101 lines
2.9 KiB
C
101 lines
2.9 KiB
C
/**
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* \file
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* <!--
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* This file is part of BeRTOS.
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*
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* Bertos is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*
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* As a special exception, you may use this file as part of a free software
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* library without restriction. Specifically, if other files instantiate
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* templates or use macros or inline functions from this file, or you compile
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* this file and link it with other files to produce an executable, this
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* file does not by itself cause the resulting executable to be covered by
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* the GNU General Public License. This exception does not however
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* invalidate any other reasons why the executable file might be covered by
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* the GNU General Public License.
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*
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* Copyright 2004, 2008 Develer S.r.l. (http://www.develer.com/)
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* -->
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*
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* \author Giovanni Bajo <rasky@develer.com>
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*
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* \brief DSP5680x task switching support
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*/
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void asm_switch_context(void ** new_sp /* R2 */, void ** save_sp /* R3 */);
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asm void asm_switch_context(void ** new_sp, void ** save_sp)
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{
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lea (SP)+
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; From the manual:
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; The compiler uses page 0 address locations X: 0x0030 - 0x003F as register
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; variables. Frequently accessed local variables are assigned to the page 0
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; registers instead of to stack locations so that load and store instructions
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; are shortened. Addresses X: 0x0030 - 0x0037 (page 0 registers MR0-MR7) are
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; volatile registers and can be overwritten. The remaining registers (page 0
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; registers MR8-MR15) are treated as non-volatile and, if used by a routine,
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; must be saved on entry and restored on exit.
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;
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; So, register 0x30-0x37 are caller-save, while 0x38-0x3F are callee-save.
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move x:<$38,y1
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move y1,x:(SP)+
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move x:<$39,y1
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move y1,x:(SP)+
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move x:<$3A,y1
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move y1,x:(SP)+
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move x:<$3B,y1
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move y1,x:(SP)+
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move x:<$3C,y1
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move y1,x:(SP)+
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move x:<$3D,y1
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move y1,x:(SP)+
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move x:<$3E,y1
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move y1,x:(SP)+
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move x:<$3F,y1
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move y1,x:(SP)
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;
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; Switch stacks
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nop
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move SP, x:(R3)
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nop
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move x:(R2), SP
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nop
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;
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; restore all saved registers
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;
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pop y1
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move y1,x:<$3F
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pop y1
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move y1,x:<$3E
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pop y1
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move y1,x:<$3D
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pop y1
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move y1,x:<$3C
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pop y1
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move y1,x:<$3B
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pop y1
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move y1,x:<$3A
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pop y1
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move y1,x:<$39
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pop y1
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move y1,x:<$38
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; SR is already pushed on the stack (normal call context). Use RTI to restore
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; it, so that interrupt status is preserved across the tasks.
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rti
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}
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