os_cpu_a.s

这是一个用于在S3C44B0开发板（网上公版）

;**********************************************************************
;****************************************************
; $Workfile:   os_cpu_a.S   for SkyEye simulator    $  
; $Revision: 1.1.1.1 $
; $Author: skyeye $
; $Email:   lmcs00;mails.tsinghua.edu.cn            $
; $Date: 2003/02/19 02:42:22 $
;****************************************************
;****************************************************
; $Workfile:   os_cpu_a.S   for SkyEye simulator    $  
; $Revision: 1.1.1.1 $
; $Author: skyeye $
; $Email:   chenyu;hpclab.cs.tsinghua.edu.cn        $
; $Email:   lmcs00;mails.tsinghua.edu.cn            $
; $Date: 2003/02/19 02:42:22 $
;****************************************************
;****************************************************
; $Workfile:   os_cpu_a.S   for SkyEye simulator    $  
; $Revision: 1.1.1.1 $
; $Author: skyeye $
; $Email:   chenyu;hpclab.cs.tsinghua.edu.cn        $
; $Email:   lmcs00;mails.tsinghua.edu.cn            $
; $Date: 2003/02/19 02:42:22 $
;****************************************************
; BASED ON
;***************************************************
; $Workfile:   Os_cpu_a.s  $
; $Revision: 1.1.1.1 $
; $Author: skyeye $
; $Date: 2003/02/19 02:42:22 $
; **************************************************

;********************************************************************/
      AREA	|subr|, 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	OSTCBCur 
	IMPORT  OSRunning
	 
OSStartHighRdy
        MSR     CPSR_cxsf,#0xD3         ; Switch to SVC mode with IRQ and FIQ disabled

        BL 	OSTaskSwHook             ; Call user-defined hook function

        LDR 	r4,=OSRunning            ; Indicate that multitasking has started
        MOV 	r5, #1                   
        STRB 	r5, [r4]                 ; OSRunning = true
        
        LDR     r5, =OSTCBCur           
        LDR 	r4, =OSTCBHighRdy        ; Get highest priority task TCB address
        LDR 	r4, [r4]                 ; get stack pointer
        LDR 	sp, [r4]                 ; switch to the new stack
        
        STR     r4, [r5]                
; next two lines removed by YJ
        LDMFD 	sp!, {r4}                ; pop new task s spsr_cxsf
        MSR 	spsr_cxsf, r4
        LDMFD 	sp!, {r4}                ; pop new task s psr
        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:
;	The whole function is executed in CRITICAL state. See OSSched().
;
;   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
        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
; next two lines removed by YJ
;        MRS 	r4, spsr
;        STMFD 	sp!, {r4}                ; push current spsr_cxsf

        BL 	OSTaskSwHook                 ; call Task Switch Hook
        
        LDR 	r4, =OSTCBCur            ; Get current task TCB address
        LDR		r5, [r4]
        STR 	sp, [r5]                 ; store sp in preempted tasks s TCB

; OSIntCtxSw does the remainder work, so
; following removed by YJ-------------------------------------------<<
;_OSCtxSw
		

        LDR     R4,=OSPrioCur         ; OSPrioCur = OSPrioHighRdy
        LDR     R5,=OSPrioHighRdy
        LDRB    R6,[R5]
        STRB    R6,[R4]
        
        LDR     R4,=OSTCBCur          ; Get the current task's OS_TCB address
        LDR     R6,=OSTCBHighRdy      ; Get highest priority task's OS_TCB address
        LDR     R6,[R6]
        LDR     SP,[R6]                 ; get new task's stack pointer

        STR     R6,[R4]                 ; OSTCBCur = OSTCBHighRdy

       
     

;; next two lines removed by YJ
        LDMFD 	sp!, {r4}                ; pop new task spsr_cxsf
        MSR 	spsr_cxsf, r4

