RISC-V 中断子系统分析——PLIC 中断处理

// drivers/rtc/rtc-goldfish.c
static int goldfish_rtc_probe(struct platform_device *pdev)
{
···
	err = devm_request_irq(&pdev->dev, rtcdrv->irq,
			       goldfish_rtc_interrupt,
			       0, pdev->name, rtcdrv); // 申请 irq
···
}

devm_request_irq(&pdev->dev, rtcdrv->irq, goldfish_rtc_interrupt,0, pdev->name, rtcdrv);

——>devm_request_threaded_irq(&pdev->dev,  rtcdrv->irq, goldfish_rtc_interrupt, NULL, 0,pdev->name, dev_id);

————>request_threaded_irq( rtcdrv->irq, goldfish_rtc_interrupt, NULL, 0, pdev->name, dev_id);

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/rtc.h>
struct rtc_time time; // 保存时间值
struct rtc_wkalrm alrm; // 保存闹钟值
int main(int argc,char **argv)
{
        int fd=open("/dev/rtc0",O_RDWR); // 2==O_RDWR
        if(fd<0){
                printf("驱动设备文件打开失败!\r\n");
                return 0;
        }
        alrm.enabled=1;
        alrm.pending=0;
        ioctl(fd,RTC_RD_TIME,&time);
        time.tm_sec+=5; // 5 秒后闹钟产生
        alrm.time=time;
        ioctl(fd,RTC_WKALM_SET,&alrm);
        ioctl(fd,RTC_ALM_READ,&time);
        printf("ALM %d-%d-%d %d:%d:%d\r\n",time.tm_year+1900,time.tm_mon+1,time.tm_mday,time.tm_hour,time.tm_min,time.tm_sec);
        while(1){
                ioctl(fd,RTC_RD_TIME,&time);
                printf("now time=%d-%d-%d %d:%d:%d\r\n",time.tm_year+1900,time.tm_mon+1,time.tm_mday,time.tm_hour,time.tm_min,time.tm_sec);
                sleep(1);
        }
}

用户空间：
    main
    	open
    		ioctl
内核空间：
    rtc_dev_ioctl
    	rtc_set_alarm
    		rtc_timer_enqueue
    			__rtc_set_alarm
    				goldfish_rtc_set_alarm

// kernel/irq/handle.c
/**
 * generic_handle_arch_irq - root irq handler for architectures which do no
 *                           entry accounting themselves
 * @regs:	Register file coming from the low-level handling code
 */
asmlinkage void noinstr generic_handle_arch_irq(struct pt_regs *regs)
{
	struct pt_regs *old_regs;

	irq_enter();
	old_regs = set_irq_regs(regs);
	handle_arch_irq(regs);
	set_irq_regs(old_regs);
	irq_exit();
}

// kernel/irq/handle.c
int __init set_handle_irq(void (*handle_irq)(struct pt_regs *))
{
    if (handle_arch_irq)
        return -EBUSY;
    handle_arch_irq = handle_irq;
    return 0;
}

// drivers/irqchip/irq-riscv-intc.c
static asmlinkage void riscv_intc_irq(struct pt_regs *regs)
{
	unsigned long cause = regs->cause & ~CAUSE_IRQ_FLAG;

	if (unlikely(cause >= BITS_PER_LONG))
		panic("unexpected interrupt cause");

	switch (cause) {
#ifdef CONFIG_SMP
	case RV_IRQ_SOFT:
		/*
		 * We only use software interrupts to pass IPIs, so if a
		 * non-SMP system gets one, then we don't know what to do.
	         */
		handle_IPI(regs); // 软中断接口
		break;
#endif
	default: // 硬中断接口
		generic_handle_domain_irq(intc_domain, cause);
		break;
	}
}

// kernel/irq/irqdesc.c
int generic_handle_domain_irq(struct irq_domain *domain, unsigned int hwirq)
{
	WARN_ON_ONCE(!in_irq());
	return handle_irq_desc(irq_resolve_mapping(domain, hwirq));
}

// kernel/irq/irqdesc.c
int generic_handle_domain_irq(struct irq_domain *domain, unsigned int hwirq)
{
	WARN_ON_ONCE(!in_irq());
	struct irq_desc *my= irq_resolve_mapping(domain, hwirq);
	if(hwirq==11)
	{
		printk("[nfk test]hwirq=%u\n",hwirq);
		printk("[nfk test] irq =%d,hwirq=%d",my->irq_data.irq,my->irq_data.hwirq);
		printk("[nfk test] name =%s",my->dev_name);
	}
	return handle_irq_desc(irq_resolve_mapping(domain, hwirq));
}

