Get C1 info from acpi table and pass it to Xen. It is partially backported from
below kernel commit:
commit 991528d7348667924176f3e29addea0675298944
Author: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Date: Mon Sep 25 16:28:13 2006 -0700
ACPI: Processor native C-states using MWAIT
Intel processors starting with the Core Duo support
support processor native C-state using the MWAIT instruction.
Refer: Intel Architecture Software Developer''s Manual
http://www.intel.com/design/Pentium4/manuals/253668.htm
Platform firmware exports the support for Native C-state to OS using
ACPI _PDC and _CST methods.
Refer: Intel Processor Vendor-Specific ACPI: Interface Specification
http://www.intel.com/technology/iapc/acpi/downloads/302223.htm
With Processor Native C-state, we use ''MWAIT'' instruction
on the processor
to enter different C-states (C1, C2, C3). We won''t use the special
IO
ports to enter C-state and no SMM mode etc required to enter C-state.
Overall this will mean better C-state support.
One major advantage of using MWAIT for all C-states is, with this and
"treat interrupt as break event" feature of MWAIT, we can now get
accurate
timing for the time spent in C1, C2, .. states.
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Wei Gang <gang.wei@intel.com>
diff -r a71e987e15fc drivers/acpi/processor_idle.c
--- a/drivers/acpi/processor_idle.c Wed Oct 29 10:12:14 2008 +0000
+++ b/drivers/acpi/processor_idle.c Thu Oct 30 11:31:13 2008 +0800
@@ -654,7 +654,7 @@ static int acpi_processor_get_power_info
if (nocst)
return -ENODEV;
- current_count = 1;
+ current_count = 0;
/* Zero initialize C2 onwards and prepare for fresh CST lookup */
for (i = 2; i < ACPI_PROCESSOR_MAX_POWER; i++)
@@ -728,13 +728,17 @@ static int acpi_processor_get_power_info
cx.type = obj->integer.value;
+ /*
+ * Some buggy BIOSes won''t list C1 in _CST -
+ * Let acpi_processor_get_power_info_default() handle them later
+ */
+ if (i == 1 && cx.type != ACPI_STATE_C1)
+ current_count++;
+
/* Following check doesn''t apply to external control case */
if (!processor_pm_external() &&
(cx.type != ACPI_STATE_C1) &&
(reg->space_id != ACPI_ADR_SPACE_SYSTEM_IO))
- continue;
-
- if ((cx.type < ACPI_STATE_C2) || (cx.type > ACPI_STATE_C3))
continue;
obj = (union acpi_object *)&(element->package.elements[2]);
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