// SPDX-License-Identifier: GPL-2.0
#include <linux/bitops.h>
#include <linux/delay.h>
#include <linux/pci.h>
#include <asm/dma.h>
#include <linux/io.h>
#include <asm/processor-cyrix.h>
#include <asm/processor-flags.h>
#include <linux/timer.h>
#include <asm/pci-direct.h>
#include <asm/tsc.h>
#include <asm/cpufeature.h>
#include <linux/sched.h>
#include <linux/sched/clock.h>

#include "cpu.h"

/*
 * Read NSC/Cyrix DEVID registers (DIR) to get more detailed info. about the CPU
 */
static void __do_cyrix_devid(unsigned char *dir0, unsigned char *dir1)
{
        unsigned char ccr2, ccr3;

        /* we test for DEVID by checking whether CCR3 is writable */
        ccr3 = getCx86(CX86_CCR3);
        setCx86(CX86_CCR3, ccr3 ^ 0x80);
        getCx86(0xc0);   /* dummy to change bus */

        if (getCx86(CX86_CCR3) == ccr3) {       /* no DEVID regs. */
                ccr2 = getCx86(CX86_CCR2);
                setCx86(CX86_CCR2, ccr2 ^ 0x04);
                getCx86(0xc0);  /* dummy */

                if (getCx86(CX86_CCR2) == ccr2) /* old Cx486SLC/DLC */
                        *dir0 = 0xfd;
                else {                          /* Cx486S A step */
                        setCx86(CX86_CCR2, ccr2);
                        *dir0 = 0xfe;
                }
        } else {
                setCx86(CX86_CCR3, ccr3);  /* restore CCR3 */

                /* read DIR0 and DIR1 CPU registers */
                *dir0 = getCx86(CX86_DIR0);
                *dir1 = getCx86(CX86_DIR1);
        }
}

static void do_cyrix_devid(unsigned char *dir0, unsigned char *dir1)
{
        unsigned long flags;

        local_irq_save(flags);
        __do_cyrix_devid(dir0, dir1);
        local_irq_restore(flags);
}
/*
 * Cx86_dir0_msb is a HACK needed by check_cx686_cpuid/slop in bugs.h in
 * order to identify the Cyrix CPU model after we're out of setup.c
 *
 * Actually since bugs.h doesn't even reference this perhaps someone should
 * fix the documentation ???
 */
static unsigned char Cx86_dir0_msb = 0;

static const char Cx86_model[][9] = {
        "Cx486", "Cx486", "5x86 ", "6x86", "MediaGX ", "6x86MX ",
        "M II ", "Unknown"
};
static const char Cx486_name[][5] = {
        "SLC", "DLC", "SLC2", "DLC2", "SRx", "DRx",
        "SRx2", "DRx2"
};
static const char Cx486S_name[][4] = {
        "S", "S2", "Se", "S2e"
};
static const char Cx486D_name[][4] = {
        "DX", "DX2", "?", "?", "?", "DX4"
};
static char Cx86_cb[] = "?.5x Core/Bus Clock";
static const char cyrix_model_mult1[] = "12??43";
static const char cyrix_model_mult2[] = "12233445";

/*
 * Reset the slow-loop (SLOP) bit on the 686(L) which is set by some old
 * BIOSes for compatibility with DOS games.  This makes the udelay loop
 * work correctly, and improves performance.
 *
 * FIXME: our newer udelay uses the tsc. We don't need to frob with SLOP
 */

static void check_cx686_slop(struct cpuinfo_x86 *c)
{
        unsigned long flags;

        if (Cx86_dir0_msb == 3) {
                unsigned char ccr3, ccr5;

                local_irq_save(flags);
                ccr3 = getCx86(CX86_CCR3);
                setCx86(CX86_CCR3, (ccr3 & 0x0f) | 0x10); /* enable MAPEN */
                ccr5 = getCx86(CX86_CCR5);
                if (ccr5 & 2)
                        setCx86(CX86_CCR5, ccr5 & 0xfd);  /* reset SLOP */
                setCx86(CX86_CCR3, ccr3);                 /* disable MAPEN */
                local_irq_restore(flags);

                if (ccr5 & 2) { /* possible wrong calibration done */
                        pr_info("Recalibrating delay loop with SLOP bit reset\n");
                        calibrate_delay();
                        c->loops_per_jiffy = loops_per_jiffy;
                }
        }
}


static void set_cx86_reorder(void)
{
        u8 ccr3;

        pr_info("Enable Memory access reorder on Cyrix/NSC processor.\n");
        ccr3 = getCx86(CX86_CCR3);
        setCx86(CX86_CCR3, (ccr3 & 0x0f) | 0x10); /* enable MAPEN */

