ACPI: skip checking BM_STS if the BIOS doesn't ask for it

[net-next-2.6.git] / arch / x86 / kernel / acpi / cstate.c

diff --git a/arch/x86/kernel/acpi/cstate.c b/arch/x86/kernel/acpi/cstate.c
index 2e837f5080fe56d3ad0c87d308564cf157147624..fb7a5f052e2b8766d11115e3f7fc174fadf6ac2f 100644 (file)
--- a/arch/x86/kernel/acpi/cstate.c
+++ b/arch/x86/kernel/acpi/cstate.c
@@ -145,6 +145,15 @@ int acpi_processor_ffh_cstate_probe(unsigned int cpu,
                percpu_entry->states[cx->index].eax = cx->address;
                percpu_entry->states[cx->index].ecx = MWAIT_ECX_INTERRUPT_BREAK;
        }
+
+       /*
+        * For _CST FFH on Intel, if GAS.access_size bit 1 is cleared,
+        * then we should skip checking BM_STS for this C-state.
+        * ref: "Intel Processor Vendor-Specific ACPI Interface Specification"
+        */
+       if ((c->x86_vendor == X86_VENDOR_INTEL) && !(reg->access_size & 0x2))
+               cx->bm_sts_skip = 1;
+
        return retval;
 }
 EXPORT_SYMBOL_GPL(acpi_processor_ffh_cstate_probe);