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minix/drivers/acpi/hardware/hwregs.c

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ACPI driver - 99% of the code is Intel's ACPICA. The license is compliant with BSD and GNU and virtually all systems that use ACPI use this code, For instance it is part of the Linux kernel. - The only minix specific files are acpi.c osminixxf.c platform/acminix.h and include/minix/acpi.h - At the moment the driver does not register interrupt hooks which I believe is mainly for handling PnP, events like "battery level is low" and power management. Should not be difficult to add it if need be. - The interface to the outside world is virtually non-existent except a trivial message based service for PCI driver to query which device is connected to what IRQ line. This will evolve as more components start using this driver. VM, Scheduler and IOMMU are the possible users right now. - because of dependency on a native 64bit (long long, part of c99) it is compiled only with a gnu-like compilers which in case of Minix includes gcc llvm-gcc and clang
2010-09-02 17:44:04 +02:00
/*******************************************************************************
*
* Module Name: hwregs - Read/write access functions for the various ACPI
* control and status registers.
*
******************************************************************************/
/******************************************************************************
*
* 1. Copyright Notice
*
* Some or all of this work - Copyright (c) 1999 - 2010, Intel Corp.
* All rights reserved.
*
* 2. License
*
* 2.1. This is your license from Intel Corp. under its intellectual property
* rights. You may have additional license terms from the party that provided
* you this software, covering your right to use that party's intellectual
* property rights.
*
* 2.2. Intel grants, free of charge, to any person ("Licensee") obtaining a
* copy of the source code appearing in this file ("Covered Code") an
* irrevocable, perpetual, worldwide license under Intel's copyrights in the
* base code distributed originally by Intel ("Original Intel Code") to copy,
* make derivatives, distribute, use and display any portion of the Covered
* Code in any form, with the right to sublicense such rights; and
*
* 2.3. Intel grants Licensee a non-exclusive and non-transferable patent
* license (with the right to sublicense), under only those claims of Intel
* patents that are infringed by the Original Intel Code, to make, use, sell,
* offer to sell, and import the Covered Code and derivative works thereof
* solely to the minimum extent necessary to exercise the above copyright
* license, and in no event shall the patent license extend to any additions
* to or modifications of the Original Intel Code. No other license or right
* is granted directly or by implication, estoppel or otherwise;
*
* The above copyright and patent license is granted only if the following
* conditions are met:
*
* 3. Conditions
*
* 3.1. Redistribution of Source with Rights to Further Distribute Source.
* Redistribution of source code of any substantial portion of the Covered
* Code or modification with rights to further distribute source must include
* the above Copyright Notice, the above License, this list of Conditions,
* and the following Disclaimer and Export Compliance provision. In addition,
* Licensee must cause all Covered Code to which Licensee contributes to
* contain a file documenting the changes Licensee made to create that Covered
* Code and the date of any change. Licensee must include in that file the
* documentation of any changes made by any predecessor Licensee. Licensee
* must include a prominent statement that the modification is derived,
* directly or indirectly, from Original Intel Code.
*
* 3.2. Redistribution of Source with no Rights to Further Distribute Source.
* Redistribution of source code of any substantial portion of the Covered
* Code or modification without rights to further distribute source must
* include the following Disclaimer and Export Compliance provision in the
* documentation and/or other materials provided with distribution. In
* addition, Licensee may not authorize further sublicense of source of any
* portion of the Covered Code, and must include terms to the effect that the
* license from Licensee to its licensee is limited to the intellectual
* property embodied in the software Licensee provides to its licensee, and
* not to intellectual property embodied in modifications its licensee may
* make.
*
* 3.3. Redistribution of Executable. Redistribution in executable form of any
* substantial portion of the Covered Code or modification must reproduce the
* above Copyright Notice, and the following Disclaimer and Export Compliance
* provision in the documentation and/or other materials provided with the
* distribution.
*
* 3.4. Intel retains all right, title, and interest in and to the Original
* Intel Code.
*
* 3.5. Neither the name Intel nor any other trademark owned or controlled by
* Intel shall be used in advertising or otherwise to promote the sale, use or
* other dealings in products derived from or relating to the Covered Code
* without prior written authorization from Intel.
