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linux/drivers/acpi/acpica/hwregs.c

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/*******************************************************************************
*
* Module Name: hwregs - Read/write access functions for the various ACPI
* control and status registers.
*
******************************************************************************/
/*
* Copyright (C) 2000 - 2016, Intel Corp.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions, and the following disclaimer,
* without modification.
* 2. Redistributions in binary form must reproduce at minimum a disclaimer
* substantially similar to the "NO WARRANTY" disclaimer below
* ("Disclaimer") and any redistribution must be conditioned upon
* including a substantially similar Disclaimer requirement for further
* binary redistribution.
* 3. Neither the names of the above-listed copyright holders nor the names
* of any contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* Alternatively, this software may be distributed under the terms of the
* GNU General Public License ("GPL") version 2 as published by the Free
* Software Foundation.
*
* NO WARRANTY
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
* IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGES.
*/
#include <acpi/acpi.h>
#include "accommon.h"
#include "acevents.h"
#define _COMPONENT ACPI_HARDWARE
ACPI_MODULE_NAME("hwregs")
#if (!ACPI_REDUCED_HARDWARE)
/* Local Prototypes */
static u8
acpi_hw_get_access_bit_width(struct acpi_generic_address *reg,
u8 max_bit_width);
static acpi_status
acpi_hw_read_multiple(u32 *value,
struct acpi_generic_address *register_a,
struct acpi_generic_address *register_b);
static acpi_status
acpi_hw_write_multiple(u32 value,
struct acpi_generic_address *register_a,
struct acpi_generic_address *register_b);
#endif /* !ACPI_REDUCED_HARDWARE */
/******************************************************************************
*
* FUNCTION: acpi_hw_get_access_bit_width
*
* PARAMETERS: reg - GAS register structure
* max_bit_width - Max bit_width supported (32 or 64)
*
* RETURN: Status
*
* DESCRIPTION: Obtain optimal access bit width
*
******************************************************************************/
static u8
acpi_hw_get_access_bit_width(struct acpi_generic_address *reg, u8 max_bit_width)
{
u64 address;
if (!reg->access_width) {
/*
* Detect old register descriptors where only the bit_width field
* makes senses. The target address is copied to handle possible
* alignment issues.
*/
ACPI_MOVE_64_TO_64(&address, &reg->address);
if (!reg->bit_offset && reg->bit_width &&
ACPI_IS_POWER_OF_TWO(reg->bit_width) &&
ACPI_IS_ALIGNED(reg->bit_width, 8) &&
ACPI_IS_ALIGNED(address, reg->bit_width)) {
return (reg->bit_width);
} else {
if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_IO) {
return (32);
} else {
return (max_bit_width);
}
}
} else {
return (1 << (reg->access_width + 2));
}
}
/******************************************************************************
*
* FUNCTION: acpi_hw_validate_register
*
* PARAMETERS: reg - GAS register structure
* max_bit_width - Max bit_width 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, space_id, bit_width, and bit_offset.
*
******************************************************************************/
acpi_status
acpi_hw_validate_register(struct acpi_generic_address *reg,
u8 max_bit_width, u64 *address)
{
u8 bit_width;
u8 access_width;
/* 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 space_ID */
if ((reg->space_id != ACPI_ADR_SPACE_SYSTEM_MEMORY) &&
(reg->space_id != ACPI_ADR_SPACE_SYSTEM_IO)) {
ACPI_ERROR((AE_INFO,
"Unsupported address space: 0x%X", reg->space_id));
return (AE_SUPPORT);
}
/* Validate the access_width */
if (reg->access_width > 4) {
ACPI_ERROR((AE_INFO,
"Unsupported register access width: 0x%X",
reg->access_width));
return (AE_SUPPORT);
}
/* Validate the bit_width, convert access_width into number of bits */
access_width = acpi_hw_get_access_bit_width(reg, max_bit_width);
bit_width =
ACPI_ROUND_UP(reg->bit_offset + reg->bit_width, access_width);
if (max_bit_width < bit_width) {
ACPI_WARNING((AE_INFO,
"Requested bit width 0x%X is smaller than register bit width 0x%X",
max_bit_width, bit_width));
return (AE_SUPPORT);
}
return (AE_OK);
}
/******************************************************************************
*
* FUNCTION: acpi_hw_read
*
* 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 acpi_read, used internally since the overhead of
* 64-bit values is not needed.
