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ACPI: Disable the C2C3_FFH access mode HW has no MWAIT support

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991528d734
(ACPI: Processor native C-states using MWAIT)
started passing C2C3_FFH to _PDC to tell the BIOS
that Linux supports MWAIT for deep C-states.

However, we should first double check with the hardware
that it actually supports MWAIT before potentially exposing
a BIOS bug of an MWAIT _CST on HW that doesn't support MWAIT.

Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
Signed-off-by: Li Shaohua <shaohua.li@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
This commit is contained in:
Zhao Yakui 2008-06-17 14:39:59 +08:00 committed by Andi Kleen
parent 71b58cbb0c
commit 5b53496a5a
1 changed files with 6 additions and 0 deletions
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6
arch/x86/kernel/acpi/processor.c
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@ -56,6 +56,12 @@ static void init_intel_pdc(struct acpi_processor *pr, struct cpuinfo_x86 *c)
if (cpu_has(c, X86_FEATURE_ACPI))
buf[2] |= ACPI_PDC_T_FFH;
/*
* If mwait/monitor is unsupported, C2/C3_FFH will be disabled
*/
if (!cpu_has(c, X86_FEATURE_MWAIT))
buf[2] &= ~(ACPI_PDC_C_C2C3_FFH);
obj->type = ACPI_TYPE_BUFFER;
obj->buffer.length = 12;
obj->buffer.pointer = (u8 *) buf;