Linux-3.0.8中基于S5PV210的IRQ模块代码追踪和分析

init/main.c:

 asmlinkage void start_kernel(void)
 {
     ......
     early_irq_init();
     init_IRQ();
     ......
 }

early_irq_init()函数有两种实现，一种是基于radix tree，一种是定义静态数组，如果要使用radix tree实现的，那么需要打开SPARSE_IRQ配置选项，由于我对数据结构不了解，所以分析以下静态数组实现方式版本的。

/kernel/irq/irqdesc.c

 struct irq_desc irq_desc[NR_IRQS] __cacheline_aligned_in_smp = {
     [ ... NR_IRQS-] = {
         .handle_irq    = handle_bad_irq,
         .depth        = ,
         .lock        = __RAW_SPIN_LOCK_UNLOCKED(irq_desc->lock),
     }
 };

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

     init_irq_default_affinity();

     printk(KERN_INFO "NR_IRQS:%d\n", NR_IRQS);

     desc = irq_desc;
     count = ARRAY_SIZE(irq_desc);

     for (i = ; i < count; i++) {
         desc[i].kstat_irqs = alloc_percpu(unsigned int);
         alloc_masks(&desc[i], GFP_KERNEL, node);
         raw_spin_lock_init(&desc[i].lock);
         lockdep_set_class(&desc[i].lock, &irq_desc_lock_class);
         desc_set_defaults(i, &desc[i], node);
     }
     return arch_early_irq_init();
 }

　　第一次见到这种初始化数组全部成员为同样内容的方式，可以学习积累下。

　　NR_IRQS在arch/arm/mach-s5pv210/include/mach/irqs.h下定义：

 #define NR_IRQS            (IRQ_EINT(31) + S5P_GPIOINT_COUNT + 1)

　　上面函数的核心就是调用desc_set_defaults()来初始化上述中断描述符数组，kernel/irq/irqdesc.c:

 static void desc_set_defaults(unsigned int irq, struct irq_desc *desc, int node)
 {
     int cpu;

     desc->irq_data.irq = irq;
     desc->irq_data.chip = &no_irq_chip;
     desc->irq_data.chip_data = NULL;
     desc->irq_data.handler_data = NULL;
     desc->irq_data.msi_desc = NULL;
     irq_settings_clr_and_set(desc, ~, _IRQ_DEFAULT_INIT_FLAGS);
     irqd_set(&desc->irq_data, IRQD_IRQ_DISABLED);
     desc->handle_irq = handle_bad_irq;
     desc->depth = ;
     desc->irq_count = ;
     desc->irqs_unhandled = ;
     desc->name = NULL;
     for_each_possible_cpu(cpu)
         *per_cpu_ptr(desc->kstat_irqs, cpu) = ;
     desc_smp_init(desc, node);
 }

　　最后返回时调用的arch_early_irq_init()函数并没有做事情。

　　接着看init_IRQ():

 void __init init_IRQ(void)
 {
     machine_desc->init_irq();
 }

　　machine_desc是全局变量，定义在板文件中，由于我们使用的是s5pv210，且demo板号选的是smdkv210，所以这个全局变量就在arch/arm/mach-s5pv210/mach-s5pv210.c中：

 MACHINE_START(SMDKV210, "SMDKV210")
     /* Maintainer: Kukjin Kim <[e-mail]> */
     .boot_params    = S5P_PA_SDRAM + 0x100,
     .init_irq    = s5pv210_init_irq,
     .map_io        = smdkv210_map_io,
     .init_machine    = smdkv210_machine_init,
     .timer        = &s5p_timer,
 MACHINE_END

arch/arm/mach-s5pv210/mach-s5pv210.c中还有如下函数定义：

 void __init s5pv210_init_irq(void)
 {
     u32 vic[];    /* S5PV210 supports 4 VIC */

     /* All the VICs are fully populated. */
     vic[] = ~;
     vic[] = ~;
     vic[] = ~;
     vic[] = ~;

     s5p_init_irq(vic, ARRAY_SIZE(vic));
 }

arch/arm/plat-s5p/irq.c

 void __init s5p_init_irq(u32 *vic, u32 num_vic)
 {
 #ifdef CONFIG_ARM_VIC
     int irq;

     /* initialize the VICs */
     for (irq = ; irq < num_vic; irq++)
         vic_init(VA_VIC(irq), VIC_BASE(irq), vic[irq], );
 #endif

     s3c_init_vic_timer_irq(, IRQ_TIMER0);

     s3c_init_uart_irqs(uart_irqs, ARRAY_SIZE(uart_irqs));
 }

　　上面涉及到的函数都是去操作VIC相关的寄存器，这部分操作还不是很清楚，先不往下继续追踪了。