/*
 * File      : stack.c
 * This file is part of RT-Thread RTOS
 * COPYRIGHT (C) 2006, RT-Thread Development Team
 *
 * The license and distribution terms for this file may be
 * found in the file LICENSE in this distribution or at
 * http://www.rt-thread.org/license/LICENSE
 *
 * Change Logs:
 * Date           Author       Notes
 * 2011-05-23     aozima       first implementation for PIC32.
 */

#include <rtthread.h>

/**
 * @addtogroup PIC32
 */
/*@{*/

rt_uint32_t __attribute__((nomips16)) _get_gp(void)
{
    rt_uint32_t result;

    // get the gp reg
    asm volatile("move   %0, $28" : "=r"(result));

    return result;
}

/**
 * This function will initialize thread stack
 *
 * @param tentry the entry of thread
 * @param parameter the parameter of entry
 * @param stack_addr the beginning stack address
 * @param texit the function will be called when thread exit
 *
 * @return stack address
 */
rt_uint8_t *rt_hw_stack_init(void *tentry, void *parameter, rt_uint8_t *stack_addr, void *texit)
{
	rt_uint32_t *stk;

    /** Start at stack top */
    stk = (rt_uint32_t *)stack_addr;
	*(stk)   = (rt_uint32_t) tentry;        /* pc: Entry Point */
	*(--stk) = (rt_uint32_t) 0x00800000;    /* c0_cause: IV=1, */
	*(--stk) = (rt_uint32_t) 0;		        /* c0_badvaddr */
	*(--stk) = (rt_uint32_t) 0;             /* lo */
	*(--stk) = (rt_uint32_t) 0;	            /* hi */
	*(--stk) = (rt_uint32_t) 1; 			/* C0_SR: IE = En, */
	*(--stk) = (rt_uint32_t) texit;	        /* 31 ra */
	*(--stk) = (rt_uint32_t) 0x0000001e;	/* 30 s8 */
	*(--stk) = (rt_uint32_t) stack_addr;	/* 29 sp */
	*(--stk) = (rt_uint32_t) _get_gp();     /* 28 gp */
	*(--stk) = (rt_uint32_t) 0x0000001b;	/* 27 k1 */
	*(--stk) = (rt_uint32_t) 0x0000001a;	/* 26 k0 */
	*(--stk) = (rt_uint32_t) 0x00000019;	/* 25 t9 */
	*(--stk) = (rt_uint32_t) 0x00000018;	/* 24 t8 */
	*(--stk) = (rt_uint32_t) 0x00000017;	/* 23 s7 */
	*(--stk) = (rt_uint32_t) 0x00000016;	/* 22 s6 */
	*(--stk) = (rt_uint32_t) 0x00000015;	/* 21 s5 */
	*(--stk) = (rt_uint32_t) 0x00000014;	/* 20 s4 */
	*(--stk) = (rt_uint32_t) 0x00000013;	/* 19 s3 */
	*(--stk) = (rt_uint32_t) 0x00000012;	/* 18 s2 */
	*(--stk) = (rt_uint32_t) 0x00000011;	/* 17 s1 */
	*(--stk) = (rt_uint32_t) 0x00000010;	/* 16 s0 */
	*(--stk) = (rt_uint32_t) 0x0000000f;	/* 15 t7 */
	*(--stk) = (rt_uint32_t) 0x0000000e;	/* 14 t6 */
	*(--stk) = (rt_uint32_t) 0x0000000d;	/* 13 t5 */
	*(--stk) = (rt_uint32_t) 0x0000000c;	/* 12 t4 */
	*(--stk) = (rt_uint32_t) 0x0000000b;	/* 11 t3 */
	*(--stk) = (rt_uint32_t) 0x0000000a; 	/* 10 t2 */
	*(--stk) = (rt_uint32_t) 0x00000009;	/* 9 t1 */
	*(--stk) = (rt_uint32_t) 0x00000008;	/* 8 t0 */
	*(--stk) = (rt_uint32_t) 0x00000007;	/* 7 a3 */
	*(--stk) = (rt_uint32_t) 0x00000006;	/* 6 a2 */
	*(--stk) = (rt_uint32_t) 0x00000005;	/* 5 a1 */
	*(--stk) = (rt_uint32_t) parameter;	    /* 4 a0 */
	*(--stk) = (rt_uint32_t) 0x00000003;	/* 3 v1 */
	*(--stk) = (rt_uint32_t) 0x00000002;	/* 2 v0 */
	*(--stk) = (rt_uint32_t) 0x00000001;	/* 1 at */
	*(--stk) = (rt_uint32_t) 0x00000000;	/* 0 zero */

	/* return task's current stack address */
	return (rt_uint8_t *)stk;
}

/*@}*/