Aaron Durbin | 340ca91 | 2013-04-30 09:58:12 -0500 | [diff] [blame] | 1 | /* |
| 2 | * This file is part of the coreboot project. |
| 3 | * |
| 4 | * Copyright (C) 2013 Google, Inc. |
| 5 | * |
| 6 | * This program is free software; you can redistribute it and/or modify |
| 7 | * it under the terms of the GNU General Public License as published by |
| 8 | * the Free Software Foundation; version 2 of the License. |
| 9 | * |
| 10 | * This program is distributed in the hope that it will be useful, |
| 11 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 12 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 13 | * GNU General Public License for more details. |
Aaron Durbin | 340ca91 | 2013-04-30 09:58:12 -0500 | [diff] [blame] | 14 | */ |
| 15 | #include <stddef.h> |
| 16 | #include <timer.h> |
| 17 | |
| 18 | #define MAX_TIMER_QUEUE_ENTRIES 64 |
| 19 | |
| 20 | /* The timer queue is implemented using a min heap. Therefore the first |
| 21 | * element is the one with smallest time to expiration. */ |
| 22 | struct timer_queue { |
| 23 | int num_entries; |
| 24 | int max_entries; |
| 25 | struct timeout_callback *queue[MAX_TIMER_QUEUE_ENTRIES]; |
| 26 | }; |
| 27 | |
| 28 | static struct timer_queue global_timer_queue = { |
| 29 | .num_entries = 0, |
| 30 | .max_entries = MAX_TIMER_QUEUE_ENTRIES, |
| 31 | .queue = { 0 }, |
| 32 | }; |
| 33 | |
| 34 | static inline int timer_queue_empty(struct timer_queue *tq) |
| 35 | { |
| 36 | return tq->num_entries == 0; |
| 37 | } |
| 38 | |
| 39 | static inline int timer_queue_full(struct timer_queue *tq) |
| 40 | { |
| 41 | return tq->num_entries == tq->max_entries; |
| 42 | } |
| 43 | |
| 44 | static inline struct timeout_callback *timer_queue_head(struct timer_queue *tq) |
| 45 | { |
| 46 | if (timer_queue_empty(tq)) |
| 47 | return NULL; |
| 48 | return tq->queue[0]; |
| 49 | } |
| 50 | |
| 51 | static int timer_queue_insert(struct timer_queue *tq, |
| 52 | struct timeout_callback *tocb) |
| 53 | { |
| 54 | int index; |
| 55 | |
| 56 | /* No more slots. */ |
| 57 | if (timer_queue_full(tq)) |
| 58 | return -1; |
| 59 | |
| 60 | index = tq->num_entries; |
| 61 | tq->num_entries++; |
| 62 | tq->queue[index] = tocb; |
| 63 | |
| 64 | while (index != 0) { |
| 65 | struct timeout_callback *parent; |
| 66 | int parent_index; |
| 67 | |
| 68 | parent_index = (index - 1) / 2; |
| 69 | parent = tq->queue[parent_index]; |
| 70 | |
| 71 | /* All other ancestors are less than or equal to the current. */ |
| 72 | if (mono_time_cmp(&parent->expiration, &tocb->expiration) <= 0) |
| 73 | break; |
| 74 | |
| 75 | /* The parent is greater than current. Swap them. */ |
| 76 | tq->queue[parent_index] = tocb; |
| 77 | tq->queue[index] = parent; |
| 78 | |
| 79 | index = parent_index; |
| 80 | } |
| 81 | |
| 82 | return 0; |
| 83 | } |
| 84 | |
| 85 | /* Get the index containing the entry with smallest value. */ |
| 86 | static int timer_queue_min_child_index(struct timer_queue *tq, int index) |
| 87 | { |
| 88 | int left_child_index; |
| 89 | int right_child_index; |
| 90 | |
| 91 | left_child_index = 2 * index + 1; |
| 92 | |
| 93 | if (left_child_index >= tq->num_entries) |
