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##=============================================================================
##
##      context.S
##
##      MN10300 context switch code
##
##=============================================================================
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## -------------------------------------------                              
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## for more details.                                                        
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## ####ECOSGPLCOPYRIGHTEND####                                              
##=============================================================================
#######DESCRIPTIONBEGIN####
##
## Author(s):   nickg
## Contributors:        nickg
## Date:        1998-04-27
## Purpose:     MN10300 context switch code
## Description: This file contains implementations of the thread context 
##              switch routines. It also contains the longjmp() and setjmp()
##              routines.
##
######DESCRIPTIONEND####
##
##=============================================================================

#include <pkgconf/hal.h>

#include <cyg/hal/arch.inc>

#------------------------------------------------------------------------------
# hal_thread_switch_context
# Switch thread contexts
# D0 = address of sp of next thread to execute
# D1 = address of sp save location of current thread

        .global _hal_thread_switch_context
_hal_thread_switch_context:
        add     -8,sp           # space for SP and PSW
        mov     d2,a0           # move d2->a0 since PSW can only be
                                # saved to a data register
        hal_cpu_get_psw d2      # save PSW to d2
        mov     d2,(4,sp)       # store in stack loc
        mov     a0,d2           # retrieve old d2 value
        hal_cpu_save_all        # save entire register set
        mov     d1,a2           # move save loc addr to A2
        mov     sp,(0,a2)       # store SP in save location

        # Now load the destination thread by dropping through
        # to hal_thread_load_context
        
#------------------------------------------------------------------------------
# hal_thread_load_context
# Load thread context
# D0 = address of sp of next thread to execute
# Note that this function is also the second half of hal_thread_switch_context
# and is simply dropped into from it.
        
        .global _hal_thread_load_context
_hal_thread_load_context:

        mov     d0,a2           # move next sp loc to a2
        mov     (0,a2),sp       # load SP with new value
        hal_cpu_load_all        # load whole register set
        mov     (4,sp),d1       # retrieve saved PSW
        hal_cpu_set_psw d1      # and restore it
        add     8,sp            # skip saved SP and PSW
        ret     [],0            # and return
        
##-----------------------------------------------------------------------------
## HAL longjmp(), setjmp() implementations
## These implementations omit the usual movm [d2,d3,a2,a3],(sp)
## Which is the first instruction of all C compiled functions.  
## Note: These definitions are repeated in hal_arch.h. If changes are required
## remember to update both sets.

#define CYGARC_JMP_BUF_SP        0
#define CYGARC_JMP_BUF_D2        1
#define CYGARC_JMP_BUF_D3        2
#define CYGARC_JMP_BUF_A2        3
#define CYGARC_JMP_BUF_A3        4
#define CYGARC_JMP_BUF_LR        5

#define CYGARC_JMP_BUF_SIZE      6

        
        # This just preserves the callee save registers 
        # namely a2,a3,d2,d3
        # setjmp cannot use movm to do this as we need to keep 
        # the sp underneath all live data at all times.
        .globl _hal_setjmp
_hal_setjmp:                    # d0=env
        mov     d0,a0           # env
        mov     d2,(CYGARC_JMP_BUF_D2*4,a0)
        mov     d3,(CYGARC_JMP_BUF_D3*4,a0)
        mov     a2,(CYGARC_JMP_BUF_A2*4,a0)
        mov     a3,(CYGARC_JMP_BUF_A3*4,a0)
        mov     mdr,d1          # link saved by call (also in (0,sp))
        mov     d1,(CYGARC_JMP_BUF_LR*4,a0)     
        mov     sp,a1
        mov     a1,(CYGARC_JMP_BUF_SP*4,a0) # a1==(caller''s sp)
        clr     d0              # return 0
        ret     [],0

        # longjmp returns to caller of setjmp
        # after restoring callee save registers
        .globl _hal_longjmp
_hal_longjmp:
        mov     d0,a0
        mov     (CYGARC_JMP_BUF_D2*4,a0),d2
        mov     (CYGARC_JMP_BUF_D3*4,a0),d3
        mov     (CYGARC_JMP_BUF_A2*4,a0),a2
        mov     (CYGARC_JMP_BUF_A3*4,a0),a3
        mov     (CYGARC_JMP_BUF_LR*4,a0),d0
##      mov     d0,mdr
        mov     (CYGARC_JMP_BUF_SP*4,a0),a1 # stashed (caller''s sp)
        mov     a1,sp
        mov     d0,(0,sp)       # put link on stack
        mov     d1,d0           # return arg1
        ret     [],0            # this ignores (0,sp) and does pc=mdr

        
#------------------------------------------------------------------------------
# end of context.S