rt-thread/libcpu/arm/lpc214x/context_gcc.S

/*
 * Copyright (c) 2006-2018, RT-Thread Development Team
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Change Logs:
 * Date           Author       Notes
 */
.global rt_hw_interrupt_disable
.global rt_hw_interrupt_enable
.global rt_hw_context_switch
.global rt_hw_context_switch_to
.global rt_hw_context_switch_interrupt

.equ  NOINT, 0xc0

/*
 * rt_base_t rt_hw_interrupt_disable();
 关闭中断，关闭前返回CPSR寄存器值
 */
rt_hw_interrupt_disable:
	//EXPORT rt_hw_interrupt_disable
	MRS r0, cpsr
	ORR r1, r0, #NOINT
	MSR cpsr_c, r1
	BX	lr
	//ENDP

/*
 * void rt_hw_interrupt_enable(rt_base_t level);
  恢复中断状态
 */
rt_hw_interrupt_enable:
	//EXPORT rt_hw_interrupt_enable
	MSR cpsr_c, r0
	BX	lr
	//ENDP

/*
 * void rt_hw_context_switch(rt_uint32 from, rt_uint32 to);
 * r0 --> from
 * r1 --> to
 进行线程的上下文切换
 */
rt_hw_context_switch:
	//EXPORT rt_hw_context_switch
	STMFD	sp!, {lr}			/* push pc (lr should be pushed in place of PC) */
							    /* 把LR寄存器压入栈（这个函数返回后的下一个执行处） */
	STMFD	sp!, {r0-r12, lr}	/* push lr & register file */
								/*  把R0 – R12以及LR压入栈 */

	MRS		r4, cpsr			/*  读取CPSR寄存器到R4寄存器 */
	STMFD	sp!, {r4}			/* push cpsr */
							    /* 把R4寄存器压栈（即上一指令取出的CPSR寄存器） */
	MRS		r4, spsr		    /* 读取SPSR寄存器到R4寄存器 */
	STMFD	sp!, {r4}			/* push spsr */
								/* 把R4寄存器压栈（即SPSR寄存器） */

	STR	sp, [r0]				/* store sp in preempted tasks TCB */
								/*  把栈指针更新到TCB的sp，是由R0传入此函数 */
								/*  到这里换出线程的上下文都保存在栈中 */
	LDR	sp, [r1]				/* get new task stack pointer */
								/*  载入切换到线程的TCB的sp */
								/*  从切换到线程的栈中恢复上下文，次序和保存的时候刚好相反 */

	LDMFD	sp!, {r4}			/* pop new task spsr */
								/* 出栈到R4寄存器（保存了SPSR寄存器） */
	MSR	spsr_cxsf, r4			/* 恢复SPSR寄存器 */
	LDMFD	sp!, {r4}			/* pop new task cpsr */
								/* 出栈到R4寄存器（保存了CPSR寄存器） */
	MSR	cpsr_cxsf, r4			/*  恢复CPSR寄存器 */

	LDMFD	sp!, {r0-r12, lr, pc}	/* pop new task r0-r12, lr & pc */
									/* 对R0 – R12及LR、PC进行恢复 */
	//ENDP

rt_hw_context_switch_to:
	//EXPORT rt_hw_context_switch_to
	LDR	sp, [r0]				/* get new task stack pointer */
								/* 获得切换到线程的SP指针 */

	LDMFD	sp!, {r4}			/* pop new task spsr */
								/* 出栈R4寄存器（保存了SPSR寄存器值） */
	MSR	spsr_cxsf, r4			/* 恢复SPSR寄存器 */
	LDMFD	sp!, {r4}			/* pop new task cpsr */
								/* 出栈R4寄存器（保存了CPSR寄存器值） */
	MSR	cpsr_cxsf, r4			/* 恢复CPSR寄存器 */

	LDMFD	sp!, {r0-r12, lr, pc}	/* pop new task r0-r12, lr & pc */
									/* 恢复R0 – R12，LR及PC寄存器 */
	//ENDP

rt_hw_context_switch_interrupt:
	//EXPORT rt_hw_context_switch_interrupt
	LDR r2, =rt_thread_switch_interrupt_flag
	LDR r3, [r2]						/* 载入中断中切换标致地址 */
	CMP r3, #1							/* 等于 1 ？*/
	BEQ _reswitch						/* 如果等于1，跳转到_reswitch*/
	MOV r3, #1							/* set rt_thread_switch_interrupt_flag to 1*/
										/* 设置中断中切换标志位1 */
	STR r3, [r2]						/* */
	LDR r2, =rt_interrupt_from_thread	/* set rt_interrupt_from_thread*/
	STR r0, [r2]						/* 保存切换出线程栈指针*/
_reswitch:
	LDR r2, =rt_interrupt_to_thread		/* set rt_interrupt_to_thread*/
	STR r1, [r2]						/* 保存切换到线程栈指针*/
	BX	lr
	//ENDP

	//END