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Sender: Guenter Roeck <groeck7@gmail.com>
Subject: Re: [PATCH V7 1/2] watchdog: mtk: support pre-timeout when the bark
 irq is available
To:     Wang Qing <wangqing@vivo.com>,
        Wim Van Sebroeck <wim@linux-watchdog.org>,
        Rob Herring <robh+dt@kernel.org>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        linux-watchdog@vger.kernel.org, devicetree@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org,
        linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org
References: <1619146403-12769-1-git-send-email-wangqing@vivo.com>
 <1619146403-12769-2-git-send-email-wangqing@vivo.com>
From:   Guenter Roeck <linux@roeck-us.net>
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Message-ID: <0de7e5c8-57a2-9b27-d8a8-ed7e0b394b02@roeck-us.net>
Date:   Thu, 22 Apr 2021 20:28:58 -0700
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In-Reply-To: <1619146403-12769-2-git-send-email-wangqing@vivo.com>
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Precedence: bulk

On 4/22/21 7:53 PM, Wang Qing wrote:
> Use the bark interrupt as the pretimeout notifier if available.
> 
> When the watchdog timer expires in dual mode, an interrupt will be
> triggered first, then the timing restarts. The reset signal will be
> initiated when the timer expires again.
> 
> The pretimeout notification shall occur at timeout-sec/2.
> 
> V2:
> - panic() by default if WATCHDOG_PRETIMEOUT_GOV is not enabled.
> 
> V3:
> - Modify the pretimeout behavior, manually reset after the pretimeout
> - is processed and wait until timeout.
> 
> V4:
> - Remove pretimeout related processing. 
> - Add dual mode control separately.
> 
> V5:
> - Fix some formatting and printing problems.
> 
> V6:
> - Realize pretimeout processing through dualmode.
> 
> V7:
> - Add set_pretimeout().
> 
> Signed-off-by: Wang Qing <wangqing@vivo.com>
> ---
>  drivers/watchdog/mtk_wdt.c | 76 +++++++++++++++++++++++++++++++++++++++++++---
>  1 file changed, 71 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/watchdog/mtk_wdt.c b/drivers/watchdog/mtk_wdt.c
> index 97ca993..ab3ac5d
> --- a/drivers/watchdog/mtk_wdt.c
> +++ b/drivers/watchdog/mtk_wdt.c
> @@ -25,6 +25,7 @@
>  #include <linux/reset-controller.h>
>  #include <linux/types.h>
>  #include <linux/watchdog.h>
> +#include <linux/interrupt.h>
>  
>  #define WDT_MAX_TIMEOUT		31
>  #define WDT_MIN_TIMEOUT		1
> @@ -184,15 +185,23 @@ static int mtk_wdt_set_timeout(struct watchdog_device *wdt_dev,
>  {
>  	struct mtk_wdt_dev *mtk_wdt = watchdog_get_drvdata(wdt_dev);
>  	void __iomem *wdt_base = mtk_wdt->wdt_base;
> +	unsigned int timeout_interval = timeout;
>  	u32 reg;
>  
>  	wdt_dev->timeout = timeout;
> -
> +	/*
> +	 * In dual mode, irq will be triggered at timeout / 2
> +	 * the real timeout occurs at timeout
> +	 */
> +	if (wdt_dev->pretimeout) {
> +		wdt_dev->pretimeout = timeout / 2;

min_timeout is set to 1. I don't this works well if timeout == 1.
You'll either need to set min_timeout to 2, or handle that case.

> +		timeout_interval = wdt_dev->pretimeout;

timeout_interval is unnecessary. Just update timeout accordingly.
It needs to take the situation of timeout == 1 into account, though.

