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. But because MWAIT is unsupported on some laptops,
the different power states will be returned by the _CST object.
Maybe 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
http://bugzilla.kernel.org/show_bug.cgi?id=10807
Signed-off-by: Zhao Yakui <yakui.zhao@xxxxxxxxx>
Signed-off-by: Li Shaohua <shaohua.li@xxxxxxxxx>
---
arch/x86/kernel/acpi/processor.c | 5 +++++
1 file changed, 5 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
@@ -43,6 +43,11 @@ static void init_intel_pdc(struct acpi_p
buf[0] = ACPI_PDC_REVISION_ID;
buf[1] = 1;
buf[2] = ACPI_PDC_C_CAPABILITY_SMP;
+ /*
+ * 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;
/*
* The default of PDC_SMP_T_SWCOORD bit is set for intel x86 cpu so
--
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