linux-kernel - Re: [PATCH v2 04/11] watchdog: rzg2l_wdt: Check return status of pm_runtime

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Message-ID: <d52cded7-fef5-4bfa-a82f-6a6c77dd7ebc@tuxon.dev>
Date: Thu, 1 Feb 2024 08:11:30 +0200
From: claudiu beznea <claudiu.beznea@...on.dev>
To: Guenter Roeck <linux@...ck-us.net>, Biju Das
 <biju.das.jz@...renesas.com>, "wim@...ux-watchdog.org"
 <wim@...ux-watchdog.org>, "robh+dt@...nel.org" <robh+dt@...nel.org>,
 "krzysztof.kozlowski+dt@...aro.org" <krzysztof.kozlowski+dt@...aro.org>,
 "conor+dt@...nel.org" <conor+dt@...nel.org>,
 "geert+renesas@...der.be" <geert+renesas@...der.be>,
 "magnus.damm@...il.com" <magnus.damm@...il.com>,
 "mturquette@...libre.com" <mturquette@...libre.com>,
 "sboyd@...nel.org" <sboyd@...nel.org>,
 "p.zabel@...gutronix.de" <p.zabel@...gutronix.de>
Cc: "linux-watchdog@...r.kernel.org" <linux-watchdog@...r.kernel.org>,
 "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "linux-renesas-soc@...r.kernel.org" <linux-renesas-soc@...r.kernel.org>,
 "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
 Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
Subject: Re: [PATCH v2 04/11] watchdog: rzg2l_wdt: Check return status of
 pm_runtime_put()



On 31.01.2024 15:16, Guenter Roeck wrote:
> On 1/31/24 03:00, claudiu beznea wrote:
>>
>>
>> On 31.01.2024 12:41, Biju Das wrote:
>>> Hi Claudiu,
>>>
>>>> -----Original Message-----
>>>> From: claudiu beznea <claudiu.beznea@...on.dev>
>>>> Sent: Wednesday, January 31, 2024 10:36 AM
>>>> Subject: Re: [PATCH v2 04/11] watchdog: rzg2l_wdt: Check return status of
>>>> pm_runtime_put()
>>>>
>>>> Hi, Biju,
>>>>
>>>> On 31.01.2024 12:32, Biju Das wrote:
>>>>> Hi Claudiu,
>>>>>
>>>>> Thanks for the feedback.
>>>>>
>>>>>> -----Original Message-----
>>>>>> From: Claudiu <claudiu.beznea@...on.dev>
>>>>>> Sent: Wednesday, January 31, 2024 10:20 AM
>>>>>> Subject: [PATCH v2 04/11] watchdog: rzg2l_wdt: Check return status of
>>>>>> pm_runtime_put()
>>>>>>
>>>>>> From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>>>>>>
>>>>>> pm_runtime_put() may return an error code. Check its return status.
>>>>>>
>>>>>> Along with it the rzg2l_wdt_set_timeout() function was updated to
>>>>>> propagate the result of rzg2l_wdt_stop() to its caller.
>>>>>>
>>>>>> Fixes: 2cbc5cd0b55f ("watchdog: Add Watchdog Timer driver for
>>>>>> RZ/G2L")
>>>>>> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>>>>>> ---
>>>>>>
>>>>>> Changes in v2:
>>>>>> - propagate the return code of rzg2l_wdt_stop() to it's callers
>>>>>>
>>>>>>   drivers/watchdog/rzg2l_wdt.c | 11 +++++++++--
>>>>>>   1 file changed, 9 insertions(+), 2 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/watchdog/rzg2l_wdt.c
>>>>>> b/drivers/watchdog/rzg2l_wdt.c index d87d4f50180c..7bce093316c4
>>>>>> 100644
>>>>>> --- a/drivers/watchdog/rzg2l_wdt.c
>>>>>> +++ b/drivers/watchdog/rzg2l_wdt.c
>>>>>> @@ -144,9 +144,13 @@ static int rzg2l_wdt_start(struct
>>>>>> watchdog_device
>>>>>> *wdev)  static int rzg2l_wdt_stop(struct watchdog_device *wdev)  {
>>>>>>       struct rzg2l_wdt_priv *priv = watchdog_get_drvdata(wdev);
>>>>>> +    int ret;
>>>>>>
>>>>>>       rzg2l_wdt_reset(priv);
>>>>>> -    pm_runtime_put(wdev->parent);
>>>>>> +
>>>>>> +    ret = pm_runtime_put(wdev->parent);
>>>>>> +    if (ret < 0)
>>>>>> +        return ret;
>>>>>
>>>>> Do we need to check the return code? So far we didn't hit this
>>>> condition.
>>>>> If you are planning to do it, then just
>>>>>
>>>>> return pm_runtime_put(wdev->parent);
>>>>
>>>> pm_runtime_put() may return 1 if the device is suspended (which is not
>>>> considered error) as explained here:
>>>
>>> Oops, I missed that discussion. Out of curiosity,
>>> What watchdog framework/consumer is going to do with a
>>> Non-error return value of 1?
>>
>> Looking at this:
>> https://elixir.bootlin.com/linux/latest/source/drivers/watchdog/watchdog_dev.c#L809
>>
>> it seems that the positive values are not considered errors thus, indeed,
>> we may return directly:
>>
>> return pm_runtime_put();
>>
>> Guenter,
>>
>> With this (and previous discussion from [1]), are you OK to change it like:
>>
>> return pm_runtime_put();
>>
> 
> Instead of looking at the source, I would kindly ask you to look at the API.

OK, I'll keep the patch as is. Thank you for your input.

Claudiu Beznea

> 
> Guenter
>