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libpayload/x86/delay: Make arch_ndelay call apic_delay if delay is long

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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 <rrangel@chromium.org>
Reviewed-on: https://review.coreboot.org/28245
Reviewed-by: Martin Roth <martinroth@google.com>
Reviewed-by: Richard Spiegel <richard.spiegel@silverbackltd.com>
Reviewed-by: Julius Werner <jwerner@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
This commit is contained in:
Raul E Rangel
2018-08-20 13:03:45 -06:00
committed by Martin Roth
parent 370c116ca5
commit 9fc7b8e973
2 changed files with 14 additions and 0 deletions
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12
payloads/libpayload/arch/x86/delay.c
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@@ -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;