*
* 4. Disclaimer and Export Compliance
*
* 4.1. INTEL MAKES NO WARRANTY OF ANY KIND REGARDING ANY SOFTWARE PROVIDED
* HERE. ANY SOFTWARE ORIGINATING FROM INTEL OR DERIVED FROM INTEL SOFTWARE
* IS PROVIDED "AS IS," AND INTEL WILL NOT PROVIDE ANY SUPPORT, ASSISTANCE,
* INSTALLATION, TRAINING OR OTHER SERVICES. INTEL WILL NOT PROVIDE ANY
* UPDATES, ENHANCEMENTS OR EXTENSIONS. INTEL SPECIFICALLY DISCLAIMS ANY
* IMPLIED WARRANTIES OF MERCHANTABILITY, NONINFRINGEMENT AND FITNESS FOR A
* PARTICULAR PURPOSE.
*
* 4.2. IN NO EVENT SHALL INTEL HAVE ANY LIABILITY TO LICENSEE, ITS LICENSEES
* OR ANY OTHER THIRD PARTY, FOR ANY LOST PROFITS, LOST DATA, LOSS OF USE OR
* COSTS OF PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES, OR FOR ANY INDIRECT,
* SPECIAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THIS AGREEMENT, UNDER ANY
* CAUSE OF ACTION OR THEORY OF LIABILITY, AND IRRESPECTIVE OF WHETHER INTEL
* HAS ADVANCE NOTICE OF THE POSSIBILITY OF SUCH DAMAGES. THESE LIMITATIONS
* SHALL APPLY NOTWITHSTANDING THE FAILURE OF THE ESSENTIAL PURPOSE OF ANY
* LIMITED REMEDY.
*
* 4.3. Licensee shall not export, either directly or indirectly, any of this
* software or system incorporating such software without first obtaining any
* required license or other approval from the U. S. Department of Commerce or
* any other agency or department of the United States Government. In the
* event Licensee exports any such software from the United States or
* re-exports any such software from a foreign destination, Licensee shall
* ensure that the distribution and export/re-export of the software is in
* compliance with all laws, regulations, orders, or other restrictions of the
* U.S. Export Administration Regulations. Licensee agrees that neither it nor
* any of its subsidiaries will export/re-export any technical data, process,
* software, or service, directly or indirectly, to any country for which the
* United States government or any agency thereof requires an export license,
* other governmental approval, or letter of assurance, without first obtaining
* such license, approval or letter.
*
*****************************************************************************/
#define __HWREGS_C__
#include "acpi.h"
#include "accommon.h"
#include "acevents.h"
#define _COMPONENT ACPI_HARDWARE
ACPI_MODULE_NAME ("hwregs")
/* Local Prototypes */
static ACPI_STATUS
AcpiHwReadMultiple (
UINT32 *Value,
ACPI_GENERIC_ADDRESS *RegisterA,
ACPI_GENERIC_ADDRESS *RegisterB);
static ACPI_STATUS
AcpiHwWriteMultiple (
UINT32 Value,
ACPI_GENERIC_ADDRESS *RegisterA,
ACPI_GENERIC_ADDRESS *RegisterB);
/******************************************************************************
*
* FUNCTION: AcpiHwValidateRegister
*
* PARAMETERS: Reg - GAS register structure
* MaxBitWidth - Max BitWidth supported (32 or 64)
* Address - Pointer to where the gas->address
* is returned
*
* RETURN: Status
*
* DESCRIPTION: Validate the contents of a GAS register. Checks the GAS
* pointer, Address, SpaceId, BitWidth, and BitOffset.
*
******************************************************************************/
ACPI_STATUS
AcpiHwValidateRegister (
ACPI_GENERIC_ADDRESS *Reg,
UINT8 MaxBitWidth,
UINT64 *Address)
{
/* Must have a valid pointer to a GAS structure */
if (!Reg)
{
return (AE_BAD_PARAMETER);
}
/*
* Copy the target address. This handles possible alignment issues.
* Address must not be null. A null address also indicates an optional
* ACPI register that is not supported, so no error message.
