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

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Date:   Fri, 9 Apr 2021 19:56:45 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     王擎 <wangqing@...o.com>
Cc:     Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        linux-watchdog@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] watchdog: mtk: support pre-timeout when the bark irq is
 available

On 4/9/21 7:42 PM, 王擎 wrote:
> 
>> On 4/9/21 2:55 AM, Wang Qing wrote:
>>> Use the bark interrupt as the pretimeout notifier if available.
>>>
>>> By default, the pretimeout notification shall occur one second earlier
>>> than the timeout.
>>>
>>> Signed-off-by: Wang Qing <wangqing@...o.com>
>>> ---
>>>  drivers/watchdog/mtk_wdt.c | 47 +++++++++++++++++++++++++++++++++++++++++++---
>>>  1 file changed, 44 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/watchdog/mtk_wdt.c b/drivers/watchdog/mtk_wdt.c
>>> index 97ca993..8b919cc
>>> --- 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
>>> @@ -234,18 +235,35 @@ static int mtk_wdt_start(struct watchdog_device *wdt_dev)
>>>  	void __iomem *wdt_base = mtk_wdt->wdt_base;
>>>  	int ret;
>>>  
>>> -	ret = mtk_wdt_set_timeout(wdt_dev, wdt_dev->timeout);
>>> +	ret = mtk_wdt_set_timeout(wdt_dev, wdt_dev->timeout - wdt_dev->pretimeout);
>>
>> That looks suspiciously like the real watchdog won't happen at all.
>> What will happen if the pretimeout governor is set to none ?
>>
>> Guenter
>>
> The pretimeout governor is panic by default. If pretimeout is enabled and the governor is
> set to none, it means the timeout behavior does not need to be processed, only printing.
> 

That was not my question. My question was if the real timeout happens in that case.

Guenter