*
* LIMITATIONS: <These limitations also apply to acpi_hw_write>
* space_ID must be system_memory or system_IO.
*
******************************************************************************/
acpi_status acpi_hw_read(u32 *value, struct acpi_generic_address *reg)
{
u64 address;
u8 access_width;
u32 bit_width;
u8 bit_offset;
u64 value64;
u32 value32;
u8 index;
acpi_status status;
ACPI_FUNCTION_NAME(hw_read);
/* Validate contents of the GAS register */
status = acpi_hw_validate_register(reg, 32, &address);
if (ACPI_FAILURE(status)) {
return (status);
}
/*
* Initialize entire 32-bit return value to zero, convert access_width
* into number of bits based
*/
*value = 0;
access_width = acpi_hw_get_access_bit_width(reg, 32);
bit_width = reg->bit_offset + reg->bit_width;
bit_offset = reg->bit_offset;
/*
* Two address spaces supported: Memory or IO. PCI_Config is
* not supported here because the GAS structure is insufficient
*/
index = 0;
while (bit_width) {
if (bit_offset >= access_width) {
value32 = 0;
bit_offset -= access_width;
} else {
if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) {
status =
acpi_os_read_memory((acpi_physical_address)
address +
index *
ACPI_DIV_8
(access_width),
&value64, access_width);
value32 = (u32)value64;
} else { /* ACPI_ADR_SPACE_SYSTEM_IO, validated earlier */
status = acpi_hw_read_port((acpi_io_address)
address +
index *
ACPI_DIV_8
(access_width),
&value32,
access_width);
}
/*
* Use offset style bit masks because:
* bit_offset < access_width/bit_width < access_width, and
* access_width is ensured to be less than 32-bits by
* acpi_hw_validate_register().
*/
if (bit_offset) {
value32 &= ACPI_MASK_BITS_BELOW(bit_offset);
bit_offset = 0;
}
if (bit_width < access_width) {
value32 &= ACPI_MASK_BITS_ABOVE(bit_width);
}
}
/*
* Use offset style bit writes because "Index * AccessWidth" is
* ensured to be less than 32-bits by acpi_hw_validate_register().
*/
ACPI_SET_BITS(value, index * access_width,
ACPI_MASK_BITS_ABOVE_32(access_width), value32);
bit_width -=
bit_width > access_width ? access_width : bit_width;
index++;
}
ACPI_DEBUG_PRINT((ACPI_DB_IO,
"Read: %8.8X width %2d from %8.8X%8.8X (%s)\n",
*value, access_width, ACPI_FORMAT_UINT64(address),
acpi_ut_get_region_name(reg->space_id)));
return (status);
}
/******************************************************************************
*
* FUNCTION: acpi_hw_write
*
* 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 acpi_write, used internally since the overhead of
* 64-bit values is not needed.
*
******************************************************************************/
acpi_status acpi_hw_write(u32 value, struct acpi_generic_address *reg)
{
u64 address;
u8 access_width;
u32 bit_width;
u8 bit_offset;
u64 value64;
u32 new_value32, old_value32;
u8 index;
acpi_status status;
ACPI_FUNCTION_NAME(hw_write);
/* Validate contents of the GAS register */
status = acpi_hw_validate_register(reg, 32, &address);
if (ACPI_FAILURE(status)) {
return (status);
}
/* Convert access_width into number of bits based */
access_width = acpi_hw_get_access_bit_width(reg, 32);
bit_width = reg->bit_offset + reg->bit_width;
bit_offset = reg->bit_offset;
/*
* Two address spaces supported: Memory or IO. PCI_Config is
* not supported here because the GAS structure is insufficient
*/
index = 0;
while (bit_width) {
/*
* Use offset style bit reads because "Index * AccessWidth" is
* ensured to be less than 32-bits by acpi_hw_validate_register().
