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

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Message-ID: <247dcdfa-3761-4745-bdc8-88edf8cd06ea@roeck-us.net>
Date: Wed, 31 Jan 2024 05:14:08 -0800
From: Guenter Roeck <linux@...ck-us.net>
To: Biju Das <biju.das.jz@...renesas.com>,
 "Claudiu.Beznea" <claudiu.beznea@...on.dev>,
 "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 1/31/24 02:41, 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?
> 

You mean what the watchdog subsystem does if a driver violates its API ?
That is undefined. The API says:

* start: this is a pointer to the routine that starts the watchdog timer
   device.
   The routine needs a pointer to the watchdog timer device structure as a
   parameter. It returns zero on success or a negative errno code for failure.
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

We are not going to change the API, if that is what you are suggesting.

Thanks,
Guenter