*/
ACPI_MOVE_64_TO_64 (Address, &Reg->Address);
if (!(*Address))
{
return (AE_BAD_ADDRESS);
}
/* Validate the SpaceID */
if ((Reg->SpaceId != ACPI_ADR_SPACE_SYSTEM_MEMORY) &&
(Reg->SpaceId != ACPI_ADR_SPACE_SYSTEM_IO))
{
ACPI_ERROR ((AE_INFO,
"Unsupported address space: 0x%X", Reg->SpaceId));
return (AE_SUPPORT);
}
/* Validate the BitWidth */
if ((Reg->BitWidth != 8) &&
(Reg->BitWidth != 16) &&
(Reg->BitWidth != 32) &&
(Reg->BitWidth != MaxBitWidth))
{
ACPI_ERROR ((AE_INFO,
"Unsupported register bit width: 0x%X", Reg->BitWidth));
return (AE_SUPPORT);
}
/* Validate the BitOffset. Just a warning for now. */
if (Reg->BitOffset != 0)
{
ACPI_WARNING ((AE_INFO,
"Unsupported register bit offset: 0x%X", Reg->BitOffset));
}
return (AE_OK);
}
/******************************************************************************
*
* FUNCTION: AcpiHwRead
*
* PARAMETERS: Value - Where the value is returned
* Reg - GAS register structure
*
* RETURN: Status
*
* DESCRIPTION: Read from either memory or IO space. This is a 32-bit max
* version of AcpiRead, used internally since the overhead of
* 64-bit values is not needed.
*
* LIMITATIONS: <These limitations also apply to AcpiHwWrite>
* BitWidth must be exactly 8, 16, or 32.
* SpaceID must be SystemMemory or SystemIO.
* BitOffset and AccessWidth are currently ignored, as there has
* not been a need to implement these.
*
******************************************************************************/
ACPI_STATUS
AcpiHwRead (
UINT32 *Value,
ACPI_GENERIC_ADDRESS *Reg)
{
UINT64 Address;
ACPI_STATUS Status;
ACPI_FUNCTION_NAME (HwRead);
/* Validate contents of the GAS register */
Status = AcpiHwValidateRegister (Reg, 32, &Address);
if (ACPI_FAILURE (Status))
{
return (Status);
}
/* Initialize entire 32-bit return value to zero */
*Value = 0;
/*
* Two address spaces supported: Memory or IO. PCI_Config is
* not supported here because the GAS structure is insufficient
*/
if (Reg->SpaceId == ACPI_ADR_SPACE_SYSTEM_MEMORY)
{
Status = AcpiOsReadMemory ((ACPI_PHYSICAL_ADDRESS)
Address, Value, Reg->BitWidth);
}
else /* ACPI_ADR_SPACE_SYSTEM_IO, validated earlier */
{
Status = AcpiHwReadPort ((ACPI_IO_ADDRESS)
Address, Value, Reg->BitWidth);
}
ACPI_DEBUG_PRINT ((ACPI_DB_IO,
"Read: %8.8X width %2d from %8.8X%8.8X (%s)\n",
*Value, Reg->BitWidth, ACPI_FORMAT_UINT64 (Address),
AcpiUtGetRegionName (Reg->SpaceId)));
return (Status);
}
/******************************************************************************
*
* FUNCTION: AcpiHwWrite
*
* PARAMETERS: Value - Value to be written
* Reg - GAS register structure
*
* RETURN: Status
*
* DESCRIPTION: Write to either memory or IO space. This is a 32-bit max
* version of AcpiWrite, used internally since the overhead of
* 64-bit values is not needed.
