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@chromium.org>
Reviewed-on: http://review.coreboot.org/3158
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>
This commit is contained in:
Aaron Durbin 2013-04-30 09:58:12 -05:00 committed by Ronald G. Minnich
parent 6b0fb0dc3c
commit 340ca91f18
4 changed files with 223 additions and 0 deletions

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@ -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

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@ -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)
{

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@ -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)

198
src/lib/timer_queue.c Normal file
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@ -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);
}