        LDMFD 	sp!, {r4}                ; pop new task cpsr
        MSR 	cpsr_cxsf, r4
        LDMFD 	sp!, {r0-r12,lr,pc}      ; pop new task r0-r12,lr & pc
         MOV 	pc, lr                   ; return 
;***********************************************************************
;
; 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 	OS_IntCtxSw
;----------------------------------------------------------------
; modefied by YJ
;----------------------------------------------------------------
; added starts --------------<<
		IMPORT OSTaskSwHook
		IMPORT  OSIntCtxSwFlag
OS_IntCtxSw
		LDR     R0,=OSIntCtxSwFlag    ; OSIntCtxSwFlag = FALSE
        MOV     R1,#0
        STR     R1,[R0]
        
		LDMFD   SP!,{R0-R3,R12,LR}      ; Clean up IRQ stack
        STMFD   SP!,{R0-R3}             ; We will use R0-R3 as temporary registers
        MOV     R1,SP
        ADD     SP,SP,#16
        SUB     R2,LR,#4

		MRS     R3,SPSR                 ; Disable interrupts for when we go back to SVC mode
        ORR     R0,R3,#0xc0
        MSR     SPSR_c,R0

        LDR     R0,=.+8                 ; Switch back to SVC mode (Code below, current location + 2 instructions)
        MOVS    PC,R0                   ; Restore PC and CPSR

                                        ; SAVE OLD TASK'S CONTEXT ONTO OLD TASK'S STACK
        STMFD   SP!,{R2}                ; Push task's PC 
        STMFD   SP!,{R4-R12,LR}         ; Push task's LR,R12-R4
        MOV     R4,R1                   ; Move R0-R3 from IRQ stack to SVC stack
        MOV     R5,R3
        LDMFD   R4!,{R0-R3}             ; Load R0-R3 from IRQ stack
        STMFD   SP!,{R0-R3}             ; Push R0-R3
        STMFD   SP!,{R5}                ; Push task's CPSR
        MRS     R4,SPSR
        STMFD   SP!,{R4}                ; Push task's SPSR
        
        LDR     R4,=OSTCBCur          ; OSTCBCur->OSTCBStkPtr = SP
        LDR     R5,[R4]
        STR     SP,[R5]

        BL      OSTaskSwHook            ; call Task Switch Hook

        LDR     R4,=OSPrioCur         ; OSPrioCur = OSPrioHighRdy
        LDR     R5,=OSPrioHighRdy
        LDRB    R6,[R5]
        STRB    R6,[R4]
        
        LDR     R4,=OSTCBCur          ; OSTCBCur = OSTCBHighRdy
        LDR     R6,=OSTCBHighRdy      
        LDR     R6,[R6]
        LDR     SP,[R6]

        STR     R6,[R4]                 

        LDMFD   SP!,{R4}                ; pop new task's SPSR
    ;   AND     R4,R4,#0xffffFF3F
        MSR     SPSR_cxsf,R4
        
        LDMFD   SP!,{R4}                ; pop new task's PSR
    ;   AND     R4,R4,#0xffffFF3F
        MSR     CPSR_cxsf,R4
		LDMFD 	sp!, {r0-r12,lr,pc}		 ; pop new task r0-r12,lr & pc
; >>---------------- added ends

; removed starts ------------<<
;        IMPORT	OSIntCtxSwFlag
;OSIntCtxSw
;        LDR 	r0, =OSIntCtxSwFlag      ; OSIntCtxSwFlag = true
;        MOV 	r1, #1
;        STR 	r1, [r0]
;        
        MOV 	pc, lr                   ; return 
; >>-------------- removed ends
;----------------------------------------------------------------
; end of modification
;----------------------------------------------------------------

;/***********************************************************************
;
;yangye 2003-2-14
;changed this function name from OSTickISR to OSISR(it is not a TICK isr)
; Function: OSISR
;
; Purpose:
; 	   The IRQ interrupt handler
;
; Processing:
;    Saves context