        /* Load/Store Serialize to mem access disable (=reorder it) */
        setCx86_old(CX86_PCR0, getCx86_old(CX86_PCR0) & ~0x80);
        /* set load/store serialize from 1GB to 4GB */
        ccr3 |= 0xe0;
        setCx86(CX86_CCR3, ccr3);
}

static void set_cx86_memwb(void)
{
        pr_info("Enable Memory-Write-back mode on Cyrix/NSC processor.\n");

        /* CCR2 bit 2: unlock NW bit */
        setCx86_old(CX86_CCR2, getCx86_old(CX86_CCR2) & ~0x04);
        /* set 'Not Write-through' */
        write_cr0(read_cr0() | X86_CR0_NW);
        /* CCR2 bit 2: lock NW bit and set WT1 */
        setCx86_old(CX86_CCR2, getCx86_old(CX86_CCR2) | 0x14);
}

/*
 *      Configure later MediaGX and/or Geode processor.
 */

static void geode_configure(void)
{
        unsigned long flags;
        u8 ccr3;
        local_irq_save(flags);

        /* Suspend on halt power saving and enable #SUSP pin */
        setCx86_old(CX86_CCR2, getCx86_old(CX86_CCR2) | 0x88);

        ccr3 = getCx86(CX86_CCR3);
        setCx86(CX86_CCR3, (ccr3 & 0x0f) | 0x10);       /* enable MAPEN */


        /* FPU fast, DTE cache, Mem bypass */
        setCx86_old(CX86_CCR4, getCx86_old(CX86_CCR4) | 0x38);
        setCx86(CX86_CCR3, ccr3);                       /* disable MAPEN */

        set_cx86_memwb();
        set_cx86_reorder();

        local_irq_restore(flags);
}

static void early_init_cyrix(struct cpuinfo_x86 *c)
{
        unsigned char dir0, dir0_msn, dir1 = 0;

        __do_cyrix_devid(&dir0, &dir1);
        dir0_msn = dir0 >> 4; /* identifies CPU "family"   */

        switch (dir0_msn) {
        case 3: /* 6x86/6x86L */
                /* Emulate MTRRs using Cyrix's ARRs. */
                set_cpu_cap(c, X86_FEATURE_CYRIX_ARR);
                break;
        case 5: /* 6x86MX/M II */
                /* Emulate MTRRs using Cyrix's ARRs. */
                set_cpu_cap(c, X86_FEATURE_CYRIX_ARR);
                break;
        }
}

static void init_cyrix(struct cpuinfo_x86 *c)
{
        unsigned char dir0, dir0_msn, dir0_lsn, dir1 = 0;
        char *buf = c->x86_model_id;
        const char *p = NULL;

        /*
         * Bit 31 in normal CPUID used for nonstandard 3DNow ID;
         * 3DNow is IDd by bit 31 in extended CPUID (1*32+31) anyway
         */
        clear_cpu_cap(c, 0*32+31);

        /* Cyrix used bit 24 in extended (AMD) CPUID for Cyrix MMX extensions */
        if (test_cpu_cap(c, 1*32+24)) {
                clear_cpu_cap(c, 1*32+24);
                set_cpu_cap(c, X86_FEATURE_CXMMX);
        }

        do_cyrix_devid(&dir0, &dir1);

        check_cx686_slop(c);

        Cx86_dir0_msb = dir0_msn = dir0 >> 4; /* identifies CPU "family"   */
        dir0_lsn = dir0 & 0xf;                /* model or clock multiplier */

        /* common case step number/rev -- exceptions handled below */
        c->x86_model = (dir1 >> 4) + 1;
        c->x86_mask = dir1 & 0xf;

