/*++
Copyright (c) 1989  Microsoft Corporation

Module Name:
    cyrix.c

Abstract:
    Detects and initializes Cryix processors

Author:
    Ken Reneris (kenr) 24-Feb-1994

Environment:
    Kernel mode only.
--*/

#include "ki.h"

#define Cx486_SLC    0x0
#define Cx486_DLC    0x1
#define Cx486_SLC2   0x2
#define Cx486_DLC2   0x3
#define Cx486_SRx    0x4    // Retail Upgrade Cx486SLC
#define Cx486_DRx    0x5    // Retail Upgrade Cx486DLC
#define Cx486_SRx2   0x6    // Retail Upgrade 2x Cx486SLC
#define Cx486_DRx2   0x7    // Retail Upgrade 2x Cx486DLC
#define Cx486DX      0x1a
#define Cx486DX2     0x1b
#define M1           0x30

#define CCR0    0xC0
#define CCR1    0xC1
#define CCR2    0xC2
#define CCR3    0xC3

#define DIR0    0xFE
#define DIR1    0xFF


// SRx & DRx flags
#define CCR0_NC0        0x01        // No cache 64k @ 1M boundaries
#define CCR0_NC1        0x02        // No cache 640k - 1M
#define CCR0_A20M       0x04        // Enables A20M#
#define CCR0_KEN        0x08        // Enables KEN#
#define CCR0_FLUSH      0x10        // Enables FLUSH#

// DX flags
#define CCR1_NO_LOCK    0x10        // Ignore lock prefixes


ULONG Ke386CyrixId (VOID);
UCHAR ReadCyrixRegister (IN UCHAR    Register);
VOID WriteCyrixRegister (IN UCHAR    Register, IN UCHAR    Value);
VOID Ke386ConfigureCyrixProcessor (VOID);

#ifdef ALLOC_PRAGMA
#pragma alloc_text(PAGE,Ke386CyrixId)
#pragma alloc_text(PAGELK,Ke386ConfigureCyrixProcessor)
#endif


extern UCHAR CmpCyrixID[];


ULONG
Ke386CyrixId (
    VOID
    )
/*++
Routine Description:
    Detects and returns the Cyrix ID of the processor.
    This function only detects Cyrix processors which have internal
    cache support.

Arguments:

    Configure   - If TRUE, causes this function to alter
                  the Cyrix CCR registers for the optimal NT
                  performance.

                  If FALSE, the processors configuration is
                  not altered.
Return Value:
    Cyrix ID of the processor
    0 if not a Cyrix processor
--*/
{
    ULONG       CyrixID;
    UCHAR       r3, c;
    UCHAR       flags;
    PKPRCB      Prcb;

    CyrixID = 0;

    Prcb = KeGetCurrentPrcb();
    if (Prcb->CpuID  &&  strcmp (Prcb->VendorString, CmpCyrixID)) {


        // Not a Cyrix processor


        return 0;
    }


    // Test Div instruction to see if the flags
    // do not get altered


    _asm {
        xor     eax, eax
        sahf                    ; flags = ah

        lahf                    ; ah = flags
        mov     flags, ah       ; save flags

        mov     eax, 5
        mov     ecx, 2
        div     cl              ; 5 / 2 = ?

        lahf
        sub     flags, ah       ; flags = orig_flags - new_flags
    }

    if (flags == 0) {


        // See if the Cyrix CCR3 register bit 0x80 can be editted.


        r3 = ReadCyrixRegister(CCR3);       // Read CCR3
        c  = r3 ^ 0x80;                     // flip bit 80
        WriteCyrixRegister(CCR3, c);        // Write CCR3
        ReadCyrixRegister(CCR0);            // select new register
        c = ReadCyrixRegister(CCR3);        // Read new CCR3 value

        if (ReadCyrixRegister(CCR3) != r3) {


            // Read the Cyrix ID type register


            CyrixID = ReadCyrixRegister(DIR0) + 1;
        }

        WriteCyrixRegister(CCR3, r3);       // restore original CCR3 value
    }

    if (CyrixID > 0x7f) {
        // invalid setting
        CyrixID = 0;
    }

    return CyrixID;
}


static UCHAR
ReadCyrixRegister (
    IN UCHAR    Register
    )
/*++
Routine Description:
    Reads an internal Cyrix ID register.  Note the internal register
    space is accessed via I/O addresses which are hooked internally
    to the processor.

    The caller is responsible for only calling this function on
    a Cyrix processor.

Arguments:
    Register - Which Cyrix register to read
Return Value:
    The registers value
--*/
{
    UCHAR   Value;

    _asm {
        mov     al, Register
        cli
        out     22h, al
        in      al, 23h
        sti
        mov     Value, al
    }
    return  Value;
}


static VOID
WriteCyrixRegister (
    IN UCHAR    Register,
    IN UCHAR    Value
    )
/*++
Routine Description:
    Write an internal Cyrix ID register.  Note the internal register
    space is accessed via I/O addresses which are hooked internally to the processor.

    The caller is responsible for only calling this function on a Cyrix processor.
Arguments:
    Register - Which Cyrix register to written
    Value    - Value to write into the register
Return Value:
    The registers value
--*/
{
    _asm {
        mov     al, Register
        mov     cl, Value
        cli
        out     22h, al
        mov     al, cl
        out     23h, al
        sti
    }
}


VOID Ke386ConfigureCyrixProcessor (VOID)
{
    UCHAR   r0, r1;
    ULONG   id, rev;
    PVOID   LockHandle;

    PAGED_CODE();

    id = Ke386CyrixId();
    if (id) {
        LockHandle = MmLockPagableCodeSection (&Ke386ConfigureCyrixProcessor);

        id  = id - 1;
        rev = ReadCyrixRegister(DIR1);

        if ((id >= 0x20  &&  id <= 0x27) || ((id & 0xF0) == M1  &&  rev < 0x17)) {
            // These steppings have a write-back cache problem.
            // On these chips the L1 w/b cache can be disabled by
            // setting only the NW bit.

            _asm {
                cli

                mov     eax, cr0
                or      eax, CR0_NW
                mov     cr0, eax

                sti
            }
        }

        switch (id) {
            case Cx486_SRx:
            case Cx486_DRx:
            case Cx486_SRx2:
            case Cx486_DRx2:
                // These processors have an internal cache feature
                // let's turn it on.

                r0  = ReadCyrixRegister(CCR0);
                r0 |=  CCR0_NC1 | CCR0_FLUSH;
                r0 &= ~CCR0_NC0;
                WriteCyrixRegister(CCR0, r0);

                // Clear Non-Cacheable Region 1
                WriteCyrixRegister(0xC4, 0);
                WriteCyrixRegister(0xC5, 0);
                WriteCyrixRegister(0xC6, 0);
                break;

            case Cx486DX:
            case Cx486DX2:
                // Set NO_LOCK flag on these processors according to
                // the number of booted processors

                r1  = ReadCyrixRegister(CCR1);
                r1 |= CCR1_NO_LOCK;
                if (KeNumberProcessors > 1) {
                    r1 &= ~CCR1_NO_LOCK;
                }
                WriteCyrixRegister(CCR1, r1);
                break;
        }

        MmUnlockPagableImageSection (LockHandle);
    }
}