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

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Message-ID: <AKoADwCwDn4bllbdA00CnKoA.3.1618024305455.Hmail.wangqing@vivo.com>
Date:   Sat, 10 Apr 2021 11:11:45 +0800 (GMT+08:00)
From:   王擎 <wangqing@...o.com>
To:     Guenter Roeck <linux@...ck-us.net>
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: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
>
Yes, the real timeout will happen. After WDT timeout, IRQ is sent out instead of 
reset signal first. In order to ensure that CPU does not get stuck after IRQ is sent out, 
WDT will time again and send reset signal to reset.

Thanks.
Qing Wang.