        /* Now cook; the original recipe is by Channing Corn, from Cyrix.
         * We do the same thing for each generation: we work out
         * the model, multiplier and stepping.  Black magic included,
         * to make the silicon step/rev numbers match the printed ones.
         */

        switch (dir0_msn) {
                unsigned char tmp;

        case 0: /* Cx486SLC/DLC/SRx/DRx */
                p = Cx486_name[dir0_lsn & 7];
                break;

        case 1: /* Cx486S/DX/DX2/DX4 */
                p = (dir0_lsn & 8) ? Cx486D_name[dir0_lsn & 5]
                        : Cx486S_name[dir0_lsn & 3];
                break;

        case 2: /* 5x86 */
                Cx86_cb[2] = cyrix_model_mult1[dir0_lsn & 5];
                p = Cx86_cb+2;
                break;

        case 3: /* 6x86/6x86L */
                Cx86_cb[1] = ' ';
                Cx86_cb[2] = cyrix_model_mult1[dir0_lsn & 5];
                if (dir1 > 0x21) { /* 686L */
                        Cx86_cb[0] = 'L';
                        p = Cx86_cb;
                        (c->x86_model)++;
                } else             /* 686 */
                        p = Cx86_cb+1;
                /* Emulate MTRRs using Cyrix's ARRs. */
                set_cpu_cap(c, X86_FEATURE_CYRIX_ARR);
                /* 6x86's contain this bug */
                set_cpu_bug(c, X86_BUG_COMA);
                break;

        case 4: /* MediaGX/GXm or Geode GXM/GXLV/GX1 */
        case 11: /* GX1 with inverted Device ID */
#ifdef CONFIG_PCI
        {
                u32 vendor, device;
                /*
                 * It isn't really a PCI quirk directly, but the cure is the
                 * same. The MediaGX has deep magic SMM stuff that handles the
                 * SB emulation. It throws away the fifo on disable_dma() which
                 * is wrong and ruins the audio.
                 *
                 *  Bug2: VSA1 has a wrap bug so that using maximum sized DMA
                 *  causes bad things. According to NatSemi VSA2 has another
                 *  bug to do with 'hlt'. I've not seen any boards using VSA2
                 *  and X doesn't seem to support it either so who cares 8).
                 *  VSA1 we work around however.
                 */

                pr_info("Working around Cyrix MediaGX virtual DMA bugs.\n");
                isa_dma_bridge_buggy = 2;

                /* We do this before the PCI layer is running. However we
                   are safe here as we know the bridge must be a Cyrix
                   companion and must be present */
                vendor = read_pci_config_16(0, 0, 0x12, PCI_VENDOR_ID);
                device = read_pci_config_16(0, 0, 0x12, PCI_DEVICE_ID);

                /*
                 *  The 5510/5520 companion chips have a funky PIT.
                 */
                if (vendor == PCI_VENDOR_ID_CYRIX &&
                        (device == PCI_DEVICE_ID_CYRIX_5510 ||
                                        device == PCI_DEVICE_ID_CYRIX_5520))
                        mark_tsc_unstable("cyrix 5510/5520 detected");
        }
#endif
                c->x86_cache_size = 16; /* Yep 16K integrated cache thats it */

                /* GXm supports extended cpuid levels 'ala' AMD */
                if (c->cpuid_level == 2) {
                        /* Enable cxMMX extensions (GX1 Datasheet 54) */
                        setCx86_old(CX86_CCR7, getCx86_old(CX86_CCR7) | 1);

                        /*
                         * GXm : 0x30 ... 0x5f GXm  datasheet 51
                         * GXlv: 0x6x          GXlv datasheet 54
                         *  ?  : 0x7x
                         * GX1 : 0x8x          GX1  datasheet 56
                         */
                        if ((0x30 <= dir1 && dir1 <= 0x6f) ||
                                        (0x80 <= dir1 && dir1 <= 0x8f))
                                geode_configure();
                        return;
                } else { /* MediaGX */
                        Cx86_cb[2] = (dir0_lsn & 1) ? '3' : '4';
                        p = Cx86_cb+2;
                        c->x86_model = (dir1 & 0x20) ? 1 : 2;
                }
                break;

        case 5: /* 6x86MX/M II */
                if (dir1 > 7) {
                        dir0_msn++;  /* M II */
                        /* Enable MMX extensions (App note 108) */
                        setCx86_old(CX86_CCR7, getCx86_old(CX86_CCR7)|1);
                } else {
                        /* A 6x86MX - it has the bug. */
                        set_cpu_bug(c, X86_BUG_COMA);
                }
                tmp = (!(dir0_lsn & 7) || dir0_lsn & 1) ? 2 : 0;
                Cx86_cb[tmp] = cyrix_model_mult2[dir0_lsn & 7];
                p = Cx86_cb+tmp;
                if (((dir1 & 0x0f) > 4) || ((dir1 & 0xf0) == 0x20))
                        (c->x86_model)++;
                /* Emulate MTRRs using Cyrix's ARRs. */
                set_cpu_cap(c, X86_FEATURE_CYRIX_ARR);
                break;