*
******************************************************************************/
ACPI_STATUS
AcpiHwWrite (
UINT32 Value,
ACPI_GENERIC_ADDRESS *Reg)
{
UINT64 Address;
ACPI_STATUS Status;
ACPI_FUNCTION_NAME (HwWrite);
/* Validate contents of the GAS register */
Status = AcpiHwValidateRegister (Reg, 32, &Address);
if (ACPI_FAILURE (Status))
{
return (Status);
}
/*
* Two address spaces supported: Memory or IO. PCI_Config is
* not supported here because the GAS structure is insufficient
*/
if (Reg->SpaceId == ACPI_ADR_SPACE_SYSTEM_MEMORY)
{
Status = AcpiOsWriteMemory ((ACPI_PHYSICAL_ADDRESS)
Address, Value, Reg->BitWidth);
}
else /* ACPI_ADR_SPACE_SYSTEM_IO, validated earlier */
{
Status = AcpiHwWritePort ((ACPI_IO_ADDRESS)
Address, Value, Reg->BitWidth);
}
ACPI_DEBUG_PRINT ((ACPI_DB_IO,
"Wrote: %8.8X width %2d to %8.8X%8.8X (%s)\n",
Value, Reg->BitWidth, ACPI_FORMAT_UINT64 (Address),
AcpiUtGetRegionName (Reg->SpaceId)));
return (Status);
}
/*******************************************************************************
*
* FUNCTION: AcpiHwClearAcpiStatus
*
* PARAMETERS: None
*
* RETURN: Status
*
* DESCRIPTION: Clears all fixed and general purpose status bits
*
******************************************************************************/
ACPI_STATUS
AcpiHwClearAcpiStatus (
void)
{
ACPI_STATUS Status;
ACPI_CPU_FLAGS LockFlags = 0;
ACPI_FUNCTION_TRACE (HwClearAcpiStatus);
ACPI_DEBUG_PRINT ((ACPI_DB_IO, "About to write %04X to %8.8X%8.8X\n",
ACPI_BITMASK_ALL_FIXED_STATUS,
ACPI_FORMAT_UINT64 (AcpiGbl_XPm1aStatus.Address)));
LockFlags = AcpiOsAcquireLock (AcpiGbl_HardwareLock);
/* Clear the fixed events in PM1 A/B */
Status = AcpiHwRegisterWrite (ACPI_REGISTER_PM1_STATUS,
ACPI_BITMASK_ALL_FIXED_STATUS);
if (ACPI_FAILURE (Status))
{
goto UnlockAndExit;
}
/* Clear the GPE Bits in all GPE registers in all GPE blocks */
Status = AcpiEvWalkGpeList (AcpiHwClearGpeBlock, NULL);
UnlockAndExit:
AcpiOsReleaseLock (AcpiGbl_HardwareLock, LockFlags);
return_ACPI_STATUS (Status);
}
/*******************************************************************************
*
* FUNCTION: AcpiHwGetRegisterBitMask
*
* PARAMETERS: RegisterId - Index of ACPI Register to access
*
* RETURN: The bitmask to be used when accessing the register
*
* DESCRIPTION: Map RegisterId into a register bitmask.
*
******************************************************************************/
ACPI_BIT_REGISTER_INFO *
AcpiHwGetBitRegisterInfo (
UINT32 RegisterId)
{
ACPI_FUNCTION_ENTRY ();
if (RegisterId > ACPI_BITREG_MAX)
{
ACPI_ERROR ((AE_INFO, "Invalid BitRegister ID: 0x%X", RegisterId));
return (NULL);
}
return (&AcpiGbl_BitRegisterInfo[RegisterId]);
}
/******************************************************************************
*
* FUNCTION: AcpiHwWritePm1Control
*
* PARAMETERS: Pm1aControl - Value to be written to PM1A control
* Pm1bControl - Value to be written to PM1B control
*
* RETURN: Status
*
* DESCRIPTION: Write the PM1 A/B control registers. These registers are
* different than than the PM1 A/B status and enable registers
* in that different values can be written to the A/B registers.
* Most notably, the SLP_TYP bits can be different, as per the
* values returned from the _Sx predefined methods.
*
******************************************************************************/
ACPI_STATUS
AcpiHwWritePm1Control (
UINT32 Pm1aControl,
UINT32 Pm1bControl)
{
ACPI_STATUS Status;
ACPI_FUNCTION_TRACE (HwWritePm1Control);
Status = AcpiHwWrite (Pm1aControl, &AcpiGbl_FADT.XPm1aControlBlock);
if (ACPI_FAILURE (Status))
{
return_ACPI_STATUS (Status);
}
if (AcpiGbl_FADT.XPm1bControlBlock.Address)
{
Status = AcpiHwWrite (Pm1bControl, &AcpiGbl_FADT.XPm1bControlBlock);
}
return_ACPI_STATUS (Status);
}
/******************************************************************************
*
* FUNCTION: AcpiHwRegisterRead
*
* PARAMETERS: RegisterId - ACPI Register ID
* ReturnValue - Where the register value is returned
*
* RETURN: Status and the value read.
