1、概述
通过风扇FG脚获取风扇转速。
2、分析
根据风扇规格书可知风扇风速=60/(2*脉冲周期),周期T=1/频率。那么我们需要获取FG脚上的脉冲频率,即可获取风扇风速。
3、解决方法
利用边沿触发中断利用定时器获取1s进入中断的次数即可获取脉冲频率。
(1)注册检测脚
gpio-pwms { compatible = "gpio-pwms"; pinctrl-names = "default"; pwm1 { label = "pwm1"; gpios = <&pio 0 6 GPIO_ACTIVE_HIGH>; gpios-fg = <&pio 0 17 GPIO_ACTIVE_HIGH>; }; pwm2 { label = "pwm2"; gpios = <&pio 6 9 GPIO_ACTIVE_HIGH>; gpios-fg = <&pio 0 3 GPIO_ACTIVE_HIGH>; }; pwm3{ label = "pwm3"; gpios = <&pio 6 11 GPIO_ACTIVE_HIGH>; gpios-fg = <&pio 0 21 GPIO_ACTIVE_HIGH>; }; pwm4{ label = "pwm4"; gpios = <&pio 6 12 GPIO_ACTIVE_HIGH>; gpios-fg = <&pio 0 20 GPIO_ACTIVE_HIGH>; }; };
(2)编写驱动
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解析dts文件,获取fg脚
for_each_child_of_node(node, fg) { enum of_gpio_flags flagsfg; if (!of_find_property(fg, "gpios-fg", NULL)) { pdata->npwms--; printk( "Fail to find gpios-fg\n"); continue; } pwm = &pdata->pwms[i++]; pwm->gpio_fg = of_get_named_gpio_flags(fg,"gpios-fg", 0, &flagsfg); printk("pwm->gpio-fg=%d,flags=%d",pwm->gpio_fg,flagsfg); if (pwm->gpio_fg < 0) { error = pwm->gpio_fg; if (error != -ENOENT) { if (error != -EPROBE_DEFER) dev_err(dev, "Failed to get gpio-fg flags, error: %d\n", error); return ERR_PTR(error); } } }
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申请中断
switch(gpiofg) { case 17: error= devm_gpio_request(dev, gpiofg,"fan1_FG"); break; case 3: error= devm_gpio_request(dev, gpiofg,"fan2_FG"); break; case 21: error= devm_gpio_request(dev, gpiofg,"fan3_FG"); break; case 20: error= devm_gpio_request(dev, gpiofg,"fan4_FG"); break; default: break; } if (error){ printk( "unable to request gpio %u, err=%d\n", gpiofg, error); } gpwm->irq_fg= gpio_to_irq(gpiofg); //获取一个gpio对应的中断号 if (gpwm->irq_fg < 0) { printk("return irq number error!"); } switch(gpiofg) { case 17: pin1FGirq = gpwm->irq_fg; INIT_WORK(&gpwm->gpiofg_work, fan1_speed); //初始化工作队列 irq_set_irq_type(gpwm->irq_fg, IRQ_TYPE_EDGE_FALLING); //设置触发类型 error = devm_request_irq(&pdev->dev, gpwm->irq_fg, get_fan_speed_irq_handler, IRQF_SHARED,"fan1_FG", gpwm); //申请中断设置中断类型为 共享中断 break; case 3: pin2FGirq = gpwm->irq_fg; INIT_WORK(&gpwm->gpiofg_work, fan2_speed); error = devm_request_irq(&pdev->dev, gpwm->irq_fg, get_fan_speed_irq_handler, IRQF_SHARED,"fan2_FG", gpwm); break; case 21: pin3FGirq = gpwm->irq_fg; INIT_WORK(&gpwm->gpiofg_work, fan3_speed); error = devm_request_irq(&pdev->dev, gpwm->irq_fg, get_fan_speed_irq_handler, IRQF_SHARED,"fan3_FG", gpwm); break; case 20: pin4FGirq = gpwm->irq_fg; INIT_WORK(&gpwm->gpiofg_work, fan4_speed); error = devm_request_irq(&pdev->dev, gpwm->irq_fg, get_fan_speed_irq_handler, IRQF_SHARED,"fan4_FG", gpwm); break; default: break; } if (error) { printk( "failed to request irq, err=%d\n", error); } disable_irq(gpwm->irq_fg); //默认关闭中断 }
