/**
* @file
*
* Clock Tick Device Driver
*
* History:
* + Original driver was go32 clock by Joel Sherrill
* + go32 clock driver hardware code was inserted into new
* boilerplate when the pc386 BSP by:
* Pedro Miguel Da Cruz Neto Romano <pmcnr@camoes.rnl.ist.utl.pt>
* Jose Rufino <ruf@asterix.ist.utl.pt>
* + Reworked by Joel Sherrill to use clock driver template.
* This removes all boilerplate and leave original hardware
* code I developed for the go32 BSP.
*/
/*
* COPYRIGHT (c) 1989-2012.
* 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.rtems.com/license/LICENSE.
*/
#include <bsp.h>
#include <bsp/irq.h>
#include <bspopts.h>
#include <libcpu/cpuModel.h>
#define CLOCK_VECTOR 0
volatile uint32_t pc386_microseconds_per_isr;
volatile uint32_t pc386_isrs_per_tick;
uint32_t pc386_clock_click_count;
/* forward declaration */
void Clock_isr(void *param);
void Clock_driver_support_at_tick_tsc(void);
void Clock_driver_support_at_tick_empty(void);
uint32_t bsp_clock_nanoseconds_since_last_tick_tsc(void);
uint32_t bsp_clock_nanoseconds_since_last_tick_i8254(void);
void Clock_isr_handler(rtems_irq_hdl_param param);
int clockIsOn(const rtems_irq_connect_data* unused);
void clockOff(const rtems_irq_connect_data* unused);
void Clock_driver_install_handler(void);
void Clock_driver_support_initialize_hardware(void);
/*
* Roughly the number of cycles per tick and per nanosecond. Note that these
* will be wildly inaccurate if the chip speed changes due to power saving
* or thermal modes.
*
* NOTE: These are only used when the TSC method is used.
*/
uint64_t pc586_tsc_per_tick;
uint64_t pc586_nanoseconds_per_tick;
uint64_t pc586_tsc_at_tick;
/* this driver may need to count ISRs per tick */
#define CLOCK_DRIVER_ISRS_PER_TICK pc386_isrs_per_tick
/* if so, the driver may use the count in Clock_driver_support_at_tick */
#ifdef CLOCK_DRIVER_ISRS_PER_TICK
extern volatile uint32_t Clock_driver_isrs;
#endif
#define READ_8254( _lsb, _msb ) \
do { outport_byte(TIMER_MODE, TIMER_SEL0|TIMER_LATCH); \
inport_byte(TIMER_CNTR0, _lsb); \
inport_byte(TIMER_CNTR0, _msb); \
} while (0)
/*
* Hooks which get swapped based upon which nanoseconds since last
* tick method is preferred.
*/
void (*Clock_driver_support_at_tick)(void) = NULL;
uint32_t (*Clock_driver_nanoseconds_since_last_tick)(void) = NULL;
/*
* What do we do at each clock tick?
*/
void Clock_driver_support_at_tick_tsc(void)
{
#ifdef CLOCK_DRIVER_ISRS_PER_TICK
/*
* The driver is multiple ISRs per clock tick.
*/
if (!Clock_driver_isrs)
pc586_tsc_at_tick = rdtsc();
#else
/*
* The driver is one ISR per clock tick.
*/
pc586_tsc_at_tick = rdtsc();
#endif
}
void Clock_driver_support_at_tick_empty(void)
{
}
#define Clock_driver_support_install_isr( _new, _old ) \
do { \
_old = NULL; \
} while(0)
extern volatile uint32_t Clock_driver_isrs;
/*
* Get nanoseconds using Pentium-compatible TSC register
*/
uint32_t bsp_clock_nanoseconds_since_last_tick_tsc(void)
{
uint64_t diff_nsec;
diff_nsec = rdtsc() - pc586_tsc_at_tick;
/*
* At this point, with a hypothetical 10 GHz CPU clock and 100 Hz tick
* clock, diff_nsec <= 27 bits.
*/
diff_nsec *= pc586_nanoseconds_per_tick; /* <= 54 bits */
diff_nsec /= pc586_tsc_per_tick;
if (diff_nsec > pc586_nanoseconds_per_tick)
/*
* Hmmm... Some drift or rounding. Pin the value to 1 nanosecond before
* the next tick.
*/
/* diff_nsec = pc586_nanoseconds_per_tick - 1; */
diff_nsec = 12345;
return (uint32_t)diff_nsec;
}
/*
* Get nanoseconds using 8254 timer chip
*/
uint32_t bsp_clock_nanoseconds_since_last_tick_i8254(void)
{
uint32_t usecs, clicks, isrs;
uint32_t usecs1, usecs2;
uint8_t lsb, msb;
rtems_interrupt_level level;
/*
* Fetch all the data in an interrupt critical section.
*/
rtems_interrupt_disable(level);
READ_8254(lsb, msb);
isrs = Clock_driver_isrs;
rtems_interrupt_enable(level);
/*
* Now do the math
*/
/* convert values read into counter clicks */
clicks = ((msb << 8) | lsb);
/* whole ISRs we have done since the last tick */
usecs1 = (pc386_isrs_per_tick - isrs - 1) * pc386_microseconds_per_isr;
/* the partial ISR we in the middle of now */
usecs2 = pc386_microseconds_per_isr - TICK_TO_US(clicks);
/* total microseconds */
usecs = usecs1 + usecs2;
#if 0
printk( "usecs1=%d usecs2=%d ", usecs1, usecs2 );
printk( "maxclicks=%d clicks=%d ISRs=%d ISRsper=%d usersPer=%d usecs=%d\n",
pc386_clock_click_count, clicks,
Clock_driver_isrs, pc386_isrs_per_tick,
pc386_microseconds_per_isr, usecs );
#endif
/* return it in nanoseconds */
return usecs * 1000;
}
/*
* Calibrate CPU cycles per tick. Interrupts should be disabled.
