AR9331中Linux内核启动中与IRQ中断相关的文件

先列出框架，具体后继再来分析。

首先是lds文件，该文件设置了各个section在FLASH或RAM中的先后顺序。

位于~/openwrt1407/build_dir/target-mips_34kc_uClibc-0.9.33.2/linux-ar71xx_generic/linux-3.10.49/arch/mips/kernel/vmlinux.lds

另外一个名字相似的，~/openwrt1407/build_dir/target-mips_34kc_uClibc-0.9.33.2/linux-ar71xx_generic/linux-3.10.49/arch/mips/kernel/vmlinux.lds.S

...
#undef mips
#define mips mips
OUTPUT_ARCH(mips)
ENTRY(kernel_entry)
PHDRS {
    text PT_LOAD FLAGS(7);    /* RWX */
    note PT_NOTE FLAGS(4);    /* R__ */
}

#ifdef CONFIG_32BIT
    #ifdef CONFIG_CPU_LITTLE_ENDIAN
        jiffies     = jiffies_64;
    #else
        jiffies     = jiffies_64 + 4;
    #endif
#else
    jiffies     = jiffies_64;
#endif

SECTIONS
{
...

表明入口地址为kernel_entry，该符号在：~/openwrt1407/build_dir/target-mips_34kc_uClibc-0.9.33.2/linux-ar71xx_generic/linux-3.10.49/arch/mips/kernel/head.S中定义

...
NESTED(kernel_entry, 16, sp)            # kernel entry point

    kernel_entry_setup            # cpu specific setup

    setup_c0_status_pri

    /* We might not get launched at the address the kernel is linked to,
       so we jump there.  */
    PTR_LA    t0, 0f
    jr    t0
0:

#ifdef CONFIG_MIPS_MT_SMTC
    /*
     * In SMTC kernel, "CLI" is thread-specific, in TCStatus.
     * We still need to enable interrupts globally in Status,
     * and clear EXL/ERL.
     *
     * TCContext is used to track interrupt levels under
     * service in SMTC kernel. Clear for boot TC before
     * allowing any interrupts.
     */
    mtc0    zero, CP0_TCCONTEXT

    mfc0    t0, CP0_STATUS
    ori    t0, t0, 0xff1f
    xori    t0, t0, 0x001e
    mtc0    t0, CP0_STATUS
#endif /* CONFIG_MIPS_MT_SMTC */

    PTR_LA        t0, __bss_start        # clear .bss
    LONG_S        zero, (t0)
    PTR_LA        t1, __bss_stop - LONGSIZE
1:
    PTR_ADDIU    t0, LONGSIZE
    LONG_S        zero, (t0)
    bne        t0, t1, 1b

    LONG_S        a0, fw_arg0        # firmware arguments
    LONG_S        a1, fw_arg1
    LONG_S        a2, fw_arg2
    LONG_S        a3, fw_arg3

    MTC0        zero, CP0_CONTEXT    # clear context register
    PTR_LA        $28, init_thread_union
    /* Set the SP after an empty pt_regs.  */
    PTR_LI        sp, _THREAD_SIZE - 32 - PT_SIZE
    PTR_ADDU    sp, $28
    back_to_back_c0_hazard
    set_saved_sp    sp, t0, t1
    PTR_SUBU    sp, 4 * SZREG        # init stack pointer

    j        start_kernel
    END(kernel_entry)
...

最终跳到kernel_entry中，该函数在~/openwrt1407/build_dir/target-mips_34kc_uClibc-0.9.33.2/linux-ar71xx_generic/linux-3.10.49/init/main.c中定义：

asmlinkage void __init start_kernel(void)
{
    char * command_line;
    extern const struct kernel_param __start___param[], __stop___param[];

    /*
     * Need to run as early as possible, to initialize the
     * lockdep hash:
     */
    lockdep_init();
    smp_setup_processor_id();
    debug_objects_early_init();

    /*
     * Set up the the initial canary ASAP:
     */
    boot_init_stack_canary();

    cgroup_init_early();

    local_irq_disable();
    early_boot_irqs_disabled = true;

/*
 * Interrupts are still disabled. Do necessary setups, then
 * enable them
 */
    boot_cpu_init();
    page_address_init();
    pr_notice("%s", linux_banner);
    setup_arch(&command_line);
    mm_init_owner(&init_mm, &init_task);
    mm_init_cpumask(&init_mm);
    setup_command_line(command_line);
    setup_nr_cpu_ids();
    setup_per_cpu_areas();
    smp_prepare_boot_cpu();    /* arch-specific boot-cpu hooks */

    build_all_zonelists(NULL, NULL);
    page_alloc_init();

    pr_notice("Kernel command line: %s
", boot_command_line);
    parse_early_param();
    parse_args("Booting kernel", static_command_line, __start___param,
           __stop___param - __start___param,
           -1, -1, &unknown_bootoption);

    jump_label_init();

