Subject: ACPI: Disable the C2C3_FFH access mode if MWAIT is unsupported
From: Zhao Yakui <yakui.zhao@xxxxxxxxx>
After the following commit is merged, C2C3_FFH mode will be enabled and
passed into the _PDC object. If the BIOS thinks that MWAIT is supported and
the CPU doesn't support MWAIT, the incorrect power states will be returned
by the _CST object. So it will be better to disable C2C3_FFH access mode
if MWAIT is unsupported.
commit 991528d7348667924176f3e29addea0675298944
Author: Venkatesh Pallipadi <venkatesh.pallipadi@xxxxxxxxx>
Date: Mon Sep 25 16:28:13 2006 -0700
ACPI: Processor native C-states using MWAIT
Signed-off-by: Zhao Yakui <yakui.zhao@xxxxxxxxx>
Signed-off-by: Li Shaohua <shaohua.li@xxxxxxxxx>
---
arch/x86/kernel/acpi/processor.c | 6 ++++++
1 file changed, 6 insertions(+)
Index: linux-2.6/arch/x86/kernel/acpi/processor.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/acpi/processor.c
+++ linux-2.6/arch/x86/kernel/acpi/processor.c
@@ -61,6 +61,12 @@ static void init_intel_pdc(struct acpi_p
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;
--
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