From 14796fca2bd22acc73dd0887248d003b0f441d08 Mon Sep 17 00:00:00 2001
From: Len Brown <len.brown@intel.com>
Date: Tue, 18 Jan 2011 20:48:27 -0500
Subject: [PATCH 1/2] intel_idle: disable NHM/WSM HW C-state auto-demotion
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@intel.com>
---
arch/x86/include/asm/msr-index.h | 4 ++++
drivers/idle/intel_idle.c | 20 ++++++++++++++++++++
2 files changed, 24 insertions(+)
diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index 4d0dfa0d998e..b75eeab2b1ea 100644
--- 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
diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
index 1fa091e05690..32b25bcaf865 100644
--- 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: "
@@ -84,6 +85,12 @@ static int intel_idle(struct cpuidle_device *dev, struct cpuidle_state *state);
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;
+
/*
* Set this flag for states where the HW flushes the TLB for us
* and so we don't need cross-calls to keep it consistent.
@@ -281,6 +288,15 @@ static struct notifier_block setup_broadcast_notifier = {
.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()
*/
@@ -324,6 +340,8 @@ 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 */
@@ -436,6 +454,8 @@ static int intel_idle_cpuidle_devices_init(void)
return -EIO;
}
}
+ if (auto_demotion_disable_flags)
+ smp_call_function(auto_demotion_disable, NULL, 1);
return 0;
}
From bfb53ccf1c734b1907df7189eef4c08489827951 Mon Sep 17 00:00:00 2001
From: Len Brown <len.brown@intel.com>
Date: Wed, 16 Feb 2011 01:32:48 -0500
Subject: [PATCH 2/2] intel_idle: disable Atom/Lincroft HW C-state
auto-demotion
Just as we had to disable auto-demotion for NHM/WSM,
we need to do the same for Atom (Lincroft version).
In particular, auto-demotion will prevent Lincroft
from entering the S0i3 idle power saving state.
https://bugzilla.kernel.org/show_bug.cgi?id=25252
Signed-off-by: Len Brown <len.brown@intel.com>
---
arch/x86/include/asm/msr-index.h | 1 +
drivers/idle/intel_idle.c | 4 ++++
2 files changed, 5 insertions(+)
diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index b75eeab2b1ea..43a18c77676d 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -39,6 +39,7 @@
#define MSR_NHM_SNB_PKG_CST_CFG_CTL 0x000000e2
#define NHM_C3_AUTO_DEMOTE (1UL << 25)
#define NHM_C1_AUTO_DEMOTE (1UL << 26)
+#define ATM_LNC_C6_AUTO_DEMOTE (1UL << 25)
#define MSR_MTRRcap 0x000000fe
#define MSR_IA32_BBL_CR_CTL 0x00000119
diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
index 32b25bcaf865..4a5c4a44ffb1 100644
--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -345,8 +345,12 @@ static int intel_idle_probe(void)
break;
case 0x1C: /* 28 - Atom Processor */
+ cpuidle_state_table = atom_cstates;
+ break;
+
case 0x26: /* 38 - Lincroft Atom Processor */
cpuidle_state_table = atom_cstates;
+ auto_demotion_disable_flags = ATM_LNC_C6_AUTO_DEMOTE;
break;
case 0x2A: /* SNB */