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2004-05-22 Till Strauman <strauman@slac.stanford.edu>

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PR 619/bsps
	* mpc6xx/clock/c_clock.c: The PPC decrementer must be reloaded on each
	clock tick. Currently, this is done by just reloading a fixed value.
	The attached patch takes into account the time that elapsed since the
	decrementer crossed zero in order to adjust the value to be
	re-loaded. Without the patch, the effective system clock cycle is
	increased by the exception handler latency.
This commit is contained in:
Joel Sherrill
2004-05-22 15:14:03 +00:00
parent cfc43898e6
commit 01c96bfb75
2 changed files with 33 additions and 12 deletions
Download Patch File Download Diff File Expand all files Collapse all files

10
c/src/lib/libcpu/powerpc/ChangeLog
View File

@@ -1,3 +1,13 @@
2004-05-22 Till Strauman <strauman@slac.stanford.edu>
PR 619/bsps
* mpc6xx/clock/c_clock.c: The PPC decrementer must be reloaded on each
clock tick. Currently, this is done by just reloading a fixed value.
The attached patch takes into account the time that elapsed since the
decrementer crossed zero in order to adjust the value to be
re-loaded. Without the patch, the effective system clock cycle is
increased by the exception handler latency.
2003-09-04 Joel Sherrill <joel@OARcorp.com> 2003-09-04 Joel Sherrill <joel@OARcorp.com>
* mpc6xx/clock/c_clock.c, mpc6xx/clock/c_clock.h, * mpc6xx/clock/c_clock.c, mpc6xx/clock/c_clock.h,

25
c/src/lib/libcpu/powerpc/mpc6xx/clock/c_clock.c
View File

@@ -73,21 +73,23 @@ void clockOn(void* unused)
* Return values: NONE * Return values: NONE
* *
*/ */
void clockIsr() void clockIsr()
{ {
int decr;
/* /*
* The driver has seen another tick. * The driver has seen another tick.
*/ */
do {
PPC_Set_decrementer( Clock_Decrementer_value ); asm volatile ("mfdec %0; add %0, %0, %1; mtdec %0":"=r"(decr):"r"(Clock_Decrementer_value));
Clock_driver_ticks += 1; Clock_driver_ticks += 1;
/* /*
* Real Time Clock counter/timer is set to automatically reload. * Real Time Clock counter/timer is set to automatically reload.
*/ */
rtems_clock_tick(); rtems_clock_tick();
} while ( decr < 0 );
} }
int clockIsOn(void* unused) int clockIsOn(void* unused)
@@ -144,6 +146,18 @@ rtems_device_driver Clock_initialize(
Clock_Decrementer_value = (BSP_bus_frequency/BSP_time_base_divisor)* Clock_Decrementer_value = (BSP_bus_frequency/BSP_time_base_divisor)*
(rtems_configuration_get_microseconds_per_tick()/1000); (rtems_configuration_get_microseconds_per_tick()/1000);
/* set the decrementer now, prior to installing the handler
* so no interrupts will happen in a while.
*/
PPC_Set_decrementer( (unsigned)-1 );
/* if a decrementer exception was pending, it is cleared by
* executing the default (nop) handler at this point;
* The next exception will then be taken by our clock handler.
* Clock handler installation initializes the decrementer to
* the correct value.
*/
if (!BSP_connect_clock_handler ()) { if (!BSP_connect_clock_handler ()) {
printk("Unable to initialize system clock\n"); printk("Unable to initialize system clock\n");
rtems_fatal_error_occurred(1); rtems_fatal_error_occurred(1);
@@ -190,10 +204,7 @@ rtems_device_driver Clock_control(
clockIsr(); clockIsr();
else if (args->command == rtems_build_name('N', 'E', 'W', ' ')) else if (args->command == rtems_build_name('N', 'E', 'W', ' '))
{ {
if (!BSP_connect_clock_handler ()) { Clock_initialize(major, minor, 0);
printk("Error installing clock interrupt handler!\n");
rtems_fatal_error_occurred(1);
}
} }
done: done:
return RTEMS_SUCCESSFUL; return RTEMS_SUCCESSFUL;