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-rw-r--r--src/lib/timer_queue.c198
1 files changed, 198 insertions, 0 deletions
diff --git a/src/lib/timer_queue.c b/src/lib/timer_queue.c
new file mode 100644
index 0000000000..8d11f107a8
--- /dev/null
+++ b/src/lib/timer_queue.c
@@ -0,0 +1,198 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright (C) 2013 Google, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+#include <stddef.h>
+#include <timer.h>
+
+#define MAX_TIMER_QUEUE_ENTRIES 64
+
+/* The timer queue is implemented using a min heap. Therefore the first
+ * element is the one with smallest time to expiration. */
+struct timer_queue {
+ int num_entries;
+ int max_entries;
+ struct timeout_callback *queue[MAX_TIMER_QUEUE_ENTRIES];
+};
+
+static struct timer_queue global_timer_queue = {
+ .num_entries = 0,
+ .max_entries = MAX_TIMER_QUEUE_ENTRIES,
+ .queue = { 0 },
+};
+
+static inline int timer_queue_empty(struct timer_queue *tq)
+{
+ return tq->num_entries == 0;
+}
+
+static inline int timer_queue_full(struct timer_queue *tq)
+{
+ return tq->num_entries == tq->max_entries;
+}
+
+static inline struct timeout_callback *timer_queue_head(struct timer_queue *tq)
+{
+ if (timer_queue_empty(tq))
+ return NULL;
+ return tq->queue[0];
+}
+
+static int timer_queue_insert(struct timer_queue *tq,
+ struct timeout_callback *tocb)
+{
+ int index;
+
+ /* No more slots. */
+ if (timer_queue_full(tq))
+ return -1;
+
+ index = tq->num_entries;
+ tq->num_entries++;
+ tq->queue[index] = tocb;
+
+ while (index != 0) {
+ struct timeout_callback *parent;
+ int parent_index;
+
+ parent_index = (index - 1) / 2;
+ parent = tq->queue[parent_index];
+
+ /* All other ancestors are less than or equal to the current. */
+ if (mono_time_cmp(&parent->expiration, &tocb->expiration) <= 0)
+ break;
+
+ /* The parent is greater than current. Swap them. */
+ tq->queue[parent_index] = tocb;
+ tq->queue[index] = parent;
+
+ index = parent_index;
+ }
+
+ return 0;
+}
+
+/* Get the index containing the entry with smallest value. */
+static int timer_queue_min_child_index(struct timer_queue *tq, int index)
+{
+ int left_child_index;
+ int right_child_index;
+
+ left_child_index = 2 * index + 1;
+
+ if (left_child_index >= tq->num_entries)
+ return -1;
+
+ right_child_index = left_child_index + 1;
+
+ if (right_child_index >= tq->num_entries)
+ return left_child_index;
+
+ if (mono_time_cmp(&tq->queue[left_child_index]->expiration,
+ &tq->queue[right_child_index]->expiration) < 0) {
+ return left_child_index;
+ }
+ return right_child_index;
+}
+
+static void timer_queue_remove_head(struct timer_queue *tq)
+{
+ int index;
+ struct timeout_callback *tocb;
+
+ /* In order to remove the head the deepest child is replaced in the
+ * head slot and bubbled down the tree. */
+ tq->num_entries--;
+ tocb = tq->queue[tq->num_entries];
+ tq->queue[0] = tocb;
+
+ index = 0;
+ while (1) {
+ int min_child_index;
+ struct timeout_callback *child;
+
+ min_child_index = timer_queue_min_child_index(tq, index);
+
+ /* No more entries to compare against. */
+ if (min_child_index < 0)
+ break;
+
+ child = tq->queue[min_child_index];
+
+ /* Current index is the correct place since it is smaller or
+ * equal to the smallest child. */
+ if (mono_time_cmp(&tocb->expiration, &child->expiration) <= 0)
+ break;
+
+ /* Need to swap with smallest child. */
+ tq->queue[min_child_index] = tocb;
+ tq->queue[index] = child;
+
+ index = min_child_index;
+ }
+}
+
+static struct timeout_callback *
+timer_queue_expired(struct timer_queue *tq, struct mono_time *current_time)
+{
+ struct timeout_callback *tocb;
+
+ tocb = timer_queue_head(tq);
+
+ if (tocb == NULL)
+ return NULL;
+
+ /* The timeout callback hasn't expired yet. */
+ if (mono_time_before(current_time, &tocb->expiration))
+ return NULL;
+
+ timer_queue_remove_head(tq);
+
+ return tocb;
+}
+
+int timer_sched_callback(struct timeout_callback *tocb, unsigned long us)
+{
+ struct mono_time current_time;
+
+ if ((long)us< 0)
+ return -1;
+
+ timer_monotonic_get(&current_time);
+ tocb->expiration = current_time;
+ mono_time_add_usecs(&tocb->expiration, us);
+
+ /* The expiration overflowed. */
+ if (us != 0 && !mono_time_before(&current_time, &tocb->expiration))
+ return -1;
+
+ return timer_queue_insert(&global_timer_queue, tocb);
+}
+
+int timers_run(void)
+{
+ struct timeout_callback *tocb;
+ struct mono_time current_time;
+
+ timer_monotonic_get(&current_time);
+ tocb = timer_queue_expired(&global_timer_queue, &current_time);
+
+ if (tocb != NULL)
+ tocb->callback(tocb);
+
+ return !timer_queue_empty(&global_timer_queue);
+}