diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h index ada38e89f3b54b5a16900ee0117cd139978d0061..b18fdeadc17b7e223a8caa24d418647bc1fb1e9b 100644 --- a/arch/x86/include/asm/apic.h +++ b/arch/x86/include/asm/apic.h @@ -174,6 +174,7 @@ extern void lapic_assign_system_vectors(void); extern void lapic_assign_legacy_vector(unsigned int isairq, bool replace); extern void lapic_online(void); extern void lapic_offline(void); +extern bool apic_needs_pit(void); #else /* !CONFIG_X86_LOCAL_APIC */ static inline void lapic_shutdown(void) { } @@ -187,6 +188,7 @@ static inline void init_bsp_APIC(void) { } static inline void apic_intr_mode_init(void) { } static inline void lapic_assign_system_vectors(void) { } static inline void lapic_assign_legacy_vector(unsigned int i, bool r) { } +static inline bool apic_needs_pit(void) { return true; } #endif /* !CONFIG_X86_LOCAL_APIC */ #ifdef CONFIG_X86_X2APIC diff --git a/arch/x86/include/asm/time.h b/arch/x86/include/asm/time.h index cef818b16045f6b1d8e511133081b72173d52d8b..8ac563abb567b3f4254beb5b35214cd83e30da3e 100644 --- a/arch/x86/include/asm/time.h +++ b/arch/x86/include/asm/time.h @@ -7,6 +7,7 @@ extern void hpet_time_init(void); extern void time_init(void); +extern bool pit_timer_init(void); extern struct clock_event_device *global_clock_event; diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c index 569843f9cbcf4224dec4fcc7ffde88b9d48dcfaa..4703f927176f2f41393a82dc558940da8d8d3198 100644 --- a/arch/x86/kernel/apic/apic.c +++ b/arch/x86/kernel/apic/apic.c @@ -819,6 +819,33 @@ static int __init lapic_init_clockevent(void) return 0; } +bool __init apic_needs_pit(void) +{ + /* + * If the frequencies are not known, PIT is required for both TSC + * and apic timer calibration. + */ + if (!tsc_khz || !cpu_khz) + return true; + + /* Is there an APIC at all? */ + if (!boot_cpu_has(X86_FEATURE_APIC)) + return true; + + /* Deadline timer is based on TSC so no further PIT action required */ + if (boot_cpu_has(X86_FEATURE_TSC_DEADLINE_TIMER)) + return false; + + /* APIC timer disabled? */ + if (disable_apic_timer) + return true; + /* + * The APIC timer frequency is known already, no PIT calibration + * required. If unknown, let the PIT be initialized. + */ + return lapic_timer_period == 0; +} + static int __init calibrate_APIC_clock(void) { struct clock_event_device *levt = this_cpu_ptr(&lapic_events); diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c index fa3b85b222e315dc28269e0f2f435434ace1a7a2..0784aeb0356bc28269719ad7feeeded959517fbd 100644 --- a/arch/x86/kernel/apic/io_apic.c +++ b/arch/x86/kernel/apic/io_apic.c @@ -58,6 +58,7 @@ #include <asm/acpi.h> #include <asm/dma.h> #include <asm/timer.h> +#include <asm/time.h> #include <asm/i8259.h> #include <asm/setup.h> #include <asm/irq_remapping.h> @@ -2130,6 +2131,9 @@ static inline void __init check_timer(void) unsigned long flags; int no_pin1 = 0; + if (!global_clock_event) + return; + local_irq_save(flags); /* diff --git a/arch/x86/kernel/i8253.c b/arch/x86/kernel/i8253.c index 0d307a657abbb253d4679471bd1ac202279ff447..2b7999a1a50a83b07084e93903786e15479684b8 100644 --- a/arch/x86/kernel/i8253.c +++ b/arch/x86/kernel/i8253.c @@ -8,6 +8,7 @@ #include <linux/timex.h> #include <linux/i8253.h> +#include <asm/apic.h> #include <asm/hpet.h> #include <asm/time.h> #include <asm/smp.h> @@ -18,10 +19,32 @@ */ struct clock_event_device *global_clock_event; -void __init setup_pit_timer(void) +/* + * Modern chipsets can disable the PIT clock which makes it unusable. It + * would be possible to enable the clock but the registers are chipset + * specific and not discoverable. Avoid the whack a mole game. + * + * These platforms have discoverable TSC/CPU frequencies but this also + * requires to know the local APIC timer frequency as it normally is + * calibrated against the PIT interrupt. + */ +static bool __init use_pit(void) +{ + if (!IS_ENABLED(CONFIG_X86_TSC) || !boot_cpu_has(X86_FEATURE_TSC)) + return true; + + /* This also returns true when APIC is disabled */ + return apic_needs_pit(); +} + +bool __init pit_timer_init(void) { + if (!use_pit()) + return false; + clockevent_i8253_init(true); global_clock_event = &i8253_clockevent; + return true; } #ifndef CONFIG_X86_64 diff --git a/arch/x86/kernel/time.c b/arch/x86/kernel/time.c index fddaefc51fb6d7ead6630ec8bfedae9bcb94d582..548dc9aee252925b0f148e9178ff935084e27042 100644 --- a/arch/x86/kernel/time.c +++ b/arch/x86/kernel/time.c @@ -81,8 +81,11 @@ static void __init setup_default_timer_irq(void) /* Default timer init function */ void __init hpet_time_init(void) { - if (!hpet_enable()) - setup_pit_timer(); + if (!hpet_enable()) { + if (!pit_timer_init()) + return; + } + setup_default_timer_irq(); }