1 /* 2 * Copyright (c) 2015 Wind River Systems, Inc. 3 * Copyright (c) 2019 Intel Corporation 4 * 5 * SPDX-License-Identifier: Apache-2.0 6 */ 7 8 /** 9 * @file 10 * @brief Timer driver API 11 * 12 * Declare API implemented by system timer driver and used by kernel components. 13 */ 14 15 #ifndef ZEPHYR_INCLUDE_DRIVERS_SYSTEM_TIMER_H_ 16 #define ZEPHYR_INCLUDE_DRIVERS_SYSTEM_TIMER_H_ 17 18 #include <stdbool.h> 19 #include <zephyr/types.h> 20 21 #ifdef __cplusplus 22 extern "C" { 23 #endif 24 25 /** 26 * @brief System Clock APIs 27 * @defgroup clock_apis System Clock APIs 28 * @{ 29 */ 30 31 /** 32 * @brief Set system clock timeout 33 * 34 * Informs the system clock driver that the next needed call to 35 * sys_clock_announce() will not be until the specified number of ticks 36 * from the current time have elapsed. Note that spurious calls 37 * to sys_clock_announce() are allowed (i.e. it's legal to announce 38 * every tick and implement this function as a noop), the requirement 39 * is that one tick announcement should occur within one tick BEFORE 40 * the specified expiration (that is, passing ticks==1 means "announce 41 * the next tick", this convention was chosen to match legacy usage). 42 * Similarly a ticks value of zero (or even negative) is legal and 43 * treated identically: it simply indicates the kernel would like the 44 * next tick announcement as soon as possible. 45 * 46 * Note that ticks can also be passed the special value K_TICKS_FOREVER, 47 * indicating that no future timer interrupts are expected or required 48 * and that the system is permitted to enter an indefinite sleep even 49 * if this could cause rollover of the internal counter (i.e. the 50 * system uptime counter is allowed to be wrong 51 * 52 * Note also that it is conventional for the kernel to pass INT_MAX 53 * for ticks if it wants to preserve the uptime tick count but doesn't 54 * have a specific event to await. The intent here is that the driver 55 * will schedule any needed timeout as far into the future as 56 * possible. For the specific case of INT_MAX, the next call to 57 * sys_clock_announce() may occur at any point in the future, not just 58 * at INT_MAX ticks. But the correspondence between the announced 59 * ticks and real-world time must be correct. 60 * 61 * A final note about SMP: note that the call to sys_clock_set_timeout() 62 * is made on any CPU, and reflects the next timeout desired globally. 63 * The resulting calls(s) to sys_clock_announce() must be properly 64 * serialized by the driver such that a given tick is announced 65 * exactly once across the system. The kernel does not (cannot, 66 * really) attempt to serialize things by "assigning" timeouts to 67 * specific CPUs. 68 * 69 * @param ticks Timeout in tick units 70 * @param idle Hint to the driver that the system is about to enter 71 * the idle state immediately after setting the timeout 72 */ 73 void sys_clock_set_timeout(int32_t ticks, bool idle); 74 75 /** 76 * @brief Timer idle exit notification 77 * 78 * This notifies the timer driver that the system is exiting the idle 79 * and allows it to do whatever bookkeeping is needed to restore timer 80 * operation and compute elapsed ticks. 81 * 82 * @note Legacy timer drivers also use this opportunity to call back 83 * into sys_clock_announce() to notify the kernel of expired ticks. 84 * This is allowed for compatibility, but not recommended. The kernel 85 * will figure that out on its own. 86 */ 87 void sys_clock_idle_exit(void); 88 89 /** 90 * @brief Announce time progress to the kernel 91 * 92 * Informs the kernel that the specified number of ticks have elapsed 93 * since the last call to sys_clock_announce() (or system startup for 94 * the first call). The timer driver is expected to delivery these 95 * announcements as close as practical (subject to hardware and 96 * latency limitations) to tick boundaries. 97 * 98 * @param ticks Elapsed time, in ticks 99 */ 100 void sys_clock_announce(int32_t ticks); 101 102 /** 103 * @brief Ticks elapsed since last sys_clock_announce() call 104 * 105 * Queries the clock driver for the current time elapsed since the 106 * last call to sys_clock_announce() was made. The kernel will call 107 * this with appropriate locking, the driver needs only provide an 108 * instantaneous answer. 109 */ 110 uint32_t sys_clock_elapsed(void); 111 112 /** 113 * @brief Disable system timer. 114 * 115 * @note Not all system timer drivers has the capability of being disabled. 116 * The config @kconfig{CONFIG_SYSTEM_TIMER_HAS_DISABLE_SUPPORT} can be used to 117 * check if the system timer has the capability of being disabled. 118 */ 119 void sys_clock_disable(void); 120 121 /** 122 * @brief Hardware cycle counter 123 * 124 * Timer drivers are generally responsible for the system cycle 125 * counter as well as the tick announcements. This function is 126 * generally called out of the architecture layer (@see 127 * arch_k_cycle_get_32()) to implement the cycle counter, though the 128 * user-facing API is owned by the architecture, not the driver. The 129 * rate must match CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC. 130 * 131 * @note 132 * If the counter clock is large enough for this to wrap its full range 133 * within a few seconds (i.e. CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC is greater 134 * than 50Mhz) then it is recommended to also implement 135 * sys_clock_cycle_get_64(). 136 * 137 * @return The current cycle time. This should count up monotonically 138 * through the full 32 bit space, wrapping at 0xffffffff. Hardware 139 * with fewer bits of precision in the timer is expected to synthesize 140 * a 32 bit count. 141 */ 142 uint32_t sys_clock_cycle_get_32(void); 143 144 /** 145 * @brief 64 bit hardware cycle counter 146 * 147 * As for sys_clock_cycle_get_32(), but with a 64 bit return value. 148 * Not all hardware has 64 bit counters. This function need be 149 * implemented only if CONFIG_TIMER_HAS_64BIT_CYCLE_COUNTER is set. 150 * 151 * @note 152 * If the counter clock is large enough for sys_clock_cycle_get_32() to wrap 153 * its full range within a few seconds (i.e. CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC 154 * is greater than 50Mhz) then it is recommended to implement this API. 155 * 156 * @return The current cycle time. This should count up monotonically 157 * through the full 64 bit space, wrapping at 2^64-1. Hardware with 158 * fewer bits of precision in the timer is generally not expected to 159 * implement this API. 160 */ 161 uint64_t sys_clock_cycle_get_64(void); 162 163 /** 164 * @} 165 */ 166 167 #ifdef __cplusplus 168 } 169 #endif 170 171 #endif /* ZEPHYR_INCLUDE_DRIVERS_SYSTEM_TIMER_H_ */ 172
