linux-kernel - Re: [PATCH V6 1/2] watchdog: mtk: support pre-timeout when the bark irq is available

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Message-ID: <740481ed-97e0-3439-1af2-bc54cdb28536@roeck-us.net>
Date:   Wed, 21 Apr 2021 20:31:21 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Wang Qing <wangqing@...o.com>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Rob Herring <robh+dt@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        linux-watchdog@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V6 1/2] watchdog: mtk: support pre-timeout when the bark
 irq is available

On 4/21/21 7:45 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.
> 
> Signed-off-by: Wang Qing <wangqing@...o.com>
> ---
>  drivers/watchdog/mtk_wdt.c | 53 +++++++++++++++++++++++++++++++++++++++++-----
>  1 file changed, 48 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/watchdog/mtk_wdt.c b/drivers/watchdog/mtk_wdt.c
> index 97ca993..ebc648b
> --- 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 +185,22 @@ 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;
>  	u32 reg;
>  
> -	wdt_dev->timeout = timeout;
> +	timeout_interval = wdt_dev->timeout = timeout;
> +	/*
> +	 * In dual mode, irq will be triggered at timeout/2
> +	 * the real timeout occurs at timeout
> +	 */
> +	if (wdt_dev->pretimeout)
> +		timeout_interval = wdt_dev->pretimeout = timeout/2;

Please run checkpatch --strict and fix what it reports.
Also, there should be a set_pretimeout function to set the
pretimeout. It is ok to update it here, but it should be set
in its own function to make sure that the actual value
is reported back to userspace.

Thanks,
Guenter

>  
>  	/*
>  	 * 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 +247,25 @@ 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 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 |
> @@ -253,6 +273,14 @@ 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,
> @@ -267,7 +295,7 @@ 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 +307,22 @@ 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;
>