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/* $Id: thread.hh,v 1.9 2008-04-27 16:33:42 sybreon Exp $
** 
** AEMB2 HI-PERFORMANCE CPU 
** Copyright (C) 2004-2007 Shawn Tan Ser Ngiap <shawn.tan@aeste.net>
**  
** This file is part of AEMB.
**
** AEMB 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 3 of the License, or
** (at your option) any later version.
**
** AEMB 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 AEMB.  If not, see <http://www.gnu.org/licenses/>.
*/

/**
   Basic thread functions
   @file thread.hh  

   These functions deal with the various hardware threads. It also
   provides simple mechanisms for toggling semaphores.
 */

#include "aemb/msr.hh"

#ifndef AEMB_THREAD_HH
#define AEMB_THREAD_HH

#ifdef __cplusplus
namespace aemb {
#endif

  /**
     Checks to see if currently executing Thread 1
     @return true if is Thread 1
  */
  
  inline int isThread1() 
  {
    int rmsr = getMSR();
    return ((rmsr & MSR_HTX) && (rmsr & MSR_PHA));
  }
  
  /**
     Checks to see if currently executing Thread 0
     @return true if is Thread 0
  */
  
  inline int isThread0()
  {
    int rmsr = getMSR();
    return ((rmsr & MSR_HTX) && (!(rmsr & MSR_PHA)));
  }
  
  /**
     Checks to see if it is multi-threaded or not.
     @return true if thread capable
  */
  inline int isThreaded()
  {
    int rmsr = getMSR();
    return (rmsr & MSR_HTX);
  }

  /**
     Hardware Mutex Signal.  
     Unlock the hardware mutex, which is unlocked on reset.
   */
  inline void _mtx_free()
  {
    int tmp;
    asm volatile ("msrclr %0, %1":"=r"(tmp):"K"(MSR_MTX));
  }

  /**
     Hardware Mutex Wait.

     Waits until the hardware mutex is unlocked. This should be used
     as part of a larger software mutex mechanism.
   */
  inline void _mtx_lock()
  {
    int rmsr;
    do 
      {
        asm volatile ("msrset %0, %1":"=r"(rmsr):"K"(MSR_MTX)); 
      }
    while (rmsr & MSR_MTX);    
  }
    
  // TODO: Extend this library to include threading mechanisms such as
  // semaphores, mutexes and such.

  /**
     Semaphore struct.     
     Presently implemented as software solution but a hardware one may be
     required as the threads are hardware.
  */
  
  typedef int semaphore;

  /**
     Software Semaphore Signal.

     Increment the semaphore and run. This is a software mechanism.
  */
  inline void signal(volatile semaphore _sem) 
  { 
    _mtx_lock();
    _sem++; 
    _mtx_free();
  }
    
  /**
     Software Semaphore Wait.

     Decrement the semaphore and block if < 0. This is a software
     mechanism.
  */
  inline void wait(volatile semaphore _sem) 
  {
    _mtx_lock();
    _sem--; 
    _mtx_free();
    while (_sem < 0); 
  }

  semaphore __mutex_rendezvous0 = 0; ///< internal rendezvous mutex
  semaphore __mutex_rendezvous1 = 1; ///< internal rendezvous mutex

  /**
     Implements a simple rendezvous mechanism
   */

  inline void rendezvous()
  {
    if (isThread1())
      {
        wait(__mutex_rendezvous0);
        signal(__mutex_rendezvous1);
      }
    else
      {
        signal(__mutex_rendezvous0);
        wait(__mutex_rendezvous1);
      }
  }

#ifdef __cplusplus
}
#endif

#endif

/*
  $Log: not supported by cvs2svn $
  Revision 1.8  2008/04/26 19:31:35  sybreon
  Made headers C compatible.

  Revision 1.7  2008/04/26 18:05:22  sybreon
  Minor cosmetic changes.

  Revision 1.6  2008/04/23 14:19:39  sybreon
  Fixed minor bugs.
  Initial use of hardware mutex.

  Revision 1.5  2008/04/20 16:35:53  sybreon
  Added C/C++ compatible #ifdef statements

  Revision 1.4  2008/04/12 14:07:26  sybreon
  added a rendezvous function

  Revision 1.3  2008/04/11 15:53:24  sybreon
  changed MSR bits

  Revision 1.2  2008/04/11 11:34:30  sybreon
  changed semaphore case

  Revision 1.1  2008/04/09 19:48:37  sybreon
  Added new C++ files

*/