/*-------------------------------------------------------------------------+
| timer.c v1.1 - PC386 BSP - 1997/08/07
+--------------------------------------------------------------------------+
| This file contains the PC386 timer package.
+--------------------------------------------------------------------------+
| NOTE: It is important that the timer start/stop overhead be determined
| when porting or modifying this code.
+--------------------------------------------------------------------------+
| (C) Copyright 1997 -
| - NavIST Group - Real-Time Distributed Systems and Industrial Automation
|
| http://pandora.ist.utl.pt
|
| Instituto Superior Tecnico * Lisboa * PORTUGAL
+--------------------------------------------------------------------------+
| Disclaimer:
|
| This file is provided "AS IS" without warranty of any kind, either
| expressed or implied.
+--------------------------------------------------------------------------+
| This code is base on:
| timer.c,v 1.7 1995/12/19 20:07:43 joel Exp - go32 BSP
|
| Rosimildo daSilva -ConnectTel, Inc - Fixed infinite loop in the Calibration
| routine. I've seen this problems with faster machines ( pentiums ). Sometimes
| RTEMS just hangs at startup.
|
| With the following copyright notice:
| **************************************************************************
| * COPYRIGHT (c) 1989-1998.
| * On-Line Applications Research Corporation (OAR).
| * Copyright assigned to U.S. Government, 1994.
| *
| * The license and distribution terms for this file may be
| * found in found in the file LICENSE in this distribution or at
| * http://www.OARcorp.com/rtems/license.html.
| **************************************************************************
|
| $Id$
+--------------------------------------------------------------------------*/
#include <stdlib.h>
#include <bsp.h>
#include <irq.h>
/*-------------------------------------------------------------------------+
| Constants
+--------------------------------------------------------------------------*/
#define AVG_OVERHEAD 0 /* 0.1 microseconds to start/stop timer. */
#define LEAST_VALID 1 /* Don't trust a value lower than this. */
#define SLOW_DOWN_IO 0x80 /* io which does nothing */
#define TWO_MS (rtems_unsigned32)(2000) /* TWO_MS = 2000us (sic!) */
#define MSK_NULL_COUNT 0x40 /* bit counter available for reading */
#define CMD_READ_BACK_STATUS 0xE2 /* command read back status */
/*-------------------------------------------------------------------------+
| Global Variables
+--------------------------------------------------------------------------*/
volatile rtems_unsigned32 Ttimer_val;
rtems_boolean Timer_driver_Find_average_overhead = TRUE;
unsigned int loop1ms;
/*-------------------------------------------------------------------------+
| External Prototypes
+--------------------------------------------------------------------------*/
extern void timerisr(void);
/* timer (int 08h) Interrupt Service Routine (defined in 'timerisr.s') */
/*-------------------------------------------------------------------------+
| Pentium optimized timer handling.
+--------------------------------------------------------------------------*/
#if defined(pentium)
/*-------------------------------------------------------------------------+
| Function: rdtsc
| Description: Read the value of PENTIUM on-chip cycle counter.
| Global Variables: None.
| Arguments: None.
| Returns: Value of PENTIUM on-chip cycle counter.
+--------------------------------------------------------------------------*/
static inline unsigned long long
rdtsc(void)
{
/* Return the value of the on-chip cycle counter. */
unsigned long long result;
asm volatile(".byte 0x0F, 0x31" : "=A" (result));
return result;
} /* rdtsc */
/*-------------------------------------------------------------------------+
| Function: Timer_exit
| Description: Timer cleanup routine at RTEMS exit. NOTE: This routine is
| not really necessary, since there will be a reset at exit.
| Global Variables: None.
| Arguments: None.
| Returns: Nothing.
+--------------------------------------------------------------------------*/
void
Timer_exit(void)
{
} /* Timer_exit */
/*-------------------------------------------------------------------------+
| Function: Timer_initialize
| Description: Timer initialization routine.
| Global Variables: Ttimer_val.
| Arguments: None.
| Returns: Nothing.
