/* SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause */
/*
 * Copyright (C) 2024-2025 Intel Corporation
 */
#include <net/gso.h>
#include <linux/ieee80211.h>
#include <net/ip.h>

#include "iwl-drv.h"
#include "iwl-utils.h"

#ifdef CONFIG_INET
int iwl_tx_tso_segment(struct sk_buff *skb, unsigned int num_subframes,
                       netdev_features_t netdev_flags,
                       struct sk_buff_head *mpdus_skbs)
{
        struct sk_buff *tmp, *next;
        struct ieee80211_hdr *hdr = (void *)skb->data;
        char cb[sizeof(skb->cb)];
        u16 i = 0;
        unsigned int tcp_payload_len;
        unsigned int mss = skb_shinfo(skb)->gso_size;
        bool ipv4 = (skb->protocol == htons(ETH_P_IP));
        bool qos = ieee80211_is_data_qos(hdr->frame_control);
        u16 ip_base_id = ipv4 ? ntohs(ip_hdr(skb)->id) : 0;

        skb_shinfo(skb)->gso_size = num_subframes * mss;
        memcpy(cb, skb->cb, sizeof(cb));

        next = skb_gso_segment(skb, netdev_flags);
        skb_shinfo(skb)->gso_size = mss;
        skb_shinfo(skb)->gso_type = ipv4 ? SKB_GSO_TCPV4 : SKB_GSO_TCPV6;

        if (IS_ERR(next) && PTR_ERR(next) == -ENOMEM)
                return -ENOMEM;

        if (WARN_ONCE(IS_ERR(next),
                      "skb_gso_segment error: %d\n", (int)PTR_ERR(next)))
                return PTR_ERR(next);

        if (next)
                consume_skb(skb);

        skb_list_walk_safe(next, tmp, next) {
                memcpy(tmp->cb, cb, sizeof(tmp->cb));
                /*
                 * Compute the length of all the data added for the A-MSDU.
                 * This will be used to compute the length to write in the TX
                 * command. We have: SNAP + IP + TCP for n -1 subframes and
                 * ETH header for n subframes.
                 */
                tcp_payload_len = skb_tail_pointer(tmp) -
                        skb_transport_header(tmp) -
                        tcp_hdrlen(tmp) + tmp->data_len;

                if (ipv4)
                        ip_hdr(tmp)->id = htons(ip_base_id + i * num_subframes);

                if (tcp_payload_len > mss) {
                        skb_shinfo(tmp)->gso_size = mss;
                        skb_shinfo(tmp)->gso_type = ipv4 ? SKB_GSO_TCPV4 :
                                                           SKB_GSO_TCPV6;
                } else {
                        if (qos) {
                                u8 *qc;

                                if (ipv4)
                                        ip_send_check(ip_hdr(tmp));

                                qc = ieee80211_get_qos_ctl((void *)tmp->data);
                                *qc &= ~IEEE80211_QOS_CTL_A_MSDU_PRESENT;
                        }
                        skb_shinfo(tmp)->gso_size = 0;
                }

                skb_mark_not_on_list(tmp);
                __skb_queue_tail(mpdus_skbs, tmp);
                i++;
        }

        return 0;
}
IWL_EXPORT_SYMBOL(iwl_tx_tso_segment);
#endif /* CONFIG_INET */

static u32 iwl_div_by_db(u32 value, u8 db)
{
        /*
         * 2^32 * 10**(i / 10) for i = [1, 10], skipping 0 and simply stopping
         * at 10 dB and looping instead of using a much larger table.
         *
         * Using 64 bit math is overkill, but means the helper does not require
         * a limit on the input range.
         */
        static const u32 db_to_val[] = {
                0xcb59185e, 0xa1866ba8, 0x804dce7a, 0x65ea59fe, 0x50f44d89,
                0x404de61f, 0x331426af, 0x2892c18b, 0x203a7e5b, 0x1999999a,
        };

        while (value && db > 0) {
                u8 change = min_t(u8, db, ARRAY_SIZE(db_to_val));

                value = (((u64)value) * db_to_val[change - 1]) >> 32;

                db -= change;
        }

        return value;
}

s8 iwl_average_neg_dbm(const u8 *neg_dbm_values, u8 len)
{
        int average_magnitude;
        u32 average_factor;
        int sum_magnitude = -128;
        u32 sum_factor = 0;
        int i, count = 0;

        /*
         * To properly average the decibel values (signal values given in dBm)
         * we need to do the math in linear space.  Doing a linear average of
         * dB (dBm) values is a bit annoying though due to the large range of
         * at least -10 to -110 dBm that will not fit into a 32 bit integer.
         *
         * A 64 bit integer should be sufficient, but then we still have the
         * problem that there are no directly usable utility functions
         * available.
         *
         * So, lets not deal with that and instead do much of the calculation
         * with a 16.16 fixed point integer along with a base in dBm. 16.16 bit
         * gives us plenty of head-room for adding up a few values and even
         * doing some math on it. And the tail should be accurate enough too
         * (1/2^16 is somewhere around -48 dB, so effectively zero).
         *
         * i.e. the real value of sum is:
         *      sum = sum_factor / 2^16 * 10^(sum_magnitude / 10) mW
         *
         * However, that does mean we need to be able to bring two values to
         * a common base, so we need a helper for that.
         *
         * Note that this function takes an input with unsigned negative dBm
         * values but returns a signed dBm (i.e. a negative value).
         */

        for (i = 0; i < len; i++) {
                int val_magnitude;
                u32 val_factor;

                /* Assume invalid */
                if (neg_dbm_values[i] == 0xff)
                        continue;

                val_factor = 0x10000;
                val_magnitude = -neg_dbm_values[i];

                if (val_magnitude <= sum_magnitude) {
                        u8 div_db = sum_magnitude - val_magnitude;

                        val_factor = iwl_div_by_db(val_factor, div_db);
                        val_magnitude = sum_magnitude;
                } else {
                        u8 div_db = val_magnitude - sum_magnitude;

                        sum_factor = iwl_div_by_db(sum_factor, div_db);
                        sum_magnitude = val_magnitude;
                }

                sum_factor += val_factor;
                count++;
        }

        /* No valid noise measurement, return a very high noise level */
        if (count == 0)
                return 0;

        average_magnitude = sum_magnitude;
        average_factor = sum_factor / count;

        /*
         * average_factor will be a number smaller than 1.0 (0x10000) at this
         * point. What we need to do now is to adjust average_magnitude so that
         * average_factor is between -0.5 dB and 0.5 dB.
         *
         * Just do -1 dB steps and find the point where
         *   -0.5 dB * -i dB = 0x10000 * 10^(-0.5/10) / i dB
         *                   = div_by_db(0xe429, i)
         * is smaller than average_factor.
         */
        for (i = 0; average_factor < iwl_div_by_db(0xe429, i); i++) {
                /* nothing */
        }

        return clamp(average_magnitude - i, -128, 0);
}
IWL_EXPORT_SYMBOL(iwl_average_neg_dbm);