*/
new_value32 = ACPI_GET_BITS(&value, index * access_width,
ACPI_MASK_BITS_ABOVE_32
(access_width));
if (bit_offset >= access_width) {
bit_offset -= access_width;
} else {
/*
* Use offset style bit masks because access_width is ensured
* to be less than 32-bits by acpi_hw_validate_register() and
* bit_offset/bit_width is less than access_width here.
*/
if (bit_offset) {
new_value32 &= ACPI_MASK_BITS_BELOW(bit_offset);
}
if (bit_width < access_width) {
new_value32 &= ACPI_MASK_BITS_ABOVE(bit_width);
}
if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) {
if (bit_offset || bit_width < access_width) {
/*
* Read old values in order not to modify the bits that
* are beyond the register bit_width/bit_offset setting.
*/
status =
acpi_os_read_memory((acpi_physical_address)
address +
index *
ACPI_DIV_8
(access_width),
&value64,
access_width);
old_value32 = (u32)value64;
/*
* Use offset style bit masks because access_width is
* ensured to be less than 32-bits by
* acpi_hw_validate_register() and bit_offset/bit_width is
* less than access_width here.
*/
if (bit_offset) {
old_value32 &=
ACPI_MASK_BITS_ABOVE
(bit_offset);
bit_offset = 0;
}
if (bit_width < access_width) {
old_value32 &=
ACPI_MASK_BITS_BELOW
(bit_width);
}
new_value32 |= old_value32;
}
value64 = (u64)new_value32;
status =
acpi_os_write_memory((acpi_physical_address)
address +
index *
ACPI_DIV_8
(access_width),
value64, access_width);
} else { /* ACPI_ADR_SPACE_SYSTEM_IO, validated earlier */
if (bit_offset || bit_width < access_width) {
/*
* Read old values in order not to modify the bits that
* are beyond the register bit_width/bit_offset setting.
*/
status =
acpi_hw_read_port((acpi_io_address)
address +
index *
ACPI_DIV_8
(access_width),
&old_value32,
access_width);
/*
* Use offset style bit masks because access_width is
* ensured to be less than 32-bits by
* acpi_hw_validate_register() and bit_offset/bit_width is
* less than access_width here.
*/
if (bit_offset) {
old_value32 &=
ACPI_MASK_BITS_ABOVE
(bit_offset);
bit_offset = 0;
}
if (bit_width < access_width) {
old_value32 &=
ACPI_MASK_BITS_BELOW
(bit_width);
}
new_value32 |= old_value32;
}
status = acpi_hw_write_port((acpi_io_address)
address +
index *
ACPI_DIV_8
(access_width),
new_value32,
access_width);
}
}
/*
* Index * access_width is ensured to be less than 32-bits by
* acpi_hw_validate_register().
*/
bit_width -=
bit_width > access_width ? access_width : bit_width;
index++;
}
ACPI_DEBUG_PRINT((ACPI_DB_IO,
"Wrote: %8.8X width %2d to %8.8X%8.8X (%s)\n",
value, access_width, ACPI_FORMAT_UINT64(address),
acpi_ut_get_region_name(reg->space_id)));
return (status);
}
#if (!ACPI_REDUCED_HARDWARE)
/*******************************************************************************
*
* FUNCTION: acpi_hw_clear_acpi_status
*
* PARAMETERS: None
*
* RETURN: Status
*
* DESCRIPTION: Clears all fixed and general purpose status bits
*
******************************************************************************/
acpi_status acpi_hw_clear_acpi_status(void)
{
acpi_status status;
acpi_cpu_flags lock_flags = 0;
ACPI_FUNCTION_TRACE(hw_clear_acpi_status);
ACPI_DEBUG_PRINT((ACPI_DB_IO, "About to write %04X to %8.8X%8.8X\n",
ACPI_BITMASK_ALL_FIXED_STATUS,
ACPI_FORMAT_UINT64(acpi_gbl_xpm1a_status.address)));
lock_flags = acpi_os_acquire_lock(acpi_gbl_hardware_lock);
/* Clear the fixed events in PM1 A/B */
status = acpi_hw_register_write(ACPI_REGISTER_PM1_STATUS,
ACPI_BITMASK_ALL_FIXED_STATUS);
acpi_os_release_lock(acpi_gbl_hardware_lock, lock_flags);
if (ACPI_FAILURE(status)) {
goto exit;
}
/* Clear the GPE Bits in all GPE registers in all GPE blocks */
status = acpi_ev_walk_gpe_list(acpi_hw_clear_gpe_block, NULL);
exit:
return_ACPI_STATUS(status);
}
/*******************************************************************************
*
* FUNCTION: acpi_hw_get_bit_register_info
*
* PARAMETERS: register_id - Index of ACPI Register to access
*
* RETURN: The bitmask to be used when accessing the register
*
* DESCRIPTION: Map register_id into a register bitmask.