+--------------------------------------------------------------------------*/
void
Timer_initialize(void)
{
static rtems_boolean First = TRUE;
if (First)
{
First = FALSE;
atexit(Timer_exit); /* Try not to hose the system at exit. */
}
Ttimer_val = rdtsc(); /* read starting time */
} /* Timer_initialize */
/*-------------------------------------------------------------------------+
| Function: Read_timer
| Description: Read hardware timer value.
| Global Variables: Ttimer_val, Timer_driver_Find_average_overhead.
| Arguments: None.
| Returns: Nothing.
+--------------------------------------------------------------------------*/
rtems_unsigned32
Read_timer(void)
{
register rtems_unsigned32 total;
total = (rtems_unsigned32)(rdtsc() - Ttimer_val);
if (Timer_driver_Find_average_overhead)
return total;
else if (total < LEAST_VALID)
return 0; /* below timer resolution */
else
return (total - AVG_OVERHEAD);
} /* Read_timer */
#else /* pentium */
/*-------------------------------------------------------------------------+
| Non-Pentium timer handling.
+--------------------------------------------------------------------------*/
#define US_PER_ISR 250 /* Number of micro-seconds per timer interruption */
/*-------------------------------------------------------------------------+
| Function: Timer_exit
| Description: Timer cleanup routine at RTEMS exit. NOTE: This routine is
| not really necessary, since there will be a reset at exit.
| Global Variables: None.
| Arguments: None.
| Returns: Nothing.
+--------------------------------------------------------------------------*/
static void
timerOff(const rtems_raw_irq_connect_data* used)
{
/*
* disable interrrupt at i8259 level
*/
BSP_irq_disable_at_i8259s(used->idtIndex - BSP_IRQ_VECTOR_BASE);
/* reset timer mode to standard (DOS) value */
outport_byte(TIMER_MODE, TIMER_SEL0|TIMER_16BIT|TIMER_RATEGEN);
outport_byte(TIMER_CNTR0, 0);
outport_byte(TIMER_CNTR0, 0);
} /* Timer_exit */
static void
timerOn(const rtems_raw_irq_connect_data* used)
{
/* load timer for US_PER_ISR microsecond period */
outport_byte(TIMER_MODE, TIMER_SEL0|TIMER_16BIT|TIMER_RATEGEN);
outport_byte(TIMER_CNTR0, US_TO_TICK(US_PER_ISR) >> 0 & 0xff);
outport_byte(TIMER_CNTR0, US_TO_TICK(US_PER_ISR) >> 8 & 0xff);
/*
* enable interrrupt at i8259 level
*/
BSP_irq_enable_at_i8259s(used->idtIndex - BSP_IRQ_VECTOR_BASE);
}
static int
timerIsOn(const rtems_raw_irq_connect_data *used)
{
return BSP_irq_enabled_at_i8259s(used->idtIndex - BSP_IRQ_VECTOR_BASE);}
static rtems_raw_irq_connect_data timer_raw_irq_data = {
BSP_PERIODIC_TIMER + BSP_IRQ_VECTOR_BASE,
timerisr,
timerOn,
timerOff,
timerIsOn
};
/*-------------------------------------------------------------------------+
| Function: Timer_exit
| Description: Timer cleanup routine at RTEMS exit. NOTE: This routine is
| not really necessary, since there will be a reset at exit.
| Global Variables: None.
| Arguments: None.
| Returns: Nothing.
+--------------------------------------------------------------------------*/
void
Timer_exit(void)
{
i386_delete_idt_entry (&timer_raw_irq_data);
} /* Timer_exit */
/*-------------------------------------------------------------------------+
| Function: Timer_initialize
| Description: Timer initialization routine.
| Global Variables: Ttimer_val.
| Arguments: None.
| Returns: Nothing.
