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/*
 *  Clock Tick Device Driver
 *
 *  This routine utilizes the Decrementer Register common to the PPC family.
 *
 *  The tick frequency is directly programmed to the configured number of
 *  microseconds per tick.
 *
 *  COPYRIGHT (c) 1989-1997.
 *  On-Line Applications Research Corporation (OAR).
 *  Copyright assigned to U.S. Government, 1994.
 *
 *  The license and distribution terms for this file may in
 *  the file LICENSE in this distribution or at
 *  http://www.OARcorp.com/rtems/license.html.
 *
 *  $Id: clock.c,v 1.2 2001-09-27 12:01:03 chris Exp $
 */
 
#include <stdlib.h>
 
#include <bsp.h>
#include <rtems/libio.h>
#include <assert.h>
 
/*
 *  The Real Time Clock Counter Timer uses this trap type.
 */
 
#define CLOCK_VECTOR PPC_IRQ_DECREMENTER
 
/*
 *  Clock ticks since initialization
 */
 
volatile rtems_unsigned32 Clock_driver_ticks;
 
/*
 *  This is the value programmed into the count down timer.
 */
 
rtems_unsigned32 Clock_Decrementer_value;
 
rtems_isr_entry  Old_ticker;
 
void Clock_exit( void );
 
/*
 * These are set by clock driver during its init
 */
 
rtems_device_major_number rtems_clock_major = ~0;
rtems_device_minor_number rtems_clock_minor;
 
#define PPC_Set_decrementer( _clicks ) \
  do { \
    asm volatile( "mtdec %0" : "=r" ((_clicks)) : "r" ((_clicks)) ); \
  } while (0)
 
 
/*
 *  Clock_isr
 *
 *  This is the clock tick interrupt handler.
 *
 *  Input parameters:
 *    vector - vector number
 *
 *  Output parameters:  NONE
 *
 *  Return values:      NONE
 *
 */
rtems_isr Clock_isr(
  rtems_vector_number  vector,
  CPU_Interrupt_frame *frame
)
{
  /*
   *  Set the decrementer.
   */
 
  PPC_Set_decrementer( Clock_Decrementer_value );
 
  /*
   *  The driver has seen another tick.
   */
 
  Clock_driver_ticks += 1;
 
  /*
   *  Real Time Clock counter/timer is set to automatically reload.
   */
 
  rtems_clock_tick();
}
 
/*
 *  Install_clock
 *
 *  This routine actually performs the hardware initialization for the clock.
 *
 *  Input parameters:
 *    clock_isr - clock interrupt service routine entry point
 *
 *  Output parameters:  NONE
 *
 *  Return values:      NONE
 *
 */
 
extern int CLOCK_SPEED;
 
void Install_clock(
  rtems_isr_entry clock_isr
)
{
  Clock_driver_ticks = 0;
 
  Old_ticker = (rtems_isr_entry) set_vector( clock_isr, CLOCK_VECTOR, 1 );
 
  PPC_Set_decrementer( Clock_Decrementer_value );
 
  atexit( Clock_exit );
}
 
/*
 *  Clock_exit
 *
 *  This routine allows the clock driver to exit by masking the interrupt and
 *  disabling the clock's counter.
 *
 *  Input parameters:   NONE
 *
 *  Output parameters:  NONE
 *
 *  Return values:      NONE
 *
 */
 
void Clock_exit( void )
{
  /* nothing to do */; 
 
  /* do not restore old vector */
}
 
/*
 *  Clock_initialize
 *
 *  This routine initializes the clock driver.
 *
 *  Input parameters:
 *    major - clock device major number
 *    minor - clock device minor number
 *    parg  - pointer to optional device driver arguments
 *
 *  Output parameters:  NONE
 *
 *  Return values:
 *    rtems_device_driver status code
 */
 
rtems_device_driver Clock_initialize(
  rtems_device_major_number major,
  rtems_device_minor_number minor,
  void *pargp
)
{
  Clock_Decrementer_value = (int) &CPU_PPC_CLICKS_PER_MS *
                       (BSP_Configuration.microseconds_per_tick / 1000);
 
  Install_clock( (rtems_isr_entry) Clock_isr );
 
  /*
   * make major/minor avail to others such as shared memory driver
   */
 
  rtems_clock_major = major;
  rtems_clock_minor = minor;
 
  return RTEMS_SUCCESSFUL;
}
 
/*
 *  Clock_control
 *
 *  This routine is the clock device driver control entry point.
 *
 *  Input parameters:
 *    major - clock device major number
 *    minor - clock device minor number
 *    parg  - pointer to optional device driver arguments
 *
 *  Output parameters:  NONE
 *
 *  Return values:
 *    rtems_device_driver status code
 */
 
rtems_device_driver Clock_control(
  rtems_device_major_number major,
  rtems_device_minor_number minor,
  void *pargp
)
{
    rtems_unsigned32 isrlevel;
    rtems_libio_ioctl_args_t *args = pargp;
 
    if (args == 0)
        goto done;
 
    /*
     * This is hokey, but until we get a defined interface
     * to do this, it will just be this simple...
     */
 
    if (args->command == rtems_build_name('I', 'S', 'R', ' '))
    {
        Clock_isr( CLOCK_VECTOR, pargp );
    }
    else if (args->command == rtems_build_name('N', 'E', 'W', ' '))
    {
      rtems_interrupt_disable( isrlevel );
       (void) set_vector( args->buffer, CLOCK_VECTOR, 1 );
      rtems_interrupt_enable( isrlevel );
    }
 
done:
    return RTEMS_SUCCESSFUL;
}