// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * xor.c : Multiple Devices driver for Linux
 *
 * Copyright (C) 1996, 1997, 1998, 1999, 2000,
 * Ingo Molnar, Matti Aarnio, Jakub Jelinek, Richard Henderson.
 *
 * Dispatch optimized RAID-5 checksumming functions.
 */

#define BH_TRACE 0
#include <linux/module.h>
#include <linux/gfp.h>
#include <linux/raid/xor.h>
#include <linux/jiffies.h>
#include <linux/preempt.h>
#include <asm/xor.h>

#ifndef XOR_SELECT_TEMPLATE
#define XOR_SELECT_TEMPLATE(x) (x)
#endif

/* The xor routines to use.  */
static struct xor_block_template *active_template;

void
xor_blocks(unsigned int src_count, unsigned int bytes, void *dest, void **srcs)
{
        unsigned long *p1, *p2, *p3, *p4;

        p1 = (unsigned long *) srcs[0];
        if (src_count == 1) {
                active_template->do_2(bytes, dest, p1);
                return;
        }

        p2 = (unsigned long *) srcs[1];
        if (src_count == 2) {
                active_template->do_3(bytes, dest, p1, p2);
                return;
        }

        p3 = (unsigned long *) srcs[2];
        if (src_count == 3) {
                active_template->do_4(bytes, dest, p1, p2, p3);
                return;
        }

        p4 = (unsigned long *) srcs[3];
        active_template->do_5(bytes, dest, p1, p2, p3, p4);
}
EXPORT_SYMBOL(xor_blocks);

/* Set of all registered templates.  */
static struct xor_block_template *__initdata template_list;

#ifndef MODULE
static void __init do_xor_register(struct xor_block_template *tmpl)
{
        tmpl->next = template_list;
        template_list = tmpl;
}

static int __init register_xor_blocks(void)
{
        active_template = XOR_SELECT_TEMPLATE(NULL);

        if (!active_template) {
#define xor_speed       do_xor_register
                // register all the templates and pick the first as the default
                XOR_TRY_TEMPLATES;
#undef xor_speed
                active_template = template_list;
        }
        return 0;
}
#endif

#define BENCH_SIZE      4096
#define REPS            800U

static void __init
do_xor_speed(struct xor_block_template *tmpl, void *b1, void *b2)
{
        int speed;
        unsigned long reps;
        ktime_t min, start, t0;

        tmpl->next = template_list;
        template_list = tmpl;

        preempt_disable();

        reps = 0;
        t0 = ktime_get();
        /* delay start until time has advanced */
        while ((start = ktime_get()) == t0)
                cpu_relax();
        do {
                mb(); /* prevent loop optimization */
                tmpl->do_2(BENCH_SIZE, b1, b2);
                mb();
        } while (reps++ < REPS || (t0 = ktime_get()) == start);
        min = ktime_sub(t0, start);

        preempt_enable();

        // bytes/ns == GB/s, multiply by 1000 to get MB/s [not MiB/s]
        speed = (1000 * reps * BENCH_SIZE) / (unsigned int)ktime_to_ns(min);
        tmpl->speed = speed;

        pr_info("   %-16s: %5d MB/sec\n", tmpl->name, speed);
}

static int __init
calibrate_xor_blocks(void)
{
        void *b1, *b2;
        struct xor_block_template *f, *fastest;

        fastest = XOR_SELECT_TEMPLATE(NULL);

        if (fastest) {
                printk(KERN_INFO "xor: automatically using best "
                                 "checksumming function   %-10s\n",
                       fastest->name);
                goto out;
        }

        b1 = (void *) __get_free_pages(GFP_KERNEL, 2);
        if (!b1) {
                printk(KERN_WARNING "xor: Yikes!  No memory available.\n");
                return -ENOMEM;
        }
        b2 = b1 + 2*PAGE_SIZE + BENCH_SIZE;

        /*
         * If this arch/cpu has a short-circuited selection, don't loop through
         * all the possible functions, just test the best one
         */

#define xor_speed(templ)        do_xor_speed((templ), b1, b2)

        printk(KERN_INFO "xor: measuring software checksum speed\n");
        template_list = NULL;
        XOR_TRY_TEMPLATES;
        fastest = template_list;
        for (f = fastest; f; f = f->next)
                if (f->speed > fastest->speed)
                        fastest = f;

        pr_info("xor: using function: %s (%d MB/sec)\n",
               fastest->name, fastest->speed);

#undef xor_speed

        free_pages((unsigned long)b1, 2);
out:
        active_template = fastest;
        return 0;
}

static __exit void xor_exit(void) { }

MODULE_DESCRIPTION("RAID-5 checksumming functions");
MODULE_LICENSE("GPL");

#ifndef MODULE
/* when built-in xor.o must initialize before drivers/md/md.o */
core_initcall(register_xor_blocks);
#endif

module_init(calibrate_xor_blocks);
module_exit(xor_exit);