1 /* 2 * Copyright (c) 2018 Intel Corporation 3 * 4 * SPDX-License-Identifier: Apache-2.0 5 */ 6 7 #include <zephyr/kernel.h> 8 #include <zephyr/drivers/timer/system_timer.h> 9 #include <zephyr/sys_clock.h> 10 #include <kernel_arch_interface.h> 11 z_impl_k_busy_wait(uint32_t usec_to_wait)12void z_impl_k_busy_wait(uint32_t usec_to_wait) 13 { 14 SYS_PORT_TRACING_FUNC_ENTER(k_thread, busy_wait, usec_to_wait); 15 if (usec_to_wait == 0U) { 16 SYS_PORT_TRACING_FUNC_EXIT(k_thread, busy_wait, usec_to_wait); 17 return; 18 } 19 20 #if defined(CONFIG_ARCH_HAS_CUSTOM_BUSY_WAIT) 21 arch_busy_wait(usec_to_wait); 22 #elif defined(CONFIG_SYS_CLOCK_EXISTS) 23 uint32_t start_cycles = k_cycle_get_32(); 24 uint32_t cycles_to_wait = k_us_to_cyc_ceil32(usec_to_wait); 25 26 for (;;) { 27 uint32_t current_cycles = k_cycle_get_32(); 28 29 /* this handles the rollover on an unsigned 32-bit value */ 30 if ((current_cycles - start_cycles) >= cycles_to_wait) { 31 break; 32 } 33 } 34 #else 35 /* 36 * Crude busy loop for the purpose of being able to configure out 37 * system timer support. 38 */ 39 unsigned int loops_per_usec = CONFIG_BUSYWAIT_CPU_LOOPS_PER_USEC; 40 unsigned int loops = loops_per_usec * usec_to_wait; 41 42 while (loops-- > 0) { 43 arch_nop(); 44 } 45 #endif 46 47 SYS_PORT_TRACING_FUNC_EXIT(k_thread, busy_wait, usec_to_wait); 48 } 49 50 #ifdef CONFIG_USERSPACE z_vrfy_k_busy_wait(uint32_t usec_to_wait)51static inline void z_vrfy_k_busy_wait(uint32_t usec_to_wait) 52 { 53 z_impl_k_busy_wait(usec_to_wait); 54 } 55 #include <syscalls/k_busy_wait_mrsh.c> 56 #endif /* CONFIG_USERSPACE */ 57