+--------------------------------------------------------------------------*/
void
Timer_initialize(void)
{
static rtems_boolean First = TRUE;
if (First)
{
First = FALSE;
atexit(Timer_exit); /* Try not to hose the system at exit. */
if (!i386_set_idt_entry (&timer_raw_irq_data)) {
printk("raw handler connexion failed\n");
rtems_fatal_error_occurred(1);
}
}
/* wait for ISR to be called at least once */
Ttimer_val = 0;
while (Ttimer_val == 0)
continue;
Ttimer_val = 0;
} /* Timer_initialize */
/*-------------------------------------------------------------------------+
| Function: Read_timer
| Description: Read hardware timer value.
| Global Variables: Ttimer_val, Timer_driver_Find_average_overhead.
| Arguments: None.
| Returns: Nothing.
+--------------------------------------------------------------------------*/
rtems_unsigned32
Read_timer(void)
{
register rtems_unsigned32 total, clicks;
register rtems_unsigned8 lsb, msb;
outport_byte(TIMER_MODE, TIMER_SEL0|TIMER_LATCH);
inport_byte(TIMER_CNTR0, lsb);
inport_byte(TIMER_CNTR0, msb);
clicks = (msb << 8) | lsb;
total = (Ttimer_val * US_PER_ISR) + (US_PER_ISR - TICK_TO_US(clicks));
if (Timer_driver_Find_average_overhead)
return total;
else if (total < LEAST_VALID)
return 0; /* below timer resolution */
else
return (total - AVG_OVERHEAD);
}
#endif /* pentium */
/*-------------------------------------------------------------------------+
| Function: Empty_function
| Description: Empty function used in time tests.
| Global Variables: None.
| Arguments: None.
| Returns: Nothing.
+--------------------------------------------------------------------------*/
rtems_status_code Empty_function(void)
{
return RTEMS_SUCCESSFUL;
} /* Empty function */
/*-------------------------------------------------------------------------+
| Function: Set_find_average_overhead
| Description: Set internal Timer_driver_Find_average_overhead flag value.
| Global Variables: Timer_driver_Find_average_overhead.
| Arguments: find_flag - new value of the flag.
| Returns: Nothing.
+--------------------------------------------------------------------------*/
void
Set_find_average_overhead(rtems_boolean find_flag)
{
Timer_driver_Find_average_overhead = find_flag;
} /* Set_find_average_overhead */
/*-------------------------------------------------------------------------+
| Description: Loads timer 0 with value passed as arguemnt.
| Returns: Nothing.
+--------------------------------------------------------------------------*/
inline void loadTimerValue( unsigned short loadedValue )
{
outport_byte(TIMER_MODE, TIMER_SEL0|TIMER_16BIT|TIMER_RATEGEN);
outport_byte(TIMER_CNTR0, loadedValue >> 0 & 0xff);
outport_byte(TIMER_CNTR0, loadedValue >> 8 & 0xff);
}
/*-------------------------------------------------------------------------+
| Description: Waits until the counter on timer 0 reaches 0.
| Returns: Nothing.
+--------------------------------------------------------------------------*/
inline void waitTimerStatus( void )
{
unsigned char status;
outport_byte(TIMER_MODE, CMD_READ_BACK_STATUS); /* read Status counter 0 */
inport_byte(TIMER_CNTR0, status);
while (status & MSK_NULL_COUNT){ /* wait for counter ready */
outport_byte(TIMER_MODE, CMD_READ_BACK_STATUS);
inport_byte(TIMER_CNTR0, status);
}
}
/*-------------------------------------------------------------------------+
| Description: Reads the current value of the timer, and converts the
| number of ticks to micro-seconds.
| Returns: current number of microseconds since last value loaded..
