linux-kernel - Re: [PATCH v4 3/3] watchdog: qcom: register a restart notifier

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Date:	Thu, 25 Sep 2014 20:20:23 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Josh Cartwright <joshc@...eaurora.org>,
	Wim Van Sebroeck <wim@...ana.be>,
	linux-watchdog@...r.kernel.org
CC:	linux-arm-msm@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Kumar Gala <galak@...eaurora.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 3/3] watchdog: qcom: register a restart notifier

On 09/25/2014 03:51 PM, Josh Cartwright wrote:
> The WDT's BITE_TIME warm-reset behavior can be leveraged as a last
> resort mechanism for triggering chip reset.  Usually, other restart
> methods (such as PS_HOLD) are preferrable for issuing a more complete
> reset of the chip.  As such, keep the priority of the watchdog notifier
> low.
>
> Signed-off-by: Josh Cartwright <joshc@...eaurora.org>

Reviewed-by: Guenter Roeck <linux@...ck-us.net>

> ---
>   drivers/watchdog/qcom-wdt.c | 38 ++++++++++++++++++++++++++++++++++++++
>   1 file changed, 38 insertions(+)
>
> diff --git a/drivers/watchdog/qcom-wdt.c b/drivers/watchdog/qcom-wdt.c
> index 68db322..aa85618 100644
> --- a/drivers/watchdog/qcom-wdt.c
> +++ b/drivers/watchdog/qcom-wdt.c
> @@ -11,11 +11,13 @@
>    *
>    */
>   #include <linux/clk.h>
> +#include <linux/delay.h>
>   #include <linux/io.h>
>   #include <linux/kernel.h>
>   #include <linux/module.h>
>   #include <linux/of.h>
>   #include <linux/platform_device.h>
> +#include <linux/reboot.h>
>   #include <linux/watchdog.h>
>
>   #define WDT_RST		0x0
> @@ -26,6 +28,7 @@ struct qcom_wdt {
>   	struct watchdog_device	wdd;
>   	struct clk		*clk;
>   	unsigned long		rate;
> +	struct notifier_block	restart_nb;
>   	void __iomem		*base;
>   };
>
> @@ -84,6 +87,32 @@ static const struct watchdog_info qcom_wdt_info = {
>   	.identity	= KBUILD_MODNAME,
>   };
>
> +static int qcom_wdt_restart(struct notifier_block *nb, unsigned long action,
> +			    void *data)
> +{
> +	struct qcom_wdt *wdt = container_of(nb, struct qcom_wdt, restart_nb);
> +	u32 timeout;
> +
> +	/*
> +	 * Trigger watchdog bite:
> +	 *    Setup BITE_TIME to be 128ms, and enable WDT.
> +	 */
> +	timeout = 128 * wdt->rate / 1000;
> +
> +	writel(0, wdt->base + WDT_EN);
> +	writel(1, wdt->base + WDT_RST);
> +	writel(timeout, wdt->base + WDT_BITE_TIME);
> +	writel(1, wdt->base + WDT_EN);
> +
> +	/*
> +	 * Actually make sure the above sequence hits hardware before sleeping.
> +	 */
> +	wmb();
> +
> +	msleep(150);
> +	return NOTIFY_DONE;
> +}
> +
>   static int qcom_wdt_probe(struct platform_device *pdev)
>   {
>   	struct qcom_wdt *wdt;
> @@ -147,6 +176,14 @@ static int qcom_wdt_probe(struct platform_device *pdev)
>   		goto err_clk_unprepare;
>   	}
>
> +	/*
> +	 * WDT restart notifier has priority 0 (use as a last resort)
> +	 */
> +	wdt->restart_nb.notifier_call = qcom_wdt_restart;
> +	ret = register_restart_handler(&wdt->restart_nb);
> +	if (ret)
> +		dev_err(&pdev->dev, "failed to setup restart handler\n");
> +
>   	platform_set_drvdata(pdev, wdt);
>   	return 0;
>
> @@ -159,6 +196,7 @@ static int qcom_wdt_remove(struct platform_device *pdev)
>   {
>   	struct qcom_wdt *wdt = platform_get_drvdata(pdev);
>
> +	unregister_restart_handler(&wdt->restart_nb);
>   	watchdog_unregister_device(&wdt->wdd);
>   	clk_disable_unprepare(wdt->clk);
>   	return 0;
>

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