From 9fc7b8e973fca05381be66e7053ffa301c9dbe33 Mon Sep 17 00:00:00 2001 From: Raul E Rangel Date: Mon, 20 Aug 2018 13:03:45 -0600 Subject: [PATCH] libpayload/x86/delay: Make arch_ndelay call apic_delay if delay is long This reduces power consumption on grunt by over 3W when sitting at the depthcharge recovery screen. BUG=b:109749762 TEST=Booted grunt in the recovery screen and made sure it continued to work. Change-Id: Id079c099ee4cf6a07724241af4400063f4551668 Signed-off-by: Raul E Rangel Reviewed-on: https://review.coreboot.org/28245 Reviewed-by: Martin Roth Reviewed-by: Richard Spiegel Reviewed-by: Julius Werner Tested-by: build bot (Jenkins) --- payloads/libpayload/arch/x86/apic.c | 2 ++ payloads/libpayload/arch/x86/delay.c | 12 ++++++++++++ 2 files changed, 14 insertions(+) diff --git a/payloads/libpayload/arch/x86/apic.c b/payloads/libpayload/arch/x86/apic.c index 079f456eec..99eff27aad 100644 --- a/payloads/libpayload/arch/x86/apic.c +++ b/payloads/libpayload/arch/x86/apic.c @@ -210,6 +210,8 @@ static void apic_init_timer(void) /* Set APIC init counter to MAX and count for 1 ms */ apic_write32(APIC_TIMER_INIT_COUNT, UINT32_MAX); + /* This is safe because apic_initialized() returns false so + * arch_ndelay() falls back to a busy loop. */ mdelay(1); ticks_per_ms = 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 +#include /* 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;