Re: [PATCH 1/2] watchdog: s3c2410_wdt: Use Use devm_clk_get[_optional]_enabled() helpers

[Krzysztof Kozlowski]

On 05/03/2023 12:15, Uwe Kleine-König wrote:
> Hello Guenter,
> 
> On Sat, Mar 04, 2023 at 02:10:47PM -0800, Guenter Roeck wrote:
>> On 3/4/23 13:46, Christophe JAILLET wrote:
>>> Le 04/03/2023 à 17:56, Guenter Roeck a écrit :
>>>> The devm_clk_get[_optional]_enabled() helpers:
>>>>      - call devm_clk_get[_optional]()
>>>>      - call clk_prepare_enable() and register what is needed in order to
>>>>        call clk_disable_unprepare() when needed, as a managed resource.
>>>>
>>>> This simplifies the code and avoids the calls to clk_disable_unprepare().
>>>>
>>>> While at it, use dev_err_probe consistently, and use its return value
>>>> to return the error code.
>>>>
>>>> Cc: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
>>>> Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
>>>> ---
>>>>   drivers/watchdog/s3c2410_wdt.c | 45 +++++++---------------------------
>>>>   1 file changed, 9 insertions(+), 36 deletions(-)
>>>>
>>>> diff --git a/drivers/watchdog/s3c2410_wdt.c b/drivers/watchdog/s3c2410_wdt.c
>>>> index 200ba236a72e..a1fcb79b0b7c 100644
>>>> --- a/drivers/watchdog/s3c2410_wdt.c
>>>> +++ b/drivers/watchdog/s3c2410_wdt.c
>>>> @@ -661,35 +661,17 @@ static int s3c2410wdt_probe(struct platform_device *pdev)
>>>>       if (IS_ERR(wdt->reg_base))
>>>>           return PTR_ERR(wdt->reg_base);
>>>> -    wdt->bus_clk = devm_clk_get(dev, "watchdog");
>>>> -    if (IS_ERR(wdt->bus_clk)) {
>>>> -        dev_err(dev, "failed to find bus clock\n");
>>>> -        return PTR_ERR(wdt->bus_clk);
>>>> -    }
>>>> -
>>>> -    ret = clk_prepare_enable(wdt->bus_clk);
>>>> -    if (ret < 0) {
>>>> -        dev_err(dev, "failed to enable bus clock\n");
>>>> -        return ret;
>>>> -    }
>>>> +    wdt->bus_clk = devm_clk_get_enabled(dev, "watchdog");
>>>> +    if (IS_ERR(wdt->bus_clk))
>>>> +        return dev_err_probe(dev, PTR_ERR(wdt->bus_clk), "failed to get bus clock\n");
>>>>       /*
>>>>        * "watchdog_src" clock is optional; if it's not present -- just skip it
>>>>        * and use "watchdog" clock as both bus and source clock.
>>>>        */
>>>> -    wdt->src_clk = devm_clk_get_optional(dev, "watchdog_src");
>>>> -    if (IS_ERR(wdt->src_clk)) {
>>>> -        dev_err_probe(dev, PTR_ERR(wdt->src_clk),
>>>> -                  "failed to get source clock\n");
>>>> -        ret = PTR_ERR(wdt->src_clk);
>>>> -        goto err_bus_clk;
>>>> -    }
>>>> -
>>>> -    ret = clk_prepare_enable(wdt->src_clk);
>>>> -    if (ret) {
>>>> -        dev_err(dev, "failed to enable source clock\n");
>>>> -        goto err_bus_clk;
>>>> -    }
>>>> +    wdt->src_clk = devm_clk_get_optional_enabled(dev, "watchdog_src");
>>>> +    if (IS_ERR(wdt->src_clk))
>>>> +        return dev_err_probe(dev, PTR_ERR(wdt->src_clk), "failed to get source clock\n");
>>>>       wdt->wdt_device.min_timeout = 1;
>>>>       wdt->wdt_device.max_timeout = s3c2410wdt_max_timeout(wdt);
>>>> @@ -710,7 +692,7 @@ static int s3c2410wdt_probe(struct platform_device *pdev)
>>>>                    S3C2410_WATCHDOG_DEFAULT_TIME);
>>>>           } else {
>>>>               dev_err(dev, "failed to use default timeout\n");
>>>> -            goto err_src_clk;
>>>> +            return ret;
>>>
>>> Hi,
>>>
>>> Nit: this also could be "return dev_err_probe()"
>>>
>>>>           }
>>>>       }
>>>> @@ -718,7 +700,7 @@ static int s3c2410wdt_probe(struct platform_device *pdev)
>>>>                      pdev->name, pdev);
>>>>       if (ret != 0) {
>>>>           dev_err(dev, "failed to install irq (%d)\n", ret);
>>>> -        goto err_src_clk;
>>>> +        return ret;
>>>
>>> Nit: this also could be "return dev_err_probe()"
>>>
>>
>> The primary reason to call dev_err_probe() is that the error may be
>> -EPROBE_DEFER, in which case the error message is suppressed.
>> That is not the case for those two functions; they never return
>> -EPROBE_DEFER. Calling dev_err_probe() would give the false impression
>> that the functions _might_ return -EPROBE_DEFER.
> 
> That is subjective. In my book dev_err_probe() handling -EPROBE_DEFER is
> only one aspect. Another is that using it allows to have return and error
> message in a single line and also that if already other exit paths use
> it to get a consistent style for the emitted messages. Having said that
> *I* wouldn't assume that the previous call might return -EPROBE_DEFER
> just because dev_err_probe() is used.
> 

I agree with this. I stopped looking at dev_err_probe() as related to
deferred probe. It is just useful helper in the context of probe. With
or without defer.

Best regards,
Krzysztof