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中断服务程序
static irqreturn_t get_fan_speed_irq_handler(int irq, void *dev_id) { struct pwm_chip *gpiofg_data = dev_id; schedule_work(&gpiofg_data->gpiofg_work); //schedule_work(work)来通知内核线程,然后中断结束后,再去继续执行work对应的func函数 return IRQ_HANDLED; } 注意: //中断服务程序的返回值必须为IRQ_HANDLED /** * enum irqreturn * @IRQ_NONE interrupt was not from this device or was not handled * @IRQ_HANDLED interrupt was handled by this device * @IRQ_WAKE_THREAD handler requests to wake the handler thread */ enum irqreturn { IRQ_NONE = (0 << 0), IRQ_HANDLED = (1 << 0), IRQ_WAKE_THREAD = (1 << 1), };
中断服务程序有三个返回值,三个值代表不同意思,如果返回值为IR_NONE,系统会认为这个中断没有被处理(但是中断程序执行了),当 未处理中断次数超过100000次时,系统会disable掉这个中断。系统会认为中断卡死了,这是共享中断的特性,会根据中断服务程序的返回值判断中断程序是否被处理。
当一个中断号上有多个中断共享的时候,该中断来的时候,内核会依次调用共享该中断号的各个中断处理函数,如果中断处理函数检测到该中断不是自己的中断时就会返回IRQ_NONE,这时内核就会调用下一个中断处理函数,而这些中断处理函数中必须至少有一个返回IRQ_HANDLED告知内核该中断是自己的中断,已经正常处理,若内核依次调用完所有该中断号的中断处理函数仍未得到IRQ_HANDLED的返回值,内核就会报告上述错误,并在该中断出现一定次数后关闭该中断。即只有中断处理函数返回 IRQ_HANDLED ,这个中断才是被正确完成的。
中断卡死的处理过程:
//Linux-4.14.25/kernel/irq/spurious.c irq = irq_desc_get_irq(desc); if (unlikely(try_misrouted_irq(irq, desc, action_ret))) { int ok = misrouted_irq(irq); if (action_ret == IRQ_NONE) desc->irqs_unhandled -= ok; } desc->irq_count++; if (likely(desc->irq_count < 100000)) return; desc->irq_count = 0; if (unlikely(desc->irqs_unhandled > 99900)) { /* * The interrupt is stuck */ __report_bad_irq(desc, action_ret); /* * Now kill the IRQ */ printk(KERN_EMERG "Disabling IRQ #%d\n", irq); desc->istate |= IRQS_SPURIOUS_DISABLED; desc->depth++; irq_disable(desc); mod_timer(&poll_spurious_irq_timer, jiffies + POLL_SPURIOUS_IRQ_INTERVAL); } desc->irqs_unhandled = 0; }
查看中断信息:
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工作队列的任务
static void fan1_speed(struct work_struct *ws) { pinFG1_frequency++; } static void fan2_speed(struct work_struct *ws) { pinFG2_frequency++; } static void fan3_speed(struct work_struct *ws) { pinFG3_frequency++; } static void fan4_speed(struct work_struct *ws) { pinFG4_frequency++; }
工作队列的介绍
在中断处理中,经常用到工作队列,这样便能缩短中断处理时的时间
//工作队列初始化函数
INIT_WORK(work, func);
中断中通过调用schedule_work(work)来通知内核线程,然后中断结束后,再去继续执行work对应的func函数
示例
当中断来了,立马调用schedule_work(work),然后退出.
