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https://github.com/fergalmoran/ladybird.git
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bc213ad7a2
For now, this can only query microseconds since boot. Use this to print a timestamp every second. This busy-loops until a second has passed. This might be a good first use of interrupts soon. qemu used to not implement this timer at some point, but it seems to work fine even in qemu now (qemu v 5.2.0).
52 lines
1.1 KiB
C++
52 lines
1.1 KiB
C++
/*
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* Copyright (c) 2021, Nico Weber <thakis@chromium.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <Kernel/Prekernel/Arch/aarch64/MMIO.h>
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#include <Kernel/Prekernel/Arch/aarch64/Timer.h>
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namespace Prekernel {
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// "12.1 System Timer Registers" / "10.2 System Timer Registers"
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struct TimerRegisters {
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u32 control_and_status;
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u32 counter_low;
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u32 counter_high;
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u32 compare[4];
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};
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// Bits of the `control_and_status` register.
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// See "CS register" in Broadcom doc for details.
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enum FlagBits {
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SystemTimerMatch0 = 1 << 0,
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SystemTimerMatch1 = 1 << 1,
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SystemTimerMatch2 = 1 << 2,
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SystemTimerMatch3 = 1 << 3,
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};
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Timer::Timer()
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: m_registers(MMIO::the().peripheral<TimerRegisters>(0x3000))
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{
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}
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Timer& Timer::the()
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{
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static Timer instance;
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return instance;
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}
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u64 Timer::microseconds_since_boot()
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{
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u32 high = m_registers->counter_high;
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u32 low = m_registers->counter_low;
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if (high != m_registers->counter_high) {
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high = m_registers->counter_high;
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low = m_registers->counter_low;
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}
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return (static_cast<u64>(high) << 32) | low;
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}
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}
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