// kernel/irq/irqdomain.c
struct irq_desc *__irq_resolve_mapping(struct irq_domain *domain,
				       irq_hw_number_t hwirq,
				       unsigned int *irq)
{
	struct irq_desc *desc = NULL;
	struct irq_data *data;
...//查找 desc 不是用的以上代码，故省略
	rcu_read_lock();
	/* Check if the hwirq is in the linear revmap. */
	if (hwirq < domain->revmap_size){
		if(hwirq==11)
			printk("hwirq < domain->revmap_size\n"); // 经验证，走的这条路获取到了 irq_data
		data = rcu_dereference(domain->revmap[hwirq]); // 在 RCU 保护机制下，通过 domain->revmap[hwirq] 找到了 irq_data，
	}
	else
		data = radix_tree_lookup(&domain->revmap_tree, hwirq);
	if (likely(data)) {
		if(hwirq==11)
			printk("hwirq is in the linear revmap\n");
		desc = irq_data_to_desc(data); // container_of，已知成员变量地址，求出结构体起始地址
		if (irq)
			*irq = data->irq;
	}
	rcu_read_unlock();
	return desc;
}

// kernel/irq/irqdomain.c
static void irq_domain_set_mapping(struct irq_domain *domain,
				   irq_hw_number_t hwirq,
				   struct irq_data *irq_data)
{
	if (irq_domain_is_nomap(domain))
		return;
	if(hwirq==11)
	{
		printk("[nfk test] irq_domain_set_mapping,hwirq=%d\n",hwirq);
		dump_stack();
	}

	mutex_lock(&domain->revmap_mutex);
	if (hwirq < domain->revmap_size)
		rcu_assign_pointer(domain->revmap[hwirq], irq_data);
	else
		radix_tree_insert(&domain->revmap_tree, hwirq, irq_data);
	mutex_unlock(&domain->revmap_mutex);
}

// kernel/irq/irqdomain.c
static void irq_domain_insert_irq(int virq)
{
	struct irq_data *data;

	for (data = irq_get_irq_data(virq); data; data = data->parent_data) {//获取 irq_data
...
	}

	irq_clear_status_flags(virq, IRQ_NOREQUEST);
}

// kernel/irq/irqdesc.c
static void irq_insert_desc(unsigned int irq, struct irq_desc *desc)
{
	if(irq==1)
	{
		printk("irq_insert_desc irq=1\n");
		dump_stack();
	}

	radix_tree_insert(&irq_desc_tree, irq, desc);
}

// drivers/rtc/rtc-goldfish.c
static int goldfish_rtc_probe(struct platform_device *pdev)
{
···
	err = devm_request_irq(&pdev->dev, rtcdrv->irq,
			       goldfish_rtc_interrupt,
			       0, pdev->name, rtcdrv); // 申请 irq
···
}

// drivers/irqchip/irq-sifive-plic.c
static int __init plic_init(struct device_node *node,
		struct device_node *parent)
{
    ...
    /* Find parent domain and register chained handler */
    if (!plic_parent_irq && irq_find_host(parent.np)) {//注册处理函数
        plic_parent_irq = irq_of_parse_and_map(node, i);
        if (plic_parent_irq)
            irq_set_chained_handler(plic_parent_irq,
                                    plic_handle_irq); // 为 parent 设置中断处理函数
        printk("[nfk test]set chained handler\n");
    }
    ...
}

# cat /proc/interrupts
           CPU0       CPU1       CPU2       CPU3
  1:          1          0          0          0  SiFive PLIC  11 Edge      101000.rtc
  2:        315          0          0          0  SiFive PLIC  10 Edge      ttyS0
  3:         11          0          0          0  SiFive PLIC   8 Edge      virtio0
  4:        103          0          0          0  SiFive PLIC   7 Edge      virtio1
  5:      20719      20725      20725      20728  RISC-V INTC   5 Edge      riscv-timer
IPI0:        35         23         26         31  Rescheduling interrupts
IPI1:       763        247        211        683  Function call interrupts
IPI2:         0          0          0          0  CPU stop interrupts
IPI3:         0          0          0          0  IRQ work interrupts
IPI4:         0          0          0          0  Timer broadcast interrupts