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// The local APIC manages internal (non-I/O) interrupts.
// See Chapter 8 & Appendix C of Intel processor manual volume 3.
#include "types.h"
#include "traps.h"
// Local APIC registers, divided by 4 for use as uint[] indices.
#define ID (0x0020/4) // ID
#define VER (0x0030/4) // Version
#define TPR (0x0080/4) // Task Priority
#define EOI (0x00B0/4) // EOI
#define SVR (0x00F0/4) // Spurious Interrupt Vector
#define ENABLE 0x00000100 // Unit Enable
#define ESR (0x0280/4) // Error Status
#define ICRLO (0x0300/4) // Interrupt Command
#define INIT 0x00000500 // INIT/RESET
#define STARTUP 0x00000600 // Startup IPI
#define DELIVS 0x00001000 // Delivery status
#define ASSERT 0x00004000 // Assert interrupt (vs deassert)
#define LEVEL 0x00008000 // Level triggered
#define BCAST 0x00080000 // Send to all APICs, including self.
#define ICRHI (0x0310/4) // Interrupt Command [63:32]
#define TIMER (0x0320/4) // Local Vector Table 0 (TIMER)
#define X1 0x0000000B // divide counts by 1
#define PERIODIC 0x00020000 // Periodic
#define PCINT (0x0340/4) // Performance Counter LVT
#define LINT0 (0x0350/4) // Local Vector Table 1 (LINT0)
#define LINT1 (0x0360/4) // Local Vector Table 2 (LINT1)
#define ERROR (0x0370/4) // Local Vector Table 3 (ERROR)
#define MASKED 0x00010000 // Interrupt masked
#define TICR (0x0380/4) // Timer Initial Count
#define TCCR (0x0390/4) // Timer Current Count
#define TDCR (0x03E0/4) // Timer Divide Configuration
volatile uint *lapic; // Initialized in mp.c
//PAGEBREAK!
void
lapic_init(int c)
{
if(!lapic)
return;
// Enable local APIC; set spurious interrupt vector.
lapic[SVR] = ENABLE | (IRQ_OFFSET+IRQ_SPURIOUS);
// The timer repeatedly counts down at bus frequency
// from lapic[TICR] and then issues an interrupt.
// Lapic[TCCR] is the current counter value.
// If xv6 cared more about precise timekeeping, the
// values of TICR and TCCR would be calibrated using
// an external time source.
lapic[TDCR] = X1;
lapic[TICR] = 10000000;
lapic[TCCR] = 10000000;
lapic[TIMER] = PERIODIC | (IRQ_OFFSET + IRQ_TIMER);
// Disable logical interrupt lines.
lapic[LINT0] = MASKED;
lapic[LINT1] = MASKED;
// Disable performance counter overflow interrupts
// on machines that provide that interrupt entry.
if(((lapic[VER]>>16) & 0xFF) >= 4)
lapic[PCINT] = MASKED;
// Map error interrupt to IRQ_ERROR.
lapic[ERROR] = IRQ_OFFSET+IRQ_ERROR;
// Clear error status register (requires back-to-back writes).
lapic[ESR] = 0;
lapic[ESR] = 0;
// Ack any outstanding interrupts.
lapic[EOI] = 0;
// Send an Init Level De-Assert to synchronise arbitration ID's.
lapic[ICRHI] = 0;
lapic[ICRLO] = BCAST | INIT | LEVEL;
while(lapic[ICRLO] & DELIVS)
;
// Enable interrupts on the APIC (but not on the processor).
lapic[TPR] = 0;
}
int
cpu(void)
{
if(lapic)
return lapic[ID]>>24;
return 0;
}
// Acknowledge interrupt.
void
lapic_eoi(void)
{
if(lapic)
lapic[EOI] = 0;
}
// Spin for a given number of microseconds.
// On real hardware would want to tune this dynamically.
static void
microdelay(int us)
{
volatile int j = 0;
while(us-- > 0)
for(j=0; j<10000; j++);
}
// Start additional processor running bootstrap code at addr.
// See Appendix B of MultiProcessor Specification.
void
lapic_startap(uchar apicid, uint addr)
{
int i;
volatile int j = 0;
// Send INIT interrupt to reset other CPU.
lapic[ICRHI] = apicid<<24;
lapic[ICRLO] = INIT | LEVEL;
microdelay(10);
// Send startup IPI (twice!) to enter bootstrap code.
for(i = 0; i < 2; i++){
lapic[ICRHI] = apicid<<24;
lapic[ICRLO] = STARTUP | (addr>>12);
for(j=0; j<10000; j++); // 200us
}
}
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