*/
static void calibrate_tsc(void)
{
uint64_t begin_time;
uint8_t then_lsb, then_msb, now_lsb, now_msb;
uint32_t i;
pc586_nanoseconds_per_tick =
rtems_configuration_get_microseconds_per_tick() * 1000;
/*
* We just reset the timer, so we know we're at the beginning of a tick.
*/
/*
* Count cycles. Watching the timer introduces a several microsecond
* uncertaintity, so let it cook for a while and divide by the number of
* ticks actually executed.
*/
begin_time = rdtsc();
for (i = rtems_clock_get_ticks_per_second() * pc386_isrs_per_tick;
i != 0; --i ) {
/* We know we've just completed a tick when timer goes from low to high */
then_lsb = then_msb = 0xff;
do {
READ_8254(now_lsb, now_msb);
if ((then_msb < now_msb) ||
((then_msb == now_msb) && (then_lsb < now_lsb)))
break;
then_lsb = now_lsb;
then_msb = now_msb;
} while (1);
}
pc586_tsc_per_tick = rdtsc() - begin_time;
/* Initialize "previous tick" counters */
pc586_tsc_at_tick = rdtsc();
#if 0
printk( "CPU clock at %u MHz\n", (uint32_t)(pc586_tsc_per_tick / 1000000));
#endif
pc586_tsc_per_tick /= rtems_clock_get_ticks_per_second();
}
static void clockOn(
const rtems_irq_connect_data* unused
)
{
pc386_isrs_per_tick = 1;
pc386_microseconds_per_isr = rtems_configuration_get_microseconds_per_tick();
while (US_TO_TICK(pc386_microseconds_per_isr) > 65535) {
pc386_isrs_per_tick *= 10;
pc386_microseconds_per_isr /= 10;
}
pc386_clock_click_count = US_TO_TICK(pc386_microseconds_per_isr);
BSP_irq_enable_at_i8259s( BSP_PERIODIC_TIMER - BSP_IRQ_VECTOR_BASE );
#if 0
printk( "configured usecs per tick=%d \n",
rtems_configuration_get_microseconds_per_tick() );
printk( "Microseconds per ISR =%d\n", pc386_microseconds_per_isr );
printk( "final ISRs per=%d\n", pc386_isrs_per_tick );
printk( "final timer counts=%d\n", pc386_clock_click_count );
#endif
outport_byte(TIMER_MODE, TIMER_SEL0|TIMER_16BIT|TIMER_RATEGEN);
outport_byte(TIMER_CNTR0, pc386_clock_click_count >> 0 & 0xff);
outport_byte(TIMER_CNTR0, pc386_clock_click_count >> 8 & 0xff);
/*
* Now calibrate cycles per tick. Do this every time we
* turn the clock on in case the CPU clock speed has changed.
*/
if ( x86_has_tsc() )
calibrate_tsc();
}
void clockOff(const rtems_irq_connect_data* unused)
{
/* reset timer mode to standard (BIOS) value */
outport_byte(TIMER_MODE, TIMER_SEL0 | TIMER_16BIT | TIMER_RATEGEN);
outport_byte(TIMER_CNTR0, 0);
outport_byte(TIMER_CNTR0, 0);
} /* Clock_exit */
int clockIsOn(const rtems_irq_connect_data* unused)
{
return ((i8259s_cache & 0x1) == 0);
}
bool Clock_isr_enabled = false;
void Clock_isr_handler(
rtems_irq_hdl_param param
)
{
if ( Clock_isr_enabled )
Clock_isr( param );
}
static rtems_irq_connect_data clockIrqData = {
BSP_PERIODIC_TIMER,
Clock_isr_handler,
0,
clockOn,
clockOff,
clockIsOn
};
void Clock_driver_install_handler(void)
{
if (!BSP_install_rtems_irq_handler (&clockIrqData)) {
printk("Unable to install system clock ISR handler\n");
rtems_fatal_error_occurred(1);
}
}
void Clock_driver_support_initialize_hardware(void)
{
bool use_tsc = false;
bool use_8254 = false;
#if (CLOCK_DRIVER_USE_TSC == 1)
use_tsc = true;
#endif
#if (CLOCK_DRIVER_USE_8254 == 1)
use_8254 = true;
#endif
if ( !use_tsc && !use_8254 ) {
if ( x86_has_tsc() ) use_tsc = true;
else use_8254 = true;
}
if ( use_8254 ) {
/* printk( "Use 8254\n" ); */
Clock_driver_support_at_tick = Clock_driver_support_at_tick_empty;
Clock_driver_nanoseconds_since_last_tick =
bsp_clock_nanoseconds_since_last_tick_i8254;
} else {
/* printk( "Use TSC\n" ); */
Clock_driver_support_at_tick = Clock_driver_support_at_tick_tsc;
Clock_driver_nanoseconds_since_last_tick =
bsp_clock_nanoseconds_since_last_tick_tsc;
}
/* Shell installs nanosecond handler before calling
* Clock_driver_support_initialize_hardware() :-(
* so we do it again now that we're ready.
*/
rtems_clock_set_nanoseconds_extension(
Clock_driver_nanoseconds_since_last_tick
);
Clock_isr_enabled = true;
}
#define Clock_driver_support_shutdown_hardware() \
do { \
BSP_remove_rtems_irq_handler (&clockIrqData); \
} while (0)
#include "../../../shared/clockdrv_shell.h"