*
* DESCRIPTION: Read from the specified ACPI register
*
******************************************************************************/
ACPI_STATUS
AcpiHwRegisterRead (
UINT32 RegisterId,
UINT32 *ReturnValue)
{
UINT32 Value = 0;
ACPI_STATUS Status;
ACPI_FUNCTION_TRACE (HwRegisterRead);
switch (RegisterId)
{
case ACPI_REGISTER_PM1_STATUS: /* PM1 A/B: 16-bit access each */
Status = AcpiHwReadMultiple (&Value,
&AcpiGbl_XPm1aStatus,
&AcpiGbl_XPm1bStatus);
break;
case ACPI_REGISTER_PM1_ENABLE: /* PM1 A/B: 16-bit access each */
Status = AcpiHwReadMultiple (&Value,
&AcpiGbl_XPm1aEnable,
&AcpiGbl_XPm1bEnable);
break;
case ACPI_REGISTER_PM1_CONTROL: /* PM1 A/B: 16-bit access each */
Status = AcpiHwReadMultiple (&Value,
&AcpiGbl_FADT.XPm1aControlBlock,
&AcpiGbl_FADT.XPm1bControlBlock);
/*
* Zero the write-only bits. From the ACPI specification, "Hardware
* Write-Only Bits": "Upon reads to registers with write-only bits,
* software masks out all write-only bits."
*/
Value &= ~ACPI_PM1_CONTROL_WRITEONLY_BITS;
break;
case ACPI_REGISTER_PM2_CONTROL: /* 8-bit access */
Status = AcpiHwRead (&Value, &AcpiGbl_FADT.XPm2ControlBlock);
break;
case ACPI_REGISTER_PM_TIMER: /* 32-bit access */
Status = AcpiHwRead (&Value, &AcpiGbl_FADT.XPmTimerBlock);
break;
case ACPI_REGISTER_SMI_COMMAND_BLOCK: /* 8-bit access */
Status = AcpiHwReadPort (AcpiGbl_FADT.SmiCommand, &Value, 8);
break;
default:
ACPI_ERROR ((AE_INFO, "Unknown Register ID: 0x%X",
RegisterId));
Status = AE_BAD_PARAMETER;
break;
}
if (ACPI_SUCCESS (Status))
{
*ReturnValue = Value;
}
return_ACPI_STATUS (Status);
}
/******************************************************************************
*
* FUNCTION: AcpiHwRegisterWrite
*
* PARAMETERS: RegisterId - ACPI Register ID
* Value - The value to write
*
* RETURN: Status
*
* DESCRIPTION: Write to the specified ACPI register
*
* NOTE: In accordance with the ACPI specification, this function automatically
* preserves the value of the following bits, meaning that these bits cannot be
* changed via this interface:
*
* PM1_CONTROL[0] = SCI_EN
* PM1_CONTROL[9]
* PM1_STATUS[11]
*
* ACPI References:
* 1) Hardware Ignored Bits: When software writes to a register with ignored
* bit fields, it preserves the ignored bit fields
* 2) SCI_EN: OSPM always preserves this bit position
*
******************************************************************************/
ACPI_STATUS
AcpiHwRegisterWrite (
UINT32 RegisterId,
UINT32 Value)
{
ACPI_STATUS Status;
UINT32 ReadValue;
ACPI_FUNCTION_TRACE (HwRegisterWrite);
switch (RegisterId)
{
case ACPI_REGISTER_PM1_STATUS: /* PM1 A/B: 16-bit access each */
/*
* Handle the "ignored" bit in PM1 Status. According to the ACPI
* specification, ignored bits are to be preserved when writing.
* Normally, this would mean a read/modify/write sequence. However,
* preserving a bit in the status register is different. Writing a
* one clears the status, and writing a zero preserves the status.
* Therefore, we must always write zero to the ignored bit.
*
* This behavior is clarified in the ACPI 4.0 specification.
*/
Value &= ~ACPI_PM1_STATUS_PRESERVED_BITS;
Status = AcpiHwWriteMultiple (Value,
&AcpiGbl_XPm1aStatus,
&AcpiGbl_XPm1bStatus);
break;
case ACPI_REGISTER_PM1_ENABLE: /* PM1 A/B: 16-bit access each */
Status = AcpiHwWriteMultiple (Value,
&AcpiGbl_XPm1aEnable,
&AcpiGbl_XPm1bEnable);
break;
case ACPI_REGISTER_PM1_CONTROL: /* PM1 A/B: 16-bit access each */
/*
* Perform a read first to preserve certain bits (per ACPI spec)
* Note: This includes SCI_EN, we never want to change this bit
*/
Status = AcpiHwReadMultiple (&ReadValue,
&AcpiGbl_FADT.XPm1aControlBlock,
&AcpiGbl_FADT.XPm1bControlBlock);
if (ACPI_FAILURE (Status))
{
goto Exit;
}
/* Insert the bits to be preserved */
ACPI_INSERT_BITS (Value, ACPI_PM1_CONTROL_PRESERVED_BITS, ReadValue);
/* Now we can write the data */
Status = AcpiHwWriteMultiple (Value,
&AcpiGbl_FADT.XPm1aControlBlock,
&AcpiGbl_FADT.XPm1bControlBlock);
break;
case ACPI_REGISTER_PM2_CONTROL: /* 8-bit access */
/*
* For control registers, all reserved bits must be preserved,
* as per the ACPI spec.
