/*      $NetBSD: cpu_in_cksum_neon.c,v 1.2 2025/06/19 22:00:54 andvar Exp $     */

/*-
 * Copyright (c) 2012 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Matt Thomas of 3am Software Foundry.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/cdefs.h>

__KERNEL_RCSID(0, "$NetBSD: cpu_in_cksum_neon.c,v 1.2 2025/06/19 22:00:54 andvar Exp $");

#include <sys/param.h>
#include <sys/cpu.h>
#include <sys/mbuf.h>

#include <netinet/in.h>
#include <netinet/ip.h>

uint32_t cpu_in_cksum_neon(const void *, size_t);
uint32_t cpu_in_cksum_neon_v4hdr(const void *);

int
cpu_in_cksum(struct mbuf *m, int len, int off, uint32_t initial_sum)
{
        uint32_t csum = initial_sum;
        int odd = 0;

        /*
         * Taken control of the NEON PCU.
         */
        vfp_hijack();

        /*
         * Fast path for the normal ip_header
         */
        if (off == 0
            && csum == 0
            && len == sizeof(struct ip)
            && ((uintptr_t)m->m_data & 3) == 0
            && m->m_len >= len) {
                csum = cpu_in_cksum_neon_v4hdr(m->m_data);

                /*
                 * We are now down with NEON.
                 */
                vfp_surrender();

                if (csum == 0x10000)    /* note 0x10000 - 0xffff == 1 */
                        return 1;
                return csum == 0 ? 0xffff : csum;       /* never return 0. */
        }

        /*
         * Skip the initial mbufs
         */
        while (m->m_len >= off) {
                m = m->m_next;
                off -= m->m_len;
                KASSERT(m != NULL);
        }

        for (; len > 0; m = m->m_next, off = 0) {
                KASSERT(m != NULL);
                int dlen = MIN(m->m_len - off, len);
                const void *dptr = m->m_data + off;
                /*
                 * This routine will add based on the memory layout so
                 * if the previous len was odd or the this buffer starts
                 * on an odd address, shift the csum by 8 so its properly
                 * aligned.  It will be taken care of when we do the final
                 * checksum fold.
                 */
                uint32_t tmpsum = cpu_in_cksum_neon(dptr, dlen);
                if (odd ^ ((uint32_t)dptr & 1))
                        tmpsum <<= 8;
                /*
                 * Accumulate checksum, folding will be done later
                 */
                csum += tmpsum;
                odd ^= dlen & 1;
                len -= dlen;
        }

        /*
         * We are now down with NEON.
         */
        vfp_surrender();

        /*
         * Time to fold the checksum
         */
        csum = (csum >> 16) + (csum & 0xffff);
        /*
         * Now it could be 0x1xxxx so fold again
         */
        csum = (csum >> 16) + (csum & 0xffff);

        KASSERT(csum <= 0x10000);
        if (csum == 0x10000)    /* note 0x10000 - 0xffff == 1 */
                return 1;
        return csum == 0 ? 0xffff : csum;       /* never return 0. */
}