simple_bus.cpp

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  more contributor license agreements.  See the NOTICE file distributed
  with this work for additional information regarding copyright ownership.
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 *****************************************************************************/

/*****************************************************************************
 
  simple_bus.cpp : The bus.

                   The main_action process is active at falling clock edge.

       		   Handling of the requests. A request can result in 
		   different requests to slaves. These are atomic requests 
		   and cannot be interrupted. A slave can take several 
		   cycles to complete: each time the request has to be 
		   re-issued to the slave. Once the slave transaction 
		   is completed, the m_current_request is cleared, and 
		   the request form is updated (address+=4, data++). 

		   When m_current_request is clear, the next request is
		   selected. This can be the same one, if the transfer is
		   not completed (burst-mode), or it can be a request with
		   a higher priority. Intrusion to a non-locked burst-mode
		   transaction is possible. 

		   When a transaction sets a lock, then the corresponding
		   field in the request is set to SIMPLE_BUS_LOCK_SET. If
		   the locked transaction is granted by the arbiter for the
		   first time, the lock is set to SIMPLE_BUS_LOCK_GRANTED. 
		   At the end of the transaction, the lock is set to 
		   SIMPLE_BUS_LOCK_SET. If now a new locked request is made,
		   with the same priority, the status of the lock is set
		   to SIMPLE_BUS_LOCK_GRANTED, and the arbiter will pick
		   this transaction to be the best. If the locked trans-
		   action was not selected by the arbiter in the first 
		   round (request with higher priority preceeded), then the
		   lock is not set. After the completion of the transaction,
		   the lock is set from SIMPLE_BUS_LOCK_SET (set during the
		   bus-interface function), to SIMPLE_BUS_LOCK_NO. 
		   
		   The bus is derived from the following interfaces, and
		   contains the implementation of these: 
		   - blocking : burst_read/burst_write
		   - non-blocking : read/write/get_status
		   - direct : direct_read/direct_write
 
  Original Author: Ric Hilderink, Synopsys, Inc., 2001-10-11
 
 *****************************************************************************/
 
/*****************************************************************************
 
  MODIFICATION LOG - modifiers, enter your name, affiliation, date and
  changes you are making here.
 
      Name, Affiliation, Date:
  Description of Modification:
 
 *****************************************************************************/

#include "simple_bus.h"

void simple_bus::end_of_elaboration()
{
  // perform a static check for overlapping memory areas of the slaves
  bool no_overlap;
  for (int i = 1; i < slave_port.size(); ++i) {
    simple_bus_slave_if *slave1 = slave_port[i];
    for (int j = 0; j < i; ++j) {
      simple_bus_slave_if *slave2 = slave_port[j]; 
      no_overlap = ( slave1->end_address() < slave2->start_address() ) ||
               ( slave1->start_address() > slave2->end_address() );
      if ( !no_overlap ) {
        sb_fprintf(stdout,"Error: overlapping address spaces of 2 slaves : \n");
        sb_fprintf(stdout,"slave %i : %0X..%0X\n",i,slave1->start_address(),slave1->end_address()); 
        sb_fprintf(stdout,"slave %i : %0X..%0X\n",j,slave2->start_address(),slave2->end_address());
        exit(0);
      }
    }
  }
}

//----------------------------------------------------------------------------
//-- process
//----------------------------------------------------------------------------

void simple_bus::main_action()
{
  // m_current_request is cleared after the slave is done with a
  // single data transfer. Burst requests require the arbiter to
  // select the request again.

  if (!m_current_request)
    m_current_request = get_next_request();
  else
    // monitor slave wait states
    if (m_verbose)
      sb_fprintf(stdout, "%s SLV [%d]\n", sc_time_stamp().to_string().c_str(),
		 m_current_request->address);
  if (m_current_request)
    handle_request();
  if (!m_current_request)
    clear_locks();
}

//----------------------------------------------------------------------------
//-- direct BUS interface
//----------------------------------------------------------------------------

bool simple_bus::direct_read(int *data, unsigned int address)
{
  if (address%4 != 0 ) {// address not word alligned
    sb_fprintf(stdout, "  BUS ERROR --> address %04X not word alligned\n",address);
    return false; 
  }
  simple_bus_slave_if *slave = get_slave(address);
  if (!slave) return false;
  return slave->direct_read(data, address);
}

bool simple_bus::direct_write(int *data, unsigned int address)
{
  if (address%4 != 0 ) {// address not word alligned
    sb_fprintf(stdout, "  BUS ERROR --> address %04X not word alligned\n",address);
    return false; 
  }
  simple_bus_slave_if *slave = get_slave(address);
  if (!slave) return false;
  return slave->direct_write(data, address);
}

