From: Len Brown <len.brown@xxxxxxxxx> 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> --- arch/x86/include/asm/msr-index.h | 4 ++++ drivers/idle/intel_idle.c | 20 ++++++++++++++++++++ 2 files changed, 24 insertions(+), 0 deletions(-) diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h index 4d0dfa0..b75eeab 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 7acb32e..88998ac 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: " @@ -85,6 +86,12 @@ 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 int 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. * If this flag is set, SW flushes the TLB, so even if the @@ -285,6 +292,16 @@ static struct notifier_block __cpuinitdata setup_broadcast_notifier = { .notifier_call = setup_broadcast_cpuhp_notify, }; +static long auto_demotion_disable(void *enable_bits) +{ + unsigned long long msr_bits; + + rdmsrl(MSR_NHM_SNB_PKG_CST_CFG_CTL, msr_bits); + msr_bits &= ~((unsigned long long)enable_bits); + wrmsrl(MSR_NHM_SNB_PKG_CST_CFG_CTL, msr_bits); + return 0; +} + /* * intel_idle_probe() */ @@ -328,6 +345,7 @@ 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 */ @@ -440,6 +458,8 @@ static int intel_idle_cpuidle_devices_init(void) return -EIO; } } + if (auto_demotion_disable_flags) + smp_call_function(auto_demotion_disable, (void *)auto_demotion_disable_flags, 1); return 0; } -- 1.7.4.1.26.g00e6e -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
