linux-kernel - Re: [PATCH v1] watchdog: starfive: Fix the probe return error if PM and early

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Date:   Wed, 26 Apr 2023 09:49:48 +0800
From:   Xingyu Wu <xingyu.wu@...rfivetech.com>
To:     Guenter Roeck <linux@...ck-us.net>,
        <linux-watchdog@...r.kernel.org>,
        "Wim Van Sebroeck" <wim@...ux-watchdog.org>
CC:     Samin Guo <samin.guo@...rfivetech.com>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1] watchdog: starfive: Fix the probe return error if PM
 and early_enable are both disabled

On 2023/4/25 22:06, Guenter Roeck wrote:
> On 4/25/23 03:04, Xingyu Wu wrote:
>> When the starfive watchdog driver uses 'pm_runtime_put_sync()' as probe
>> return value at last and 'early_enable' is disabled, it could return the
>> error '-ENOSYS' if the CONFIG_PM is disabled, but the driver should works
>> normally.
>>
>> Add a check to make sure the PM is enabled and then use
>> 'pm_runtime_put_sync()' as return value when 'early_enable' is disabled.
>>
>> Fixes: db728ea9c7be ("drivers: watchdog: Add StarFive Watchdog driver")
>> Signed-off-by: Xingyu Wu <xingyu.wu@...rfivetech.com>
>> ---
>>
>> Hi, Guenter and Wim,
>>
>> This patch fixes the issue of StarFive watchdog driver and rebases on
>> the master branch of linux-next.
>>
>> Thanks.
>>   ---
>>   drivers/watchdog/starfive-wdt.c | 3 ++-
>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/watchdog/starfive-wdt.c b/drivers/watchdog/starfive-wdt.c
>> index 1995cceca51e..51e487e09960 100644
>> --- a/drivers/watchdog/starfive-wdt.c
>> +++ b/drivers/watchdog/starfive-wdt.c
>> @@ -492,7 +492,8 @@ static int starfive_wdt_probe(struct platform_device *pdev)
>>           goto err_exit;
>>         if (!early_enable)
>> -        return pm_runtime_put_sync(&pdev->dev);
>> +        if (pm_runtime_enabled(&pdev->dev))
>> +            return pm_runtime_put_sync(&pdev->dev);
>>   
> 
> Why not just
> 
>     if (!early_enable)
>         pm_runtime_put_sync(&pdev->dev)
> 
> like almost every other caller of pm_runtime_put_sync() ?
> 

The function of pm_runtime_put_sync() is that:

static inline int pm_runtime_put_sync(struct device *dev)
{
	return __pm_runtime_idle(dev, RPM_GET_PUT);
}

and when do not enable CONFIG_PM, the __pm_runtime_idle() is that:

static inline int __pm_runtime_idle(struct device *dev, int rpmflags)
{
	return -ENOSYS;
}

If I do not open PM, it will return error saying probe failed
but it works fine without PM. I had tested that and probe really
was failed. So I should add this check before using pm_runtime_put_sync().

Best regards,
Xingyu Wu