From 14796fca2bd22acc73dd0887248d003b0f441d08 Mon Sep 17 00:00:00 2001 From: Len Brown Date: Tue, 18 Jan 2011 20:48:27 -0500 Subject: 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 --- drivers/idle/intel_idle.c | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) (limited to 'drivers/idle') 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 #include #include +#include #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; } -- cgit v1.2.1