// SPDX-License-Identifier: GPL-2.0
#include <linux/init.h>
#include <linux/mm.h>

#include <asm/mtrr.h>
#include <asm/msr.h>

#include "mtrr.h"

static struct {
        unsigned long high;
        unsigned long low;
} centaur_mcr[8];

static u8 centaur_mcr_reserved;
static u8 centaur_mcr_type;     /* 0 for winchip, 1 for winchip2 */

/**
 * centaur_get_free_region - Get a free MTRR.
 *
 * @base: The starting (base) address of the region.
 * @size: The size (in bytes) of the region.
 *
 * Returns: the index of the region on success, else -1 on error.
 */
static int
centaur_get_free_region(unsigned long base, unsigned long size, int replace_reg)
{
        unsigned long lbase, lsize;
        mtrr_type ltype;
        int i, max;

        max = num_var_ranges;
        if (replace_reg >= 0 && replace_reg < max)
                return replace_reg;

        for (i = 0; i < max; ++i) {
                if (centaur_mcr_reserved & (1 << i))
                        continue;
                mtrr_if->get(i, &lbase, &lsize, &ltype);
                if (lsize == 0)
                        return i;
        }

        return -ENOSPC;
}

static void
centaur_get_mcr(unsigned int reg, unsigned long *base,
                unsigned long *size, mtrr_type * type)
{
        *base = centaur_mcr[reg].high >> PAGE_SHIFT;
        *size = -(centaur_mcr[reg].low & 0xfffff000) >> PAGE_SHIFT;
        *type = MTRR_TYPE_WRCOMB;               /* write-combining  */

        if (centaur_mcr_type == 1 && ((centaur_mcr[reg].low & 31) & 2))
                *type = MTRR_TYPE_UNCACHABLE;
        if (centaur_mcr_type == 1 && (centaur_mcr[reg].low & 31) == 25)
                *type = MTRR_TYPE_WRBACK;
        if (centaur_mcr_type == 0 && (centaur_mcr[reg].low & 31) == 31)
                *type = MTRR_TYPE_WRBACK;
}

static void
centaur_set_mcr(unsigned int reg, unsigned long base,
                unsigned long size, mtrr_type type)
{
        unsigned long low, high;

        if (size == 0) {
                /* Disable */
                high = low = 0;
        } else {
                high = base << PAGE_SHIFT;
                if (centaur_mcr_type == 0) {
                        /* Only support write-combining... */
                        low = -size << PAGE_SHIFT | 0x1f;
                } else {
                        if (type == MTRR_TYPE_UNCACHABLE)
                                low = -size << PAGE_SHIFT | 0x02; /* NC */
                        else
                                low = -size << PAGE_SHIFT | 0x09; /* WWO, WC */
                }
        }
        centaur_mcr[reg].high = high;
        centaur_mcr[reg].low = low;
        wrmsr(MSR_IDT_MCR0 + reg, low, high);
}

static int
centaur_validate_add_page(unsigned long base, unsigned long size, unsigned int type)
{
        /*
         * FIXME: Winchip2 supports uncached
         */
        if (type != MTRR_TYPE_WRCOMB &&
            (centaur_mcr_type == 0 || type != MTRR_TYPE_UNCACHABLE)) {
                pr_warn("mtrr: only write-combining%s supported\n",
                           centaur_mcr_type ? " and uncacheable are" : " is");
                return -EINVAL;
        }
        return 0;
}

const struct mtrr_ops centaur_mtrr_ops = {
        .var_regs          = 8,
        .set               = centaur_set_mcr,
        .get               = centaur_get_mcr,
        .get_free_region   = centaur_get_free_region,
        .validate_add_page = centaur_validate_add_page,
        .have_wrcomb       = positive_have_wrcomb,
};