mirror of
https://github.com/RGBCube/serenity
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4292b0ead7
This is a basic Timer class based on the aarch64 RPi Timer. It uses the hart-local timer, as defined by the privileged ISA.
89 lines
2.5 KiB
C++
89 lines
2.5 KiB
C++
/*
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* Copyright (c) 2023, Sönke Holz <sholz8530@gmail.com>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <AK/Format.h>
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#include <AK/NeverDestroyed.h>
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#include <Kernel/Arch/riscv64/SBI.h>
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#include <Kernel/Arch/riscv64/Timer.h>
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namespace Kernel::RISCV64 {
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Timer::Timer()
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: HardwareTimer(to_underlying(CSR::SCAUSE::SupervisorTimerInterrupt) & ~CSR::SCAUSE_INTERRUPT_MASK)
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{
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// FIXME: Actually query the frequency of the timer from the device tree.
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// Based on the "/cpus/timebase-frequency" device tree node for the QEMU virt machine
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m_frequency = 10'000'000; // in Hz
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set_interrupt_interval_usec(m_frequency / OPTIMAL_TICKS_PER_SECOND_RATE);
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enable_interrupt_mode();
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}
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Timer::~Timer() = default;
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NonnullLockRefPtr<Timer> Timer::initialize()
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{
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return adopt_lock_ref(*new Timer);
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}
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u64 Timer::microseconds_since_boot()
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{
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return RISCV64::CSR::read(RISCV64::CSR::Address::TIME);
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}
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bool Timer::handle_irq(RegisterState const& regs)
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{
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auto result = HardwareTimer::handle_irq(regs);
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set_compare(microseconds_since_boot() + m_interrupt_interval);
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return result;
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}
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u64 Timer::update_time(u64& seconds_since_boot, u32& ticks_this_second, bool query_only)
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{
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// Should only be called by the time keeper interrupt handler!
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u64 current_value = microseconds_since_boot();
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u64 delta_ticks = m_main_counter_drift;
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if (current_value >= m_main_counter_last_read) {
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delta_ticks += current_value - m_main_counter_last_read;
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} else {
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// the counter wrapped around
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delta_ticks += (NumericLimits<u64>::max() - m_main_counter_last_read + 1) + current_value;
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}
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u64 ticks_since_last_second = (u64)ticks_this_second + delta_ticks;
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auto ticks_per_second = frequency();
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seconds_since_boot += ticks_since_last_second / ticks_per_second;
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ticks_this_second = ticks_since_last_second % ticks_per_second;
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if (!query_only) {
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m_main_counter_drift = 0;
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m_main_counter_last_read = current_value;
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}
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// Return the time passed (in ns) since last time update_time was called
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return (delta_ticks * 1000000000ull) / ticks_per_second;
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}
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void Timer::enable_interrupt_mode()
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{
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set_compare(microseconds_since_boot() + m_interrupt_interval);
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enable_irq();
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}
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void Timer::set_interrupt_interval_usec(u32 interrupt_interval)
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{
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m_interrupt_interval = interrupt_interval;
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}
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void Timer::set_compare(u64 compare)
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{
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if (SBI::Timer::set_timer(compare).is_error())
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MUST(SBI::Legacy::set_timer(compare));
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}
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}
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