        case 0xf:  /* Cyrix 486 without DEVID registers */
                switch (dir0_lsn) {
                case 0xd:  /* either a 486SLC or DLC w/o DEVID */
                        dir0_msn = 0;
                        p = Cx486_name[!!boot_cpu_has(X86_FEATURE_FPU)];
                        break;

                case 0xe:  /* a 486S A step */
                        dir0_msn = 0;
                        p = Cx486S_name[0];
                        break;
                }
                break;

        default:  /* unknown (shouldn't happen, we know everyone ;-) */
                dir0_msn = 7;
                break;
        }
        strcpy(buf, Cx86_model[dir0_msn & 7]);
        if (p)
                strcat(buf, p);
        return;
}

/*
 * Handle National Semiconductor branded processors
 */
static void init_nsc(struct cpuinfo_x86 *c)
{
        /*
         * There may be GX1 processors in the wild that are branded
         * NSC and not Cyrix.
         *
         * This function only handles the GX processor, and kicks every
         * thing else to the Cyrix init function above - that should
         * cover any processors that might have been branded differently
         * after NSC acquired Cyrix.
         *
         * If this breaks your GX1 horribly, please e-mail
         * info-linux@ldcmail.amd.com to tell us.
         */

        /* Handle the GX (Formally known as the GX2) */

        if (c->x86 == 5 && c->x86_model == 5)
                cpu_detect_cache_sizes(c);
        else
                init_cyrix(c);
}

/*
 * Cyrix CPUs without cpuid or with cpuid not yet enabled can be detected
 * by the fact that they preserve the flags across the division of 5/2.
 * PII and PPro exhibit this behavior too, but they have cpuid available.
 */

/*
 * Perform the Cyrix 5/2 test. A Cyrix won't change
 * the flags, while other 486 chips will.
 */
static inline int test_cyrix_52div(void)
{
        unsigned int test;

        __asm__ __volatile__(
             "sahf\n\t"         /* clear flags (%eax = 0x0005) */
             "div %b2\n\t"      /* divide 5 by 2 */
             "lahf"             /* store flags into %ah */
             : "=a" (test)
             : "0" (5), "q" (2)
             : "cc");

        /* AH is 0x02 on Cyrix after the divide.. */
        return (unsigned char) (test >> 8) == 0x02;
}

static void cyrix_identify(struct cpuinfo_x86 *c)
{
        /* Detect Cyrix with disabled CPUID */
        if (c->x86 == 4 && test_cyrix_52div()) {
                unsigned char dir0, dir1;

                strcpy(c->x86_vendor_id, "CyrixInstead");
                c->x86_vendor = X86_VENDOR_CYRIX;

                /* Actually enable cpuid on the older cyrix */

                /* Retrieve CPU revisions */

                do_cyrix_devid(&dir0, &dir1);

                dir0 >>= 4;

                /* Check it is an affected model */

                if (dir0 == 5 || dir0 == 3) {
                        unsigned char ccr3;
                        unsigned long flags;
                        pr_info("Enabling CPUID on Cyrix processor.\n");
                        local_irq_save(flags);
                        ccr3 = getCx86(CX86_CCR3);
                        /* enable MAPEN  */
                        setCx86(CX86_CCR3, (ccr3 & 0x0f) | 0x10);
                        /* enable cpuid  */
                        setCx86_old(CX86_CCR4, getCx86_old(CX86_CCR4) | 0x80);
                        /* disable MAPEN */
                        setCx86(CX86_CCR3, ccr3);
                        local_irq_restore(flags);
                }
        }
}

static const struct cpu_dev cyrix_cpu_dev = {
        .c_vendor       = "Cyrix",
        .c_ident        = { "CyrixInstead" },
        .c_early_init   = early_init_cyrix,
        .c_init         = init_cyrix,
        .c_identify     = cyrix_identify,
        .c_x86_vendor   = X86_VENDOR_CYRIX,
};

cpu_dev_register(cyrix_cpu_dev);

static const struct cpu_dev nsc_cpu_dev = {
        .c_vendor       = "NSC",
        .c_ident        = { "Geode by NSC" },
        .c_init         = init_nsc,
        .c_x86_vendor   = X86_VENDOR_NSC,
};

cpu_dev_register(nsc_cpu_dev);