中断结束后,内核便会调用_work对应的func函数,最后才来读取按键值,上报按键值,这样就大大缩短了中断处理时间
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定时器初始化
static void fan1_init_timer(void) { fan1timer.expires = jiffies+100;//设定 超时时间,100代表1秒? timer_setup(&fan1timer, fan1_timer, 0); add_timer(&fan1timer); //添加定时器,定时器开始生效 enable_irq(pin1FGirq); } static void fan2_init_timer(void) { fan2timer.expires = jiffies+100;//设定 超时时间,100代表1秒 timer_setup(&fan2timer, fan2_timer, 0); //准备timer,并设置超时时执行的函数。 add_timer(&fan2timer); //添加定时器,定时器开始生效 enable_irq(pin2FGirq); } static void fan3_init_timer(void) { fan3timer.expires = jiffies+100;//设定 超时时间,100代表1秒 timer_setup(&fan3timer, fan3_timer, 0); add_timer(&fan3timer); //添加定时器,定时器开始生效 enable_irq(pin3FGirq); } static void fan4_init_timer(void) { fan4timer.expires = jiffies+100;//设定 超时时间,100代表1秒 timer_setup(&fan4timer, fan4_timer, 0); add_timer(&fan4timer); //添加定时器,定时器开始生效 enable_irq(pin4FGirq); }
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定时器超时处理函数
static void fan1_timer(struct timer_list *t) { pinFG_frequency[0] = pinFG1_frequency; pinFG1_frequency = 0; mod_timer(&fan1timer,jiffies+100); // 修改定时器的expire } static void fan2_timer(struct timer_list *t) { pinFG_frequency[1] = pinFG2_frequency; pinFG2_frequency = 0; mod_timer(&fan2timer,jiffies+100); } static void fan3_timer(struct timer_list *t) { pinFG_frequency[2] = pinFG3_frequency; pinFG3_frequency = 0; mod_timer(&fan3timer,jiffies+100); } static void fan4_timer(struct timer_list *t) { pinFG_frequency[3] = pinFG4_frequency; pinFG4_frequency = 0; mod_timer(&fan4timer,jiffies+100); }
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read函数(应用层read会调用到这个函数)
ssize_t pwm_drv_read (struct file *filp, char __user *userbuf, size_t count, loff_t *fpos) { int ret=0, i = 0,j=0; unsigned char tmp[8] ={0}; //应用层从内核读取数据时,只能一个字节一个字节读,所以将频率short型数据要分成两个单字节数据读。 while(i<8) { tmp[i] = pinFG_frequency[j]>>8 ; tmp[i+1] = pinFG_frequency[j]; i+=2; j++; } ret= copy_to_user(userbuf, tmp, sizeof(tmp)/sizeof(tmp[0])); if(ret==1) { printk("copy data error!\n"); ret = -1; } return ret;
(3)应用层获取数据
void fan_get_rotating_speed(uint16_t *arg,uint8_t len) { int fd=-1,ret=-1,i=0,j=0; uint8_t recv_buff[8]={0}; uint16_t pinFG_Freqency[4]={0}; printf("fan_get_rotating_speed\n"); fd = open(dev_fan[0].description,O_RDWR ); if(fd < 0) { printf("failed to open pwm0 failed!\n"); } //读取数据 ret = read(fd,recv_buff,len*2); if(ret<0) { printf("get fan rotating speed error!"); } //将8个字节的数据合成4个short型数据 while(i<8) { pinFG_Freqency[j] = (unsigned short)recv_buff[i]<<8|recv_buff[i+1]; i+=2; j++; } //计算转速 for(i=0;i<len;i++) { arg[i]=(uint16_t)((60*pinFG_Freqency[i])/2); } close(fd); }
driver-ipollo.c中去调用
else if (strcasecmp(option, "getallstats") == 0) { char tmp_str[64] = { 0 }; uint16_t fan_speed[4]={0}; fan_get_rotating_speed(fan_speed,sizeof(fan_speed)/sizeof(fan_speed[0])); sprintf(tmp_str, "\"fanspeed[0:%d]:[1:%d][2:%d][3:%d]\"",fan_speed[0],fan_speed[1],fan_speed[2],fan_speed[3]); strcat(replybuf, tmp_str);
可通过命令去获取风速:
echo -n "ascset|0,getallstats" | nc 192.168.1.100 4028 && echo