/*

    LEON2/3 LIBIO low-level routines 
    Written by Jiri Gaisler.
    Copyright (C) 2004  Gaisler Research AB

    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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

*/ 

#include <asm-leon/contextswitch.h>
#include <asm-leon/leonbare_kernel.h>
#include <asm-leon/leonbare_debug.h>
#include <asm-leon/stack.h>
#include <asm-leon/leonstack.h>
#include <asm-leon/irq.h>

struct leonbare_kernel leonbare_kernel;

/*
 * queue 0: [ <acc=2>],
 * queue 1: [ <acc=10>, <acc=8>,<acc=8>,<acc=1> ],
 * queue 2: [ ... ],
 * ...
 * queue n: [ ... ]
 *
 *  Seach through ready queue [0 - LEONBARE_RUNQ_READY_NR-1] for the
 *  first thread in a queue'ss head to discover
 *  leonbare_thread_tick_callback() will put threads that have their th_caccount
 *  consumed into the prepare-run queues. th_caccount is already initialized
 *  to the value for the next schedule round. So all there is to do is to
 *  move the to prepare-run queues to run queues [0 - LEONBARE_RUNQ_READY_NR-1].
 *  return the first thread in any queue, similary to leonbare_sched_next().
 *  Using LEONBARE_KR_RUNQ_WHICH and leonbare_thread.th_runq_which one can
 *  determine weather the thread is in a runqueue or a prepare-runqueue:
 *  LEONBARE_KR_RUNQ_WHICH == leonbare_thread.th_runq_which : thread in runqueue
 *  LEONBARE_KR_RUNQ_WHICH != leonbare_thread.th_runq_which : thread in prepare-runqueue
 *  after a leonbare_thread_tick_callback() or a run queue change, call
 *  leonbare_sched_update() to update LEONBARE_KR_NEXT and
 *  LEONBARE_KR_NEED_SCHEDULE
 */
int leonbare_sched_update()
{
    int idx;
    leonbare_thread_t n = 0;
    int i = 0;
    LEONBARE_VERIFYIRQDISABLED();
    LEONBARE_VERIFYSCHED();
    for (i = 0; i < LEONBARE_RUNQ_READY_NR; i++) {
        leonbare_thread_t c;
        if (!LBTAILQ_EMPTY(LEONBARE_KR_RUNQ(i))) {
            n = LBTAILQ_FIRST(LEONBARE_KR_RUNQ(i));
	    break;
        }
    } 
    if (!n) {
	for (idx = 0; idx < LEONBARE_RUNQ_READY_NR; idx++) {
	    struct leonbare_thread_queue *h0 =
		(struct leonbare_thread_queue *)LEONBARE_KR_RUNQ(idx);
	    struct leonbare_thread_queue *h1 = (struct leonbare_thread_queue *)
		LEONBARE_KR_RUNQ(idx + LEONBARE_RUNQ_PREPARE_IDX);
	    if (LBTAILQ_EMPTY(h1)) {
		LBTAILQ_INIT(h0);
	    } else {
		*h0 = *h1;
		if (LBTAILQ_FIRST(h0)) {
		    LBTAILQ_FIRST(h0)->th_runq.tqe_prev = &(h0)->tqh_first;
		}
		if (!n) {
		    n = LBTAILQ_FIRST(h0);
		}
	    }
	}
	for (idx = 0; idx < LEONBARE_RUNQ_READY_NR; idx++) {
	    LBTAILQ_INIT(LEONBARE_KR_RUNQ(idx + LEONBARE_RUNQ_PREPARE_IDX));
	} 
	LEONBARE_KR_RUNQ_WHICH++;
	LEONBARE_VERIFYSCHED();
	LEONBARE_PRINTQUEUES();
    }
    LEONBARE_KR_NEXT = n;
    return (LEONBARE_KR_NEED_SCHEDULE);
}

