tlb.s

Windows CE 6.0 BSP for VOIPAC Board (PXA270) Version 2b.

//
// Copyright (c) Microsoft Corporation.  All rights reserved.
//
//
// Use of this source code is subject to the terms of the Microsoft end-user
// license agreement (EULA) under which you licensed this SOFTWARE PRODUCT.
// If you did not accept the terms of the EULA, you are not authorized to use
// this source code. For a copy of the EULA, please see the LICENSE.RTF on your
// install media.
//
#include <kxmips.h>
#include <nkintr.h>

#define KSEG0_BASE          0x80000000

//------------------------------------------------------------------------------

        .text
        .globl  OEMTLBSize
        .globl	Au1InstallTLBHandler

OEMTLBSize:
        .word   31
        
//------------------------------------------------------------------------------
//
//  Function:     OALClearTLB
//
//  Clear all TLB entries. Because MIPS has unified TLB and there isn't simple
//  way how to find TLB entry for address full TLB is cleared each time.
//
LEAF_ENTRY(OALClearTLB)

        .set noreorder
        .text
        
        mfc0    t0, psr                 // Save current psr
        mfc0    t1, entryhi             // Save current asid
        nop
        andi    t2, t0, 0xFFFE          // Mask interrupts
        mtc0    t2, psr                 // Disable interrupts
        nop                             // fill delay slot
        li      t2, KSEG0_BASE          // Unmapped address
        lw      t3, OEMTLBSize          // (t3) = index & loop counter
        mfc0    t4, wired               // (t4) = loop limit

10:     mtc0    zero, entrylo0          // Clear entrylo0 - Invalid entry
        mtc0    zero, entrylo1          // Clear entrylo1 - Invalid entry
        mtc0    t2, entryhi             // Clear entryhi - Ivalid address
        mtc0    t3, index               // Set index
        add     t2, 0x2000
        nop                             // Fill delay slot
        tlbwi                           // Write entry (indexed)
        nop
        bne     t3, t4, 10b             // If not zero do next one
        addu    t3,  -1                 // Decrement index, loop counter

        mtc0    t1, entryhi             // Restore asid
        mtc0    t0, psr                 // Restore psr

        j       ra
        sync
        
        .end OALClearTlb

//------------------------------------------------------------------------------



//------------------------------------------------------------------------------
//
//  Function:     Au1InstallTLBHandler
//
//  Install AU1 specific TLB miss handler. The TLB miss handler has
//  some kind of hazard that requires flushing instruction pipeline.
//
LEAF_ENTRY(Au1InstallTLBHandler)


        // (1) Only install it when we're not profiler build, for profiler build
        //     is jumping to TLBMissHandler already.
        // (2) We're assuming that the 1st instruction of TLBMissHandler to be
        //     "mfc0 k0, badvaddr" and we will not install the handler if this is not 
        //     the case (profiler build).

        li      t0, 0x401A4000              // (t0) = code-byte for 'mfc0 k0, badvaddr'
        li      t1, 0xa0000000              // (t1) = address of TLB exception vector (uncached)
        lw      t2, (t1)                    // (t2) = 1st instruction of TLB miss handler

        bne     t0, t2, Au1Done             // do nothing if the 1st instruction is not 'mfc0 k0, badvaddr'
        nop

        // replace the handler with the code below
        la      t0, Au1TLBMissHandler

        // copy 4 instructions
        // (t0) = address of AU1 handler
        // (t1) = address of the TLB exception vector

        lw      a0, (t0)
        lw      a1, 4(t0)
        lw      a2, 8(t0)
        lw      a3, 12(t0)
        
        sw      a0, (t1)
        sw      a1,	4(t1)
        sw      a2,	8(t1)
        sw      a3, 12(t1)

Au1Done:
        j       ra
        nop

Au1TLBMissHandler:

        la      k0, TLBMissHandler          // 2 DWORDS
        j       k0                          // 1 DWORD
        ssnop                               // 1 DWORD

        .end Au1InstallTLBHandler