| /* |
| * Copyright (c) 2011-2015 Wind River Systems, Inc. |
| * |
| * SPDX-License-Identifier: Apache-2.0 |
| */ |
| /** |
| * @file CPU power management code for IA-32 |
| * |
| * This module provides an implementation of the architecture-specific |
| * k_cpu_idle() primitive required by the kernel idle loop component. |
| * It can be called within an implementation of _sys_power_save_idle(), |
| * which is provided for the kernel by the platform. |
| * |
| * The module also provides an implementation of k_cpu_atomic_idle(), which |
| * atomically re-enables interrupts and enters low power mode. |
| * |
| * INTERNAL |
| * These implementations of k_cpu_idle() and k_cpu_atomic_idle() could be |
| * used when operating as a Hypervisor guest. More specifically, the Hypervisor |
| * supports the execution of the 'hlt' instruction from a guest (results in a |
| * VM exit), and more importantly, the Hypervisor will respect the |
| * single instruction delay slot after the 'sti' instruction as required |
| * by k_cpu_atomic_idle(). |
| */ |
| |
| #include <zephyr.h> |
| #include <logging/kernel_event_logger.h> |
| #include <arch/cpu.h> |
| |
| #ifdef CONFIG_BOOT_TIME_MEASUREMENT |
| extern u64_t __idle_time_stamp; /* timestamp when CPU went idle */ |
| #endif |
| |
| /** |
| * |
| * @brief Power save idle routine for IA-32 |
| * |
| * This function will be called by the kernel idle loop or possibly within |
| * an implementation of _sys_power_save_idle in the kernel when the |
| * '_sys_power_save_flag' variable is non-zero. The IA-32 'hlt' instruction |
| * will be issued causing a low-power consumption sleep mode. |
| * |
| * @return N/A |
| */ |
| void k_cpu_idle(void) |
| { |
| _int_latency_stop(); |
| _sys_k_event_logger_enter_sleep(); |
| #if defined(CONFIG_BOOT_TIME_MEASUREMENT) |
| __idle_time_stamp = (u64_t)k_cycle_get_32(); |
| #endif |
| |
| __asm__ volatile ( |
| "sti\n\t" |
| "hlt\n\t"); |
| } |
| |
| /** |
| * |
| * @brief Atomically re-enable interrupts and enter low power mode |
| * |
| * INTERNAL |
| * The requirements for k_cpu_atomic_idle() are as follows: |
| * 1) The enablement of interrupts and entering a low-power mode needs to be |
| * atomic, i.e. there should be no period of time where interrupts are |
| * enabled before the processor enters a low-power mode. See the comments |
| * in k_lifo_get(), for example, of the race condition that |
| * occurs if this requirement is not met. |
| * |
| * 2) After waking up from the low-power mode, the interrupt lockout state |
| * must be restored as indicated in the 'imask' input parameter. |
| * |
| * @return N/A |
| */ |
| |
| void k_cpu_atomic_idle(unsigned int imask) |
| { |
| _int_latency_stop(); |
| _sys_k_event_logger_enter_sleep(); |
| |
| __asm__ volatile ( |
| "sti\n\t" |
| /* |
| * The following statement appears in "Intel 64 and IA-32 |
| * Architectures Software Developer's Manual", regarding the 'sti' |
| * instruction: |
| * |
| * "After the IF flag is set, the processor begins responding to |
| * external, maskable interrupts after the next instruction is |
| * executed." |
| * |
| * Thus the IA-32 implementation of k_cpu_atomic_idle() will |
| * atomically re-enable interrupts and enter a low-power mode. |
| */ |
| "hlt\n\t"); |
| |
| /* restore interrupt lockout state before returning to caller */ |
| if (!(imask & 0x200)) { |
| _int_latency_start(); |
| __asm__ volatile("cli"); |
| } |
| } |