[18/55] intel_idle: disable NHM/WSM HW C-state auto-demotion
From: Greg KH
Date: Fri Mar 25 2011 - 20:26:00 EST
2.6.37-stable review patch. If anyone has any objections, please let us know.
------------------
From: Len Brown <len.brown@xxxxxxxxx>
commit 14796fca2bd22acc73dd0887248d003b0f441d08 upstream.
Hardware C-state auto-demotion is a mechanism where the HW overrides
the OS C-state request, instead demoting to a shallower state,
which is less expensive, but saves less power.
Modern Linux should generally get exactly the states it requests.
In particular, when a CPU is taken off-line, it must not be demoted, else
it can prevent the entire package from reaching deep C-states.
https://bugzilla.kernel.org/show_bug.cgi?id=25252
Signed-off-by: Len Brown <len.brown@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>
---
arch/x86/include/asm/msr-index.h | 4 ++++
drivers/idle/intel_idle.c | 20 ++++++++++++++++++++
2 files changed, 24 insertions(+)
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -36,6 +36,10 @@
#define MSR_IA32_PERFCTR1 0x000000c2
#define MSR_FSB_FREQ 0x000000cd
+#define MSR_NHM_SNB_PKG_CST_CFG_CTL 0x000000e2
+#define NHM_C3_AUTO_DEMOTE (1UL << 25)
+#define NHM_C1_AUTO_DEMOTE (1UL << 26)
+
#define MSR_MTRRcap 0x000000fe
#define MSR_IA32_BBL_CR_CTL 0x00000119
--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -62,6 +62,7 @@
#include <linux/notifier.h>
#include <linux/cpu.h>
#include <asm/mwait.h>
+#include <asm/msr.h>
#define INTEL_IDLE_VERSION "0.4"
#define PREFIX "intel_idle: "
@@ -85,6 +86,12 @@ static int intel_idle(struct cpuidle_dev
static struct cpuidle_state *cpuidle_state_table;
/*
+ * Hardware C-state auto-demotion may not always be optimal.
+ * Indicate which enable bits to clear here.
+ */
+static unsigned long long auto_demotion_disable_flags;
+
+/*
* States are indexed by the cstate number,
* which is also the index into the MWAIT hint array.
* Thus C0 is a dummy.
@@ -276,6 +283,15 @@ static struct notifier_block setup_broad
.notifier_call = setup_broadcast_cpuhp_notify,
};
+static void auto_demotion_disable(void *dummy)
+{
+ unsigned long long msr_bits;
+
+ rdmsrl(MSR_NHM_SNB_PKG_CST_CFG_CTL, msr_bits);
+ msr_bits &= ~auto_demotion_disable_flags;
+ wrmsrl(MSR_NHM_SNB_PKG_CST_CFG_CTL, msr_bits);
+}
+
/*
* intel_idle_probe()
*/
@@ -319,6 +335,8 @@ static int intel_idle_probe(void)
case 0x25: /* Westmere */
case 0x2C: /* Westmere */
cpuidle_state_table = nehalem_cstates;
+ auto_demotion_disable_flags =
+ (NHM_C1_AUTO_DEMOTE | NHM_C3_AUTO_DEMOTE);
break;
case 0x1C: /* 28 - Atom Processor */
@@ -431,6 +449,8 @@ static int intel_idle_cpuidle_devices_in
return -EIO;
}
}
+ if (auto_demotion_disable_flags)
+ smp_call_function(auto_demotion_disable, NULL, 1);
return 0;
}
--
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