[coreboot-gerrit] Patch set updated for coreboot: 010641f coreboot: add timer queue implementation
Aaron Durbin (adurbin@google.com)
gerrit at coreboot.org
Tue Apr 30 20:21:17 CEST 2013
Aaron Durbin (adurbin at google.com) just uploaded a new patch set to gerrit, which you can find at http://review.coreboot.org/3158
-gerrit
commit 010641ff9a394d6fa90c95aae08ca52ef86a80fb
Author: Aaron Durbin <adurbin at chromium.org>
Date: Tue Apr 30 09:58:12 2013 -0500
coreboot: add timer queue implementation
A timer queue provides the mechanism for calling functions
in the future by way of a callback. It utilizes the MONOTONIC_TIMER
to track time through the boot. The implementation is a min-heap
for keeping track of the next-to-expire callback.
Change-Id: Ia56bab8444cd6177b051752342f53b53d5f6afc1
Signed-off-by: Aaron Durbin <adurbin at chromium.org>
---
src/Kconfig | 6 ++
src/include/timer.h | 18 +++++
src/lib/Makefile.inc | 1 +
src/lib/timer_queue.c | 198 ++++++++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 223 insertions(+)
diff --git a/src/Kconfig b/src/Kconfig
index a49643e..ab2a927 100644
--- a/src/Kconfig
+++ b/src/Kconfig
@@ -318,6 +318,12 @@ config HAVE_MONOTONIC_TIMER
help
The board/chipset provides a monotonic timer.
+config TIMER_QUEUE
+ def_bool n
+ depends on HAVE_MONOTONIC_TIMER
+ help
+ Provide a timer queue for performing time-based callbacks.
+
config HIGH_SCRATCH_MEMORY_SIZE
hex
default 0x0
diff --git a/src/include/timer.h b/src/include/timer.h
index 2b112dd..e950c81 100644
--- a/src/include/timer.h
+++ b/src/include/timer.h
@@ -38,6 +38,17 @@ struct rela_time {
long microseconds;
};
+/* A timeout_callback structure is used for the book keeping for scheduling
+ * work in the future. When a callback is called the structure can be
+ * re-used for scheduling as it is not being tracked by the core timer
+ * library any more. */
+struct timeout_callback {
+ void *priv;
+ void (*callback)(struct timeout_callback *tocb);
+ /* Not for public use. The timer library uses the fields below. */
+ struct mono_time expiration;
+};
+
/* Obtain the current monotonic time. The assumption is that the time counts
* up from the value 0 with value 0 being the point when the timer was
* initialized. Additionally, the timer is assumed to only be valid for the
@@ -49,6 +60,13 @@ struct rela_time {
* of 10 seconds. */
void timer_monotonic_get(struct mono_time *mt);
+/* Returns 1 if callbacks still present in the queue. 0 if no timers left. */
+int timers_run(void);
+
+/* Schedule a callback to be ran microseconds from time of invocation.
+ * 0 returned on success, < 0 on error. */
+int timer_sched_callback(struct timeout_callback *tocb, unsigned long us);
+
/* Add microseconds to an absoute time. */
static inline void mono_time_add_usecs(struct mono_time *mt, long us)
{
diff --git a/src/lib/Makefile.inc b/src/lib/Makefile.inc
index e8b1485..7306e6d 100644
--- a/src/lib/Makefile.inc
+++ b/src/lib/Makefile.inc
@@ -90,6 +90,7 @@ ramstage-$(CONFIG_COLLECT_TIMESTAMPS) += timestamp.c
ramstage-$(CONFIG_COVERAGE) += libgcov.c
ramstage-$(CONFIG_MAINBOARD_DO_NATIVE_VGA_INIT) += edid.c
ramstage-y += memrange.c
+ramstage-$(CONFIG_TIMER_QUEUE) += timer_queue.c
# The CBMEM implementations are chosen based on CONFIG_DYNAMIC_CBMEM.
ifeq ($(CONFIG_DYNAMIC_CBMEM),y)
diff --git a/src/lib/timer_queue.c b/src/lib/timer_queue.c
new file mode 100644
index 0000000..8d11f10
--- /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(¤t_time);
+ tocb->expiration = current_time;
+ mono_time_add_usecs(&tocb->expiration, us);
+
+ /* The expiration overflowed. */
+ if (us != 0 && !mono_time_before(¤t_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(¤t_time);
+ tocb = timer_queue_expired(&global_timer_queue, ¤t_time);
+
+ if (tocb != NULL)
+ tocb->callback(tocb);
+
+ return !timer_queue_empty(&global_timer_queue);
+}
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