disable_irq与disable_irq_nosync使用场景

Linux设备驱动，关于中断屏蔽有两个接口：disable_irq和disable_irq_nosync，该两接口使用场景如下：

1、disable_irq：在非中断处理函数中使用，会阻塞；

2、disable_irq_nosync：在中断处理函数中使用，不会阻塞；用于屏蔽相应中断；

一、为什么要屏蔽中断？

使能中断后，一旦触发中断，系统会进入中断处理函数；如果下一个中断触发的时候，前一个中断处理函数已经完成，这是理想状态，不会发生异常；如果前一个中断处理函数还未完成，那么就会导致中断嵌套。为了不出现中断嵌套，必须在中断处理函数中屏蔽中断，待中断处理完成后，再主动使能中断。

二、disable_irq不能放在中断处理函数中

如果在中断处理函数中使用disable_irq屏蔽相应中断，系统将会出现死锁状态，最后死机，然后重启。（已验证）

三、enable_irq配套使用

当中断处理函数已经完成所有工作，在返回之前需要主动调用接口enable_irq使能中断，否则该中断将一直被屏蔽。（已验证）

四、附上距离传感器中断处理处理函数

//PS中断处理
static irqreturn_t ltr559_irq_handler(int irq, void *arg)
{
struct ltr559_data *data = (struct ltr559_data *)arg;

//printk("%s\n",__func__);

if (NULL == data)
return IRQ_HANDLED;

//后面必须有使能中断
disable_irq_nosync(data->irq);
//屏蔽中断，不会造成死锁
schedule_delayed_work(&data->ps_work, 0);
//调用延时工作队列
return IRQ_HANDLED;
}

//PS工作任务
//重要接口
static void ltr559_ps_work_func(struct work_struct *work)
{
struct ltr559_data *data = container_of(work, struct ltr559_data, ps_work.work);
struct i2c_client *client=data->client;
int als_ps_status;
int psval_lo, psval_hi, psdata;
static u32 ps_state_last = 2;
//Far as default.

mutex_lock(&data->op_lock);

als_ps_status = i2c_smbus_read_byte_data(client, LTR559_ALS_PS_STATUS);
//printk("%s ps_open_state=%d, als_ps_status=0x%x\n",__func__,data->ps_open_state,als_ps_status);
if (als_ps_status < 0)
goto workout;
/* Here should check data status,ignore interrupt status. */
/* Bit 0: PS Data
* Bit 1: PS interrupt
* Bit 2: ASL Data
* Bit 3: ASL interrupt
* Bit 4: ASL Gain 0: ALS measurement data is in dynamic range 2 (2 to 64k lux)
*                 1: ALS measurement data is in dynamic range 1 (0.01 to 320 lux)
*/

//使能情况
if ((data->ps_open_state == 1) && (als_ps_status & 0x02)) {
psval_lo = i2c_smbus_read_byte_data(client, LTR559_PS_DATA_0);
if (psval_lo < 0) {
psdata = psval_lo;
goto workout;
}
psval_hi = i2c_smbus_read_byte_data(client, LTR559_PS_DATA_1);
if (psval_hi < 0) {
psdata = psval_hi;
goto workout;
}
psdata = ((psval_hi & 7) << 8) | psval_lo;
printk("%s: psdata=%d(0x%x), near_thrd=%u, far_thrd=%u, dynamic_noise=%u\n",
  __func__, psdata, (u32)psdata, data->platform_data->prox_threshold,
  data->platform_data->prox_hsyteresis_threshold, data->dynamic_noise);

if(psdata >= data->platform_data->prox_threshold){

data->ps_state = 0; //near
ltr559_set_ps_threshold(client, LTR559_PS_THRES_LOW_0, data->platform_data->prox_hsyteresis_threshold);
ltr559_set_ps_threshold(client, LTR559_PS_THRES_UP_0, 0x07ff);
printk("%s: near, update near_thrd=%u, far_thrd=%u\n",
  __func__, 0x7ff, data->platform_data->prox_hsyteresis_threshold);
} else if (psdata <= data->platform_data->prox_hsyteresis_threshold){
data->ps_state = 1; //far

//该宏已经定义
#if defined(CONFIG_PICCOLO_COMMON)
  if (data->dynamic_noise > 20 && psdata < (data->dynamic_noise - 50) ) {
 data->dynamic_noise = psdata;
 if(psdata < 100) {
 }else if(psdata < 200){
 data->platform_data->prox_threshold = psdata+230;
 data->platform_data->prox_hsyteresis_threshold = psdata+180;
 }else if(psdata < 500){
 data->platform_data->prox_threshold = psdata+280;
 data->platform_data->prox_hsyteresis_threshold = psdata+230;
 }else if(psdata < 1500){
 data->platform_data->prox_threshold = psdata+420;
 data->platform_data->prox_hsyteresis_threshold = psdata+350;
 }else{  
 data->platform_data->prox_threshold= 1800;
 data->platform_data->prox_hsyteresis_threshold= 1700;
 pr_err("ltr559 the proximity sensor rubber or structure is error!\n");
 }
 printk("%s: NEW prox_threshold=%u, prox_hsyteresis_threshold=%u !!!\n",
__func__, data->platform_data->prox_threshold,
    data->platform_data->prox_hsyteresis_threshold);
  }
#endif

ltr559_set_ps_threshold(client, LTR559_PS_THRES_LOW_0, 0);
ltr559_set_ps_threshold(client, LTR559_PS_THRES_UP_0, data->platform_data->prox_threshold);
printk("%s: far, update near_thrd=%u, far_thrd=0\n",
  __func__, data->platform_data->prox_threshold);
} else {
data->ps_state = ps_state_last;
}

printk("%s: ps_state_last = %u, ps_state = %u\n", __func__, ps_state_last, data->ps_state);
if((ps_state_last != data->ps_state) || (data->ps_state == 0)) //need report the input event constant when near 
{
//上报数据
input_report_abs(data->input_dev_ps, ABS_DISTANCE, data->ps_state);
input_sync(data->input_dev_ps);
printk("%s: report ABS_DISTANCE=%s\n",__func__, data->ps_state ? "far" : "near");

ps_state_last = data->ps_state; 
//Report ABS value only if the state changed.
}
else
printk("%s: ps_state still %s\n", __func__, data->ps_state ? "far" : "near");
}
workout:
enable_irq(data->irq);
//使能
irq
mutex_unlock(&data->op_lock);
//解锁
}