rt-thread/libcpu/arm/armv6/context_gcc.S

/*
 * File      : context.S
 * This file is part of RT-Thread RTOS
 * COPYRIGHT (C) 2006, RT-Thread Development Team
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, write to the Free Software Foundation, Inc.,
 *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Change Logs:
 * Date           Author       Notes
 * 2011-01-13     weety    copy from mini2440
 */

/*!
 * \addtogroup ARMv6
 */
/*@{*/

#include <rtconfig.h>

#define NOINT          0xc0
#define FPEXC_EN       (1 << 30) /* VFP enable bit */

/*
 * rt_base_t rt_hw_interrupt_disable();
 */
.globl rt_hw_interrupt_disable
rt_hw_interrupt_disable:
    mrs r0, cpsr
    cpsid if
    bx  lr

/*
 * void rt_hw_interrupt_enable(rt_base_t level);
 */
.globl rt_hw_interrupt_enable
rt_hw_interrupt_enable:
    msr cpsr_c, r0
    bx  lr

/*
 * void rt_hw_context_switch(rt_uint32 from, rt_uint32 to);
 * r0 --> from
 * r1 --> to
 */
.globl rt_hw_context_switch
rt_hw_context_switch:
    stmfd   sp!, {lr}       @ push pc (lr should be pushed in place of PC)
    stmfd   sp!, {r0-r12, lr}   @ push lr & register file

    mrs r4, cpsr
    tst lr, #0x01
    orrne r4, r4, #0x20     @ it's thumb code

    stmfd sp!, {r4}         @ push cpsr

    str sp, [r0]            @ store sp in preempted tasks TCB
    ldr sp, [r1]            @ get new task stack pointer

    ldmfd sp!, {r4}         @ pop new task cpsr to spsr
    msr spsr_cxsf, r4
#ifdef RT_USING_VFP
    vmrs    r0, fpexc
    bic     r0, r0, #FPEXC_EN    @ always disable VFP so we can 
                                 @ lazily save/restore the old state.
    vmsr    fpexc, r0
#endif
_do_switch:
    ldmfd sp!, {r0-r12, lr, pc}^  @ pop new task r0-r12, lr & pc, copy spsr to cpsr

/*
 * void rt_hw_context_switch_to(rt_uint32 to);
 * r0 --> to
 */
.globl rt_hw_context_switch_to
rt_hw_context_switch_to:
    ldr sp, [r0]            @ get new task stack pointer

    ldmfd sp!, {r4}         @ pop new task spsr
    msr spsr_cxsf, r4

    bic r4, r4, #0x20       @ must be ARM mode
    msr cpsr_cxsf, r4
#ifdef RT_USING_VFP
    vmrs    r0, fpexc
    bic     r0, r0, #FPEXC_EN    @ always disable VFP so we can 
                                 @ lazily save/restore the old state.
    vmsr    fpexc, r0
#endif
    ldmfd sp!, {r0-r12, lr, pc}^   @ pop new task r0-r12, lr & pc

/*
 * void rt_hw_context_switch_interrupt(rt_uint32 from, rt_uint32 to);
 */
.globl rt_thread_switch_interrupt_flag
.globl rt_interrupt_from_thread
.globl rt_interrupt_to_thread
.globl rt_hw_context_switch_interrupt
rt_hw_context_switch_interrupt:
    ldr r2, =rt_thread_switch_interrupt_flag
    ldr r3, [r2]
    cmp r3, #1
    beq _reswitch
    mov r3, #1              @ set rt_thread_switch_interrupt_flag to 1
    str r3, [r2]
    ldr r2, =rt_interrupt_from_thread   @ set rt_interrupt_from_thread
    str r0, [r2]
_reswitch:
    ldr r2, =rt_interrupt_to_thread     @ set rt_interrupt_to_thread
    str r1, [r2]
    bx  lr