linux-kernel - Re: [PATCH v2 4/7] thermal: exynos: simplify regulator (de)initialization

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Date:   Tue, 3 Oct 2023 11:06:00 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Marek Szyprowski <m.szyprowski@...sung.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        m.majewski2@...sung.com,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "linux-samsung-soc@...r.kernel.org" 
        <linux-samsung-soc@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc:     Bartlomiej Zolnierkiewicz <bzolnier@...il.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Amit Kucheria <amitk@...nel.org>,
        Zhang Rui <rui.zhang@...el.com>,
        ALIM AKHTAR <alim.akhtar@...sung.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH v2 4/7] thermal: exynos: simplify regulator
 (de)initialization

On 29/09/2023 14:00, Marek Szyprowski wrote:
> On 29.09.2023 13:45, Daniel Lezcano wrote:
>> On 29/09/2023 13:03, Marek Szyprowski wrote:
>>> On 29.09.2023 12:46, Daniel Lezcano wrote:
>>>> On 26/09/2023 13:02, Mateusz Majewski wrote:
>>>>> Hi,
>>>>>
>>>>>> This is not equivalent. If regulator is provided and enable fails, 
>>>>>> the
>>>>>> old code is nicely returning error. Now, it will print misleading
>>>>>> message - failed to get regulator - and continue.
>>>>>>
>>>>>> While this simplifies the code, it ignores important running
>>>>>> condition -
>>>>>> having regulator enabled.
>>>>>
>>>>> Would doing this be correct?
>>>>>
>>>>> ret = devm_regulator_get_enable_optional(&pdev->dev, "vtmu");
>>>>> switch (ret) {
>>>>> case 0:
>>>>> case -ENODEV:
>>>>
>>>> Not sure to understand why -NODEV is not an error
>>>
>>>
>>> Because this what devm_regulator_get_enable_optional() returns if no
>>> regulator is defined. I also got confused by this a few times.
>>
>> The code before this change calls devm_regulator_get_optional() which 
>> returns -ENODEV too, right ? But there is no special case for this error.
>>
>> So this change uses devm_regulator_get_enable_optional() and handle 
>> the ENODEV as a non-error, so there is a change in the behavior.
> 
> 
> It looks that the original code ignores any non-EPROBE_DEFER errors from 
> devm_regulator_get_optional(). That's a bug, indeed.

How about separate change fixing it? I know the same code will be
changed twice, but it will be easier to backport and analyze in case of
issues.

Best regards,
Krzysztof