ARM-Linux驱动--Watch Dog Timer(看门狗)驱动分析

时间：11-20 来源：互联网点击：

//获取IO端口资源，这里IORESOURCE_MEM和平台设备中资源的定义一致
res=platform_get_resource(pdev,IORESOURCE_MEM,0);
if(res==NULL){
dev_err(dev,"nomemoryresourcespecified\n");
return-ENOENT;
}
size=(res->end-res->start)+1;
//申请内存空间
wdt_mem=request_mem_region(res->start,size,pdev->name);
if(wdt_mem==NULL){
dev_err(dev,"failedtogetmemoryregion\n");
ret=-ENOENT;
gotoerr_req;
}
//地址映射，wdt_base为基地址
wdt_base=ioremap(res->start,size);
if(wdt_base==NULL){
dev_err(dev,"failedtoioremap()region\n");
ret=-EINVAL;
gotoerr_req;
}
DBG("probe:mappedwdt_base=%p\n",wdt_base);
//从平台设备中获取中断号
wdt_irq=platform_get_resource(pdev,IORESOURCE_IRQ,0);
if(wdt_irq==NULL){
dev_err(dev,"noirqresourcespecified\n");
ret=-ENOENT;
gotoerr_map;
}
//注册中断，中断处理函数s3c2410wdt_irq()
ret=request_irq(wdt_irq->start,s3c2410wdt_irq,0,pdev->name,pdev);
if(ret!=0){
dev_err(dev,"failedtoinstallirq(%d)\n",ret);
gotoerr_map;
}
//获取系统时钟
wdt_clock=clk_get(&pdev->dev,"watchdog");
if(IS_ERR(wdt_clock)){
dev_err(dev,"failedtofindwatchdogclocksource\n");
ret=PTR_ERR(wdt_clock);
gotoerr_irq;
}
//使能时钟
clk_enable(wdt_clock);
/*seeifwecanactuallysettherequestedtimermargin,andif
*not,trythedefaultvalue*/
if(s3c2410wdt_set_heartbeat(tmr_margin))
{//这里第一次设置计时周期为tmr_margin，如果设置不成功，则重新设置为默认值
started=s3c2410wdt_set_heartbeat(
CONFIG_S3C2410_WATCHDOG_DEFAULT_TIME);
if(started==0)
dev_info(dev,
"tmr_marginvalueoutofrange,default%dused\n",
CONFIG_S3C2410_WATCHDOG_DEFAULT_TIME);
else
dev_info(dev,"defaulttimervalueisoutofrange,cannotstart\n");
}
//注册设备
ret=misc_register(&s3c2410wdt_miscdev);
if(ret)
{
dev_err(dev,"cannotregistermiscdevonminor=%d(%d)\n",
WATCHDOG_MINOR,ret);
gotoerr_clk;
}
if(tmr_atboot&&started==0)
{
dev_info(dev,"startingwatchdogtimer\n");
s3c2410wdt_start();//启动看门狗
}
elseif(!tmr_atboot)
{
/*ifwerenotenablingthewatchdog,thenensureitis
*disabledifithasbeenleftrunningfromthebootloader
*orothersource*/
s3c2410wdt_stop();
}
/*printoutastatementofreadiness*/
wtcon=readl(wdt_base+S3C2410_WTCON);
dev_info(dev,"watchdog%sactive,reset%sabled,irq%sabled\n",
(wtcon&S3C2410_WTCON_ENABLE)?"":"in",
(wtcon&S3C2410_WTCON_RSTEN)?"":"dis",
(wtcon&S3C2410_WTCON_INTEN)?"":"en");
//设置GPB10端口为输出端口，用于点亮LED10
s3c2410_gpio_cfgpin(S3C2410_GPB10,S3C2410_GPB10_OUTP);
return0;
//出错跳转表，异常处理
err_clk:
clk_disable(wdt_clock);
clk_put(wdt_clock);
err_irq:
free_irq(wdt_irq->start,pdev);
err_map:
iounmap(wdt_base);
err_req:
release_resource(wdt_mem);
kfree(wdt_mem);
returnret;
}
//设备移除函数，释放资源和映射
staticints3c2410wdt_remove(structplatform_device*dev)
{
release_resource(wdt_mem);
kfree(wdt_mem);
wdt_mem=NULL;
free_irq(wdt_irq->start,dev);
wdt_irq=NULL;
clk_disable(wdt_clock);
clk_put(wdt_clock);
wdt_clock=NULL;
iounmap(wdt_base);
misc_deregister(&s3c2410wdt_miscdev);
return0;
}
//关闭看门狗
staticvoids3c2410wdt_shutdown(structplatform_device*dev)
{
s3c2410wdt_stop();
}
//定义平台设备驱动
staticstructplatform_drivers3c2410wdt_driver={
.probe=s3c2410wdt_probe,
.remove=s3c2410wdt_remove,
.shutdown=s3c2410wdt_shutdown,
.driver={
.owner=THIS_MODULE,
.name="s3c2410-wdt",//该名称参照内核源码中该资源的名称，两者必须一致
},
};
staticcharbanner[]__initdata=
KERN_INFO"S3C2410WatchdogTimer,(c)2004SimtecElectronics\n";
//驱动安装时执行
staticint__initwatchdog_init(void)
{
printk(banner);
returnplatform_driver_register(&s3c2410wdt_driver);//注册设备
}
//驱动移除是执行
staticvoid__exitwatchdog_exit(void)
{
platform_driver_unregister(&s3c2410wdt_driver);//移除设备
}
module_init(watchdog_init);
module_exit(watchdog_exit);
MODULE_AUTHOR("YanMing");
MODULE_DESCRIPTION("S3C2410WatchdogDeviceDriver");
MODULE_LICENSE("GPL");
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);

设置默认不是重启机器，而是执行中断函数，当不喂狗，计数器减到0，点亮LED，然后喂狗，重新计数。

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