blob: 1c4630cb5dbe15785fdcec7234023d4a4339a31e [file] [log] [blame]
// CPU count detection
//
// Copyright (C) 2008 Kevin O'Connor <kevin@koconnor.net>
// Copyright (C) 2006 Fabrice Bellard
//
// This file may be distributed under the terms of the GNU GPLv3 license.
#include "util.h" // dprintf
#include "config.h" // CONFIG_*
#define CPUID_APIC (1 << 9)
#define APIC_BASE ((u8 *)0xfee00000)
#define APIC_ICR_LOW 0x300
#define APIC_SVR 0x0F0
#define APIC_ID 0x020
#define APIC_LVT3 0x370
#define APIC_ENABLED 0x0100
static inline void writel(void *addr, u32 val)
{
*(volatile u32 *)addr = val;
}
static inline void writew(void *addr, u16 val)
{
*(volatile u16 *)addr = val;
}
static inline void writeb(void *addr, u8 val)
{
*(volatile u8 *)addr = val;
}
static inline u32 readl(const void *addr)
{
return *(volatile const u32 *)addr;
}
static inline u16 readw(const void *addr)
{
return *(volatile const u16 *)addr;
}
static inline u8 readb(const void *addr)
{
return *(volatile const u8 *)addr;
}
asm(
".globl smp_ap_boot_code_start\n"
".globl smp_ap_boot_code_end\n"
" .code16\n"
"smp_ap_boot_code_start:\n"
" xor %ax, %ax\n"
" mov %ax, %ds\n"
" incw " __stringify(BUILD_CPU_COUNT_ADDR) "\n"
"1:\n"
" hlt\n"
" jmp 1b\n"
"smp_ap_boot_code_end:\n"
" .code32\n"
);
extern u8 smp_ap_boot_code_start;
extern u8 smp_ap_boot_code_end;
static int smp_cpus;
/* find the number of CPUs by launching a SIPI to them */
int
smp_probe(void)
{
if (smp_cpus)
return smp_cpus;
smp_cpus = 1;
u32 eax, ebx, ecx, cpuid_features;
cpuid(1, &eax, &ebx, &ecx, &cpuid_features);
if (cpuid_features & CPUID_APIC) {
/* enable local APIC */
u32 val = readl(APIC_BASE + APIC_SVR);
val |= APIC_ENABLED;
writel(APIC_BASE + APIC_SVR, val);
writew((void *)BUILD_CPU_COUNT_ADDR, 1);
/* copy AP boot code */
memcpy((void *)BUILD_AP_BOOT_ADDR, &smp_ap_boot_code_start,
&smp_ap_boot_code_end - &smp_ap_boot_code_start);
/* broadcast SIPI */
writel(APIC_BASE + APIC_ICR_LOW, 0x000C4500);
u32 sipi_vector = BUILD_AP_BOOT_ADDR >> 12;
writel(APIC_BASE + APIC_ICR_LOW, 0x000C4600 | sipi_vector);
usleep(10*1000);
smp_cpus = readw((void *)BUILD_CPU_COUNT_ADDR);
}
dprintf(1, "Found %d cpu(s)\n", smp_cpus);
return smp_cpus;
}