*
******************************************************************************/
struct acpi_bit_register_info *acpi_hw_get_bit_register_info(u32 register_id)
{
ACPI_FUNCTION_ENTRY();
if (register_id > ACPI_BITREG_MAX) {
ACPI_ERROR((AE_INFO, "Invalid BitRegister ID: 0x%X",
register_id));
return (NULL);
}
return (&acpi_gbl_bit_register_info[register_id]);
}
/******************************************************************************
*
* FUNCTION: acpi_hw_write_pm1_control
*
* PARAMETERS: pm1a_control - Value to be written to PM1A control
* pm1b_control - 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 acpi_hw_write_pm1_control(u32 pm1a_control, u32 pm1b_control)
{
acpi_status status;
ACPI_FUNCTION_TRACE(hw_write_pm1_control);
status =
acpi_hw_write(pm1a_control, &acpi_gbl_FADT.xpm1a_control_block);
if (ACPI_FAILURE(status)) {
return_ACPI_STATUS(status);
}
if (acpi_gbl_FADT.xpm1b_control_block.address) {
status =
acpi_hw_write(pm1b_control,
&acpi_gbl_FADT.xpm1b_control_block);
}
return_ACPI_STATUS(status);
}
/******************************************************************************
*
* FUNCTION: acpi_hw_register_read
*
* PARAMETERS: register_id - ACPI Register ID
* return_value - Where the register value is returned
*
* RETURN: Status and the value read.
*
* DESCRIPTION: Read from the specified ACPI register
*
******************************************************************************/
acpi_status acpi_hw_register_read(u32 register_id, u32 *return_value)
{
u32 value = 0;
acpi_status status;
ACPI_FUNCTION_TRACE(hw_register_read);
switch (register_id) {
case ACPI_REGISTER_PM1_STATUS: /* PM1 A/B: 16-bit access each */
status = acpi_hw_read_multiple(&value,
&acpi_gbl_xpm1a_status,
&acpi_gbl_xpm1b_status);
break;
case ACPI_REGISTER_PM1_ENABLE: /* PM1 A/B: 16-bit access each */
status = acpi_hw_read_multiple(&value,
&acpi_gbl_xpm1a_enable,
&acpi_gbl_xpm1b_enable);
break;
case ACPI_REGISTER_PM1_CONTROL: /* PM1 A/B: 16-bit access each */
status = acpi_hw_read_multiple(&value,
&acpi_gbl_FADT.
xpm1a_control_block,
&acpi_gbl_FADT.
xpm1b_control_block);
/*
* 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 =
acpi_hw_read(&value, &acpi_gbl_FADT.xpm2_control_block);
break;
case ACPI_REGISTER_PM_TIMER: /* 32-bit access */
status = acpi_hw_read(&value, &acpi_gbl_FADT.xpm_timer_block);
break;
case ACPI_REGISTER_SMI_COMMAND_BLOCK: /* 8-bit access */
status =
acpi_hw_read_port(acpi_gbl_FADT.smi_command, &value, 8);
break;
default:
ACPI_ERROR((AE_INFO, "Unknown Register ID: 0x%X", register_id));
status = AE_BAD_PARAMETER;
break;
}
if (ACPI_SUCCESS(status)) {
*return_value = value;
}
return_ACPI_STATUS(status);
}
/******************************************************************************
*
* FUNCTION: acpi_hw_register_write
*
* PARAMETERS: register_id - 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 acpi_hw_register_write(u32 register_id, u32 value)
{
acpi_status status;
u32 read_value;
ACPI_FUNCTION_TRACE(hw_register_write);
switch (register_id) {
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 = acpi_hw_write_multiple(value,
&acpi_gbl_xpm1a_status,
&acpi_gbl_xpm1b_status);
break;
case ACPI_REGISTER_PM1_ENABLE: /* PM1 A/B: 16-bit access each */
status = acpi_hw_write_multiple(value,
&acpi_gbl_xpm1a_enable,
&acpi_gbl_xpm1b_enable);
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 = acpi_hw_read_multiple(&read_value,
&acpi_gbl_FADT.
