/*  os_cpu_c.c
 *
 *	Motorola Coldfire MCF5307 port to MicroC/OS-II
 *
 *  Ross Berteig
 *  Cheshire Engineering Corp
 *  650 Sierra Madre Villa, Suite 201
 *  Pasadena  CA 91107
 *  +1-626-351-5493       +1-626-351-8645 FAX
 *  Ross@CheshireEng.com, www.CheshireEng.com
 *
 *  Copyright (C) 1998 Cheshire Engineering Corporation.
 *  Based on a port to uCOS version 1.x by David Fiddes.
 *  Portions Copyright (C) 1997 David Fiddes, D.J.Fiddes@hw.ac.uk
 *  Anything that no longer works is probably not his fault.
 */

#define  OS_CPU_GLOBALS
#include "includes.h"


/*  TaskCallSite
 *
 *	Provide a simulated call site for every task function.
 *
 *  This allows a task function which accidentally returns to
 *  delete itself.
 *
 *  The actual fake return address used in the stack frame is
 *  the label _CallSite, corresponding to the extern CallSite()
 *  declaration (which makes the compiler happier since it is
 *  visible at compile time).
 */
void TaskCallSite()
{
    asm (" nop ");
    asm ("_CallSite: nop ");
    //printf("!!!!! Task at prio %d function returned.\n", OSPrioCur);
    OSTaskDel(OS_PRIO_SELF);
    asm (" HALT ");
}
extern void CallSite(void);

/*
 * The INITIAL_SR makes each task start up with the following
 * attributes:
 *    1. supervisor mode
 *    2. all interrupts enabled
 */
#define INITIAL_SR 0x2000


/*  OSTaskStkInit
 *
 *	Build the initial stack frame for a new task.
 *
 *  Note that the ColdFire stack *must* be 4 byte aligned, and
 *  that the exception flag word at the top contains an alignment
 *  code describing the initial misalignment at the time of
 *  the exception.
 *
 *  This code will adjust the passed top of stack for the
 *  required alignment *before* building the stack frame
 *  and thus use the constant value 4 for the format field
 *  in the exception frame.
 *
 *  The stack will contain an exception taken after the call of
 *  the task function and before the execution of any of the
 *  task function prolog.  A dummy return address will be pushed
 *  pointing to a call site which will fall into a call to
 *  OSDeleteTask() to delete any task whos function returns.
 *
 *  (high address)
 *                +------+------+------+------+
 *  TOP_OF_STACK: |           pdata           |
 *                +------+------+------+------+
 *                |   dummy return address    |
 *                +------+------+------+------+
 *                | format, vector, fault, SR |
 *                +------+------+------+------+
 *                |PC of exception (task func)|
 *                +------+------+------+------+
 *                |             A6            |
 *                +------+------+------+------+
 *                |                           |
 *                            . . .
 *                |                           |
 *                +------+------+------+------+
 *                |        A1 (pdata)         |
 *                +------+------+------+------+
 *                |                           |
 *                            . . .
 *                |                           |
 *                +------+------+------+------+
 *   SP --->      |             D0            |
 *                +------+------+------+------+
 *   (low address)
 */
void *OSTaskStkInit(void (*task)(void *pd), void  *pdata, void  *ptos,
		    INT16U opt)
{
    OS_STK *stk;
    UBYTE  err;
    long stkframe;
    
    stk = (OS_STK *)ptos;		// load temporary stack pointer
    stkframe = 0x40000000;		// default format field
    switch ( (long) ptos & (long) 0x00000003 )
    {
	case 0: //format field 0100
#define LOFFSETBY(src,o) (OS_STK *)((long)(src) + (o))
	    stk = LOFFSETBY(stk, -0);
	    //stkframe = 0x40000000;
	    break;

	case 1: //format field 0101
	    stk = LOFFSETBY(stk, -1);
	    //stkframe = 0x50000000;
	    break;

	case 2: //format field 0110
	    stk = LOFFSETBY(stk, -2);
	    //stkframe = 0x60000000;
	    break;

	case 3: //format field 0111
	    stk = LOFFSETBY(stk, -3);
	    //stkframe = 0x70000000;
	    break;
#undef LOFFSETBY
    }
    stkframe = stkframe | INITIAL_SR;
    *stk   = 0;
    *--stk = (OS_STK)pdata;		/* Task "function" parameters */
    *--stk = (OS_STK)CallSite;		/* Dummy return address part */

    /*
     *  Build the balance of an exception frame.  See Section 3.4 in
     *  the MCF5307 User's Manual for exception frame details.
     */
    *--stk           = (long)task;	/* Task PC */
    *--stk           = (long)stkframe;	/* Format and status */

    /*
     *  And include all the registers as for the
     *		lea	   -60(a7),a7
     *		movem.l  d0-d7/a0-a6,(a7)
     *  instructions used at the top of all interrupts.
     *  For debugging, use meaningful values for most registers.
     *  Arguably, registers should be initialized to 0 instead.
     *
     *  To support tasks built with the register calling convention,
     *  the only argument (which is a pointer) is also passed in
     *  register a1.
     */
    *--stk           = (OS_STK)ptos;	/* a6 */
    *--stk           = 0xa5L;		/* a5 */
    *--stk           = 0xa4L;		/* a4 */
    *--stk           = 0xa3L;		/* a3 */
    *--stk           = 0xa2L;		/* a2 */
    *--stk           = (OS_STK)pdata;	/* a1 */
    *--stk           = 0xa0L;		/* a0 */
    *--stk           = 0xd7L;		/* d7 */
    *--stk           = 0xd6L;		/* d6 */
    *--stk           = 0xd5L;		/* d5 */
    *--stk           = 0xd4L;		/* d4 */
    *--stk           = 0xd3L;		/* d3 */
    *--stk           = 0xd2L;		/* d2 */
    *--stk           = 0xd1L;		/* d1 */
    *--stk           = 0xd0L;		/* d0 */
    return (void *)stk;
}


#if OS_CPU_HOOKS_EN
void OSTaskCreateHook(OS_TCB *ptcb)
{
}

void OSTaskDelHook(OS_TCB *ptcb)
{
}

void OSTaskSwHook(void)
{
}

void OSTaskStatHook(void)
{
}

void OSTimeTickHook(void)
{
}
#endif