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 45 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 50 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 55 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 60 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 65 of file hpet.c.

◆ HPET_FEMTOSECONDS_PER_SECOND

#define HPET_FEMTOSECONDS_PER_SECOND 1000000000000000ULL

The number of femtoseconds in one second.

Definition at line 70 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 32 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 112 of file hpet.c.

Here is the caller graph for this function:

◆ 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 123 of file hpet.c.

Here is the caller graph for this function:

◆ 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 133 of file hpet.c.

Here is the caller graph for this function:

◆ 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 143 of file hpet.c.

Here is the call graph for this function:

◆ hpet_reset_counter()

static void hpet_reset_counter ( void )

inlinestatic

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

Definition at line 158 of file hpet.c.

Here is the call graph for this function:

Here is the caller graph for this function:

◆ 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 170 of file hpet.c.

Here is the call graph for this function:

Here is the caller graph for this function:

◆ hpet_init()

static uint64_t hpet_init ( void )

static

Initialize the HPET.

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

Definition at line 205 of file hpet.c.

Here is the call graph for this function:

Here is the caller graph for this function:

◆ hpet_deinit()

static void hpet_deinit ( void )

static

Deinitialize the HPET.

Definition at line 264 of file hpet.c.

Here is the call graph for this function:

Here is the caller graph for this function:

Variable Documentation

◆ hpet

hpet_t* hpet

static

Pointer to the HPET ACPI table.

Definition at line 95 of file hpet.c.

◆ address

uintptr_t address

static

Mapped virtual address of the HPET registers.

Definition at line 96 of file hpet.c.

◆ period

uint64_t period

static

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

Definition at line 97 of file hpet.c.

◆ counter

atomic_uint64_t counter = ATOMIC_VAR_INIT(0)

static

Accumulated nanosecond counter, used to avoid overflows.

Definition at line 99 of file hpet.c.

◆ counterLock

seqlock_t counterLock = SEQLOCK_CREATE()

static

Seqlock for the accumulated counter.

Definition at line 100 of file hpet.c.

◆ overflowThreadTid

tid_t overflowThreadTid = 0

static

Thread ID of the overflow thread.

Definition at line 102 of file hpet.c.

◆ overflowQueue

wait_queue_t overflowQueue = WAIT_QUEUE_CREATE(overflowQueue)

static

Wait queue for the overflow thread.

Definition at line 103 of file hpet.c.

◆ overflowShouldStop

atomic_bool overflowShouldStop = ATOMIC_VAR_INIT(false)

static

Flag to signal the overflow thread to stop.

Definition at line 104 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 193 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