High Precision Event Timer. More...

Collaboration diagram for HPET:

Detailed Description

High Precision Event Timer.

Note: Since the HPET might be 32bit it could overflow rather quickly, so we implement a system for checking roughly when it will overflow and accumulate the counter into a 64 bit nanosecond counter.

See also: OSDev HPET

Data Structures
struct	hpet_t
	High Precision Event Timer structure. More...

Macros
#define	HPET_CAP_COUNTER_CLK_PERIOD_SHIFT 32
	The bit offset of the clock period in the capabilities register.

#define	HPET_CONF_ENABLE_CNF_BIT (1 << 0)
	The bit to set to enable the HPET in the configuration register.

#define	HPET_CONF_LEG_RT_CNF_BIT (1 << 1)
	The bit to set to enable legacy replacement mode in the configuration register.

#define	HPET_ADDRESS_SPACE_MEMORY 0
	If `hpet_t::addressSpaceId` is equal to this, the address is in system memory space.

#define	HPET_ADDRESS_SPACE_IO 1
	If `hpet_t::addressSpaceId` is equal to this, the address is in system I/O space.

#define	HPET_FEMTOSECONDS_PER_SECOND 1000000000000000ULL
	The number of femtoseconds in one second.

Enumerations
enum	hpet_register_t { HPET_REG_GENERAL_CAPABILITIES_ID = 0x000 , HPET_REG_GENERAL_CONFIG = 0x010 , HPET_REG_GENERAL_INTERRUPT = 0x020 , HPET_REG_MAIN_COUNTER_VALUE = 0x0F0 , HPET_REG_TIMER0_CONFIG_CAP = 0x100 , HPET_REG_TIMER0_COMPARATOR = 0x108 }
	HPET register offsets. More...

Functions
static void	hpet_write (hpet_register_t reg, uint64_t value)
	Write to an HPET register.

static uint64_t	hpet_read (hpet_register_t reg)
	Read from an HPET register.

static clock_t	hpet_ns_per_tick (void)
	Get the HPET clock period in nanoseconds.

static clock_t	hpet_read_ns_counter (void)
	Safely read the HPET counter value in nanoseconds.

static void	hpet_reset_counter (void)
	Reset the HPET main counter to zero and enable the HPET.

static void	hpet_overflow_thread (void *arg)
	Thread function that periodically accumulates the HPET counter to prevent overflow.

static uint64_t	hpet_init (void)
	Initialize the HPET.

static void	hpet_deinit (void)
	Deinitialize the HPET.

Variables
static hpet_t *	hpet
	Pointer to the HPET ACPI table.

static uintptr_t	address
	Mapped virtual address of the HPET registers.

static uint64_t	period
	Main counter tick period in femtoseconds (10^-15 s).

static atomic_uint64_t	counter = ATOMIC_VAR_INIT(0)
	Accumulated nanosecond counter, used to avoid overflows.

static seqlock_t	counterLock = SEQLOCK_CREATE()
	Seqlock for the accumulated counter.

static tid_t	overflowThreadTid = 0
	Thread ID of the overflow thread.

static wait_queue_t	overflowQueue = WAIT_QUEUE_CREATE(overflowQueue)
	Wait queue for the overflow thread.

static atomic_bool	overflowShouldStop = ATOMIC_VAR_INIT(false)
	Flag to signal the overflow thread to stop.

static clock_source_t	source
	Structure to describe the HPET to the sys time subsystem.

Macro Definition Documentation

◆ HPET_CAP_COUNTER_CLK_PERIOD_SHIFT

#define HPET_CAP_COUNTER_CLK_PERIOD_SHIFT 32

The bit offset of the clock period in the capabilities register.

Definition at line 44 of file hpet.c.

◆ HPET_CONF_ENABLE_CNF_BIT

#define HPET_CONF_ENABLE_CNF_BIT (1 << 0)

The bit to set to enable the HPET in the configuration register.

Definition at line 49 of file hpet.c.

◆ HPET_CONF_LEG_RT_CNF_BIT

#define HPET_CONF_LEG_RT_CNF_BIT (1 << 1)

The bit to set to enable legacy replacement mode in the configuration register.

Definition at line 54 of file hpet.c.

◆ HPET_ADDRESS_SPACE_MEMORY

#define HPET_ADDRESS_SPACE_MEMORY 0

If hpet_t::addressSpaceId is equal to this, the address is in system memory space.

Definition at line 59 of file hpet.c.

◆ HPET_ADDRESS_SPACE_IO

#define HPET_ADDRESS_SPACE_IO 1

If hpet_t::addressSpaceId is equal to this, the address is in system I/O space.

Definition at line 64 of file hpet.c.

◆ HPET_FEMTOSECONDS_PER_SECOND

#define HPET_FEMTOSECONDS_PER_SECOND 1000000000000000ULL

The number of femtoseconds in one second.

Definition at line 69 of file hpet.c.

