mmu.s

使用三星ARM2410的eboot程序

;
; 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.
;
; Module Name:
;
;   mmu.s
;
; Abstract:
;
;   This module contains code for setting up a page table, enabling the MMU,
;   and enabling the Dcache.  It is used to set up for the bootloader.
;
; Author:
;
;    Thomas Fenwick (thomasf) 04-Feb-97
;
; Environment:
;
;    Kernel mode only.
;
; Revision History:
;
;   Janet Schneider (v-janets) 06-November-1997
;   Scott Shell (scottsh) 18-Jan-1999               Revised for Hornet
;
;   Revised from armtrap.s
;
;--

    INCLUDE kxarm.h

MemoryMap   EQU 0x2a4       ; From ksarm.h - to get this to compile

BANK_SIZE   EQU 0x00100000  ; 1MB per bank in MemoryMap array
BANK_SHIFT  EQU 20

;
;   Define RAM space for the Page Tables:
;

PHYBASE     EQU 0x30000000  ; physical start
;PTs     EQU 0x30010000  ; 1st level page table address (PHYBASE + 0x10000)
PTs     EQU 0x31E00000
                    ; save room for interrupt vectors.

    MACRO
    MTC15   $cpureg, $cp15reg
    mcr p15, 0, $cpureg, $cp15reg, c0, 0
    MEND

    MACRO
    MFC15   $cpureg, $cp15reg
    mrc p15, 0, $cpureg, $cp15reg, c0, 0
    MEND

    TEXTAREA

    IMPORT  main

; KernelStart - Set up the MMU and Dcache for bootloader
;
; This routine will initialize the first-level page table based up the contents
; of the MemoryMap array and enable the MMU and caches.
;
;   Entry   (r0) = pointer to MemoryMap array in physical memory
;   Exit    returns if MemoryMap is invalid

; For Catfish, we are always in RAM.

    LEAF_ENTRY KernelStart

15  mov r11, r0         ; (r11) = &MemoryMap (save pointer)
    ldr r10, =PTs       ; (r10) = 1st level page table

; Setup 1st level page table (using section descriptor) 
; Fill in first level page table entries to create "un-mapped" regions
; from the contents of the MemoryMap array.
;
;   (r10) = 1st level page table
;   (r11) = ptr to MemoryMap array

    add r10, r10, #0x2000   ; (r10) = ptr to 1st PTE for "unmapped space"

    mov r0, #0x0E       ; (r0) = PTE for 0: 1MB cachable bufferable
    orr r0, r0, #0x400      ; set kernel r/w permission
20  mov r1, r11         ; (r1) = ptr to MemoryMap array

        
25  ldr r2, [r1], #4        ; (r2) = virtual address to map Bank at
    ldr r3, [r1], #4        ; (r3) = physical address to map from
    ldr r4, [r1], #4        ; (r4) = num MB to map

    cmp r4, #0                  ; End of table?
    beq %F29

    ldr r5, =0x1FF00000
    and r2, r2, r5              ; VA needs 512MB, 1MB aligned.                

    ldr r5, =0xFFF00000
    and r3, r3, r5              ; PA needs 4GB, 1MB aligned.

    add r2, r10, r2, LSR #18
    add r0, r0, r3              ; (r0) = PTE for next physical page

28  str r0, [r2], #4
    add r0, r0, #0x00100000     ; (r0) = PTE for next physical page
    sub r4, r4, #1              ; Decrement number of MB left 
    cmp r4, #0
    bne %B28                    ; Map next MB

    bic r0, r0, #0xF0000000     ; Clear Section Base Address Field
    bic r0, r0, #0x0FF00000     ; Clear Section Base Address Field
    b   %B25                    ; Get next element
        
29  tst r0, #8
    bic r0, r0, #0x0C       ; clear cachable & bufferable bits in PTE
    add r10, r10, #0x0800   ; (r10) = ptr to 1st PTE for "unmapped uncached space"
    bne %B20            ; go setup PTEs for uncached space
    sub r10, r10, #0x3000   ; (r10) = restore address of 1st level page table


; setup mmu to map (VA == 0) to (PA == 0x30000000)

    ldr r0, =PTs        ; PTE entry for VA = 0
    ldr r1, =0x3000040E     ; uncache/unbuffer/rw, PA base == 0x30000000
    str r1, [r0]

; uncached area

    add r0, r0, #0x0800     ; PTE entry for VA = 0x0200.0000 , uncached 
    ldr r1, =0x30000402     ; uncache/unbuffer/rw, base == 0x30000000
    str r1, [r0]
    
; Comment:
; The following loop is to direct map RAM VA == PA. i.e. 
;   VA == 0x30XXXXXX => PA == 0x30XXXXXX for S3C2400
; Fill in 8 entries to have a direct mapping for DRAM

    ldr r10, =PTs       ; restore address of 1st level page table
    ldr r0,  =PHYBASE

    add r10, r10, #(0x3000 / 4) ; (r10) = ptr to 1st PTE for 0x30000000

    add r0, r0, #0x1E       ; 1MB cachable bufferable
    orr r0, r0, #0x400      ; set kernel r/w permission
    mov r1, #0 
    mov r3, #64
35  mov r2, r1          ; (r2) = virtual address to map Bank at
    cmp r2, #0x20000000:SHR:BANK_SHIFT
    add r2, r10, r2, LSL #BANK_SHIFT-18
    strlo   r0, [r2]
    add r0, r0, #0x00100000 ; (r0) = PTE for next physical page
    subs    r3, r3, #1
    add r1, r1, #1
    bgt %B35

    ldr r10, =PTs       ; (r10) = restore address of 1st level page table

;
; The page tables and exception vectors are setup. Initialize the MMU and turn
; it on.

    mov     r1, #1
    MTC15   r1, c3                  ; setup access to domain 0
    MTC15   r10, c2
    mcr     p15, 0, r0, c8, c7, 0   ; flush I+D TLBs
    mov     r1, #0x0071             ; Enable: MMU
    orr     r1, r1, #0x0004     ; Enable the cache

    ldr     r0, =VirtualStart

    cmp     r0, #0                  ; make sure no stall on "mov pc,r0" below
    MTC15   r1, c1                  ; enable the MMU & Caches
    mov     pc, r0                  ;  & jump to new virtual address
    nop

; MMU & caches now enabled.
;
;   (r10) = physcial address of 1st level page table

VirtualStart

    mov sp, #0x8C000000
    add sp, sp, #0x30000    ; arbitrary initial super-page stack pointer
    b   main

    END