+--------------------------------------------------------------------------*/
inline unsigned short readCurrentTimer()
{
unsigned short lsb, msb;
outport_byte(TIMER_MODE, TIMER_SEL0|TIMER_LATCH);
inport_byte(TIMER_CNTR0, lsb);
inport_byte(TIMER_CNTR0, msb);
return TICK_TO_US( ( msb << 8 ) | lsb );
}
/*-------------------------------------------------------------------------+
* clockbits - Read low order bits of timer 0 (the TOD clock)
* This works only for the 8254 chips used in ATs and 386s.
*
* The timer runs in mode 3 (square wave mode), counting down
* by twos, twice for each cycle. So it is necessary to read back the
* OUTPUT pin to see which half of the cycle we're in. I.e., the OUTPUT
* pin forms the most significant bit of the count. Unfortunately,
* the 8253 in the PC/XT lacks a command to read the OUTPUT pin...
*
* The PC's clock design is soooo brain damaged...
*
* Rosimildo - I've got this routine from the KA9Q32 distribution and
* have updated it for the RTEMS environment.
+--------------------------------------------------------------------------*/
unsigned int clockbits(void)
{
unsigned int stat,count1, count;
do
{
outport_byte( 0x43, 0xc2 ); /* latch timer 0 count and status for reading */
inport_byte( 0x40, stat ); /* get status of timer 0 */
inport_byte( 0x40, count1 ); /* lsb of count */
inport_byte( 0x40, count ); /* msb of count */
count = count1 | ( count << 8 );
} while(stat & 0x40); /* reread if NULL COUNT bit set */
stat = (stat & 0x80) << 8; /* Shift OUTPUT to msb of 16-bit word */
if(count == 0)
return stat ^ 0x8000; /* return complement of OUTPUT bit */
else
return count | stat; /* Combine OUTPUT with counter */
}
/*-------------------------------------------------------------------------+
| Function: Calibrate_loop_1ms
| Description: Set loop variable to calibrate a 1ms loop
| Global Variables: loop1ms
| Arguments: none
| Returns: Nothing.
+--------------------------------------------------------------------------*/
void
Calibrate_loop_1ms(void)
{
unsigned int i;
unsigned short loadedValue, offset;
unsigned int timerValue, t1_ref, t2_ref=0;
rtems_interrupt_level level;
printk( "Calibrate_loop_1ms is starting, please wait ( but not too loooong. )\n" );
loop1ms = 200;
timerValue = 0;
/* Let's load the timer with 2ms, initially */
loadedValue = US_TO_TICK( 2000 );
rtems_interrupt_disable(level);
/*
* Compute the offset to apply due to read counter register
*/
offset = 0;
loadTimerValue( loadedValue + offset );
waitTimerStatus();
t1_ref = clockbits();
offset = loadedValue - readCurrentTimer();
while( timerValue < 1000 )
{
loop1ms++;
loadTimerValue( loadedValue + offset );
waitTimerStatus();
t1_ref = clockbits();
for( i=0; i < loop1ms; i++ )
outport_byte( SLOW_DOWN_IO, 0 ); /* write is # 1us */
t2_ref = clockbits();
timerValue = TICK_TO_US( t1_ref - t2_ref ); /* timer0 is decrementing number of ticks */
}
printk( "Calibrate_loop_1ms timerValue=%d, loop1ms=%d, t1_ref=%x, clockbits=%x, delta=%d\n",
timerValue, loop1ms, t1_ref, t2_ref, t1_ref - t2_ref );
rtems_interrupt_enable(level);
}
/*-------------------------------------------------------------------------+
| Function: Wait_X_1ms
| Description: loop which waits at least timeToWait ms
| Global Variables: loop1ms
| Arguments: timeToWait
| Returns: Nothing.
+--------------------------------------------------------------------------*/
void
Wait_X_ms( unsigned int timeToWait){
unsigned int i, j;
for (j=0; j<timeToWait ; j++)
for (i=0; i<loop1ms; i++)
outport_byte(SLOW_DOWN_IO, 0); /* write is # 1us */
}