//----------------------------------------------------------------------------
//-- non-blocking BUS interface
//----------------------------------------------------------------------------

void simple_bus::read(unsigned int unique_priority
		      , int *data
		      , unsigned int address
		      , bool lock)
{
  if (m_verbose)
    sb_fprintf(stdout, "%s %s : read(%d) @ %x\n",
	       sc_time_stamp().to_string().c_str(), name(), unique_priority, address);
  
  simple_bus_request *request = get_request(unique_priority);

  // abort when the request is still not finished
  sc_assert((request->status == SIMPLE_BUS_OK) ||
	    (request->status == SIMPLE_BUS_ERROR));

  request->do_write           = false; // we are reading
  request->address            = address;
  request->end_address        = address;
  request->data               = data;

  if (lock)
    request->lock = (request->lock == SIMPLE_BUS_LOCK_SET) ? 
      SIMPLE_BUS_LOCK_GRANTED : SIMPLE_BUS_LOCK_SET;

  request->status = SIMPLE_BUS_REQUEST;
}

void simple_bus::write(unsigned int unique_priority
		       , int *data
		       , unsigned int address
		       , bool lock)
{
  if (m_verbose) 
    sb_fprintf(stdout, "%s %s : write(%d) @ %x\n",
	       sc_time_stamp().to_string().c_str(), name(), unique_priority, address);

  simple_bus_request *request = get_request(unique_priority);

  // abort when the request is still not finished
  sc_assert((request->status == SIMPLE_BUS_OK) ||
	    (request->status == SIMPLE_BUS_ERROR));

  request->do_write           = true; // we are writing
  request->address            = address;
  request->end_address        = address;
  request->data               = data;

  if (lock)
    request->lock = (request->lock == SIMPLE_BUS_LOCK_SET) ?
      SIMPLE_BUS_LOCK_GRANTED : SIMPLE_BUS_LOCK_SET;

  request->status = SIMPLE_BUS_REQUEST;
}

simple_bus_status simple_bus::get_status(unsigned int unique_priority)
{
  return get_request(unique_priority)->status;
}

//----------------------------------------------------------------------------
//-- blocking BUS interface
//----------------------------------------------------------------------------

simple_bus_status simple_bus::burst_read(unsigned int unique_priority
					 , int *data
					 , unsigned int start_address
					 , unsigned int length
					 , bool lock)
{
  if (m_verbose) 
  {
    sb_fprintf(stdout, "%s %s : burst_read(%d) @ %x\n",
	sc_time_stamp().to_string().c_str(), name(), unique_priority, 
	start_address);
  }
	
  simple_bus_request *request = get_request(unique_priority);

  request->do_write           = false; // we are reading
  request->address            = start_address;
  request->end_address        = start_address + (length-1)*4;
  request->data               = data;

  if (lock)
    request->lock = (request->lock == SIMPLE_BUS_LOCK_SET) ? 
      SIMPLE_BUS_LOCK_GRANTED : SIMPLE_BUS_LOCK_SET;

  request->status = SIMPLE_BUS_REQUEST;

  wait(request->transfer_done);
  wait(clock->posedge_event());
  return request->status;
}

simple_bus_status simple_bus::burst_write(unsigned int unique_priority
					  , int *data
					  , unsigned int start_address
					  , unsigned int length
					  , bool lock)
{
  if (m_verbose) 
    sb_fprintf(stdout, "%s %s : burst_write(%d) @ %x\n",
	       sc_time_stamp().to_string().c_str(), name(), unique_priority, 
	       start_address);
	
  simple_bus_request *request = get_request(unique_priority);

  request->do_write           = true; // we are writing
  request->address            = start_address;
  request->end_address        = start_address + (length-1)*4;
  request->data               = data;

  if (lock)
    request->lock = (request->lock == SIMPLE_BUS_LOCK_SET) ? 
      SIMPLE_BUS_LOCK_GRANTED : SIMPLE_BUS_LOCK_SET;

  request->status = SIMPLE_BUS_REQUEST;

  wait(request->transfer_done);
  wait(clock->posedge_event());
  return request->status;
}