xpm1a_control_block,
&acpi_gbl_FADT.
xpm1b_control_block);
if (ACPI_FAILURE(status)) {
goto exit;
}
/* Insert the bits to be preserved */
ACPI_INSERT_BITS(value, ACPI_PM1_CONTROL_PRESERVED_BITS,
read_value);
/* Now we can write the data */
status = acpi_hw_write_multiple(value,
&acpi_gbl_FADT.
xpm1a_control_block,
&acpi_gbl_FADT.
xpm1b_control_block);
break;
case ACPI_REGISTER_PM2_CONTROL: /* 8-bit access */
/*
* For control registers, all reserved bits must be preserved,
* as per the ACPI spec.
*/
status =
acpi_hw_read(&read_value,
&acpi_gbl_FADT.xpm2_control_block);
if (ACPI_FAILURE(status)) {
goto exit;
}
/* Insert the bits to be preserved */
ACPI_INSERT_BITS(value, ACPI_PM2_CONTROL_PRESERVED_BITS,
read_value);
status =
acpi_hw_write(value, &acpi_gbl_FADT.xpm2_control_block);
break;
case ACPI_REGISTER_PM_TIMER: /* 32-bit access */
status = acpi_hw_write(value, &acpi_gbl_FADT.xpm_timer_block);
break;
case ACPI_REGISTER_SMI_COMMAND_BLOCK: /* 8-bit access */
/* SMI_CMD is currently always in IO space */
status =
acpi_hw_write_port(acpi_gbl_FADT.smi_command, value, 8);
break;
default:
ACPI_ERROR((AE_INFO, "Unknown Register ID: 0x%X", register_id));
status = AE_BAD_PARAMETER;
break;
}
exit:
return_ACPI_STATUS(status);
}
/******************************************************************************
*
* FUNCTION: acpi_hw_read_multiple
*
* PARAMETERS: value - Where the register value is returned
* register_a - First ACPI register (required)
* register_b - Second ACPI register (optional)
*
* RETURN: Status
*
* DESCRIPTION: Read from the specified two-part ACPI register (such as PM1 A/B)
*
******************************************************************************/
static acpi_status
acpi_hw_read_multiple(u32 *value,
struct acpi_generic_address *register_a,
struct acpi_generic_address *register_b)
{
u32 value_a = 0;
u32 value_b = 0;
acpi_status status;
/* The first register is always required */
status = acpi_hw_read(&value_a, register_a);
if (ACPI_FAILURE(status)) {
return (status);
}
/* Second register is optional */
if (register_b->address) {
status = acpi_hw_read(&value_b, register_b);
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 = (value_a | value_b);
return (AE_OK);
}
/******************************************************************************
*
* FUNCTION: acpi_hw_write_multiple
*
* PARAMETERS: value - The value to write
* register_a - First ACPI register (required)
* register_b - Second ACPI register (optional)
*
* RETURN: Status
*
* DESCRIPTION: Write to the specified two-part ACPI register (such as PM1 A/B)
*
******************************************************************************/
static acpi_status
acpi_hw_write_multiple(u32 value,
struct acpi_generic_address *register_a,
struct acpi_generic_address *register_b)
{
acpi_status status;
/* The first register is always required */
status = acpi_hw_write(value, register_a);
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 (register_b->address) {
status = acpi_hw_write(value, register_b);
}
return (status);
}
#endif /* !ACPI_REDUCED_HARDWARE */
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