*/
Status = AcpiHwRead (&ReadValue, &AcpiGbl_FADT.XPm2ControlBlock);
if (ACPI_FAILURE (Status))
{
goto Exit;
}
/* Insert the bits to be preserved */
ACPI_INSERT_BITS (Value, ACPI_PM2_CONTROL_PRESERVED_BITS, ReadValue);
Status = AcpiHwWrite (Value, &AcpiGbl_FADT.XPm2ControlBlock);
break;
case ACPI_REGISTER_PM_TIMER: /* 32-bit access */
Status = AcpiHwWrite (Value, &AcpiGbl_FADT.XPmTimerBlock);
break;
case ACPI_REGISTER_SMI_COMMAND_BLOCK: /* 8-bit access */
/* SMI_CMD is currently always in IO space */
Status = AcpiHwWritePort (AcpiGbl_FADT.SmiCommand, Value, 8);
break;
default:
ACPI_ERROR ((AE_INFO, "Unknown Register ID: 0x%X",
RegisterId));
Status = AE_BAD_PARAMETER;
break;
}
Exit:
return_ACPI_STATUS (Status);
}
/******************************************************************************
*
* FUNCTION: AcpiHwReadMultiple
*
* PARAMETERS: Value - Where the register value is returned
* RegisterA - First ACPI register (required)
* RegisterB - Second ACPI register (optional)
*
* RETURN: Status
*
* DESCRIPTION: Read from the specified two-part ACPI register (such as PM1 A/B)
*
******************************************************************************/
static ACPI_STATUS
AcpiHwReadMultiple (
UINT32 *Value,
ACPI_GENERIC_ADDRESS *RegisterA,
ACPI_GENERIC_ADDRESS *RegisterB)
{
UINT32 ValueA = 0;
UINT32 ValueB = 0;
ACPI_STATUS Status;
/* The first register is always required */
Status = AcpiHwRead (&ValueA, RegisterA);
if (ACPI_FAILURE (Status))
{
return (Status);
}
/* Second register is optional */
if (RegisterB->Address)
{
Status = AcpiHwRead (&ValueB, RegisterB);
if (ACPI_FAILURE (Status))
{
return (Status);
}
}
/*
* OR the two return values together. No shifting or masking is necessary,
* because of how the PM1 registers are defined in the ACPI specification:
*
* "Although the bits can be split between the two register blocks (each
* register block has a unique pointer within the FADT), the bit positions
* are maintained. The register block with unimplemented bits (that is,
* those implemented in the other register block) always returns zeros,
* and writes have no side effects"
*/
*Value = (ValueA | ValueB);
return (AE_OK);
}
/******************************************************************************
*
* FUNCTION: AcpiHwWriteMultiple
*
* PARAMETERS: Value - The value to write
* RegisterA - First ACPI register (required)
* RegisterB - Second ACPI register (optional)
*
* RETURN: Status
*
* DESCRIPTION: Write to the specified two-part ACPI register (such as PM1 A/B)
*
******************************************************************************/
static ACPI_STATUS
AcpiHwWriteMultiple (
UINT32 Value,
ACPI_GENERIC_ADDRESS *RegisterA,
ACPI_GENERIC_ADDRESS *RegisterB)
{
ACPI_STATUS Status;
/* The first register is always required */
Status = AcpiHwWrite (Value, RegisterA);
if (ACPI_FAILURE (Status))
{
return (Status);
}
/*
* Second register is optional
*
* No bit shifting or clearing is necessary, because of how the PM1
* registers are defined in the ACPI specification:
*
* "Although the bits can be split between the two register blocks (each
* register block has a unique pointer within the FADT), the bit positions
* are maintained. The register block with unimplemented bits (that is,
* those implemented in the other register block) always returns zeros,
* and writes have no side effects"
*/
if (RegisterB->Address)
{
Status = AcpiHwWrite (Value, RegisterB);
}
return (Status);
}
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