> +	}
>  	/*
>  	 * One bit is the value of 512 ticks
>  	 * The clock has 32 KHz
>  	 */
> -	reg = WDT_LENGTH_TIMEOUT(timeout << 6) | WDT_LENGTH_KEY;
> +	reg = WDT_LENGTH_TIMEOUT(timeout_interval << 6) | WDT_LENGTH_KEY;
>  	iowrite32(reg, wdt_base + WDT_LENGTH);
>  
>  	mtk_wdt_ping(wdt_dev);
> @@ -239,13 +248,46 @@ static int mtk_wdt_start(struct watchdog_device *wdt_dev)
>  		return ret;
>  
>  	reg = ioread32(wdt_base + WDT_MODE);
> -	reg &= ~(WDT_MODE_IRQ_EN | WDT_MODE_DUAL_EN);
> +	if (wdt_dev->pretimeout)
> +		reg |= (WDT_MODE_IRQ_EN | WDT_MODE_DUAL_EN);
> +	else
> +		reg &= ~(WDT_MODE_IRQ_EN | WDT_MODE_DUAL_EN);
>  	reg |= (WDT_MODE_EN | WDT_MODE_KEY);
>  	iowrite32(reg, wdt_base + WDT_MODE);
>  
>  	return 0;
>  }
>  
> +static int mtk_wdt_set_pretimeout(struct watchdog_device *wdd,
> +					unsigned int timeout)
> +{
> +	struct mtk_wdt_dev *mtk_wdt = watchdog_get_drvdata(wdd);
> +	void __iomem *wdt_base = mtk_wdt->wdt_base;
> +	u32 reg = ioread32(wdt_base + WDT_MODE);
> +
> +	if (timeout && !wdd->pretimeout) {
> +		wdd->pretimeout = wdd->timeout / 2;
> +		reg |= (WDT_MODE_IRQ_EN | WDT_MODE_DUAL_EN);
> +	} else if (!timeout && wdd->pretimeout) {
> +		wdd->pretimeout = 0;
> +		reg &= ~(WDT_MODE_IRQ_EN | WDT_MODE_DUAL_EN);
> +	} else
> +		return 0;
> +
> +	iowrite32(reg, wdt_base + WDT_MODE);

What is the point of setting the mode here ? It will
be set again in mtk_wdt_set_timeout(). Seems to me all
you need to do here is to set wdd->pretimeout,
then call mtk_wdt_set_timeout().

Guenter

> +
> +	return mtk_wdt_set_timeout(wdd, wdd->timeout);
> +}
> +
> +static irqreturn_t mtk_wdt_isr(int irq, void *arg)
> +{
> +	struct watchdog_device *wdd = arg;
> +
> +	watchdog_notify_pretimeout(wdd);
> +
> +	return IRQ_HANDLED;
> +}
> +
>  static const struct watchdog_info mtk_wdt_info = {
>  	.identity	= DRV_NAME,
>  	.options	= WDIOF_SETTIMEOUT |
> @@ -253,12 +295,21 @@ static const struct watchdog_info mtk_wdt_info = {
>  			  WDIOF_MAGICCLOSE,
>  };
>  
> +static const struct watchdog_info mtk_wdt_pt_info = {
> +	.identity	= DRV_NAME,
> +	.options	= WDIOF_SETTIMEOUT |
> +			  WDIOF_PRETIMEOUT |
> +			  WDIOF_KEEPALIVEPING |
> +			  WDIOF_MAGICCLOSE,
> +};
> +
>  static const struct watchdog_ops mtk_wdt_ops = {
>  	.owner		= THIS_MODULE,
>  	.start		= mtk_wdt_start,
>  	.stop		= mtk_wdt_stop,
>  	.ping		= mtk_wdt_ping,
>  	.set_timeout	= mtk_wdt_set_timeout,
> +	.set_pretimeout	= mtk_wdt_set_pretimeout,
>  	.restart	= mtk_wdt_restart,
>  };
>  
> @@ -267,7 +318,7 @@ static int mtk_wdt_probe(struct platform_device *pdev)
>  	struct device *dev = &pdev->dev;
>  	struct mtk_wdt_dev *mtk_wdt;
>  	const struct mtk_wdt_data *wdt_data;
> -	int err;
> +	int err, irq;
>  
>  	mtk_wdt = devm_kzalloc(dev, sizeof(*mtk_wdt), GFP_KERNEL);
>  	if (!mtk_wdt)
> @@ -279,7 +330,22 @@ static int mtk_wdt_probe(struct platform_device *pdev)
>  	if (IS_ERR(mtk_wdt->wdt_base))
>  		return PTR_ERR(mtk_wdt->wdt_base);
>  
> -	mtk_wdt->wdt_dev.info = &mtk_wdt_info;
> +	irq = platform_get_irq(pdev, 0);
> +	if (irq > 0) {
> +		err = devm_request_irq(&pdev->dev, irq, mtk_wdt_isr, 0, "wdt_bark",
> +					&mtk_wdt->wdt_dev);
> +		if (err)
> +			return err;
> +
> +		mtk_wdt->wdt_dev.info = &mtk_wdt_pt_info;
> +		mtk_wdt->wdt_dev.pretimeout = WDT_MAX_TIMEOUT / 2;
> +	} else {
> +		if (irq == -EPROBE_DEFER)
> +			return -EPROBE_DEFER;
> +
> +		mtk_wdt->wdt_dev.info = &mtk_wdt_info;
> +	}
> +
>  	mtk_wdt->wdt_dev.ops = &mtk_wdt_ops;
>  	mtk_wdt->wdt_dev.timeout = WDT_MAX_TIMEOUT;
>  	mtk_wdt->wdt_dev.max_hw_heartbeat_ms = WDT_MAX_TIMEOUT * 1000;
>