// SPDX-License-Identifier: GPL-2.0 OR Linux-OpenIB
/*
 * Copyright (c) 2019, Mellanox Technologies inc.  All rights reserved.
 */

#include <linux/dim.h>

static int rdma_dim_step(struct dim *dim)
{
        if (dim->tune_state == DIM_GOING_RIGHT) {
                if (dim->profile_ix == (RDMA_DIM_PARAMS_NUM_PROFILES - 1))
                        return DIM_ON_EDGE;
                dim->profile_ix++;
                dim->steps_right++;
        }
        if (dim->tune_state == DIM_GOING_LEFT) {
                if (dim->profile_ix == 0)
                        return DIM_ON_EDGE;
                dim->profile_ix--;
                dim->steps_left++;
        }

        return DIM_STEPPED;
}

static int rdma_dim_stats_compare(struct dim_stats *curr,
                                  struct dim_stats *prev)
{
        /* first stat */
        if (!prev->cpms)
                return DIM_STATS_SAME;

        if (IS_SIGNIFICANT_DIFF(curr->cpms, prev->cpms))
                return (curr->cpms > prev->cpms) ? DIM_STATS_BETTER :
                                                DIM_STATS_WORSE;

        if (IS_SIGNIFICANT_DIFF(curr->cpe_ratio, prev->cpe_ratio))
                return (curr->cpe_ratio > prev->cpe_ratio) ? DIM_STATS_BETTER :
                                                DIM_STATS_WORSE;

        return DIM_STATS_SAME;
}

static bool rdma_dim_decision(struct dim_stats *curr_stats, struct dim *dim)
{
        int prev_ix = dim->profile_ix;
        u8 state = dim->tune_state;
        int stats_res;
        int step_res;

        if (state != DIM_PARKING_ON_TOP && state != DIM_PARKING_TIRED) {
                stats_res = rdma_dim_stats_compare(curr_stats,
                                                   &dim->prev_stats);

                switch (stats_res) {
                case DIM_STATS_SAME:
                        if (curr_stats->cpe_ratio <= 50 * prev_ix)
                                dim->profile_ix = 0;
                        break;
                case DIM_STATS_WORSE:
                        dim_turn(dim);
                        fallthrough;
                case DIM_STATS_BETTER:
                        step_res = rdma_dim_step(dim);
                        if (step_res == DIM_ON_EDGE)
                                dim_turn(dim);
                        break;
                }
        }

        dim->prev_stats = *curr_stats;

        return dim->profile_ix != prev_ix;
}

void rdma_dim(struct dim *dim, u64 completions)
{
        struct dim_sample *curr_sample = &dim->measuring_sample;
        struct dim_stats curr_stats;
        u32 nevents;

        dim_update_sample_with_comps(curr_sample->event_ctr + 1, 0, 0,
                                     curr_sample->comp_ctr + completions,
                                     &dim->measuring_sample);

        switch (dim->state) {
        case DIM_MEASURE_IN_PROGRESS:
                nevents = curr_sample->event_ctr - dim->start_sample.event_ctr;
                if (nevents < DIM_NEVENTS)
                        break;
                if (!dim_calc_stats(&dim->start_sample, curr_sample, &curr_stats))
                        break;
                if (rdma_dim_decision(&curr_stats, dim)) {
                        dim->state = DIM_APPLY_NEW_PROFILE;
                        schedule_work(&dim->work);
                        break;
                }
                fallthrough;
        case DIM_START_MEASURE:
                dim->state = DIM_MEASURE_IN_PROGRESS;
                dim_update_sample_with_comps(curr_sample->event_ctr, 0, 0,
                                             curr_sample->comp_ctr,
                                             &dim->start_sample);
                break;
        case DIM_APPLY_NEW_PROFILE:
                break;
        }
}
EXPORT_SYMBOL(rdma_dim);