    /*
     * These use large bootmem allocations and must precede
     * kmem_cache_init()
     */
    setup_log_buf(0);
    pidhash_init();
    vfs_caches_init_early();
    sort_main_extable();
    trap_init();
    mm_init();

    /*
     * Set up the scheduler prior starting any interrupts (such as the
     * timer interrupt). Full topology setup happens at smp_init()
     * time - but meanwhile we still have a functioning scheduler.
     */
    sched_init();
    /*
     * Disable preemption - early bootup scheduling is extremely
     * fragile until we cpu_idle() for the first time.
     */
    preempt_disable();
    if (WARN(!irqs_disabled(), "Interrupts were enabled *very* early, fixing it
"))
        local_irq_disable();
    idr_init_cache();
    perf_event_init();
    rcu_init();
    tick_nohz_init();
    radix_tree_init();
    /* init some links before init_ISA_irqs() */
    early_irq_init();
    init_IRQ();
    tick_init();
    init_timers();
    hrtimers_init();
    softirq_init();
    timekeeping_init();
    time_init();
    profile_init();
    call_function_init();
    WARN(!irqs_disabled(), "Interrupts were enabled early
");
    early_boot_irqs_disabled = false;
    local_irq_enable();

    kmem_cache_init_late();

    /*
     * HACK ALERT! This is early. We're enabling the console before
     * we've done PCI setups etc, and console_init() must be aware of
     * this. But we do want output early, in case something goes wrong.
     */
    console_init();
    if (panic_later)
        panic(panic_later, panic_param);

    lockdep_info();

    /*
     * Need to run this when irqs are enabled, because it wants
     * to self-test [hard/soft]-irqs on/off lock inversion bugs
     * too:
     */
    locking_selftest();

#ifdef CONFIG_BLK_DEV_INITRD
    if (initrd_start && !initrd_below_start_ok &&
        page_to_pfn(virt_to_page((void *)initrd_start)) < min_low_pfn) {
        pr_crit("initrd overwritten (0x%08lx < 0x%08lx) - disabling it.
",
            page_to_pfn(virt_to_page((void *)initrd_start)),
            min_low_pfn);
        initrd_start = 0;
    }
#endif
    page_cgroup_init();
    debug_objects_mem_init();
    kmemleak_init();
    setup_per_cpu_pageset();
    numa_policy_init();
    if (late_time_init)
        late_time_init();
    sched_clock_init();
    calibrate_delay();
    pidmap_init();
    anon_vma_init();
#ifdef CONFIG_X86
    if (efi_enabled(EFI_RUNTIME_SERVICES))
        efi_enter_virtual_mode();
#endif
    thread_info_cache_init();
    cred_init();
    fork_init(totalram_pages);
    proc_caches_init();
    buffer_init();
    key_init();
    security_init();
    dbg_late_init();
    vfs_caches_init(totalram_pages);
    signals_init();
    /* rootfs populating might need page-writeback */
    page_writeback_init();
#ifdef CONFIG_PROC_FS
    proc_root_init();
#endif
    cgroup_init();
    cpuset_init();
    taskstats_init_early();
    delayacct_init();

    check_bugs();

    acpi_early_init(); /* before LAPIC and SMP init */
    sfi_init_late();

    if (efi_enabled(EFI_RUNTIME_SERVICES)) {
        efi_late_init();
        efi_free_boot_services();
    }

    ftrace_init();

    /* Do the rest non-__init'ed, we're now alive */
    rest_init();
}

上面调用了两个IRQ初始化函数early_irq_init和init_IRQ，分别在~/openwrt1407/build_dir/target-mips_34kc_uClibc-0.9.33.2/linux-ar71xx_generic/linux-3.10.49/kernel/irq/irqdesc.c和~/openwrt1407/build_dir/target-mips_34kc_uClibc-0.9.33.2/linux-ar71xx_generic/linux-3.10.49/arch/mips/kernel/irq.c中。

early_irq_init函数

int __init early_irq_init(void)
{
    int i, initcnt, node = first_online_node;
    struct irq_desc *desc;

    init_irq_default_affinity();

    /* Let arch update nr_irqs and return the nr of preallocated irqs */
    initcnt = arch_probe_nr_irqs();
    printk(KERN_INFO "NR_IRQS:%d nr_irqs:%d %d
", NR_IRQS, nr_irqs, initcnt);

    if (WARN_ON(nr_irqs > IRQ_BITMAP_BITS))
        nr_irqs = IRQ_BITMAP_BITS;

    if (WARN_ON(initcnt > IRQ_BITMAP_BITS))
        initcnt = IRQ_BITMAP_BITS;

    if (initcnt > nr_irqs)
        nr_irqs = initcnt;

    for (i = 0; i < initcnt; i++) {
        desc = alloc_desc(i, node, NULL);
        set_bit(i, allocated_irqs);
        irq_insert_desc(i, desc);
    }
    return arch_early_irq_init();
}

init_IRQ函数

void __init init_IRQ(void)
{
    int i;

