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

#include <asm/processor-cyrix.h>
#include <asm/processor-flags.h>
#include <asm/mtrr.h>
#include <asm/msr.h>

#include "mtrr.h"

static void
cyrix_get_arr(unsigned int reg, unsigned long *base,
              unsigned long *size, mtrr_type * type)
{
        unsigned char arr, ccr3, rcr, shift;
        unsigned long flags;

        arr = CX86_ARR_BASE + (reg << 1) + reg; /* avoid multiplication by 3 */

        local_irq_save(flags);

        ccr3 = getCx86(CX86_CCR3);
        setCx86(CX86_CCR3, (ccr3 & 0x0f) | 0x10);       /* enable MAPEN */
        ((unsigned char *)base)[3] = getCx86(arr);
        ((unsigned char *)base)[2] = getCx86(arr + 1);
        ((unsigned char *)base)[1] = getCx86(arr + 2);
        rcr = getCx86(CX86_RCR_BASE + reg);
        setCx86(CX86_CCR3, ccr3);                       /* disable MAPEN */

        local_irq_restore(flags);

        shift = ((unsigned char *) base)[1] & 0x0f;
        *base >>= PAGE_SHIFT;

        /*
         * Power of two, at least 4K on ARR0-ARR6, 256K on ARR7
         * Note: shift==0xf means 4G, this is unsupported.
         */
        if (shift)
                *size = (reg < 7 ? 0x1UL : 0x40UL) << (shift - 1);
        else
                *size = 0;

        /* Bit 0 is Cache Enable on ARR7, Cache Disable on ARR0-ARR6 */
        if (reg < 7) {
                switch (rcr) {
                case 1:
                        *type = MTRR_TYPE_UNCACHABLE;
                        break;
                case 8:
                        *type = MTRR_TYPE_WRBACK;
                        break;
                case 9:
                        *type = MTRR_TYPE_WRCOMB;
                        break;
                case 24:
                default:
                        *type = MTRR_TYPE_WRTHROUGH;
                        break;
                }
        } else {
                switch (rcr) {
                case 0:
                        *type = MTRR_TYPE_UNCACHABLE;
                        break;
                case 8:
                        *type = MTRR_TYPE_WRCOMB;
                        break;
                case 9:
                        *type = MTRR_TYPE_WRBACK;
                        break;
                case 25:
                default:
                        *type = MTRR_TYPE_WRTHROUGH;
                        break;
                }
        }
}

/*
 * cyrix_get_free_region - get a free ARR.
 *
 * @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
cyrix_get_free_region(unsigned long base, unsigned long size, int replace_reg)
{
        unsigned long lbase, lsize;
        mtrr_type ltype;
        int i;

        switch (replace_reg) {
        case 7:
                if (size < 0x40)
                        break;
                fallthrough;
        case 6:
        case 5:
        case 4:
                return replace_reg;
        case 3:
        case 2:
        case 1:
        case 0:
                return replace_reg;
        }
        /* If we are to set up a region >32M then look at ARR7 immediately */
        if (size > 0x2000) {
                cyrix_get_arr(7, &lbase, &lsize, &ltype);
                if (lsize == 0)
                        return 7;
                /* Else try ARR0-ARR6 first  */
        } else {
                for (i = 0; i < 7; i++) {
                        cyrix_get_arr(i, &lbase, &lsize, &ltype);
                        if (lsize == 0)
                                return i;
                }
                /*
                 * ARR0-ARR6 isn't free
                 * try ARR7 but its size must be at least 256K
                 */
                cyrix_get_arr(i, &lbase, &lsize, &ltype);
                if ((lsize == 0) && (size >= 0x40))
                        return i;
        }
        return -ENOSPC;
}

static u32 cr4, ccr3;

static void prepare_set(void)
{
        u32 cr0;

        /*  Save value of CR4 and clear Page Global Enable (bit 7)  */
        if (boot_cpu_has(X86_FEATURE_PGE)) {
                cr4 = __read_cr4();
                __write_cr4(cr4 & ~X86_CR4_PGE);
        }

        /*
         * Disable and flush caches.
         * Note that wbinvd flushes the TLBs as a side-effect
         */
        cr0 = read_cr0() | X86_CR0_CD;
        wbinvd();
        write_cr0(cr0);
        wbinvd();

        /* Cyrix ARRs - everything else was excluded at the top */
        ccr3 = getCx86(CX86_CCR3);

        /* Cyrix ARRs - everything else was excluded at the top */
        setCx86(CX86_CCR3, (ccr3 & 0x0f) | 0x10);
}

static void post_set(void)
{
        /* Flush caches and TLBs */
        wbinvd();

        /* Cyrix ARRs - everything else was excluded at the top */
        setCx86(CX86_CCR3, ccr3);

        /* Enable caches */
        write_cr0(read_cr0() & ~X86_CR0_CD);

        /* Restore value of CR4 */
        if (boot_cpu_has(X86_FEATURE_PGE))
                __write_cr4(cr4);
}

static void cyrix_set_arr(unsigned int reg, unsigned long base,
                          unsigned long size, mtrr_type type)
{
        unsigned char arr, arr_type, arr_size;

        arr = CX86_ARR_BASE + (reg << 1) + reg; /* avoid multiplication by 3 */

        /* count down from 32M (ARR0-ARR6) or from 2G (ARR7) */
        if (reg >= 7)
                size >>= 6;

        size &= 0x7fff;         /* make sure arr_size <= 14 */
        for (arr_size = 0; size; arr_size++, size >>= 1)
                ;

        if (reg < 7) {
                switch (type) {
                case MTRR_TYPE_UNCACHABLE:
                        arr_type = 1;
                        break;
                case MTRR_TYPE_WRCOMB:
                        arr_type = 9;
                        break;
                case MTRR_TYPE_WRTHROUGH:
                        arr_type = 24;
                        break;
                default:
                        arr_type = 8;
                        break;
                }
        } else {
                switch (type) {
                case MTRR_TYPE_UNCACHABLE:
                        arr_type = 0;
                        break;
                case MTRR_TYPE_WRCOMB:
                        arr_type = 8;
                        break;
                case MTRR_TYPE_WRTHROUGH:
                        arr_type = 25;
                        break;
                default:
                        arr_type = 9;
                        break;
                }
        }

        prepare_set();

        base <<= PAGE_SHIFT;
        setCx86(arr + 0,  ((unsigned char *)&base)[3]);
        setCx86(arr + 1,  ((unsigned char *)&base)[2]);
        setCx86(arr + 2, (((unsigned char *)&base)[1]) | arr_size);
        setCx86(CX86_RCR_BASE + reg, arr_type);

        post_set();
}

const struct mtrr_ops cyrix_mtrr_ops = {
        .var_regs          = 8,
        .set               = cyrix_set_arr,
        .get               = cyrix_get_arr,
        .get_free_region   = cyrix_get_free_region,
        .validate_add_page = generic_validate_add_page,
        .have_wrcomb       = positive_have_wrcomb,
};