嵌入式内核及驱动开发之学习笔记（十一） 中断优化处理
ARM cortex-A系列的内核不支持中断嵌套。在内核中断函数中，如果中断处理时间过长，产生中断嵌套，重者系统崩溃，轻者也会影响其他事件处理。这也是中断中不能使用延时函数的原因。
但是有些高实时性设备（比如网卡），就是需要处理大量的业务。为了满足中断处理时间尽量短的原则，我们将一些简单的处理放在中断中实现，这个阶段叫做中断的上半部；其他一些复杂、耗时间的操作丢给内核线程，让内核来调度其执行，这是中断的下半部。
中断事件 --> 跳转中断入口 --> 中断中执行简单处理 --> 并启动内核调度复杂的处理 --> 结束中断
处理方式
- softirq： 处理比较快，但是内核级别的机制，需要修改整个内核源码，不推荐也不常用
- tasklet： 内部实现实际调用了softirq
- workqueue: 工作队列
tasklet
启动"下半部"实际上就是把结构体描述的对象丢给内核线程的动作。
结构体
struct tasklet_struct
{
struct tasklet_struct *next;
unsigned long state;
atomic_t count;
void (*func)(unsigned long); // 下半部的实现逻辑
unsigned long data; // 传递给func
}; 1.初始化对象
struct tasklet_struct mytasklet;
tasklet_init(struct tasklet_struct * t, void(* func)(unsigned long), unsigned long data)
2.构造"下半部"实现逻辑
void key_tasklet_half_irq(unsigned long data)
{
//............
//............
}
3."上半部"启动"下半部"
tasklet_schedule(&key_dev->mytasklet);
4.（在模块卸载时）注销内核线程中的对象
tasklet_kill(&key_dev->mytasklet);
完成的例子（驱动程序）
//key_drv.c
#include <linux/init.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_irq.h>
#include <linux/interrupt.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/device.h>
#include <linux/wait.h>
#include <linux/sched.h>
#include <linux/poll.h>
#include <asm/io.h>
#include <asm/uaccess.h>
irqreturn_t key_irq_handler(int irqno, void *devid);
void key_tasklet_half_irq(struct work_struct *work);
ssize_t key_drv_read (struct file *, char __user *, size_t, loff_t *);
ssize_t key_drv_write (struct file *, const char __user *, size_t, loff_t *);
int key_drv_open (struct inode *, struct file *);
int key_drv_close (struct inode *, struct file *);
#define GPXCON_REG 0x11000C20
#define KEY_ENTER 28
const struct file_operations key_fops = {
.open = key_drv_open,
.read = key_drv_read,
.write = key_drv_write,
.release = key_drv_close,
};
struct key_event{
int code; // 按键的类型
int value; // 状态
};
struct key_desc{
unsigned int dev_major;
struct class *cls;
struct device *dev;
int irqno;
void *reg_base;
int key_state; //表示是否有数据
struct key_event event;
struct tasklet_struct mytasklet;
};
struct key_desc *key_dev;
int get_irqno_from_node(void)
{
//从设备树路径，查找节点
struct device_node *np = of_find_node_by_path("/key_int_node");
if(np){
printk("find node ok\n");
}else{
printk("find node failed\n");
}
int irqno = irq_of_parse_and_map(np, 0);
printk("irqno = %d\n", irqno);
return irqno;
}
static int __init key_drv_init(void)
{
int ret;
//对象实例化
key_dev = kzalloc(sizeof(struct key_desc), GFP_KERNEL);
//申请主设备号
key_dev->dev_major = register_chrdev(0, "key_drv", &key_fops);
//创建设备结点
key_dev->cls = class_create(THIS_MODULE, "key_cls");
key_dev->dev = device_create(key_dev->cls, NULL,
MKDEV(key_dev->dev_major,0), NULL, "key0");
//硬件初始化
key_dev->irqno = get_irqno_from_node();
ret = request_irq(key_dev->irqno, key_irq_handler, IRQF_TRIGGER_FALLING|IRQF_TRIGGER_RISING,
"key3_eint10", NULL);
if(ret != 0)
{
printk("request_irq error\n");
return ret;
}
key_dev->reg_base = ioremap(GPXCON_REG, 8);
//初始化tasklet
tasklet_init(&key_dev->mytasklet, key_tasklet_half_irq, 45);
return 0;
}
static void __exit key_drv_exit(void)
{
tasklet_kill(&key_dev->mytasklet);
iounmap(key_dev->reg_base); //去映射
free_irq(key_dev->irqno, NULL); //释放中断资源
device_destroy(key_dev->cls, MKDEV(key_dev->dev_major,0)); //
class_destroy(key_dev->cls); //
unregister_chrdev(key_dev->dev_major, "key_drv"); //注销主设备号
kfree(key_dev); //释放结构体内存
}
irqreturn_t key_irq_handler(int irqno, void *devid)
{
printk("-------%s-------------\n", __FUNCTION__);
// 启动下半步
tasklet_schedule(&key_dev->mytasklet);
return IRQ_HANDLED;
}
void key_tasklet_half_irq(struct work_struct *work)
{
printk("-------%s-------------\n", __FUNCTION__);
}
ssize_t key_drv_read(struct file *filp, char __user *buf, size_t count, loff_t *fpos)
{
printk("-------%s-------------\n", __FUNCTION__);
return count;
}
ssize_t key_drv_write(struct file *filp, const char __user *buf, size_t count, loff_t *fpos)
{
printk("-------%s-------------\n", __FUNCTION__);