//----------------------------------------------------------------------------
//-- BUS methods:
//
//     handle_request()   : performs atomic bus-to-slave request
//     get_request()      : BUS-interface: gets the request form of given 
//                          priority
//     get_next_request() : returns a valid request out of the list of 
//                          pending requests
//     clear_locks()      : downgrade the lock status of the requests once
//                          the transfer is done
//----------------------------------------------------------------------------

void simple_bus::handle_request()
{
  if (m_verbose)
      sb_fprintf(stdout, "%s %s Handle Slave(%d)\n",
		 sc_time_stamp().to_string().c_str(), name(), 
		 m_current_request->priority);

  m_current_request->status = SIMPLE_BUS_WAIT;
  simple_bus_slave_if *slave = get_slave(m_current_request->address);

  if ((m_current_request->address)%4 != 0 ) {// address not word aligned
    sb_fprintf(stdout, "  BUS ERROR --> address %04X not word aligned\n",m_current_request->address);
    m_current_request->status = SIMPLE_BUS_ERROR;
    m_current_request = (simple_bus_request *)0;
    return;
  }
  if (!slave) {
    sb_fprintf(stdout, "  BUS ERROR --> no slave for address %04X \n",m_current_request->address);
    m_current_request->status = SIMPLE_BUS_ERROR;
    m_current_request = (simple_bus_request *)0;
    return;
  }

  simple_bus_status slave_status = SIMPLE_BUS_OK;
  if (m_current_request->do_write)
    slave_status = slave->write(m_current_request->data, 
				m_current_request->address);
  else
    slave_status = slave->read(m_current_request->data,
			       m_current_request->address);

  if (m_verbose)
    sb_fprintf(stdout, "  --> status=(%s)\n", simple_bus_status_str[slave_status]);

  switch(slave_status)
    {
    case SIMPLE_BUS_ERROR:
      m_current_request->status = SIMPLE_BUS_ERROR;
      m_current_request->transfer_done.notify();
      m_current_request = (simple_bus_request *)0;
      break;
    case SIMPLE_BUS_OK:
      m_current_request->address+=4; //next word (byte addressing)
      m_current_request->data++;
      if (m_current_request->address > m_current_request->end_address)
	{
	  // burst-transfer (or single transfer) completed
	  m_current_request->status = SIMPLE_BUS_OK;
	  m_current_request->transfer_done.notify();
	  m_current_request = (simple_bus_request *)0;
	}
      else
	{ // more data to transfer, but the (atomic) slave transfer is done
	  m_current_request = (simple_bus_request *)0;
	}
      break;
    case SIMPLE_BUS_WAIT:
      // the slave is still processing: no clearance of the current request
      break;
    default:
      break;
    }
}

simple_bus_slave_if *simple_bus::get_slave(unsigned int address)
{
  for (int i = 0; i < slave_port.size(); ++i)
    {
      simple_bus_slave_if *slave = slave_port[i];
      if ((slave->start_address() <= address) &&
	  (address <= slave->end_address()))
	return slave;
    }
  return (simple_bus_slave_if *)0;		
}

simple_bus_request * simple_bus::get_request(unsigned int priority)
{
  simple_bus_request *request = (simple_bus_request *)0;
  for (unsigned int i = 0; i < m_requests.size(); ++i)
    {
      request = m_requests[i];
      if ((request) &&
	  (request->priority == priority))
	return request;
    }
  request = new simple_bus_request;
  request->priority = priority;
  m_requests.push_back(request);
  return request;		
}

simple_bus_request * simple_bus::get_next_request()
{
  // the slave is done with its action, m_current_request is
  // empty, so go over the bag of request-forms and compose
  // a set of likely requests. Pass it to the arbiter for the
  // final selection
  simple_bus_request_vec Q;
  for (unsigned int i = 0; i < m_requests.size(); ++i)
    {
      simple_bus_request *request = m_requests[i];
      if ((request->status == SIMPLE_BUS_REQUEST) ||
	  (request->status == SIMPLE_BUS_WAIT))
	{
	  if (m_verbose) 
	    sb_fprintf(stdout, "%s %s : request (%d) [%s]\n",
		       sc_time_stamp().to_string().c_str(), name(), 
		       request->priority, simple_bus_status_str[request->status]);
	  Q.push_back(request);
	}
    }
  if (Q.size() > 0)
    return arbiter_port->arbitrate(Q);
  return (simple_bus_request *)0;
}

void simple_bus::clear_locks()
{
  for (unsigned int i = 0; i < m_requests.size(); ++i)
    if (m_requests[i]->lock == SIMPLE_BUS_LOCK_GRANTED)
      m_requests[i]->lock = SIMPLE_BUS_LOCK_SET;
    else
      m_requests[i]->lock = SIMPLE_BUS_LOCK_NO;
}