HPET

High Precision Event Timer. More...

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
clock_t	hpet_nanoseconds_per_tick (void)
	Retrieve the number of nanoseconds per HPET tick.
uint64_t	hpet_read_counter (void)
	Read the current value of the HPET main counter.
void	hpet_reset_counter (void)
	Reset the HPET main counter to 0 and enable the HPET.
void	hpet_write (uint64_t reg, uint64_t value)
	Write a value to an HPET register.
uint64_t	hpet_read (uint64_t reg)
	Read a value from an HPET register.
void	hpet_wait (clock_t nanoseconds)
	Wait for a specified number of nanoseconds using the HPET.

Detailed Description

High Precision Event Timer.

The HPET is initalized via the ACPI sdt registration system.

See also

OSDev HPET

Macro Definition Documentation

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 56 of file hpet.h.

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 51 of file hpet.h.

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 36 of file hpet.h.

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 41 of file hpet.h.

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 46 of file hpet.h.

HPET_FEMTOSECONDS_PER_SECOND

#define HPET_FEMTOSECONDS_PER_SECOND   1000000000000000ULL

The number of femtoseconds in one second.

Definition at line 61 of file hpet.h.

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 23 of file hpet.h.

Function Documentation

hpet_nanoseconds_per_tick()

clock_t hpet_nanoseconds_per_tick

(

void

)

Retrieve the number of nanoseconds per HPET tick.

If the HPET is not initialized, this function will return 0.

Returns

Nanoseconds per tick

Definition at line 57 of file hpet.c.

References CLOCKS_PER_SEC, HPET_FEMTOSECONDS_PER_SECOND, isInitialized, and period.

Referenced by timer_accumulate(), and timer_uptime().

hpet_read()

uint64_t hpet_read

(

uint64_t

reg

)

Read a value from an HPET register.

Parameters

reg	The register to read from

Returns

The value read from the register

Definition at line 95 of file hpet.c.

References address, isInitialized, NULL, panic(), and READ_64.

Referenced by hpet_init(), and hpet_read_counter().

hpet_read_counter()

uint64_t hpet_read_counter

(

void

)

Read the current value of the HPET main counter.

If the HPET is not initialized, this function will return 0.

Returns

Current current value of the HPET main counter in ticks

Definition at line 66 of file hpet.c.

References hpet_read(), HPET_REG_MAIN_COUNTER_VALUE, and isInitialized.

Referenced by hpet_wait(), timer_accumulate(), and timer_uptime().

hpet_reset_counter()

void hpet_reset_counter

(

void

)

Reset the HPET main counter to 0 and enable the HPET.

If the HPET is not initialized, this function does nothing.

Definition at line 75 of file hpet.c.

References HPET_CONF_ENABLE_CNF_BIT, HPET_REG_GENERAL_CONFIG, HPET_REG_MAIN_COUNTER_VALUE, hpet_write(), and isInitialized.

Referenced by hpet_init(), and timer_accumulate().

hpet_wait()

void hpet_wait

(

clock_t

nanoseconds

)

Wait for a specified number of nanoseconds using the HPET.

This function uses a busy-wait loop, meaning its very CPU inefficient, but its usefull during early initialization or when you are unable to block the current thread.

Parameters

nanoseconds

The number of nanoseconds to wait

Definition at line 104 of file hpet.c.

References hpet_read_counter(), isInitialized, NULL, panic(), period, and start().

Referenced by apic_timer_ticks_per_ns(), ps2_device_init(), ps2_drain(), trampoline_send_startup_ipi(), and trampoline_wait_ready().

hpet_write()

void hpet_write	(	uint64_t	reg,
		uint64_t	value
	)

Write a value to an HPET register.

Parameters

reg	The register to write to
value	The value to write

Definition at line 86 of file hpet.c.

References address, isInitialized, NULL, panic(), and WRITE_64.

Referenced by hpet_reset_counter().