Message-ID: <58cab864-2a59-b82c-bdfe-2e805a04fd7a@starfivetech.com>
Date:   Mon, 27 Feb 2023 14:26:32 +0800
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Subject: Re: [PATCH v3 2/2] drivers: watchdog: Add StarFive Watchdog driver
Content-Language: en-US
To:     Guenter Roeck <linux@roeck-us.net>
CC:     <linux-riscv@lists.infradead.org>, <devicetree@vger.kernel.org>,
        <linux-watchdog@vger.kernel.org>,
        Wim Van Sebroeck <wim@linux-watchdog.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Rob Herring <robh+dt@kernel.org>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        "Palmer Dabbelt" <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        "Philipp Zabel" <p.zabel@pengutronix.de>,
        Samin Guo <samin.guo@starfivetech.com>,
        <linux-kernel@vger.kernel.org>, Conor Dooley <conor@kernel.org>
References: <20230220081926.267695-1-xingyu.wu@starfivetech.com>
 <20230220081926.267695-3-xingyu.wu@starfivetech.com>
 <20230223182341.GA200380@roeck-us.net>
 <8ba002ea-299c-2eaf-b1a7-d7d38a540152@starfivetech.com>
 <ae998eb6-54ce-05c4-2961-bdb2393eac64@roeck-us.net>
From:   Xingyu Wu <xingyu.wu@starfivetech.com>
In-Reply-To: <ae998eb6-54ce-05c4-2961-bdb2393eac64@roeck-us.net>
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Precedence: bulk

On 2023/2/24 23:18, Guenter Roeck wrote:
> On 2/23/23 23:42, Xingyu Wu wrote:
>> On 2023/2/24 2:23, Guenter Roeck wrote:
>>> On Mon, Feb 20, 2023 at 04:19:26PM +0800, Xingyu Wu wrote:
>>>> [...]
>>>> +
>>>> +    wdt->wdt_device.min_timeout = 1;
>>>> +    wdt->wdt_device.max_timeout = starfive_wdt_max_timeout(wdt);
>>>
>>>     wdt->wdt_device.timeout = STARFIVE_WDT_DEFAULT_TIME;
>>>
>>> should be set here. Otherwise the warning below would always be seen
>>> if the module parameter is not set.
>>>
>>>> +
>>>> +    watchdog_set_drvdata(&wdt->wdt_device, wdt);
>>>> +
>>>> +    /*
>>>> +     * see if we can actually set the requested heartbeat,
>>>> +     * and if not, try the default value.
>>>> +     */
>>>> +    watchdog_init_timeout(&wdt->wdt_device, heartbeat, dev);
>>>> +    if (wdt->wdt_device.timeout == 0 ||
>>>
>>> If wdt->wdt_device.timeout is pre-initialized, it will never be 0 here.
>>>
>>>> +        wdt->wdt_device.timeout > wdt->wdt_device.max_timeout) {
>>>
>>> That won't happen because watchdog_init_timeout() validates it and does
>>> not update the value if it is out of range.
>>>
>>>> +        dev_warn(dev, "heartbeat value out of range, default %d used\n",
>>>> +             STARFIVE_WDT_DEFAULT_TIME);
>>>> +        wdt->wdt_device.timeout = STARFIVE_WDT_DEFAULT_TIME;
>>>
>>> And this is then unnecessary. wdt->wdt_device.timeout will always be
>>> valid if it was pre-initialized.
>>
>> It is changed to be this at beginning of the driver:
>>
>> static int heartbeat = STARFIVE_WDT_DEFAULT_TIME;
>>
> 
> No, this is wrong. The static variable should be set to 0 to indicate
> "use default".
> 
>> and it is changed to be this here:
>>
>> ret = watchdog_init_timeout(&wdt->wdt_device, heartbeat, dev);
>> if (ret)
>>     return ret;
>>
>> Would that be better?
>>
> 
> No, it is worse, because it would not instantiate the watchdog at all
> if a bad heartbeat is provided.
> 

So instantiate the watchdog with hearbeat first. And if this wrong, use default timeout.
:
if (watchdog_init_timeout(&wdt->wdt_device, heartbeat, dev))
	wdt->wdt_device.timeout = STARFIVE_WDT_DEFAULT_TIME;


Best regards,
Xingyu Wu