From aefc7f9a0220a40beff9b6b3b320cbeae128d0e3 Mon Sep 17 00:00:00 2001 From: Bob Moore Date: Wed, 18 Feb 2009 14:26:02 +0800 Subject: ACPICA: For PM1B registers, do not shift value read or written The PM1B registers are mirrors of the PM1A registers with different bits actually implemented. From 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" Signed-off-by: Bob Moore Signed-off-by: Lin Ming Signed-off-by: Len Brown --- drivers/acpi/acpica/hwregs.c | 33 ++++++++++++++++++++++++--------- 1 file changed, 24 insertions(+), 9 deletions(-) (limited to 'drivers/acpi/acpica/hwregs.c') diff --git a/drivers/acpi/acpica/hwregs.c b/drivers/acpi/acpica/hwregs.c index 9c8162128c2..5a64e577975 100644 --- a/drivers/acpi/acpica/hwregs.c +++ b/drivers/acpi/acpica/hwregs.c @@ -372,9 +372,17 @@ acpi_hw_read_multiple(u32 *value, } } - /* Shift the B bits above the A bits */ - - *value = value_a | (value_b << register_a->bit_width); + /* + * 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); } @@ -406,13 +414,20 @@ acpi_hw_write_multiple(u32 value, return (status); } - /* Second register is optional */ - + /* + * 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) { - - /* Normalize the B bits before write */ - - status = acpi_write(value >> register_a->bit_width, register_b); + status = acpi_write(value, register_b); } return (status); -- cgit v1.2.3-70-g09d2