/* clock.c
*
* This routine initializes the interval timer on the
* PowerPC 403 CPU. The tick frequency is specified by the bsp.
*
* Author: Andrew Bray <andy@i-cubed.demon.co.uk>
*
* COPYRIGHT (c) 1995 by i-cubed ltd.
*
* To anyone who acknowledges that this file is provided "AS IS"
* without any express or implied warranty:
* permission to use, copy, modify, and distribute this file
* for any purpose is hereby granted without fee, provided that
* the above copyright notice and this notice appears in all
* copies, and that the name of i-cubed limited not be used in
* advertising or publicity pertaining to distribution of the
* software without specific, written prior permission.
* i-cubed limited makes no representations about the suitability
* of this software for any purpose.
*
* Derived from c/src/lib/libcpu/hppa1_1/clock/clock.c:
*
* COPYRIGHT (c) 1989, 1990, 1991, 1992, 1993, 1994.
* On-Line Applications Research Corporation (OAR).
* All rights assigned to U.S. Government, 1994.
*
* This material may be reproduced by or for the U.S. Government pursuant
* to the copyright license under the clause at DFARS 252.227-7013. This
* notice must appear in all copies of this file and its derivatives.
*
* clock.c,v 1.2 1995/05/31 16:59:06 joel Exp
*/
#include <bsp.h>
#include <clockdrv.h>
#include <stdlib.h> /* for atexit() */
extern rtems_cpu_table Cpu_table; /* owned by BSP */
volatile rtems_unsigned32 Clock_driver_ticks;
static rtems_unsigned32 pit_value, tick_time;
static rtems_boolean auto_restart;
rtems_device_driver Clock_initialize(
rtems_device_major_number major,
rtems_device_minor_number minor,
void *pargp,
rtems_id tid,
rtems_unsigned32 *rval
)
{
Install_clock(Clock_isr);
}
void
ReInstall_clock(rtems_isr_entry new_clock_isr)
{
rtems_isr_entry previous_isr;
rtems_unsigned32 isrlevel = 0;
rtems_interrupt_disable(isrlevel);
rtems_interrupt_catch(new_clock_isr, PPC_IRQ_PIT,
&previous_isr);
rtems_interrupt_enable(isrlevel);
}
static INLINE rtems_unsigned32 get_itimer(void)
{
register rtems_unsigned32 rc;
asm volatile ("mftblo %0" : "=r" ((rc)));
return rc;
}
void Install_clock(rtems_isr_entry clock_isr)
{
rtems_isr_entry previous_isr;
rtems_unsigned32 pvr, iocr;
Clock_driver_ticks = 0;
asm volatile ("mfiocr %0" : "=r" (iocr));
iocr &= ~4;
iocr |= 4; /* Select external timer clock */
asm volatile ("mtiocr %0" : "=r" (iocr) : "0" (iocr));
asm volatile ("mfpvr %0" : "=r" ((pvr)));
if (((pvr & 0xffff0000) >> 16) != 0x0020)
return; /* Not a ppc403 */
if ((pvr & 0xff00) == 0x0000) /* 403GA */
auto_restart = (pvr & 0x00f0) > 0x0000 ? 1 : 0;
else if ((pvr & 0xff00) == 0x0100) /* 403GB */
auto_restart = 1;
pit_value = BSP_Configuration.microseconds_per_tick *
Cpu_table.clicks_per_usec;
if (BSP_Configuration.ticks_per_timeslice)
{
register rtems_unsigned32 tcr;
/*
* initialize the interval here
* First tick is set to right amount of time in the future
* Future ticks will be incremented over last value set
* in order to provide consistent clicks in the face of
* interrupt overhead
*/
rtems_interrupt_catch(clock_isr, PPC_IRQ_PIT,
&previous_isr);
asm volatile ("mtpit %0" : : "r" (pit_value));
asm volatile ("mftcr %0" : "=r" ((tcr)));
tcr &= ~ 0x04400000;
tcr |= (auto_restart ? 0x04400000 : 0x04000000);
tick_time = get_itimer() + pit_value;
asm volatile ("mttcr %0" : "=r" ((tcr)) : "0" ((tcr)));
}
atexit(Clock_exit);
}
rtems_isr
Clock_isr(rtems_vector_number vector)
{
if (!auto_restart)
{
rtems_unsigned32 clicks_til_next_interrupt;
rtems_unsigned32 itimer_value;
/*
* setup for next interrupt; making sure the new value is reasonably
* in the future.... in case we lost out on an interrupt somehow
*/
itimer_value = get_itimer();
tick_time += pit_value;
/*
* how far away is next interrupt *really*
* It may be a long time; this subtraction works even if
* Clock_clicks_interrupt < Clock_clicks_low_order via
* the miracle of unsigned math.
*/
clicks_til_next_interrupt = tick_time - itimer_value;
/*
* If it is too soon then bump it up.
* This should only happen if CPU_HPPA_CLICKS_PER_TICK is too small.
* But setting it low is useful for debug, so...
*/
if (clicks_til_next_interrupt < 400)
{
tick_time = itimer_value + 1000;
clicks_til_next_interrupt = 1000;
/* XXX: count these! this should be rare */
}
/*
* If it is too late, that means we missed the interrupt somehow.
* Rather than wait 35-50s for a wrap, we just fudge it here.
*/
if (clicks_til_next_interrupt > pit_value)
{
tick_time = itimer_value + 1000;
clicks_til_next_interrupt = 1000;
/* XXX: count these! this should never happen :-) */
}
asm volatile ("mtpit %0" :: "r" (clicks_til_next_interrupt));
}
asm volatile ( "mttsr %0" :: "r" (0x08000000));
Clock_driver_ticks++;
rtems_clock_tick();
}
/*
* Called via atexit()
* Remove the clock interrupt handler by setting handler to NULL
*/
void
Clock_exit(void)
{
if ( BSP_Configuration.ticks_per_timeslice )
{
register rtems_unsigned32 tcr;
asm volatile ("mftcr %0" : "=r" ((tcr)));
tcr &= ~ 0x04400000;
asm volatile ("mttcr %0" : "=r" ((tcr)) : "0" ((tcr)));
(void) set_vector(0, PPC_IRQ_PIT, 1);
}
}
