;----------------------------------------------------------------------------- ; Copyright (c) 2003, Oren Avissar ; All rights reserved. ; ; Redistribution and use in source and binary forms, with or without ; modification, are permitted provided that the following conditions are met: ; ; * Redistributions of source code must retain the above copyright ; notice, this list of conditions and the following disclaimer. ; * Redistributions in binary form must reproduce the above copyright ; notice, this list of conditions and the following disclaimer in ; the documentation and/or other materials provided with the ; distribution. ; ; THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" ; AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE ; IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ; ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE ; LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR ; CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF ; SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS ; INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN ; CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ; ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE ; POSSIBILITY OF SUCH DAMAGE. ; ; Assembly support functions for the seos (seos.c) module ; ; Built using avr-gcc version 3.3 20030421 (prerelease) packaged ; with WinAVR 20030424. ; ;----------------------------------------------------------------------------- .file "seosasm.S" ;----------------------------------------------------------------------------- ; Start of seosasm Module .section .text ;----------------------------------------------------------------------------- ; define constants __SREG__ = 0x3f ;status register __SP_H__ = 0x3e ;high part of the stack pointer __SP_L__ = 0x3d ;low part of the stack pointer __tmp_reg__ = 0 ;temporary register ;----------------------------------------------------------------------------- ; Do the context switch ; ; NOTE: The first 40 bytes of the seosTask_t struct are organized as follows: ; regs[32] -> bytes 0-31 are used to store the regs ; sreg -> byte 32 is used to store the status register ; sp -> bytes 33-34 are used to store the stack pointer ; state -> byte 35 is the current state of the task ; run() -> bytes 36-37 store the entry point of the task ; stack -> bytes 38-39 store the stack buffer for the task ; ; This function assumes that the first parameter will be passed in registers ; r24 & r25 and the second parameter will be passed in r22 & r23 -- with the ; lower byte in the lower register. ; ; All registered are backed up and restored when doing a context switch. ; To optimize this the saving and restoring of registers that can be ; changed within a called functions can be removed. ; ; void seosasmContextSwitch(seosTask_t *oldcontext, seosTask_t *newcontext) .global seosasmContextSwitch .type seosasmContextSwitch, @function seosasmContextSwitch: ;--------------------------------------------------------------- ; Save the old context ; the parameter "oldcontext" is passed in using r24 & r25 ; ; save the contents of the Z register (r30 & r31) push r30 push r31 ; ; move the "oldcontext" pointer into the Z register (r30 & r31) mov r30,r24 mov r31,r25 ; ; save the first 30 registers std Z+0,r0 std Z+1,r1 std Z+2,r2 std Z+3,r3 std Z+4,r4 std Z+5,r5 std Z+6,r6 std Z+7,r7 std Z+8,r8 std Z+9,r9 std Z+10,r10 std Z+11,r11 std Z+12,r12 std Z+13,r13 std Z+14,r14 std Z+15,r15 std Z+16,r16 std Z+17,r17 std Z+18,r18 std Z+19,r19 std Z+20,r20 std Z+21,r21 std Z+22,r22 std Z+23,r23 std Z+24,r24 std Z+25,r25 std Z+26,r26 std Z+27,r27 std Z+28,r28 std Z+29,r29 ; ; move Z to Y so we can resore Z mov r28,r30 mov r29,r31 pop r31 pop r30 ; save Z std Y+30,r30 std Y+31,r31 ; ; save the status register in __tmp_reg__,__SREG__ std Y+32,__tmp_reg__ ; ; save the stack pointer in __tmp_reg__,__SP_L__ std Y+33,__tmp_reg__ in __tmp_reg__,__SP_H__ std Y+34,__tmp_reg__ ; ; update the state of the old task to SEOS_TASK_READY (1) ldi r30,lo8(1) std Y+35,r30 ;--------------------------------------------------------------- ;--------------------------------------------------------------- ; Move the "newcontext" pointer into the Z register (r30 & r31) ; the parameter "newcontext" is passed in using r22 & r23 ; mov r30,r22 mov r31,r23 ;--------------------------------------------------------------- ; Check if the task is being run for the first time (newly created) ; ; test if newcontext->state == SEOS_TASK_CREATED (0) ldd __tmp_reg__,Z+35 tst __tmp_reg__ brne .alreadycreated ;--------------------------------------------------------------- ; The task is being run for the first time ; ; update the state of the task to SEOS_TASK_RUNNING (2) ldi r28,lo8(2) std Z+35,r28 ; ; set the stack pointer for the new task ldd __tmp_reg__,Z+33 out __SP_L__,__tmp_reg__ ldd __tmp_reg__,Z+34 out __SP_H__,__tmp_reg__ ; ; On the AVR interrupts are dissabled when an interrupt occurs sei ;re-enable interrupts if necessary ; ; save the pointer to the new context on the stack push r22 push r23 ; ; start the new task (pass the parameter in r24 & r25) mov r24,r22 mov r25,r23 ; call newcontext->run() ldd r28,Z+36 ldd r29,Z+37 mov r30,r28 ;move the newcontext->run() pointer into Z mov r31,r29 icall ;call newcontext->run() ; ; If the task returns, restore the new context pointer ; -- pop the values into the Y register pop r29 pop r28 ; ; switch back to the default context lds r30,seos_deftask ;move seos_deftask into Z lds r31,(seos_deftask)+1 ; ; restore the stack pointer ldd __tmp_reg__,Z+33 out __SP_L__,__tmp_reg__ ldd __tmp_reg__,Z+34 out __SP_H__,__tmp_reg__ ; ; remove returned task from the scheduler's data structures. ; call _seosTaskRemove(&seos_tasktop,newcontext) mov r22,r28 ;move newcontext into r22 & r23 mov r23,r29 ldi r24,lo8(seos_tasktop) ;move &seos_tasktop into r24 & r25 ldi r25,hi8(seos_tasktop) push r28 ;save the Y register (may not be necessary w/avr-gcc) push r29 call _seosTaskRemove pop r29 ;restore the Y register pop r28 ; ; free the stack for the task ; call allocDelete(newcontext->stack) ldd r24,Y+38 ldd r25,Y+39 push r28 ;save the Y register (may not be necessary w/avr-gcc) push r29 call allocDelete pop r29 ;restore the Y register pop r28 ; ; free the task information ; call allocDelete(newcontext) mov r24,r28 mov r25,r29 call allocDelete ; ; reload the default context (seos_deftask) into Z lds r30,seos_deftask lds r31,(seos_deftask)+1 ; ; set the currently running task to the default context ; -- set seos_runningtask = seos_deftask sts seos_runningtask,r30 sts (seos_runningtask)+1,r31 ;--------------------------------------------------------------- .alreadycreated: ;--------------------------------------------------------------- ; Set the new context (stored in the Z register) ; ; update the state of the task to SEOS_TASK_RUNNING (2) ldi r28,lo8(2) std Z+35,r28 ; ; set the new stack pointer ldd __tmp_reg__,Z+33 out __SP_L__,__tmp_reg__ ldd __tmp_reg__,Z+34 out __SP_H__,__tmp_reg__ ; ; On the AVR interrupts are dissabled when an interrupt occurs sei ;re-enable interrupts if necessary ; ; set the new status register ldd __tmp_reg__,Z+32 out __SREG__,__tmp_reg__ ; ; set the first 30 registers ldd r0,Z+0 ldd r1,Z+1 ldd r2,Z+2 ldd r3,Z+3 ldd r4,Z+4 ldd r5,Z+5 ldd r6,Z+6 ldd r7,Z+7 ldd r8,Z+8 ldd r9,Z+9 ldd r10,Z+10 ldd r11,Z+11 ldd r12,Z+12 ldd r13,Z+13 ldd r14,Z+14 ldd r15,Z+15 ldd r16,Z+16 ldd r17,Z+17 ldd r18,Z+18 ldd r19,Z+19 ldd r20,Z+20 ldd r21,Z+21 ldd r22,Z+22 ldd r23,Z+23 ldd r24,Z+24 ldd r25,Z+25 ldd r26,Z+26 ldd r27,Z+27 ldd r28,Z+28 ldd r29,Z+29 ; ; save Y push r28 push r29 ; ; move Z to Y so we can set Z mov r28,r30 mov r29,r31 ldd r30,Y+30 ldd r31,Y+31 ; ; restore Y pop r29 pop r28 ;--------------------------------------------------------------- ret .size seosasmContextSwitch, .-seosasmContextSwitch ; END OF seosasmContextSwitch() ;----------------------------------------------------------------------------- ;----------------------------------------------------------------------------- ; This is called when there are no other tasks to run ; -- when the OS is idle. ; ; void seosasmIdle(void) .global seosasmIdle .type seosasmIdle, @function seosasmIdle: ; while (1); .donothing: rjmp .donothing ret .size seosasmIdle, .-seosasmIdle ; END OF seosasmIdle() ;----------------------------------------------------------------------------- ;----------------------------------------------------------------------------- ; End of seosasm Module .end ;-----------------------------------------------------------------------------