os_cpu_a.s

基于44b0X,flash:0 ram:0xc

;**********************************************************************
;****************************************************
; $Workfile:   os_cpu_a.S   for STD2.5 simulator    $  
; $Revision: 1.1.1.1 $
; $Author: chaisc
; $Date: 2003/08/13
;****************************************************


;********************************************************************/
      AREA	os_cpu_a, CODE, READONLY

;/***********************************************************************
;
; Function: OSStartHighRdy
;
; Purpose:
; 	   To start the task with the highest priority during OS startup
;
; Processing:
;    See uC/OS-II Task Level Context Switch flow chart
;
; Parameters: void
;
; Outputs:  None
;
; Returns:  void
;
; Notes:
;   Called once during OSStart()
;
;*********************************************************************/
	EXPORT 	OSStartHighRdy
	IMPORT	OSTaskSwHook
	IMPORT  OSTCBHighRdy 
	IMPORT  OSRunning

OSStartHighRdy
        BL 	OSTaskSwHook             ; Call user-defined hook function

        LDR 	r4,=OSRunning            ; Indicate that multitasking has started
        MOV 	r5, #1                   
        STRB 	r5, [r4]                 ; OSRunning = true

        LDR 	r4, =OSTCBHighRdy        ; Get highest priority task TCB address
        LDR 	r4, [r4]                 ; get stack pointer
        LDR 	sp, [r4]                 ; switch to the new stack

        LDMFD 	sp!, {r4} 
		MSR 	spsr_cxsf, r4
        LDMFD 	sp!, {r4} 
		MSR 	cpsr_cxsf, r4
        LDMFD 	sp!, {r0-r12,lr,pc}      ; pop new task s r0-r12,lr & pc

 	
;/***********************************************************************
;
; Function: OS_TASK_SW 
;
; Purpose:
; 	To perform a context switch from the Task Level.
;
; Processing:
;    See uC/OS-II Task Level Context Switch flow chart
;
; Parameters: void
;
; Outputs:  None
;
; Returns:  void
;
; Notes:
;   On entry, OSTCBCur and OSPrioCur hold the current TCB and priority
;   and OSTCBHighRdy and OSPrioHighRdy contain the same for the task
;   to be switched to.
; 
;   The following code assumes that the virtual memory is directly
;   mapped into  physical memory. If this is not true, the cache must 
;   be flushed at context switch to avoid address aliasing.
;
;*********************************************************************/
        EXPORT 	OSCtxSw
		EXPORT 	_OSCtxSw
        IMPORT	OSPrioCur
        IMPORT	OSPrioHighRdy
        IMPORT	OSTCBCur
        IMPORT	OSTaskSwHook
        IMPORT	OSTCBHighRdy
        
OSCtxSw
        STMFD 	sp!, {lr}                ; push pc (lr is actually be pushed in place of PC)
        STMFD 	sp!, {r0-r12,lr}         ; push lr & register file
        MRS 	r4, cpsr
		STMFD 	sp!, {r4}                ; push current psr
        MRS 	r4, spsr
		STMFD 	sp!, {r4}                ; push current spsr_cxsf

_OSCtxSw
        LDR 	r4, =OSPrioCur           ; OSPrioCur = OSPrioHighRdy
        LDR 	r5, =OSPrioHighRdy
        LDRB 	r6, [r5]
        STRB 	r6, [r4]
        
        LDR 	r4, =OSTCBCur            ; Get current task TCB address
        LDR 	r5, [r4]
        STR 	sp, [r5]                 ; store sp in preempted tasks s TCB

        BL 	OSTaskSwHook             ; call Task Switch Hook

        LDR 	r6, =OSTCBHighRdy        ; Get highest priority task TCB address
        LDR 	r6, [r6]
        LDR 	sp, [r6]                 ; get new task s stack pointer

        STR 	r6, [r4]                 ; set new current task TCB address

        LDMFD 	sp!, {r4}
		MSR 	spsr_cxsf, r4
        LDMFD 	sp!, {r4}
		MSR 	cpsr_cxsf, r4
       LDMFD 	sp!, {r0-r12,lr,pc}      ; pop new task r0-r12,lr & pc


;***********************************************************************
;
; Function: OSIntCtxSw
;
; Purpose:
; 	To perform a context switch from the interrupt level.
;
; Processing:
;    See uC/OS-II Interrupt Level Context Switch flow chart
;
; Parameters: void
;
; Outputs:  None
;
; Returns:  void
;
; Notes:
;   Sets up the stacks and registers to call the task level
;   context switch
;
;*********************************************************************/
        EXPORT 	OSIntCtxSw
        IMPORT	OSIntCtxSwFlag
OSIntCtxSw
        LDR 	r0, =OSIntCtxSwFlag      ; OSIntCtxSwFlag = true
        MOV 	r1, #1
        STR 	r1, [r0]
        
