diff options
| -rw-r--r-- | drivers/acpi/acpica/aclocal.h | 4 | ||||
| -rw-r--r-- | drivers/acpi/acpica/hwregs.c | 7 |
2 files changed, 11 insertions, 0 deletions
diff --git a/drivers/acpi/acpica/aclocal.h b/drivers/acpi/acpica/aclocal.h index 42ef0cbf70f8..772ee5c4ccca 100644 --- a/drivers/acpi/acpica/aclocal.h +++ b/drivers/acpi/acpica/aclocal.h @@ -781,6 +781,10 @@ struct acpi_bit_register_info { */ #define ACPI_PM1_STATUS_PRESERVED_BITS 0x0800 /* Bit 11 */ +/* Write-only bits must be zeroed by software */ + +#define ACPI_PM1_CONTROL_WRITEONLY_BITS 0x2004 /* Bits 13, 2 */ + /* For control registers, both ignored and reserved bits must be preserved */ #define ACPI_PM1_CONTROL_IGNORED_BITS 0x0201 /* Bits 9, 0(SCI_EN) */ diff --git a/drivers/acpi/acpica/hwregs.c b/drivers/acpi/acpica/hwregs.c index f8ee0a7fd44d..7b2fb602b5cb 100644 --- a/drivers/acpi/acpica/hwregs.c +++ b/drivers/acpi/acpica/hwregs.c @@ -207,6 +207,13 @@ acpi_hw_register_read(u32 register_id, u32 * return_value) 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 */ |