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/*
* This routine initializes the MC68360 Periodic Interval Timer
*
* The PIT has rather poor resolution, but it is easy to set up
* and requires no housekeeping once it is going.
*
* Based on the `gen68302' board support package, and covered by the
* original distribution terms.
*
* W. Eric Norum
* Saskatchewan Accelerator Laboratory
* University of Saskatchewan
* Saskatoon, Saskatchewan, CANADA
* eric@skatter.usask.ca
*
* $Id$
*/
/*
* Input parameters: NONE
*
* Output parameters: NONE
*
* 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.
*/
#include <stdlib.h> /* for atexit() */
#include <bsp.h>
#include <rtems/libio.h>
#include "m68360.h"
#define CLOCK_VECTOR 120
#define CLOCK_IRQ_LEVEL 6
/*
* 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;
/*
* These are set by clock driver during its init
*/
rtems_device_major_number rtems_clock_major = ~0;
rtems_device_minor_number rtems_clock_minor;
char M360DefaultWatchdogFeeder = 1;
/*
* RTEMS and hardware have different notions of clock rate.
*/
static unsigned long rtems_nsec_per_tick;
static unsigned long pit_nsec_per_tick;
/*
* Periodic interval timer interrupt handler
*/
rtems_isr
Clock_isr (rtems_vector_number vector)
{
static unsigned long nsec;
/*
* See if it's really time for a `tick'
*/
nsec += pit_nsec_per_tick;
if (nsec >= rtems_nsec_per_tick) {
nsec -= rtems_nsec_per_tick;
/*
* Perform a dummy read of DPRAM.
* This works around a bug in Rev. B of the 68360
*/
m360.dpram0[0];
/*
* Feed the watchdog
* Application code can override this by
* setting M360DefaultWatchdogFeeder to zero.
*/
if (M360DefaultWatchdogFeeder) {
m360.swsr = 0x55;
m360.swsr = 0xAA;
}
/*
* Announce the clock tick
*/
Clock_driver_ticks++;
rtems_clock_tick();
}
}
void
Clock_exit (void)
{
if (BSP_Configuration.ticks_per_timeslice ) {
/*
* Turn off periodic interval timer
*/
m360.pitr &= ~0xFF;
}
}
static void
Install_clock (rtems_isr_entry clock_isr)
{
Clock_driver_ticks = 0;
if ( BSP_Configuration.ticks_per_timeslice ) {
/*
* Choose periodic interval timer register value
* The rate at which the periodic interval timer
* can generate interrupts is almost certainly not
* the same as desired by the BSP configuration.
* Handle the difference by choosing the largest PIT
* interval which is less than or equal to the RTEMS
* interval and skipping some hardware interrupts.
* To reduce the jitter in the calls to RTEMS the
* hardware interrupt interval is never less than
* the maximum non-prescaled value from the PIT.
*
* For a 25 MHz external clock the basic clock rate is
* 40 nsec * 128 * 4 = 20.48 usec/tick
*/
int divisor;
extern int m360_clock_rate; /* This should be somewhere in a config file */
unsigned long nsec_per_chip_tick = 1000000000 / m360_clock_rate;
unsigned long nsec_per_pit_tick = 512 * nsec_per_chip_tick;
rtems_nsec_per_tick = BSP_Configuration.microseconds_per_tick * 1000;
divisor = rtems_nsec_per_tick / nsec_per_pit_tick;
if (divisor >= 256) {
divisor = 255;
}
else if (divisor == 0) {
divisor = 1;
}
pit_nsec_per_tick = nsec_per_pit_tick * divisor;
m360.pitr &= ~0x1FF;
m360.picr = (CLOCK_IRQ_LEVEL << 8) | CLOCK_VECTOR;
set_vector (clock_isr, CLOCK_VECTOR, 1);
m360.pitr |= divisor;
atexit (Clock_exit);
}
}
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) {
/*
* 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 );
}
}
return RTEMS_SUCCESSFUL;
}
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