fmql之Linux WDT - 技术栈

正点原子第52章。

基础知识

正点原子教程

fmql-dts

代码

APP代码（不需要编写驱动代码）

cpp 复制代码

static int dw_wdt_drv_probe(struct platform_device *pdev)
{
	struct device *dev = &pdev->dev;
	struct watchdog_device *wdd;
	struct dw_wdt *dw_wdt;    /* 描述SDWT设备 */
	struct resource *mem;
	struct dw_wdt_of_data *of_data = NULL;
	int ret;

   /* 实例化wdt对象 */ 
	dw_wdt = devm_kzalloc(dev, sizeof(*dw_wdt), GFP_KERNEL);
	if (!dw_wdt)
		return -ENOMEM;

    /* 获取SWDT的寄存器基地址(物理地址)
     * 并将其转换为内核当中操作使用的虚拟地址
     * 将其存放在dw_wdt->regs中
     */
	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	dw_wdt->regs = devm_ioremap_resource(dev, mem);
	if (IS_ERR(dw_wdt->regs))
		return PTR_ERR(dw_wdt->regs);

    /* 获取输入时钟 */
	dw_wdt->clk = devm_clk_get(dev, NULL);
	if (IS_ERR(dw_wdt->clk))
		return PTR_ERR(dw_wdt->clk);

    /* 使能时钟 */
	ret = clk_prepare_enable(dw_wdt->clk);
	if (ret)
		return ret;

    /* 获取时钟频率 */
	dw_wdt->rate = clk_get_rate(dw_wdt->clk);
	if (dw_wdt->rate == 0) {
		ret = -EINVAL;
		goto out_disable_clk;
	}

	dw_wdt->rst = devm_reset_control_get_optional_shared(&pdev->dev, NULL);
	if (IS_ERR(dw_wdt->rst)) {
		ret = PTR_ERR(dw_wdt->rst);
		goto out_disable_clk;
	}

	reset_control_deassert(dw_wdt->rst);

    /* 对 struct watchdog_device 对象成员变量进行了初始化 */
	wdd = &dw_wdt->wdd;
	wdd->info = &dw_wdt_ident;
	wdd->ops = &dw_wdt_ops;
	wdd->min_timeout = 1;
	wdd->max_hw_heartbeat_ms =
		dw_wdt_top_in_seconds(dw_wdt, DW_WDT_MAX_TOP) * 1000;
	wdd->parent = dev;

    /* 调用函数：
     * 初始化WDT
     */
	watchdog_set_drvdata(wdd, dw_wdt);      
	watchdog_set_nowayout(wdd, nowayout);  // 设置WDT status为WDOG_NO_WAY_OUT
	watchdog_init_timeout(wdd, 0, dev);    // 超时时间值

	/*
	 * If the watchdog is already running, use its already configured
	 * timeout. Otherwise use the default or the value provided through
	 * devicetree.
	 */
	if (dw_wdt_is_enabled(dw_wdt)) {
		wdd->timeout = dw_wdt_get_top(dw_wdt);
		set_bit(WDOG_HW_RUNNING, &wdd->status);
	} else {
		wdd->timeout = DW_WDT_DEFAULT_SECONDS;
		watchdog_init_timeout(wdd, 0, dev);
	}

	platform_set_drvdata(pdev, dw_wdt);

	watchdog_set_restart_priority(wdd, 128);

    /* 向看门狗核心层注册一个WDT设备 */
	ret = watchdog_register_device(wdd);
	if (ret)
		goto out_disable_clk;

	of_data = dev_to_ofdata(&pdev->dev);
	if (of_data && of_data->init) {
		ret = of_data->init(&pdev->dev);
		if (ret)
			goto out_disable_clk;
	}

	return 0;

out_disable_clk:
	clk_disable_unprepare(dw_wdt->clk);
	return ret;
}

cpp 复制代码

static const struct watchdog_info dw_wdt_ident = {
	.options	= WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT |
			  WDIOF_MAGICCLOSE,
	.identity	= "Synopsys DesignWare Watchdog",
};
/* options:
 * WDIOF_KEEPALIVEPING    支持喂狗
 * WDIOF_SETTIMEOUT       设置超时时间
 * WDIOF_MAGICCLOSE       当应用层关闭设备时，WDT不会停止运行
 */

static const struct watchdog_ops dw_wdt_ops = {
	.owner		= THIS_MODULE,
	.start		= dw_wdt_start,
	.stop		= dw_wdt_stop,
	.ping		= dw_wdt_ping,
	.set_timeout	= dw_wdt_set_timeout,
	.get_timeleft	= dw_wdt_get_timeleft,
	.restart	= dw_wdt_restart,
};