| /* |
| * This file is part of the libpayload project. |
| * |
| * Copyright (C) 2018 Google LLC |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * 1. Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * 2. Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution. |
| * 3. The name of the author may not be used to endorse or promote products |
| * derived from this software without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND |
| * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE |
| * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
| * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
| * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
| * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
| * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
| * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| * SUCH DAMAGE. |
| */ |
| |
| #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 |
| * running at CPU frequency, bus frequency, or some arbitrary value. We assume |
| * 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 (CONFIG(LP_ENABLE_APIC) && apic_initialized() && apic_us) |
| apic_delay(apic_us); |
| |
| if (delta > PAUSE_THRESHOLD_TICKS) |
| pause_delta = delta - PAUSE_THRESHOLD_TICKS; |
| |
| while (timer_raw_value() - start < pause_delta) |
| asm volatile("pause\n\t"); |
| |
| while (timer_raw_value() - start < delta) |
| continue; |
| } |