MaxOS::hardwarecommunication::Clock Class Reference

Driver for the APIC clock. More...

#include <clock.h>

Inheritance diagram for MaxOS::hardwarecommunication::Clock:

Public Member Functions
	Clock (AdvancedProgrammableInterruptController *apic, uint16_t time_between_events=10)
	Constructor for the Clock class.
void	delay (uint32_t milliseconds) const
	Delays the program for a specified number of milliseconds (rounded up to the nearest degree of accuracy - ensured the delay is at least the specified number of milliseconds). This on the kernel level is a busy wait, for user level see the sleep function in the Thread class.
void	calibrate (uint64_t ms_per_tick=1)
	Configures the APIC clock to fire an interrupt at a specified interval in milliseconds.
void	setup_apic_clock (LocalAPIC *local_apic) const
	Sets up the APIC clock to fire interrupts at the desired rate.
common::time_t	get_time ()
	Reads the current time from the APIC clock (in 24hr time)
Public Member Functions inherited from MaxOS::hardwarecommunication::InterruptHandler
virtual system::cpu_status_t *	handle_interrupt (system::cpu_status_t *status)
	Handles an interrupt and returns the status.

Static Public Member Functions
static Clock *	active_clock ()
	Gets the currently active clock.

Public Attributes
uint64_t	clock_accuracy = 1
	How accurate the clock is in microseconds (how often should an interrupt be raised)

Additional Inherited Members
Protected Member Functions inherited from MaxOS::hardwarecommunication::InterruptHandler
	InterruptHandler (uint8_t interrupt_number, int64_t redirect=-1, uint64_t redirect_index=0)
	Creates a new interrupt handler and registers it with the interrupt manager.
virtual	~InterruptHandler ()
	Destroys the interrupt handler and unregisters it from the interrupt manager.
Protected Attributes inherited from MaxOS::hardwarecommunication::InterruptHandler
uint8_t	m_interrupt_number
	The interrupt number this handler handles.

Detailed Description

Driver for the APIC clock.

Definition at line 124 of file clock.h.

Constructor & Destructor Documentation

Clock()

Clock::Clock ( AdvancedProgrammableInterruptController *  apic, uint16_t  time_between_events = 10  )

explicit

Constructor for the Clock class.

Parameters

apic	The apic controller for this core
time_between_events	The time between events in 10ths of a second

Definition at line 22 of file clock.cpp.

: InterruptHandler(0x20),
  m_apic(apic),
  m_ticks_between_events(time_between_events)
{
    Logger::INFO() << "Setting up Clock \n";
 
    s_active_clock = this;
 
    // Get the stats from the clock
    uint8_t status = read_hardware_clock(0xB);
 
    // Store the clock status
    m_24_hour_clock = status & 0x02;
    m_binary = status & 0x04;
}

References MaxOS::Logger::INFO().

Member Function Documentation

active_clock()

Clock * Clock::active_clock ( )

static

Gets the currently active clock.

Returns

The clock being used by the kernel

Definition at line 182 of file clock.cpp.

                           {
    return s_active_clock;
}

Referenced by MaxOS::system::Core::init(), and MaxOS::system::Core::wake_up().

calibrate()

void Clock::calibrate

(

uint64_t

ms_per_tick = 1

)

Configures the APIC clock to fire an interrupt at a specified interval in milliseconds.

Parameters

ms_per_tick

How many milliseconds per interrupt

Definition at line 118 of file clock.cpp.

                                          {
 
    Logger::INFO() << "Calibrating Clock \n";
    clock_accuracy = ms_per_tick;
 
    // Get the ticks per ms
    PIT pit(m_apic);
    m_pit_ticks_per_ms = pit.ticks_per_ms();
 
    // Calibrate the BSP apic to the desired time
    setup_apic_clock(m_apic->local_apic());
 
    Logger::DEBUG() << "Clock: Calibrated to " << ms_per_tick << "ms per kernel tick\n";
}

References clock_accuracy, MaxOS::Logger::DEBUG(), MaxOS::Logger::INFO(), MaxOS::hardwarecommunication::AdvancedProgrammableInterruptController::local_apic(), and setup_apic_clock().

Referenced by kernel_main().

delay()

void Clock::delay

(

uint32_t

milliseconds

)

const

Delays the program for a specified number of milliseconds (rounded up to the nearest degree of accuracy - ensured the delay is at least the specified number of milliseconds). This on the kernel level is a busy wait, for user level see the sleep function in the Thread class.

See also

Thread::sleep

Parameters

milliseconds

How many milliseconds to delay the program for.

Definition at line 102 of file clock.cpp.

                                             {
 
    // Round the number of milliseconds UP to the nearest clock accuracy
    uint64_t rounded_milliseconds = (milliseconds + clock_accuracy - 1) / clock_accuracy;
 
    // Wait until the time has passed
    uint64_t ticks_until_delay_is_over = m_ticks + rounded_milliseconds;
    while (m_ticks < ticks_until_delay_is_over)
        asm volatile("nop");
}

References clock_accuracy.

Referenced by MaxOS::system::Core::wake_up().

get_time()

common::time_t Clock::get_time

(

)

Reads the current time from the APIC clock (in 24hr time)

Returns

The current time in a Time struct format

Definition at line 156 of file clock.cpp.

                             {
 
    // Wait for the clock to be ready
    while (read_hardware_clock(0xA) & 0x80)
        asm volatile("nop");
 
    // Read the time from the clock
    time_t time{};
    time.year = binary_representation(read_hardware_clock(0x9)) + 2000;
    time.month = binary_representation(read_hardware_clock(0x8));
    time.day = binary_representation(read_hardware_clock(0x7));
    time.hour = binary_representation(read_hardware_clock(0x4));
    time.minute = binary_representation(read_hardware_clock(0x2));
    time.second = binary_representation(read_hardware_clock(0x0));
 
    // If the clock is using 12hr format and PM is set then add 12 to the hour
    if (!m_24_hour_clock && (time.hour & 0x80) != 0)
        time.hour = ((time.hour & 0x7F) + 12) % 24;
 
    return time;
}

setup_apic_clock()

void Clock::setup_apic_clock

(

hardwarecommunication::LocalAPIC *

local_apic

)

const

Sets up the APIC clock to fire interrupts at the desired rate.

Parameters

local_apic

The local APIC to setup the clock on

Definition at line 137 of file clock.cpp.

                                                                             {
 
    // Configure the clock to periodic mode
    uint32_t lvt = 0x20 | (1 << 17);
    local_apic->write(0x320, lvt);
 
    // Set the initial count
    local_apic->write(0x380, m_pit_ticks_per_ms * clock_accuracy);
 
    // Clear the interrupt mask for the clock
    lvt &= ~(1 << 16);
    local_apic->write(0x320, lvt);
}

References clock_accuracy, and MaxOS::hardwarecommunication::LocalAPIC::write().

Referenced by calibrate(), and MaxOS::system::Core::init().

Member Data Documentation

clock_accuracy

uint64_t MaxOS::hardwarecommunication::Clock::clock_accuracy = 1

How accurate the clock is in microseconds (how often should an interrupt be raised)

Definition at line 156 of file clock.h.

Referenced by calibrate(), delay(), and setup_apic_clock().

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The documentation for this class was generated from the following files:

• /home/runner/work/MaxOS/MaxOS/kernel/include/hardwarecommunication/clock.h
• /home/runner/work/MaxOS/MaxOS/kernel/src/hardwarecommunication/clock.cpp