Adding upstream version 4.19.249.upstream/4.19.249

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 802 insertions, 0 deletions

diff --git a/drivers/acpi/acpica/hwregs.c b/drivers/acpi/acpica/hwregs.c
new file mode 100644
index 000000000..69603ba52
--- /dev/null
+++ b/drivers/acpi/acpica/hwregs.c
@@ -0,0 +1,802 @@
+// SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0
+/*******************************************************************************
+ *
+ * Module Name: hwregs - Read/write access functions for the various ACPI
+ *                       control and status registers.
+ *
+ ******************************************************************************/
+
+#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(u64 address,
+			     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:  address             - GAS register address
+ *              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(u64 address,
+			     struct acpi_generic_address *reg, u8 max_bit_width)
+{
+	u8 access_bit_width;
+
+	/*
+	 * GAS format "register", used by FADT:
+	 *  1. Detected if bit_offset is 0 and bit_width is 8/16/32/64;
+	 *  2. access_size field is ignored and bit_width field is used for
+	 *     determining the boundary of the IO accesses.
+	 * GAS format "region", used by APEI registers:
+	 *  1. Detected if bit_offset is not 0 or bit_width is not 8/16/32/64;
+	 *  2. access_size field is used for determining the boundary of the
+	 *     IO accesses;
+	 *  3. bit_offset/bit_width fields are used to describe the "region".
+	 *
+	 * Note: This algorithm assumes that the "Address" fields should always
+	 *       contain aligned values.
+	 */
+	if (!reg->bit_offset && reg->bit_width &&
+	    ACPI_IS_POWER_OF_TWO(reg->bit_width) &&
+	    ACPI_IS_ALIGNED(reg->bit_width, 8)) {
+		access_bit_width = reg->bit_width;
+	} else if (reg->access_width) {
+		access_bit_width = ACPI_ACCESS_BIT_WIDTH(reg->access_width);
+	} else {
+		access_bit_width =
+		    ACPI_ROUND_UP_POWER_OF_TWO_8(reg->bit_offset +
+						 reg->bit_width);
+		if (access_bit_width <= 8) {
+			access_bit_width = 8;
+		} else {
+			while (!ACPI_IS_ALIGNED(address, access_bit_width >> 3)) {
+				access_bit_width >>= 1;
+			}
+		}
+	}
+
+	/* Maximum IO port access bit width is 32 */
+
+	if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_IO) {
+		max_bit_width = 32;
+	}
+
+	/*
+	 * Return access width according to the requested maximum access bit width,
+	 * as the caller should know the format of the register and may enforce
+	 * a 32-bit accesses.
+	 */
+	if (access_bit_width < max_bit_width) {
+		return (access_bit_width);
+	}
+	return (max_bit_width);
+}
+
+/******************************************************************************
+ *
+ * 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(*address, 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 64-bit max
+ *              version of acpi_read.
+ *
+ * LIMITATIONS: <These limitations also apply to acpi_hw_write>
+ *      space_ID must be system_memory or system_IO.
+ *
+ ******************************************************************************/
+
+acpi_status acpi_hw_read(u64 *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, 64, &address);
+	if (ACPI_FAILURE(status)) {
+		return (status);
+	}
+
+	/*
+	 * Initialize entire 64-bit return value to zero, convert access_width
+	 * into number of bits based
+	 */
+	*value = 0;
+	access_width = acpi_hw_get_access_bit_width(address, reg, 64);
+	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) {
+			value64 = 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);
+			} 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);
+				value64 = (u64)value32;
+			}
+		}
+
+		/*
+		 * Use offset style bit writes because "Index * AccessWidth" is
+		 * ensured to be less than 64-bits by acpi_hw_validate_register().
+		 */
+		ACPI_SET_BITS(value, index * access_width,
+			      ACPI_MASK_BITS_ABOVE_64(access_width), value64);
+
+		bit_width -=
+		    bit_width > access_width ? access_width : bit_width;
+		index++;
+	}
+
+	ACPI_DEBUG_PRINT((ACPI_DB_IO,
+			  "Read:  %8.8X%8.8X width %2d from %8.8X%8.8X (%s)\n",
+			  ACPI_FORMAT_UINT64(*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 64-bit max
+ *              version of acpi_write.
+ *
+ ******************************************************************************/
+
+acpi_status acpi_hw_write(u64 value, struct acpi_generic_address *reg)
+{
+	u64 address;
+	u8 access_width;
+	u32 bit_width;
+	u8 bit_offset;
+	u64 value64;
+	u8 index;
+	acpi_status status;
+
+	ACPI_FUNCTION_NAME(hw_write);
+
+	/* Validate contents of the GAS register */
+
+	status = acpi_hw_validate_register(reg, 64, &address);
+	if (ACPI_FAILURE(status)) {
+		return (status);
+	}
+
+	/* Convert access_width into number of bits based */
+
+	access_width = acpi_hw_get_access_bit_width(address, reg, 64);
+	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 64-bits by acpi_hw_validate_register().
+		 */
+		value64 = ACPI_GET_BITS(&value, index * access_width,
+					ACPI_MASK_BITS_ABOVE_64(access_width));
+
+		if (bit_offset >= access_width) {
+			bit_offset -= access_width;
+		} else {
+			if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) {
+				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 */
+
+				status = acpi_hw_write_port((acpi_io_address)
+							    address +
+							    index *
+							    ACPI_DIV_8
+							    (access_width),
+							    (u32)value64,
+							    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%8.8X width %2d   to %8.8X%8.8X (%s)\n",
+			  ACPI_FORMAT_UINT64(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_raw_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_raw_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;
+	u64 value64;
+	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(&value64, &acpi_gbl_FADT.xpm2_control_block);
+		if (ACPI_SUCCESS(status)) {
+			value = (u32)value64;
+		}
+		break;
+
+	case ACPI_REGISTER_PM_TIMER:	/* 32-bit access */
+
+		status = acpi_hw_read(&value64, &acpi_gbl_FADT.xpm_timer_block);
+		if (ACPI_SUCCESS(status)) {
+			value = (u32)value64;
+		}
+
+		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 = (u32)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;
+	u64 read_value64;
+
+	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_value64,
+				 &acpi_gbl_FADT.xpm2_control_block);
+		if (ACPI_FAILURE(status)) {
+			goto exit;
+		}
+		read_value = (u32)read_value64;
+
+		/* 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;
+	u64 value64;
+	acpi_status status;
+
+	/* The first register is always required */
+
+	status = acpi_hw_read(&value64, register_a);
+	if (ACPI_FAILURE(status)) {
+		return (status);
+	}
+	value_a = (u32)value64;
+
+	/* Second register is optional */
+
+	if (register_b->address) {
+		status = acpi_hw_read(&value64, register_b);
+		if (ACPI_FAILURE(status)) {
+			return (status);
+		}
+		value_b = (u32)value64;
+	}
+
+	/*
+	 * 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 */