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kolibrios-gitea/drivers/devman/acpica/hardware/hwregs.c

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acpica library git-svn-id: svn://kolibrios.org@1498 a494cfbc-eb01-0410-851d-a64ba20cac60
2010-06-18 16:39:07 +02:00
/*******************************************************************************
*
* Module Name: hwregs - Read/write access functions for the various ACPI
* control and status registers.
*
******************************************************************************/
/******************************************************************************
*
* 1. Copyright Notice
*
update acpica git-svn-id: svn://kolibrios.org@2216 a494cfbc-eb01-0410-851d-a64ba20cac60
2011-09-20 18:54:11 +02:00
* Some or all of this work - Copyright (c) 1999 - 2011, Intel Corp.
acpica library git-svn-id: svn://kolibrios.org@1498 a494cfbc-eb01-0410-851d-a64ba20cac60
2010-06-18 16:39:07 +02:00
* 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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