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