pit.c File Reference

x86: the 8254 programmable interval timer (PIT). More...

#include <core/system.h>
#include <core/string.h>
#include <core/kargs.h>
#include <cpu/io.h>
#include <platform/misc.h>

Go to the source code of this file.

Data Structures
struct	pit_cmd_register
	The PIT's command register: which channel, how it is loaded, and in which mode it counts. More...

Macros
#define	PIT_CHANNEL0   0x00
#define	PIT_CHANNEL2   0x02
#define	PIT_CMD   0x03
#define	PIT_GATE_PORT   0x61
#define	GATE2   0x01
#define	SPEAKER   0x02
#define	OUT2   0x20
#define	PIT_MODE_RATE_GENERATOR   0x2
#define	PIT_MODE_SQUARE_WAVE   0x3
#define	PIT_ACCESS_LOHIBYTE   0x3
#define	FBASE   1193182ULL

Functions
int	x86_pit_setup (struct ioaddr *io)
	Sets where the PIT's ports are.
static uint32_t	atou32 (const char *s)
	Converts a decimal string to a number.
uint32_t	x86_pit_period_set (uint32_t period_ns)
	Makes channel 0 interrupt periodically, for the scheduler's tick.
void	x86_pit_delay (uint32_t us)
	Waits us microseconds, at most 54 ms, busy.

Variables
static struct ioaddr	pit_ioaddr

Detailed Description

x86: the 8254 programmable interval timer (PIT).

Its channel 0 is the scheduler's tick when there's no APIC (IRQ 0). Its channel 2, normally the speaker's, measures short delays: to calibrate the TSC and the local APIC's timer, and to wait while starting the other CPUs.

Definition in file pit.c.

Macro Definition Documentation

FBASE

#define FBASE   1193182ULL

Definition at line 59 of file pit.c.

Referenced by x86_pit_delay(), and x86_pit_period_set().

GATE2

#define GATE2   0x01

Definition at line 24 of file pit.c.

Referenced by x86_pit_delay().

OUT2

#define OUT2   0x20

Definition at line 26 of file pit.c.

Referenced by x86_pit_delay().

PIT_ACCESS_LOHIBYTE

#define PIT_ACCESS_LOHIBYTE   0x3

Definition at line 44 of file pit.c.

Referenced by x86_pit_delay(), and x86_pit_period_set().

PIT_CHANNEL0

#define PIT_CHANNEL0   0x00

Definition at line 18 of file pit.c.

Referenced by x86_pit_period_set().

PIT_CHANNEL2

#define PIT_CHANNEL2   0x02

Definition at line 19 of file pit.c.

Referenced by x86_pit_delay().

PIT_CMD

#define PIT_CMD   0x03

Definition at line 20 of file pit.c.

Referenced by x86_pit_delay(), and x86_pit_period_set().

PIT_GATE_PORT

#define PIT_GATE_PORT   0x61

Definition at line 23 of file pit.c.

Referenced by x86_pit_delay().

PIT_MODE_RATE_GENERATOR

#define PIT_MODE_RATE_GENERATOR   0x2

Definition at line 42 of file pit.c.

PIT_MODE_SQUARE_WAVE

#define PIT_MODE_SQUARE_WAVE   0x3

Definition at line 43 of file pit.c.

Referenced by x86_pit_period_set().

SPEAKER

#define SPEAKER   0x02

Definition at line 25 of file pit.c.

Referenced by x86_pit_delay().

Function Documentation

atou32()

uint32_t atou32 ( const char * s )

static

Converts a decimal string to a number.

Definition at line 62 of file pit.c.

References atou32().

Referenced by atou32(), and x86_pit_period_set().

x86_pit_delay()

void x86_pit_delay

(

uint32_t

us

)

Waits us microseconds, at most 54 ms, busy.

Channel 2 counts down once, and its output goes high at 0; channel 0 keeps the tick.

Parameters

us	how long to wait, in microseconds

Definition at line 123 of file pit.c.

References FBASE, GATE2, io_in8(), io_out8(), IOADDR_PORT, OUT2, PIT_ACCESS_LOHIBYTE, PIT_CHANNEL2, PIT_CMD, PIT_GATE_PORT, pit_ioaddr, printk(), SPEAKER, and x86_pit_delay().

Referenced by ap_boot(), timer_calibrate(), tsc_calibrate(), and x86_pit_delay().

x86_pit_period_set()

uint32_t x86_pit_period_set

(

uint32_t

period_ns

)

Makes channel 0 interrupt periodically, for the scheduler's tick.

The i8254.div kernel argument sets the divisor directly.

Parameters

period_ns

the period wanted, in ns

Returns

the period it is, in ns (the PIT's clock divided by a whole number)

Definition at line 82 of file pit.c.

References atou32(), FBASE, io_out8(), kargs_get(), NULL, PIT_ACCESS_LOHIBYTE, PIT_CHANNEL0, PIT_CMD, pit_ioaddr, PIT_MODE_SQUARE_WAVE, printk(), and x86_pit_period_set().

Referenced by platform_timer_setup(), and x86_pit_period_set().

x86_pit_setup()

int x86_pit_setup

(

struct ioaddr *

io

)

Sets where the PIT's ports are.

Parameters

io	its ports (0x40)

Returns

0

Definition at line 52 of file pit.c.

References ioaddr::addr, ioaddr_type_str(), pit_ioaddr, printk(), and x86_pit_setup().

Referenced by x86_pc_pit_init(), and x86_pit_setup().

Variable Documentation

pit_ioaddr

struct ioaddr pit_ioaddr

static

Definition at line 16 of file pit.c.

Referenced by x86_pit_delay(), x86_pit_period_set(), and x86_pit_setup().