return 0;
}
int key_drv_open(struct inode *inode, struct file *filp)
{
printk("-------%s-------------\n", __FUNCTION__);
return 0;
}
int key_drv_close (struct inode *inode, struct file *filp)
{
printk("-------%s-------------\n", __FUNCTION__);
return 0;
}
module_init(key_drv_init);
module_exit(key_drv_exit);
MODULE_LICENSE("GPL");
演示
workqueue
结构体描述
struct work_struct {
atomic_long_t data;
struct list_head entry;
work_func_t func;
};
1.初始化对象
struct work_struct mywork;
INIT_WORK(struct work_struct *work, work_func_t func);
2.构造"下半部"实现逻辑
void work_irq_half(struct work_struct *work)
{
//...填入要实现的内容
}
3."上半部"启动"下半部"
schedule_work(&key_dev->mywork);
代码（驱动）
//key_drv.c
#include <linux/init.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_irq.h>
#include <linux/interrupt.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/device.h>
#include <linux/wait.h>
#include <linux/sched.h>
#include <linux/poll.h>
#include <asm/io.h>
#include <asm/uaccess.h>
irqreturn_t key_irq_handler(int irqno, void *devid);
void work_irq_half(struct work_struct *work);
ssize_t key_drv_read (struct file *, char __user *, size_t, loff_t *);
ssize_t key_drv_write (struct file *, const char __user *, size_t, loff_t *);
int key_drv_open (struct inode *, struct file *);
int key_drv_close (struct inode *, struct file *);
#define GPXCON_REG 0x11000C20
#define KEY_ENTER 28
const struct file_operations key_fops = {
.open = key_drv_open,
.read = key_drv_read,
.write = key_drv_write,
.release = key_drv_close,
};
struct key_event{
int code; // 按键的类型
int value; // 状态
};
struct key_desc{
unsigned int dev_major;
struct class *cls;
struct device *dev;
int irqno;
void *reg_base;
int key_state; //表示是否有数据
struct key_event event;
struct work_struct mywork;
};
struct key_desc *key_dev;
int get_irqno_from_node(void)
{
//从设备树路径，查找节点
struct device_node *np = of_find_node_by_path("/key_int_node");
if(np){
printk("find node ok\n");
}else{
printk("find node failed\n");
}
int irqno = irq_of_parse_and_map(np, 0);
printk("irqno = %d\n", irqno);
return irqno;
}
static int __init key_drv_init(void)
{
int ret;
//对象实例化
key_dev = kzalloc(sizeof(struct key_desc), GFP_KERNEL);
//申请主设备号
key_dev->dev_major = register_chrdev(0, "key_drv", &key_fops);
//创建设备结点
key_dev->cls = class_create(THIS_MODULE, "key_cls");
key_dev->dev = device_create(key_dev->cls, NULL,
MKDEV(key_dev->dev_major,0), NULL, "key0");
//硬件初始化
key_dev->irqno = get_irqno_from_node();
ret = request_irq(key_dev->irqno, key_irq_handler, IRQF_TRIGGER_FALLING|IRQF_TRIGGER_RISING,
"key3_eint10", NULL);
if(ret != 0)
{
printk("request_irq error\n");
return ret;
}
key_dev->reg_base = ioremap(GPXCON_REG, 8);
//初始化work
INIT_WORK(&key_dev->mywork, work_irq_half);
return 0;
}
static void __exit key_drv_exit(void)
{
iounmap(key_dev->reg_base); //去映射
free_irq(key_dev->irqno, NULL); //释放中断资源
device_destroy(key_dev->cls, MKDEV(key_dev->dev_major,0)); //
class_destroy(key_dev->cls); //
unregister_chrdev(key_dev->dev_major, "key_drv"); //注销主设备号
kfree(key_dev); //释放结构体内存
}
irqreturn_t key_irq_handler(int irqno, void *devid)
{
printk("-------%s-------------\n", __FUNCTION__);
// 启动下半步
schedule_work(&key_dev->mywork);
return IRQ_HANDLED;
}
void work_irq_half(struct work_struct *work)
{
printk("-------%s-------------\n", __FUNCTION__);
}
ssize_t key_drv_read(struct file *filp, char __user *buf, size_t count, loff_t *fpos)
{
printk("-------%s-------------\n", __FUNCTION__);
return count;
}
ssize_t key_drv_write(struct file *filp, const char __user *buf, size_t count, loff_t *fpos)
{
printk("-------%s-------------\n", __FUNCTION__);
return 0;
}
int key_drv_open(struct inode *inode, struct file *filp)
{
printk("-------%s-------------\n", __FUNCTION__);
return 0;
}
int key_drv_close (struct inode *inode, struct file *filp)
{
printk("-------%s-------------\n", __FUNCTION__);
return 0;
}
module_init(key_drv_init);
module_exit(key_drv_exit);
MODULE_LICENSE("GPL");
