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

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Date:   Wed, 21 Apr 2021 21:02:02 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     王擎 <wangqing@...o.com>
Cc:     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 8:46 PM, 王擎 wrote:
> 
>> 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
> 
> The reason why the set_pretimeout interface is not provided is 
> because the pretimeout is fixed after the timeout is set,  we need
> to modify timeout after setting pretimeout, which is puzzling.
> 

What you need to do is to set pretimeout = timeout / 2 if a pretimeout
is set to a value != 0. Just like we adjust timeout to valid values
when set, we adjust pretimeout as well. I don't see a problem with that.

Guenter