Enumeration Type Documentation

◆ hpet_register_t

enum hpet_register_t

HPET register offsets.

Enumerator
HPET_REG_GENERAL_CAPABILITIES_ID
HPET_REG_GENERAL_CONFIG
HPET_REG_GENERAL_INTERRUPT
HPET_REG_MAIN_COUNTER_VALUE
HPET_REG_TIMER0_CONFIG_CAP
HPET_REG_TIMER0_COMPARATOR

Definition at line 31 of file hpet.c.

Function Documentation

◆ hpet_write()

static void hpet_write	(	hpet_register_t	reg,
		uint64_t	value
	)

inlinestatic

Write to an HPET register.

Parameters

reg	The register to write to.
value	The value to write.

Definition at line 111 of file hpet.c.

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◆ hpet_read()

static uint64_t hpet_read ( hpet_register_t reg )

inlinestatic

Read from an HPET register.

Parameters

reg	The register to read from.

Returns: The value read from the register.

Definition at line 122 of file hpet.c.

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◆ hpet_ns_per_tick()

static clock_t hpet_ns_per_tick ( void )

inlinestatic

Get the HPET clock period in nanoseconds.

Returns: The HPET clock period in nanoseconds.

Definition at line 132 of file hpet.c.

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◆ hpet_read_ns_counter()

static clock_t hpet_read_ns_counter ( void )

static

Safely read the HPET counter value in nanoseconds.

Returns: The current value of the HPET counter in nanoseconds.

Definition at line 142 of file hpet.c.

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◆ hpet_reset_counter()

static void hpet_reset_counter ( void )

inlinestatic

Reset the HPET main counter to zero and enable the HPET.

Definition at line 157 of file hpet.c.

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◆ hpet_overflow_thread()

static void hpet_overflow_thread ( void * arg )

static

Thread function that periodically accumulates the HPET counter to prevent overflow.

Parameters

arg Unused.

Definition at line 169 of file hpet.c.

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◆ hpet_init()

static uint64_t hpet_init ( void )

static

Initialize the HPET.

Returns: On success, 0. On failure, ERR.

Definition at line 204 of file hpet.c.

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◆ hpet_deinit()

static void hpet_deinit ( void )

static

Deinitialize the HPET.

Definition at line 263 of file hpet.c.

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Variable Documentation

◆ hpet

hpet_t* hpet

static

Pointer to the HPET ACPI table.

Definition at line 94 of file hpet.c.

◆ address

uintptr_t address

static

Mapped virtual address of the HPET registers.

Definition at line 95 of file hpet.c.

◆ period

uint64_t period

static

Main counter tick period in femtoseconds (10^-15 s).

Definition at line 96 of file hpet.c.

◆ counter

atomic_uint64_t counter = ATOMIC_VAR_INIT(0)

static

Accumulated nanosecond counter, used to avoid overflows.

Definition at line 98 of file hpet.c.

◆ counterLock

seqlock_t counterLock = SEQLOCK_CREATE()

static

Seqlock for the accumulated counter.

Definition at line 99 of file hpet.c.

◆ overflowThreadTid

tid_t overflowThreadTid = 0

static

Thread ID of the overflow thread.

Definition at line 101 of file hpet.c.

◆ overflowQueue

wait_queue_t overflowQueue = WAIT_QUEUE_CREATE(overflowQueue)

static

Wait queue for the overflow thread.

Definition at line 102 of file hpet.c.

◆ overflowShouldStop

atomic_bool overflowShouldStop = ATOMIC_VAR_INIT(false)

static

Flag to signal the overflow thread to stop.

Definition at line 103 of file hpet.c.

◆ source

clock_source_t source

static

Initial value:

= {
    .name = "HPET",
    .precision = 0, 
    .read_ns = hpet_read_ns_counter,
    .read_epoch = NULL,
}

Structure to describe the HPET to the sys time subsystem.

Definition at line 192 of file hpet.c.

Detailed Description

Data Structures

Macros

Enumerations

Functions

Variables

Macro Definition Documentation

◆ HPET_CAP_COUNTER_CLK_PERIOD_SHIFT

◆ HPET_CONF_ENABLE_CNF_BIT

◆ HPET_CONF_LEG_RT_CNF_BIT

◆ HPET_ADDRESS_SPACE_MEMORY

◆ HPET_ADDRESS_SPACE_IO

◆ HPET_FEMTOSECONDS_PER_SECOND

Enumeration Type Documentation

◆ hpet_register_t

Function Documentation

◆ hpet_write()

◆ hpet_read()

◆ hpet_ns_per_tick()

◆ hpet_read_ns_counter()

◆ hpet_reset_counter()

◆ hpet_overflow_thread()

◆ hpet_init()

◆ hpet_deinit()

Variable Documentation

◆ hpet

◆ address

◆ period

◆ counter

◆ counterLock

◆ overflowThreadTid

◆ overflowQueue

◆ overflowShouldStop

◆ source