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/*==========================================================================
//
//      timer_pit.c
//
//      HAL timer code using the Periodic Interval Timer
//
//==========================================================================
// ####ECOSGPLCOPYRIGHTBEGIN####                                            
// -------------------------------------------                              
// This file is part of eCos, the Embedded Configurable Operating System.   
// Copyright (C) 2006 Free Software Foundation, Inc.                        
//
// eCos 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 or (at your option) any later      
// version.                                                                 
//
// eCos 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 eCos; if not, write to the Free Software Foundation, Inc.,    
// 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.            
//
// As a special exception, if other files instantiate templates or use      
// macros or inline functions from this file, or you compile this file      
// and link it with other works to produce a work based on this file,       
// this file does not by itself cause the resulting work to be covered by   
// the GNU General Public License. However the source code for this file    
// must still be made available in accordance with section (3) of the GNU   
// General Public License v2.                                               
//
// This exception does not invalidate any other reasons why a work based    
// on this file might be covered by the GNU General Public License.         
// -------------------------------------------                              
// ####ECOSGPLCOPYRIGHTEND####                                              
//==========================================================================
//#####DESCRIPTIONBEGIN####
//
// Author(s):    asl, Oliver Munz
// Contributors: asl, Oliver Munz
// Date:         2009-06-03
// Purpose:      Clock support using the PIT
// Description:
//
//####DESCRIPTIONEND####
//
//========================================================================*/
 
#include <pkgconf/hal.h>
 
#include <cyg/infra/cyg_type.h>         // base types
#include <cyg/infra/cyg_ass.h>          // assertion macros
 
#include <cyg/hal/hal_io.h>             // IO macros
#include <cyg/hal/hal_platform_ints.h>
// -------------------------------------------------------------------------
// Use system clock
void
hal_clock_initialize(cyg_uint32 period){
 
  cyg_uint32 ir;
  cyg_uint32 pimr;
 
  CYG_ASSERT(CYGNUM_HAL_INTERRUPT_RTC == CYGNUM_HAL_INTERRUPT_PITC,
             "Invalid timer interrupt");
  CYG_ASSERT(period <= AT91_PITC_VALUE_MASK,
             "Invalid timer period");
 
  pimr = (period - 1); /* This is what we want */
  HAL_READ_UINT32(AT91_PITC + AT91_PITC_PIIR, ir); /* Counter */
  ir = ir & AT91_PITC_VALUE_MASK; /* The current count */
 
  do { /* Test if the new PITC-Modulus is overrun by the counter */
    if (ir > pimr){ /* If the counter is already too high */
 
      pimr = (ir + 100) & AT91_PITC_VALUE_MASK; /* Set the comparator ahead */
      HAL_WRITE_UINT32((AT91_PITC + AT91_PITC_PIMR),
                       pimr | AT91_PITC_PIMR_PITEN);
    }
    if (ir < (period - 1)){ /* If we can try it */
      pimr = (period - 1); /* This is what we want */
      /* Set the real Period Interval timer */
      HAL_WRITE_UINT32((AT91_PITC + AT91_PITC_PIMR),
                       pimr | AT91_PITC_PIMR_PITEN);
    }
    HAL_READ_UINT32(AT91_PITC + AT91_PITC_PIMR, pimr); /* The real value */
    pimr = pimr & AT91_PITC_VALUE_MASK; /* Value */
    HAL_READ_UINT32(AT91_PITC + AT91_PITC_PIIR, ir); /* Counter */
    ir = ir & AT91_PITC_VALUE_MASK; /* The current counts */
 
  } while (ir > (period - 1) || pimr != (period - 1)); // Is it correct?
 
  /* Enable interrupt */
  HAL_WRITE_UINT32((AT91_PITC + AT91_PITC_PIMR), (period - 1) |
                   AT91_PITC_PIMR_PITEN | AT91_PITC_PIMR_PITIEN);
 
  /* Read the status register to clear any pending interrupt */
  HAL_READ_UINT32(AT91_PITC + AT91_PITC_PISR, ir);
}
 
// This routine is called during a clock interrupt.
void
hal_clock_reset(cyg_uint32 vector, cyg_uint32 period)
{
  cyg_uint32 reg;
  cyg_uint32 pimr;
 
  CYG_ASSERT(period < AT91_PITC_VALUE_MASK, "Invalid HAL clock configuration");
 
  // Check that the PIT has the right period.
  HAL_READ_UINT32((AT91_PITC + AT91_PITC_PIMR), pimr);
  if ((pimr & AT91_PITC_VALUE_MASK) != (period - 1)) {
    HAL_WRITE_UINT32((AT91_PITC + AT91_PITC_PIMR),
                     (period - 1) |
                     AT91_PITC_PIMR_PITEN |
                     AT91_PITC_PIMR_PITIEN);
  }
 
  /* Read the value register so that we clear the interrupt */
  HAL_READ_UINT32(AT91_PITC + AT91_PITC_PIVR, reg);
}
 
// Read the current value of the clock, returning the number of hardware
// "ticks" that have occurred (i.e. how far away the current value is from
// the start)
void
hal_clock_read(cyg_uint32 *pvalue)
{
  cyg_uint32 ir;
  cyg_uint32 pimr;
 
  // Check that the PIT is running. If not start it.
  HAL_READ_UINT32((AT91_PITC + AT91_PITC_PIMR),pimr);
  if (!(pimr & AT91_PITC_PIMR_PITEN)) {
    HAL_WRITE_UINT32((AT91_PITC + AT91_PITC_PIMR),
                     AT91_PITC_VALUE_MASK | AT91_PITC_PIMR_PITEN);
  }
 
  HAL_READ_UINT32(AT91_PITC + AT91_PITC_PIIR, ir);
  *pvalue = ir & AT91_PITC_VALUE_MASK;
}
 
// -------------------------------------------------------------------------
//
// Delay for some number of micro-seconds
// PIT is clocked at MCLK / 16
//
void hal_delay_us(cyg_int32 usecs)
{
  cyg_int64 ticks;
  cyg_uint32 val1, val2;
  cyg_uint32 piv;
 
  // Calculate how many PIT ticks the required number of microseconds
  // equate to. We do this calculation in 64 bit arithmetic to avoid
  // overflow.
  ticks = (((cyg_uint64)usecs) *
           ((cyg_uint64)CYGNUM_HAL_ARM_AT91_CLOCK_SPEED))/16/1000000LL;
 
  // Calculate the wrap around period.
  HAL_READ_UINT32(AT91_PITC + AT91_PITC_PIMR, piv);
  piv = (piv & AT91_PITC_VALUE_MASK) - 1;
 
  hal_clock_read(&val1);
  while (ticks > 0) {
    hal_clock_read(&val2);
    if (val2 < val1)
      ticks -= ((piv + val2) - val1); //overflow occurred
    else
      ticks -= (val2 - val1);
    val1 = val2;
  }
}
 
// timer_pit.c