source: rtems/c/src/lib/libcpu/powerpc/mpc6xx/clock/c_clock.c @ 9c325fb2

/*
 *  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) 1989-2007.
 *  On-Line Applications Research Corporation (OAR).
 *
 *  The license and distribution terms for this file may in
 *  the file LICENSE in this distribution or at
 *  http://www.rtems.com/license/LICENSE.
 *
 *  Modified to support the MPC750.
 *  Modifications Copyright (c) 1999 Eric Valette valette@crf.canon.fr
 *
 *  $Id$
 */

#include <rtems/system.h>
#include <rtems.h>
#include <rtems/libio.h>
#include <stdlib.h>                     /* for atexit() */
#include <assert.h>
#include <libcpu/c_clock.h>
#include <libcpu/cpuIdent.h>
#include <libcpu/spr.h>
#include <rtems/bspIo.h>                /* for printk() */

#include <bspopts.h>   /* for CLOCK_DRIVER_USE_FAST_IDLE */

SPR_RW(BOOKE_TCR)
SPR_RW(BOOKE_TSR)
SPR_RW(BOOKE_DECAR)
SPR_RW(DEC)

extern int BSP_connect_clock_handler (void);

/*
 *  Clock ticks since initialization
 */

volatile uint32_t   Clock_driver_ticks;

/*
 *  This is the value programmed into the count down timer.
 */

uint32_t   Clock_Decrementer_value;

/*
 * These are set by clock driver during its init
 */
 
rtems_device_major_number rtems_clock_major = ~0;
rtems_device_minor_number rtems_clock_minor;

void clockOff(void* unused)
{
rtems_interrupt_level l;

  if ( ppc_cpu_is_bookE() ) {
    rtems_interrupt_disable(l);
    _write_BOOKE_TCR(_read_BOOKE_TCR() & ~BOOKE_TCR_DIE);
    rtems_interrupt_enable(l);
  } else {
  /*
   * Nothing to do as we cannot disable all interrupts and
   * the decrementer interrupt enable is MSR_EE
   */
  }
}

void clockOn(void* unused)
{
rtems_interrupt_level l;

  PPC_Set_decrementer( Clock_Decrementer_value );

  if ( ppc_cpu_is_bookE() ) {
    _write_BOOKE_DECAR( Clock_Decrementer_value );

    rtems_interrupt_disable(l);

    /* clear pending/stale irq */
    _write_BOOKE_TSR( BOOKE_TSR_DIS );
    /* enable */
    _write_BOOKE_TCR( _read_BOOKE_TCR() | BOOKE_TCR_DIE );

    rtems_interrupt_enable(l);

  }
}

static void clockHandler(void)
{

  #if defined(CLOCK_DRIVER_USE_FAST_IDLE)
    do {
      rtems_clock_tick();
    } while ( _Thread_Executing == _Thread_Idle &&
              _Thread_Heir == _Thread_Executing);

  #else
    rtems_clock_tick();
  #endif
}

static void (*clock_handler)(void);

/*
 *  Clock_isr
 *
 *  This is the clock tick interrupt handler.
 *
 *  Input parameters:
 *    vector - vector number
 *
 *  Output parameters:  NONE
 *
 *  Return values:      NONE
 *
 */
void clockIsr(void *unused)
{
int decr;
  /*
   *  The driver has seen another tick.
   */
  do {
  register uint32_t flags;
  rtems_interrupt_disable(flags);
  asm volatile (
    "mfdec %0; add %0, %0, %1; mtdec %0"
    : "=&r"(decr)
    : "r"(Clock_Decrementer_value));
  rtems_interrupt_enable(flags);

  Clock_driver_ticks += 1;

  /*
   *  Real Time Clock counter/timer is set to automatically reload.
   */
  clock_handler();
  } while ( decr < 0 );
}

/*
 *  Clock_isr_bookE
 *
 *  This is the clock tick interrupt handler
 *  for bookE CPUs. For efficiency reasons we
 *  provide a separate handler rather than
 *  checking the CPU type each time.
 *
 *  Input parameters:
 *    vector - vector number
 *
 *  Output parameters:  NONE
 *
 *  Return values:      NONE
 *
 */
void clockIsrBookE(void *unused)
{
  /* Note: TSR bit has already been cleared in the exception handler */

  /*
   *  The driver has seen another tick.
   */

  Clock_driver_ticks += 1;

  /*
   *  Real Time Clock counter/timer is set to automatically reload.
   */
  clock_handler();

}

int clockIsOn(void* unused)
{
uint32_t   msr_value;

  _CPU_MSR_GET( msr_value );

  if ( ppc_cpu_is_bookE() && ! (_read_BOOKE_TCR() & BOOKE_TCR_DIE) )
    msr_value = 0;

  if (msr_value & MSR_EE) return 1;

  return 0;
}


/*
 *  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 )
{
  (void) BSP_disconnect_clock_handler ();
}
 
uint32_t Clock_driver_nanoseconds_since_last_tick(void)
{
  uint32_t clicks, tmp;

  PPC_Get_decrementer( clicks ); 

  /*
   * Multiply by 1000 here separately from below so we do not overflow
   * and get a negative value.
   */
  tmp = (Clock_Decrementer_value - clicks) * 1000;
  tmp /= (BSP_bus_frequency/BSP_time_base_divisor);

  return tmp * 1000;
}

/*
 *  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
)
{
rtems_interrupt_level l,tcr;

  Clock_Decrementer_value = (BSP_bus_frequency/BSP_time_base_divisor)*
            (rtems_configuration_get_microseconds_per_tick()/1000);

  /* set the decrementer now, prior to installing the handler 
   * so no interrupts will happen in a while.
   */
  PPC_Set_decrementer( (unsigned)-1 );

  /* On a bookE CPU the decrementer works differently. It doesn't
   * count past zero but we can enable auto-reload :-)
   */
  if ( ppc_cpu_is_bookE() ) {

    rtems_interrupt_disable(l);

    tcr  = _read_BOOKE_TCR();
    tcr |= BOOKE_TCR_ARE;
    tcr &= ~BOOKE_TCR_DIE;
    _write_BOOKE_TCR(tcr);

    rtems_interrupt_enable(l);

  }

  /*
   *  Set the nanoseconds since last tick handler
   */
  rtems_clock_set_nanoseconds_extension(
    Clock_driver_nanoseconds_since_last_tick
  );

  /* if a decrementer exception was pending, it is cleared by
   * executing the default (nop) handler at this point;
   * The next exception will then be taken by our clock handler.
   * Clock handler installation initializes the decrementer to
   * the correct value.
   */

  clock_handler = clockHandler;
  if (!BSP_connect_clock_handler ()) {
    printk("Unable to initialize system clock\n");
    rtems_fatal_error_occurred(1);
  }
  /* make major/minor avail to others such as shared memory driver */
 
  rtems_clock_major = major;
  rtems_clock_minor = minor;

  return RTEMS_SUCCESSFUL;
} /* Clock_initialize */
 
/*
 *  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_libio_ioctl_args_t *args = pargp;
 
    if (args == 0)
        goto done;
 
    Clock_Decrementer_value = (BSP_bus_frequency/BSP_time_base_divisor)*
      (rtems_configuration_get_microseconds_per_tick()/1000);

    if      (args->command == rtems_build_name('I', 'S', 'R', ' '))
      clockHandler();
    else if (args->command == rtems_build_name('N', 'E', 'W', ' '))
    {
        if (clock_handler == NULL)
            Clock_initialize(major, minor, 0);
        clock_handler = args->buffer;
    }
done:
    return RTEMS_SUCCESSFUL;
}