        MOV 	pc, lr                   ; return 
                
	
	
;/***********************************************************************
;
; Functions: ARMDisableInt
; 	     ARMEnableInt
;
; Purpose:
;    Disable and enable IRQ and FIQ preserving current CPU mode.
;
; Processing:
;    Push the cpsr onto the stack
;    Disable IRQ and FIQ interrupts
;    Return 
;
; Parameters: void
;
; Outputs:  None
;
; Returns:  void
;
; Notes:
;   (1) Can be called from SVC mode to protect Critical Sections. 
;   (2) Do not use these calls at interrupt level.
;   (3) Used in pairs within the same function level;
;   (4) Will restore interrupt state when called; i.e., if interrupts
;       are disabled when DisableInt is called, interrupts will still
;       still be disabled when the matching EnableInt is called.
;   (5) Uses the method described by Labrosse as "Method 2".
;
;*********************************************************************/
        EXPORT 	ARMDisableInt
ARMDisableInt
	
   mrs   r0, cpsr          ; current CSR
   mov   r1, r0            ; make a copy for masking
   orr   r1, r1, #0xC0     ; mask off int bits
   msr   cpsr_cxsf, r1     ; disable ints (IRQ and FIQ)
   and   r0, r0, #0x80     ; return FIQ bit from original CSR
   mov   pc,lr             ; return



    ;------------------------------------------------------------------------
        EXPORT 	ARMEnableInt
ARMEnableInt
   mrs   r0, cpsr          ; current CSR
   bic   r0, r0, #0xC0     ; mask on ints
   msr   cpsr_cxsf, r0     ; enable ints (IRQ and FIQ)
   mov   pc,lr             ; return

    ;------------------------------------------------------------------------
    
;*********************************************************
	
SAVED_LR_SVC	DCD   0xcfff900        ; some variables for temparal use
SAVED_LR_IRQ	DCD   0xcfffa00
SAVED_SPSR	    DCD   0xcfffb00
	
	
	IMPORT  OSIntEnter
	IMPORT  OSIntExit
	IMPORT  OSTimeTick
	IMPORT	OSIntCtxSwFlag
	EXPORT	OSTickISR

OSTickISR
	sub	lr,lr,#4
	STMFD 	sp!, {r0-r12,lr}         ; push lr & register file
    MRS 	r4, spsr
	STMFD 	sp!, {r4}                ; push current spsr_cxsf
	ldr	r0,=0x02000
	ldr	r1,=0x1e00024
	str r0,[r1]
	BL	OSIntEnter
	BL 	OSTimeTick
	BL	OSIntExit

	LDR	r0, =OSIntCtxSwFlag      ; check if OSIntCtxFlag is marked as true
	LDR 	r1, [r0]
	CMP	r1, #1	
	beq	_IntCtxSw
	
	LDMFD 	sp!, {r4}                ; get cpsr_svc from stack
	MSR     spsr_cxsf, r4                 ; prepare spsr_cxsf to return svc mode	
	LDMFD	sp!, {r0-r12, pc}^  

_IntCtxSw
        LDMFD 	sp!, {r4}                ; restore spsr_cxsf_irq 
	MSR 	spsr_cxsf, r4 	
  	str	r4, SAVED_SPSR
	LDMFD	sp!, {r0-r12, lr}        ; recover the irq stack pointer

	STR	lr, SAVED_LR_IRQ         ; save lr_irq to SAVED_LR_IRQ 	
	MOV	lr, #0x000000d3          ; change forcely cpsr to svc mode
	MSR	cpsr_cxsf, lr	
	STR     lr, SAVED_LR_SVC         ; save lr_svc to SAVED_LR_SVC
	LDR	lr, SAVED_LR_IRQ         ; get lr_irq value saved in SAVED_LR_IRQ 
	STMFD 	sp!, {lr}                ; push future task pc (lr_irq should be pushed in place of PC)
	LDR	lr, SAVED_LR_SVC         ; get lr_svc value saved in SAVED_LR_SVC 

        STMFD 	sp!, {r0-r12,lr}         ; push lr & r0-r12 register file
        ldr		r4, SAVED_SPSR
		 ;	    MRS 	r4, spsr
        STMFD 	sp!, {r4}                ; push current psr
		  ;     MRS 	r4, spsr
        STMFD 	sp!, {r4}                ; push spsr_cxsf

	B	_OSCtxSw
	
	END