************/
 691
 692 static ACPI_STATUS
 693 AcpiHwWriteMultiple (
 694     UINT32                  Value,
 695     ACPI_GENERIC_ADDRESS    *RegisterA,
 696     ACPI_GENERIC_ADDRESS    *RegisterB)
 697 {
 698     ACPI_STATUS             Status;
 699
 700
 701     /* The first register is always required */
 702
 703     Status = AcpiHwWrite (Value, RegisterA);
 704     if (ACPI_FAILURE (Status))
 705     {
 706         return (Status);
 707     }
 708
 709     /*
 710      * Second register is optional
 711      *
 712      * No bit shifting or clearing is necessary, because of how the PM1
 713      * registers are defined in the ACPI specification:
 714      *
 715      * "Although the bits can be split between the two register blocks (each
 716      * register block has a unique pointer within the FADT), the bit positions
 717      * are maintained. The register block with unimplemented bits (that is,
 718      * those implemented in the other register block) always returns zeros,
 719      * and writes have no side effects"
 720      */
 721     if (RegisterB->Address)
 722     {
 723         Status = AcpiHwWrite (Value, RegisterB);
 724     }
 725
 726     return (Status);
 727 }
 728
 729 #endif /* !ACPI_REDUCED_HARDWARE */