/* ckinit.c
*
* This file provides a template for the clock device driver initialization.
*
* COPYRIGHT (c) 1989-1999.
* On-Line Applications Research Corporation (OAR).
*
* The license and distribution terms for this file may be
* found in the file LICENSE in this distribution or at
* http://www.OARcorp.com/rtems/license.html.
*
* $Id$
*/
#include <stdlib.h>
#include <rtems.h>
#include <rtems/libio.h>
#include <bsp.h>
void Clock_exit( void );
rtems_isr Clock_isr( rtems_vector_number vector );
/*
* The interrupt vector number associated with the clock tick device
* driver.
*/
#define CLOCK_VECTOR PPC_IRQ_DECREMENTER
/*
* Clock_driver_ticks is a monotonically increasing counter of the
* number of clock ticks since the driver was initialized.
*/
volatile rtems_unsigned32 Clock_driver_ticks;
/*
* Clocks_per_tick is the number of clocks of the decrementer needed
* to fill BSP_Configuration.microseconds_per_tick.
*
* The clock rate is 1/4 the bus clock, or 16.666667 MHz, so:
*
* Clocks_per_tick = ((50/3)*1E6 clocks/sec) * (1 sec/1E6 us) * (X us/tick)
* = X * 50 / 3 clocks/tick
* where X = BSP_Configuration.microseconds_per_tick
*/
rtems_signed32 Clocks_per_tick;
/*
* These are set by clock driver during its init
*/
rtems_device_major_number rtems_clock_major = ~0;
rtems_device_minor_number rtems_clock_minor;
/*
* The previous ISR on this clock tick interrupt vector.
*/
rtems_isr_entry Old_ticker;
void Clock_exit( void );
/*
* Inline assembly routines to access the decrementer register
*/
static inline rtems_signed32 read_decrementer(void) {
rtems_signed32 result;
asm volatile ("mfdec %0" : "=r" (result) :);
return result;
}
static inline void write_decrementer(rtems_signed32 value) {
asm volatile ("mtdec %0" : : "r" (value));
}
/*
* Isr Handler
*/
rtems_isr Clock_isr(
rtems_vector_number vector
)
{
rtems_signed32 count, repeat = 0;
const rtems_signed32 period = Clocks_per_tick;
/*
* bump the number of clock driver ticks since initialization
*/
Clock_driver_ticks++;
/*
* be very paranoid and count number of "ticks" in case we missed some
*
* update the decrementer and signal rtems the appropriate number of times
*/
count = read_decrementer();
while (count < 0) {
count += period;
repeat++;
}
write_decrementer(count);
while (repeat-- > 0) {
rtems_clock_tick();
}
}
/*
* Install_clock
*
* Install a clock tick handler and reprograms the chip. This
* is used to initially establish the clock tick.
*/
void Install_clock(
rtems_isr_entry clock_isr
)
{
/*
* Initialize the clock tick device driver variables
*/
Clock_driver_ticks = 0;
switch (Falcon_SYSCR.SystemClock) {
case SYSCLK_50_MHZ:
Clocks_per_tick =
(BSP_Configuration.microseconds_per_tick * 25 + 1) / 2;
break;
case SYSCLK_60_MHZ:
Clocks_per_tick = BSP_Configuration.microseconds_per_tick * 15;
break;
case SYSCLK_67_MHZ:
Clocks_per_tick =
(BSP_Configuration.microseconds_per_tick * 50 + 1) / 3;
break;
}
/*
* If ticks_per_timeslice is configured as non-zero, then the user
* wants a clock tick.
*/
if ( BSP_Configuration.ticks_per_timeslice ) {
Old_ticker = (rtems_isr_entry) set_vector( clock_isr, CLOCK_VECTOR, 1 );
/*
* Hardware specific initialize goes here
*/
write_decrementer(Clocks_per_tick);
}
/*
* Schedule the clock cleanup routine to execute if the application exits.
*/
atexit( Clock_exit );
}
/*
* Clean up before the application exits
*/
void Clock_exit( void )
{
if ( BSP_Configuration.ticks_per_timeslice ) {
/* XXX: turn off the timer interrupts */
/* we can't really disable the timer without disabling all external
interupts. we'll slow down the decrementer to it's minimum speed. */
write_decrementer(~0);
/* XXX: If necessary, restore the old vector */
}
}
/*
* Clock_initialize
*
* Device driver entry point for clock tick driver initialization.
*/
rtems_device_driver Clock_initialize(
rtems_device_major_number major,
rtems_device_minor_number minor,
void *pargp
)
{
Install_clock( Clock_isr );
/*
* make major/minor avail to others such as shared memory driver
*/
rtems_clock_major = major;
rtems_clock_minor = minor;
return RTEMS_SUCCESSFUL;
}
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);
}
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;
}
