diff options
Diffstat (limited to 'payloads/libpayload/arch/x86/delay.c')
| -rw-r--r-- | payloads/libpayload/arch/x86/delay.c | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/payloads/libpayload/arch/x86/delay.c b/payloads/libpayload/arch/x86/delay.c index 541cf7a436..19931fbc04 100644 --- a/payloads/libpayload/arch/x86/delay.c +++ b/payloads/libpayload/arch/x86/delay.c @@ -28,6 +28,7 @@ */ #include <libpayload.h> +#include <arch/apic.h> /* The pause instruction can delay 10-140 CPU cycles, so avoid calling it when * getting close to finishing. Depending on the timer source, the timer can be @@ -35,12 +36,23 @@ * that the timer is running at the CPU frequency. */ #define PAUSE_THRESHOLD_TICKS 150 +/* Let's assume APIC interrupts take at least 100us */ +#define APIC_INTERRUPT_LATENCY_NS (100 * NSECS_PER_USEC) + + void arch_ndelay(uint64_t ns) { uint64_t delta = ns * timer_hz() / NSECS_PER_SEC; uint64_t pause_delta = 0; + uint64_t apic_us = 0; uint64_t start = timer_raw_value(); + if (ns > APIC_INTERRUPT_LATENCY_NS) + apic_us = (ns - APIC_INTERRUPT_LATENCY_NS) / NSECS_PER_USEC; + + if (IS_ENABLED(CONFIG_LP_ENABLE_APIC) && apic_initialized() && apic_us) + apic_delay(apic_us); + if (delta > PAUSE_THRESHOLD_TICKS) pause_delta = delta - PAUSE_THRESHOLD_TICKS; |