Orange Pi5 kernel

// SPDX-License-Identifier: GPL-2.0
/*
 * Dynamic byte queue limits.  See include/linux/dynamic_queue_limits.h
 *
 * Copyright (c) 2011, Tom Herbert <therbert@google.com>
 */
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/jiffies.h>
#include <linux/dynamic_queue_limits.h>
#include <linux/compiler.h>
#include <linux/export.h>
 
#define POSDIFF(A, B) ((int)((A) - (B)) > 0 ? (A) - (B) : 0)
#define AFTER_EQ(A, B) ((int)((A) - (B)) >= 0)
 
/* Records completed count and recalculates the queue limit */
void dql_completed(struct dql *dql, unsigned int count)
{
<------>unsigned int inprogress, prev_inprogress, limit;
<------>unsigned int ovlimit, completed, num_queued;
<------>bool all_prev_completed;
 
<------>num_queued = READ_ONCE(dql->num_queued);
 
<------>/* Can't complete more than what's in queue */
<------>BUG_ON(count > num_queued - dql->num_completed);
 
<------>completed = dql->num_completed + count;
<------>limit = dql->limit;
<------>ovlimit = POSDIFF(num_queued - dql->num_completed, limit);
<------>inprogress = num_queued - completed;
<------>prev_inprogress = dql->prev_num_queued - dql->num_completed;
<------>all_prev_completed = AFTER_EQ(completed, dql->prev_num_queued);
 
<------>if ((ovlimit && !inprogress) ||
<------>    (dql->prev_ovlimit && all_prev_completed)) {
<------><------>/*
<------><------> * Queue considered starved if:
<------><------> *   - The queue was over-limit in the last interval,
<------><------> *     and there is no more data in the queue.
<------><------> *  OR
<------><------> *   - The queue was over-limit in the previous interval and
<------><------> *     when enqueuing it was possible that all queued data
<------><------> *     had been consumed.  This covers the case when queue
<------><------> *     may have becomes starved between completion processing
<------><------> *     running and next time enqueue was scheduled.
<------><------> *
<------><------> *     When queue is starved increase the limit by the amount
<------><------> *     of bytes both sent and completed in the last interval,
<------><------> *     plus any previous over-limit.
<------><------> */
<------><------>limit += POSDIFF(completed, dql->prev_num_queued) +
<------><------>     dql->prev_ovlimit;
<------><------>dql->slack_start_time = jiffies;
<------><------>dql->lowest_slack = UINT_MAX;
<------>} else if (inprogress && prev_inprogress && !all_prev_completed) {
<------><------>/*
<------><------> * Queue was not starved, check if the limit can be decreased.
<------><------> * A decrease is only considered if the queue has been busy in
<------><------> * the whole interval (the check above).
<------><------> *
<------><------> * If there is slack, the amount of excess data queued above
<------><------> * the amount needed to prevent starvation, the queue limit
<------><------> * can be decreased.  To avoid hysteresis we consider the
<------><------> * minimum amount of slack found over several iterations of the
<------><------> * completion routine.
<------><------> */
<------><------>unsigned int slack, slack_last_objs;
 
<------><------>/*
<------><------> * Slack is the maximum of
<------><------> *   - The queue limit plus previous over-limit minus twice
<------><------> *     the number of objects completed.  Note that two times
<------><------> *     number of completed bytes is a basis for an upper bound
<------><------> *     of the limit.
<------><------> *   - Portion of objects in the last queuing operation that
<------><------> *     was not part of non-zero previous over-limit.  That is
<------><------> *     "round down" by non-overlimit portion of the last
<------><------> *     queueing operation.
<------><------> */
<------><------>slack = POSDIFF(limit + dql->prev_ovlimit,
<------><------>    2 * (completed - dql->num_completed));
<------><------>slack_last_objs = dql->prev_ovlimit ?
<------><------>    POSDIFF(dql->prev_last_obj_cnt, dql->prev_ovlimit) : 0;
 
<------><------>slack = max(slack, slack_last_objs);
 
<------><------>if (slack < dql->lowest_slack)
<------><------><------>dql->lowest_slack = slack;
 
<------><------>if (time_after(jiffies,
<------><------><------>       dql->slack_start_time + dql->slack_hold_time)) {
<------><------><------>limit = POSDIFF(limit, dql->lowest_slack);
<------><------><------>dql->slack_start_time = jiffies;
<------><------><------>dql->lowest_slack = UINT_MAX;
<------><------>}
<------>}
 
<------>/* Enforce bounds on limit */
<------>limit = clamp(limit, dql->min_limit, dql->max_limit);
 
<------>if (limit != dql->limit) {
<------><------>dql->limit = limit;
<------><------>ovlimit = 0;
<------>}
 
<------>dql->adj_limit = limit + completed;
<------>dql->prev_ovlimit = ovlimit;
<------>dql->prev_last_obj_cnt = dql->last_obj_cnt;
<------>dql->num_completed = completed;
<------>dql->prev_num_queued = num_queued;
}
EXPORT_SYMBOL(dql_completed);
 
void dql_reset(struct dql *dql)
{
<------>/* Reset all dynamic values */
<------>dql->limit = 0;
<------>dql->num_queued = 0;
<------>dql->num_completed = 0;
<------>dql->last_obj_cnt = 0;
<------>dql->prev_num_queued = 0;
<------>dql->prev_last_obj_cnt = 0;
<------>dql->prev_ovlimit = 0;
<------>dql->lowest_slack = UINT_MAX;
<------>dql->slack_start_time = jiffies;
}
EXPORT_SYMBOL(dql_reset);
 
void dql_init(struct dql *dql, unsigned int hold_time)
{
<------>dql->max_limit = DQL_MAX_LIMIT;
<------>dql->min_limit = 0;
<------>dql->slack_hold_time = hold_time;
<------>dql_reset(dql);
}
EXPORT_SYMBOL(dql_init);