/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
 * ChaCha stream cipher (P10 accelerated)
 *
 * Copyright 2023- IBM Corp. All rights reserved.
 */

#include <crypto/internal/simd.h>
#include <linux/kernel.h>
#include <linux/cpufeature.h>
#include <linux/sizes.h>
#include <asm/simd.h>
#include <asm/switch_to.h>

asmlinkage void chacha_p10le_8x(const struct chacha_state *state, u8 *dst,
                                const u8 *src, unsigned int len, int nrounds);

static __ro_after_init DEFINE_STATIC_KEY_FALSE(have_p10);

static void vsx_begin(void)
{
        preempt_disable();
        enable_kernel_vsx();
}

static void vsx_end(void)
{
        disable_kernel_vsx();
        preempt_enable();
}

static void chacha_p10_do_8x(struct chacha_state *state, u8 *dst, const u8 *src,
                             unsigned int bytes, int nrounds)
{
        unsigned int l = bytes & ~0x0FF;

        if (l > 0) {
                chacha_p10le_8x(state, dst, src, l, nrounds);
                bytes -= l;
                src += l;
                dst += l;
                state->x[12] += l / CHACHA_BLOCK_SIZE;
        }

        if (bytes > 0)
                chacha_crypt_generic(state, dst, src, bytes, nrounds);
}

#define hchacha_block_arch hchacha_block_generic /* not implemented yet */

static void chacha_crypt_arch(struct chacha_state *state, u8 *dst,
                              const u8 *src, unsigned int bytes, int nrounds)
{
        if (!static_branch_likely(&have_p10) || bytes <= CHACHA_BLOCK_SIZE ||
            !crypto_simd_usable())
                return chacha_crypt_generic(state, dst, src, bytes, nrounds);

        do {
                unsigned int todo = min_t(unsigned int, bytes, SZ_4K);

                vsx_begin();
                chacha_p10_do_8x(state, dst, src, todo, nrounds);
                vsx_end();

                bytes -= todo;
                src += todo;
                dst += todo;
        } while (bytes);
}

#define chacha_mod_init_arch chacha_mod_init_arch
static void chacha_mod_init_arch(void)
{
        if (cpu_has_feature(CPU_FTR_ARCH_31))
                static_branch_enable(&have_p10);
}