| 94 | return -1; |
| 95 | |
| 96 | right_child_index = left_child_index + 1; |
| 97 | |
| 98 | if (right_child_index >= tq->num_entries) |
| 99 | return left_child_index; |
| 100 | |
| 101 | if (mono_time_cmp(&tq->queue[left_child_index]->expiration, |
| 102 | &tq->queue[right_child_index]->expiration) < 0) { |
| 103 | return left_child_index; |
| 104 | } |
| 105 | return right_child_index; |
| 106 | } |
| 107 | |
| 108 | static void timer_queue_remove_head(struct timer_queue *tq) |
| 109 | { |
| 110 | int index; |
| 111 | struct timeout_callback *tocb; |
| 112 | |
| 113 | /* In order to remove the head the deepest child is replaced in the |
| 114 | * head slot and bubbled down the tree. */ |
| 115 | tq->num_entries--; |
| 116 | tocb = tq->queue[tq->num_entries]; |
| 117 | tq->queue[0] = tocb; |
| 118 | |
| 119 | index = 0; |
| 120 | while (1) { |
| 121 | int min_child_index; |
| 122 | struct timeout_callback *child; |
| 123 | |
| 124 | min_child_index = timer_queue_min_child_index(tq, index); |
| 125 | |
| 126 | /* No more entries to compare against. */ |
| 127 | if (min_child_index < 0) |
| 128 | break; |
| 129 | |
| 130 | child = tq->queue[min_child_index]; |
| 131 | |
| 132 | /* Current index is the correct place since it is smaller or |
| 133 | * equal to the smallest child. */ |
| 134 | if (mono_time_cmp(&tocb->expiration, &child->expiration) <= 0) |
| 135 | break; |
| 136 | |
| 137 | /* Need to swap with smallest child. */ |
| 138 | tq->queue[min_child_index] = tocb; |
| 139 | tq->queue[index] = child; |
| 140 | |
| 141 | index = min_child_index; |
| 142 | } |
| 143 | } |
| 144 | |
| 145 | static struct timeout_callback * |
| 146 | timer_queue_expired(struct timer_queue *tq, struct mono_time *current_time) |
| 147 | { |
| 148 | struct timeout_callback *tocb; |
| 149 | |
| 150 | tocb = timer_queue_head(tq); |
| 151 | |
| 152 | if (tocb == NULL) |
| 153 | return NULL; |
| 154 | |
| 155 | /* The timeout callback hasn't expired yet. */ |
| 156 | if (mono_time_before(current_time, &tocb->expiration)) |
| 157 | return NULL; |
| 158 | |
| 159 | timer_queue_remove_head(tq); |
| 160 | |
| 161 | return tocb; |
| 162 | } |
| 163 | |
| 164 | int timer_sched_callback(struct timeout_callback *tocb, unsigned long us) |
| 165 | { |
| 166 | struct mono_time current_time; |
| 167 | |
| 168 | if ((long)us< 0) |
| 169 | return -1; |
| 170 | |
| 171 | timer_monotonic_get(¤t_time); |
| 172 | tocb->expiration = current_time; |
| 173 | mono_time_add_usecs(&tocb->expiration, us); |
| 174 | |
| 175 | /* The expiration overflowed. */ |
| 176 | if (us != 0 && !mono_time_before(¤t_time, &tocb->expiration)) |
| 177 | return -1; |
| 178 | |
| 179 | return timer_queue_insert(&global_timer_queue, tocb); |
| 180 | } |
| 181 | |
| 182 | int timers_run(void) |
| 183 | { |
| 184 | struct timeout_callback *tocb; |
| 185 | struct mono_time current_time; |
| 186 | |
| 187 | timer_monotonic_get(¤t_time); |
| 188 | tocb = timer_queue_expired(&global_timer_queue, ¤t_time); |
| 189 | |
| 190 | if (tocb != NULL) |
| 191 | tocb->callback(tocb); |
| 192 | |
| 193 | return !timer_queue_empty(&global_timer_queue); |
| 194 | } |