#ifdef CONFIG_KGDB
    if (kgdb_early_setup)
        return;
#endif

    for (i = 0; i < NR_IRQS; i++)
        irq_set_noprobe(i);

    arch_init_irq();

#ifdef CONFIG_KGDB
    if (!kgdb_early_setup)
        kgdb_early_setup = 1;
#endif
}

上面调用的arch_init_irq函数位于~/openwrt1407/build_dir/target-mips_34kc_uClibc-0.9.33.2/linux-ar71xx_generic/linux-3.10.49/arch/mips/ath79/irq.c中

arch_init_irq函数

static void __init ath79_misc_irq_init(void)
{
    void __iomem *base = ath79_reset_base;
    int i;

    __raw_writel(0, base + AR71XX_RESET_REG_MISC_INT_ENABLE);
    __raw_writel(0, base + AR71XX_RESET_REG_MISC_INT_STATUS);

    if (soc_is_ar71xx() || soc_is_ar913x())
        ath79_misc_irq_chip.irq_mask_ack = ar71xx_misc_irq_mask;
    else if (soc_is_ar724x() ||
         soc_is_ar933x() ||
         soc_is_ar934x() ||
         soc_is_qca953x() ||
         soc_is_qca955x())
        ath79_misc_irq_chip.irq_ack = ar724x_misc_irq_ack;
    else
        BUG();

    for (i = ATH79_MISC_IRQ_BASE;
         i < ATH79_MISC_IRQ_BASE + ATH79_MISC_IRQ_COUNT; i++) {
        irq_set_chip_and_handler(i, &ath79_misc_irq_chip,
                     handle_level_irq);
    }

    irq_set_chained_handler(ATH79_CPU_IRQ(6), ath79_misc_irq_handler);
}

...

void __init arch_init_irq(void)
{
    if (soc_is_ar71xx()) {
        ath79_ip2_handler = ar71xx_ip2_handler;
        ath79_ip3_handler = ar71xx_ip3_handler;
    } else if (soc_is_ar724x()) {
        ath79_ip2_handler = ar724x_ip2_handler;
        ath79_ip3_handler = ar724x_ip3_handler;
    } else if (soc_is_ar913x()) {
        ath79_ip2_handler = ar913x_ip2_handler;
        ath79_ip3_handler = ar913x_ip3_handler;
    } else if (soc_is_ar933x()) {
        ath79_ip2_handler = ar933x_ip2_handler;
        ath79_ip3_handler = ar933x_ip3_handler;
    } else if (soc_is_ar934x()) {
        ath79_ip2_handler = ath79_default_ip2_handler;
        ath79_ip3_handler = ar934x_ip3_handler;
    } else if (soc_is_qca953x()) {
        ath79_ip2_handler = ath79_default_ip2_handler;
        ath79_ip3_handler = ath79_default_ip3_handler;
    } else if (soc_is_qca955x()) {
        ath79_ip2_handler = ath79_default_ip2_handler;
        ath79_ip3_handler = ath79_default_ip3_handler;
    } else {
        BUG();
    }

    cp0_perfcount_irq = ATH79_MISC_IRQ(5);
    mips_cpu_irq_init();
    ath79_misc_irq_init();

    if (soc_is_ar934x())
        ar934x_ip2_irq_init();
    else if (soc_is_qca955x())
        qca955x_irq_init();
}

mips_cpu_irq_init函数位于~/openwrt1407/build_dir/target-mips_34kc_uClibc-0.9.33.2/linux-ar71xx_generic/linux-3.10.49/arch/mips/kernel/irq_cpu.c中，ath79_misc_irq_init同在irq.c文件中。

void __init mips_cpu_irq_init(void)
{
    int irq_base = MIPS_CPU_IRQ_BASE;
    int i;

    /* Mask interrupts. */
    clear_c0_status(ST0_IM);
    clear_c0_cause(CAUSEF_IP);

    /* Software interrupts are used for MT/CMT IPI */
    for (i = irq_base; i < irq_base + 2; i++)
        irq_set_chip_and_handler(i, cpu_has_mipsmt ?
                     &mips_mt_cpu_irq_controller :
                     &mips_cpu_irq_controller,
                     handle_percpu_irq);

    for (i = irq_base + 2; i < irq_base + 8; i++)
        irq_set_chip_and_handler(i, &mips_cpu_irq_controller,
                     handle_percpu_irq);
}