/*  called in the timer irq handling. Decrements the 
 *  th_caccount field. On consumption of th_caccount the 
 *  thread will be removed from the ready queue nad placed into the
 *  prepare-runqueue for later readdition by leonbare_sched_readyprepare()
 *  called from gettimeofday.c's installed ticker_callback callback
 *  leonbare_thread_tick_callback() might change the kernel state in which case
 *  state on return from leonbare_thread_tick_callback() leonbare_thread_schedule_callback()
 *  will be called from rtrap_fast.S .
 */
int leonbare_thread_tick_callback()
{
    LEONBARE_PROTECT_DECL(flags);
    unsigned int r;
    volatile leonbare_thread_t c = LEONBARE_KR_CURRENT;
    leonbare_thread_t i;
    LBDEBUG_FNCALL;
    if (c && LEONBARE_KR_IS_PREEMPTION) {

	LEONBARE_PROTECT_KERNEL_START();
	{
	    
	    LEONBARE_VERIFYIRQDISABLED();
	    LEONBARE_VERIFYSCHED();
	    
	    if ((--c->th_caccount) < 0) {
		LBDEBUG_HEADER_PRINTF(LBDEBUG_QUEUE_NR, "remove %s(%x)\n",
				      LEONBARE_TH_NAME_DBG(c), c);
		LBTAILQ_REMOVE(LEONBARE_KR_RUNQ(c->th_runq_idx), c, th_runq);
		LBTAILQ_INSERT_TAIL(LEONBARE_KR_RUNQ
				  (c->th_runq_idx + LEONBARE_RUNQ_PREPARE_IDX), c,
				  th_runq);
		c->th_caccount = c->th_account;
		c->th_runq_which++;
	    } else {
		/* todo: round robbin scheme */
	    }
	}
	LEONBARE_PROTECT_KERNEL_END();
    }
    r = leonbare_sched_update();
    return r;
}

/* called from rtrap_fast.S's installed schedule_callback callback */
int leonbare_thread_schedule_callback(struct leonbare_pt_regs *ptregs)
{
    unsigned int retval;
    LBDEBUG_FNCALL;
    if (LEONBARE_KR_IS_IN_KERNEL == 0 && LEONBARE_KR_NEED_SCHEDULE) {

	leonbare_sched();
	
        //KERNEL_ENTER;
        //KERNEL_EXIT(LEONBARE_KR_NEED_SCHEDULE, retval);
    }
    LBDEBUG_FNEXIT;
}


struct leonbare_thread _thread_main;
int leonbare_thread_init()
{
    int i;
    LBDEBUG_FNCALL;

    memset((void *)&_thread_main, 0, sizeof(_thread_main));
    _thread_main.th_reentp = _impure_ptr;
    _thread_main.th_name = "<main>";
    _thread_main.th_runq_idx = 0;
    _thread_main.th_pri_idx = 0;
    _thread_main.th_account = 0;

    LBTAILQ_INIT(LEONBARE_KR_ALLQ);
    for (i = 0; i < LEONBARE_RUNQ_NR; i++) {
        LBTAILQ_INIT(LEONBARE_KR_RUNQ(i));
    }
    LBTAILQ_INIT(LEONBARE_KR_ALLM);

    /* queues */
    LBTAILQ_INSERT_TAIL(LEONBARE_KR_ALLQ, &_thread_main, th_allq);

    /* inseart into ready queue 0 at head */
    LBTAILQ_INSERT_HEAD(LEONBARE_KR_RUNQ(_thread_main.th_runq_idx), &_thread_main, th_runq);

    LEONBARE_KR_CURRENT = &_thread_main;
    LEONBARE_KR_IS_IN_KERNEL = 0;

    leonbare_init_ticks();
    schedule_callback = (schedulehandler) leonbare_thread_schedule_callback;
    ticker_callback = (tickerhandler) leonbare_thread_tick_callback;

    /* disable later */
    LEONBARE_KR_IS_PREEMPTION = 1;
    
    
    LBDEBUG_FNEXIT;
}
