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/*
* Copyright (c) 2020, Liav A. <liavalb@hotmail.co.il>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <Kernel/Arch/x86/CPU.h>
#include <Kernel/CMOS.h>
#include <Kernel/IO.h>
#include <Kernel/Time/RTC.h>
#include <Kernel/Time/TimeManagement.h>
namespace Kernel {
#define IRQ_TIMER 8
#define MAX_FREQUENCY 8000
NonnullRefPtr<RealTimeClock> RealTimeClock::create(Function<void(const RegisterState&)> callback)
{
return adopt_ref(*new RealTimeClock(move(callback)));
}
RealTimeClock::RealTimeClock(Function<void(const RegisterState&)> callback)
: HardwareTimer(IRQ_TIMER, move(callback))
{
InterruptDisabler disabler;
NonMaskableInterruptDisabler nmi_disabler;
enable_irq();
CMOS::write(0x8B, CMOS::read(0xB) | 0x40);
reset_to_default_ticks_per_second();
}
void RealTimeClock::handle_irq(const RegisterState& regs)
{
HardwareTimer::handle_irq(regs);
CMOS::read(0x8C);
}
size_t RealTimeClock::ticks_per_second() const
{
return m_frequency;
}
void RealTimeClock::reset_to_default_ticks_per_second()
{
InterruptDisabler disabler;
bool success = try_to_set_frequency(1024);
VERIFY(success);
}
// FIXME: This is a quick & dirty log base 2 with a parameter. Please provide something better in the future.
static int quick_log2(size_t number)
{
int count = 0;
while (number >>= 1)
count++;
return count;
}
bool RealTimeClock::try_to_set_frequency(size_t frequency)
{
InterruptDisabler disabler;
if (!is_capable_of_frequency(frequency))
return false;
disable_irq();
u8 previous_rate = CMOS::read(0x8A);
u8 rate = quick_log2(32768 / frequency) + 1;
dbgln("RTC: Set rate to {}", rate);
CMOS::write(0x8A, (previous_rate & 0xF0) | rate);
m_frequency = frequency;
dbgln("RTC: Set frequency to {} Hz", frequency);
enable_irq();
return true;
}
bool RealTimeClock::is_capable_of_frequency(size_t frequency) const
{
VERIFY(frequency != 0);
if (frequency > MAX_FREQUENCY)
return false;
if (32768 % frequency)
return false;
u16 divider = 32768 / frequency;
return (divider <= 16384 && divider >= 4); // Frequency can be in range of 2 Hz to 8 KHz
}
size_t RealTimeClock::calculate_nearest_possible_frequency(size_t frequency) const
{
VERIFY(frequency != 0);
return frequency;
}
}
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