Offline CPUs can save power by going into deepest cstate, subcstate instead of hlt loop. Signed-off-by: Venkatesh Pallipadi --- arch/x86/kernel/acpi/cstate.c | 51 +++++++++++++++++++++++++++++++++++++++++ 1 files changed, 51 insertions(+), 0 deletions(-) diff --git a/arch/x86/kernel/acpi/cstate.c b/arch/x86/kernel/acpi/cstate.c index bbbe4bb..5b0988a 100644 --- a/arch/x86/kernel/acpi/cstate.c +++ b/arch/x86/kernel/acpi/cstate.c @@ -150,6 +150,54 @@ void acpi_processor_ffh_cstate_enter(struct acpi_processor_cx *cx) } EXPORT_SYMBOL_GPL(acpi_processor_ffh_cstate_enter); +static unsigned long mwait_play_dead_eax; + +static void mwait_play_dead(void) +{ + if (boot_cpu_data.x86 >= 4) + wbinvd(); + + while (1) { + __monitor((void *)¤t_thread_info()->flags, 0, 0); + smp_mb(); + __mwait(mwait_play_dead_eax, 0); + } +} + +static void mwait_play_dead_init(void *unused) +{ + unsigned int eax, ebx, ecx, edx; + unsigned int highest_cstate = 0; + unsigned int highest_subcstate = 0; + int i; + + if (!boot_cpu_has(X86_FEATURE_MWAIT)) + return; + + if (boot_cpu_data.cpuid_level < CPUID_MWAIT_LEAF) + return; + + pm_play_dead = mwait_play_dead; + + cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &edx); + /* + * mwait_play_dead_eax will be 0 if EDX enumeration is not valid. + * Initialized below to cstate, sub_cstate value when EDX is valid. + */ + if (!(ecx & 0x1)) + return; + + edx >>= MWAIT_SUBSTATE_SIZE; + for (i = 0; i < 7 && edx; i++, edx >>= MWAIT_SUBSTATE_SIZE) { + if (edx & MWAIT_SUBSTATE_MASK) { + highest_cstate = i; + highest_subcstate = edx & MWAIT_SUBSTATE_MASK; + } + } + mwait_play_dead_eax = (highest_cstate << MWAIT_SUBSTATE_SIZE) | + (highest_subcstate - 1); +} + static int __init ffh_cstate_init(void) { struct cpuinfo_x86 *c = &boot_cpu_data; @@ -157,6 +205,9 @@ static int __init ffh_cstate_init(void) return -1; cpu_cstate_entry = alloc_percpu(struct cstate_entry); + + smp_call_function_single(0, mwait_play_dead_init, NULL, 1); + return 0; } -- 1.6.0.6 -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/