startup.s

老外的一个开源项目

;++
; Copyright (c) David Vescovi.  All rights reserved.
; Part of Project DrumStix
; Windows Embedded Developers Interest Group (WE-DIG) community project.
; http://www.we-dig.org
; Copyright (c) Microsoft Corporation.  All rights reserved.
;
; Abstract:
;
;	Board-level initialization for OEM-specific code.
;	Kernel flavor.
;
;--

	OPT   2					; disable listing
	INCLUDE kxarm.h
	OPT   1					; reenable listing

	IMPORT  KernelStart

	TEXTAREA
       
;------------------------------------------------------------------------
	; Included within the text section in order that a relative offset can be
	; computed in the code below.
	;
	OPT   2					; disable listing
	INCLUDE	oemaddrtab_cfg.inc
	OPT   1					; reenable listing

;-------------------------------------------------------------------------------
;
; OALStartUp: OEM kernel OAL startup code.
;
; Inputs: None.
; 
; On return: N/A.
;
; Register used: r0
;
;-------------------------------------------------------------------------------
;
	ALIGN
	LEAF_ENTRY OALStartUp

	; Compute the OEMAddressTable's physical address and 
	; load it into r0. KernelStart expects r0 to contain
	; the physical address of this table. The MMU isn't 
	; turned on until well into KernelStart.  
	;
	add     r0, pc, #g_oalAddressTable - (. + 8)
	mov     r11, r0
	b       KernelStart
	nop
	nop
	nop
	nop
	nop
	nop
    
STALL
	b       STALL               ; Spin forever.

;-------------------------------------------------------------------------------

    LTORG

;-------------------------------------------------------------------------------
;
; TurnOnBTB - Enables the Branch Target Buffer
; Turn on the BTB via cp15.1[11] - Uses r0
;

	LEAF_ENTRY TurnOnBTB

	mcr p15, 0, r0, c7, c5, 0 ; flush the icache & BTB
	mrc p15,0,r0,c1,c0,0
	orr r0, r0, #0x800
	mcr p15,0,r0,c1,c0,0

	mov  pc, lr          ; return

;------------------------------------------------------------------------------

    LTORG

;-------------------------------------------------------------------------------
;
; FreqChange - Do a Frequency Change Sequence
;
; Uses
;  r0 - arg1 - Value for Turbo Mode
;  0 = no turbo
;  1 = turbo
;

	LEAF_ENTRY FreqChange

	stmfd	sp!, {r1-r3}

    cmp     r0, #1
    bgt     FreqRet
	orr		r0, r0, #2						; set FCS=1
	mcr		p14, 0, r0, c6, c0, 0			; do Freq Change

FreqRet

	ldmfd	sp!, {r1-r3}

	mov  pc, lr          ; return


;------------------------------------------------------------------------------

    LTORG

;-------------------------------------------------------------------------------
;
; OALCPUIdle - system idle
;
; This routine is called by OEMIdle in order to enter IDLE mode
;
;       Entry   Interrupts disabled
;       Exit    none
;       Uses    r0
;
	LEAF_ENTRY OALCPUIdle

	ldr		r0, =0x01					; 1 = Idle Mode
	mcr		p14, 0, r0, c7, c0, 0		; Enter Idle mode
	mov		pc, lr						; return


    END