SH4 CPU peripheral providing timers and counters More...

Topics
	Channels
	TMU channel constants

	Direct-Access
	Low-level timer driver

	Primary Timer
	Primary timer used by the kernel.

	Uptime
	Maintaining time since system boot.

Files
file	timer.h
	Timer functionality.

file	timer.h
	Low-level timer functionality.

Functions
static timespec_t	timer_gettime (void)
	Get the current uptime of the system.

static uint64_t	timer_ms_gettime64 (void)
	Get the current uptime of the system (in milliseconds).

static uint64_t	timer_us_gettime64 (void)
	Get the current uptime of the system (in microseconds).

static uint64_t	timer_ns_gettime64 (void)
	Get the current uptime of the system (in nanoseconds).

static void	timer_ms_gettime (uint32_t secs, uint32_t msecs)
	Get the current uptime of the system (in secs and millisecs).

static void	timer_us_gettime (uint32_t secs, uint32_t usecs)
	Get the current uptime of the system (in secs and microsecs).

static void	timer_ns_gettime (uint32_t secs, uint32_t nsecs)
	Get the current uptime of the system (in secs and nanosecs).

static void	timer_spin_delay_us (unsigned short us)
	Spin-loop delay function with microsecond granularity.

static void	timer_spin_delay_ns (unsigned short ns)
	Spin-loop delay function with nanosecond granularity.

Do not use	timer_spin_sleep ()
	Spin-loop delay function with millisecond granularity.

Detailed Description

SH4 CPU peripheral providing timers and counters

The Dreamcast's SH4 includes an on-chip Timer Unit (TMU) containing 3 independent 32-bit channels (TMU0-TMU2). Each channel provides a down-counter with automatic reload and can be configured to use 1 of 7 divider circuits for its input clock. By default, KOS uses the fastest input clock for each TMU channel, providing a maximum internal resolution of 80ns ticks.

Warning: Under normal circumstances, all 3 TMU channels are reserved by KOS for various OS-related purposes. If you need a free general-purpose interval timer, consider using the Watchdog Timer.

Note: 90% of the time, you will never have a need to directly interact with this API, as it's mostly used as a kernel-level driver which backs other APIs. For example, querying for ticks, fetching the current timestamp, or putting a thread to sleep is typically done via the standard C, C++, or POSIX APIs.

Function Documentation

◆ timer_gettime()

static timespec_t timer_gettime ( void )

inlinestatic

Get the current uptime of the system.

This function retrieves the number of seconds and nanoseconds since KOS was started.

Returns: The current uptime of the system as a timespec struct.

References arch_timer_gettime().

Referenced by timer_ms_gettime(), timer_ms_gettime64(), timer_ns_gettime(), timer_ns_gettime64(), timer_us_gettime(), and timer_us_gettime64().

◆ timer_ms_gettime()

static void timer_ms_gettime	(	uint32_t *	secs,
		uint32_t *	msecs )

inlinestatic

Get the current uptime of the system (in secs and millisecs).

This function retrieves the number of seconds and milliseconds since KOS was started.

Parameters

secs	A pointer to store the number of seconds since boot into.
msecs	A pointer to store the number of milliseconds past a second since boot.

Note: To get the total number of milliseconds since boot, calculate (*secs * 1000) + *msecs, or use the timer_ms_gettime64() function.

References timer_gettime(), and uint32_t().

◆ timer_ms_gettime64()

static uint64_t timer_ms_gettime64 ( void )

inlinestatic

Get the current uptime of the system (in milliseconds).

This function retrieves the number of milliseconds since KOS was started. It is equivalent to calling timer_ms_gettime() and combining the number of seconds and milliseconds into one 64-bit value.

Returns: The number of milliseconds since KOS started.

References timer_gettime().

Referenced by thd_sleep().

◆ timer_ns_gettime()

static void timer_ns_gettime	(	uint32_t *	secs,
		uint32_t *	nsecs )

inlinestatic

Get the current uptime of the system (in secs and nanosecs).

This function retrieves the number of seconds and nanoseconds since KOS was started.

Note: To get the total number of nanoseconds since boot, calculate (*secs * 1000000000) + *nsecs, or use the timer_ns_gettime64() function.

Parameters

secs	A pointer to store the number of seconds since boot into.
nsecs	A pointer to store the number of nanoseconds past a second since boot.

References timer_gettime(), and uint32_t().

◆ timer_ns_gettime64()

static uint64_t timer_ns_gettime64 ( void )

inlinestatic

Get the current uptime of the system (in nanoseconds).

This function retrieves the number of nanoseconds since KOS was started.

Returns: The uptime in nanoseconds.

References timer_gettime().

Referenced by timer_spin_delay_ns().

◆ timer_spin_delay_ns()

static void timer_spin_delay_ns ( unsigned short ns )

inlinestatic

Spin-loop delay function with nanosecond granularity.

This function is meant as a very accurate delay function, even if threading and interrupts are disabled. It is a delay and not a sleep, which means that the CPU will be busy-looping during that time frame.

Note that the parameter is 16-bit, which means that the maximum acceptable value is 65535 nanoseconds.

Parameters

ns	The number of nanoseconds to wait for.

See also: timer_spin_delay_us, thd_sleep

References timer_ns_gettime64().

◆ timer_spin_delay_us()

static void timer_spin_delay_us ( unsigned short us )

inlinestatic

Spin-loop delay function with microsecond granularity.

This function is meant as a very accurate delay function, even if threading and interrupts are disabled. It is a delay and not a sleep, which means that the CPU will be busy-looping during that time frame. For any time frame bigger than a few hundred microseconds, it is recommended to sleep instead.

Note that the parameter is 16-bit, which means that the maximum acceptable value is 65535 microseconds.

Parameters

us	The number of microseconds to wait for.

See also: timer_spin_delay_ns, thd_sleep

References timer_us_gettime64().

◆ timer_spin_sleep()

Do not use timer_spin_sleep ( )

Spin-loop delay function with millisecond granularity.

This function should never be used, and is only used for compatibility with older code. It makes no sense to busy-wait for that long.

Parameters

ms	The number of microseconds to wait for.

See also: thd_sleep

◆ timer_us_gettime()

static void timer_us_gettime	(	uint32_t *	secs,
		uint32_t *	usecs )

inlinestatic

Get the current uptime of the system (in secs and microsecs).

This function retrieves the number of seconds and microseconds since KOS was started.

Note: To get the total number of microseconds since boot, calculate (*secs * 1000000) + *usecs, or use the timer_us_gettime64() function.

Parameters

secs	A pointer to store the number of seconds since boot into.
usecs	A pointer to store the number of microseconds past a second since boot.

References timer_gettime(), and uint32_t().

◆ timer_us_gettime64()

static uint64_t timer_us_gettime64 ( void )

inlinestatic

Get the current uptime of the system (in microseconds).

This function retrieves the number of microseconds since KOS was started.

Returns: The uptime in microseconds.

References timer_gettime().

Referenced by timer_spin_delay_us().

Topics

Files

Functions

Detailed Description

Function Documentation

◆ timer_gettime()

◆ timer_ms_gettime()

◆ timer_ms_gettime64()

◆ timer_ns_gettime()

◆ timer_ns_gettime64()

◆ timer_spin_delay_ns()

◆ timer_spin_delay_us()

◆ timer_spin_sleep()

◆ timer_us_gettime()

◆ timer_us_gettime64()