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timer: fix wrap handling for x86 PIT

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Issue #1106
This commit is contained in:
Alexander Boettcher 2014-03-03 14:13:50 +01:00 committed by Christian Helmuth
parent a604ea6851
commit 34a33e7301
1 changed files with 8 additions and 4 deletions
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12
os/src/drivers/timer/include_pit/platform_timer.h
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@ -64,12 +64,14 @@ class Platform_timer
unsigned long mutable _curr_time_usec;
unsigned long mutable _counter_init_value;
Genode::Lock mutable _update_curr_time_lock;
bool mutable _handled_wrap;
/**
* Set PIT counter value
*/
void _set_counter(Genode::uint16_t value)
{
_handled_wrap = false;
_io_port.outb(PIT_DATA_PORT_0, value & 0xff);
_io_port.outb(PIT_DATA_PORT_0, (value >> 8) & 0xff);
}
@ -104,7 +106,8 @@ class Platform_timer
_io_port(PIT_DATA_PORT_0, PIT_CMD_PORT - PIT_DATA_PORT_0 + 1),
_timer_irq(IRQ_PIT),
_curr_time_usec(0),
_counter_init_value(0)
_counter_init_value(0),
_handled_wrap(false)
{
/* operate PIT in one-shot mode */
_io_port.outb(PIT_CMD_PORT, PIT_CMD_SELECT_CHANNEL_0 |
@ -114,7 +117,7 @@ class Platform_timer
/**
* Return current time-counter value in microseconds
*
* This function has to be executed regulary,
* This function has to be executed regularly,
* at least all max_timeout() usecs.
*/
unsigned long curr_time() const
@ -134,10 +137,11 @@ class Platform_timer
curr_counter = const_cast<Platform_timer *>(this)->_read_counter(&wrapped);
/* determine the time since we looked at the counter */
if (wrapped)
if (wrapped && !_handled_wrap) {
/* the counter wrapped from 0 to 0xffff */
passed_ticks = _counter_init_value + PIT_MAX_COUNT - curr_counter;
else
_handled_wrap = true;
} else
passed_ticks = _counter_init_value - curr_counter;
_curr_time_usec += (passed_ticks*1000)/PIT_TICKS_PER_MSEC;