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Date:   Sat, 21 May 2022 16:11:37 +0200
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Subject: Re: [PATCHv2 6/6] thermal: exynos: Add runtime power management for
 tmu
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To:     Anand Moon <linux.amoon@gmail.com>
Cc:     Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        Amit Kucheria <amitk@kernel.org>,
        Zhang Rui <rui.zhang@intel.com>,
        Alim Akhtar <alim.akhtar@samsung.com>,
        Linux PM list <linux-pm@vger.kernel.org>,
        linux-samsung-soc@vger.kernel.org,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        Linux Kernel <linux-kernel@vger.kernel.org>
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From:   Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
In-Reply-To: <CANAwSgQe9uveBMgrt3VNUTmFodW3P0Pxhc28KfB8MyEogOtOjQ@mail.gmail.com>
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On 21/05/2022 11:52, Anand Moon wrote:
> Hi Krzysztof,
> 
> On Wed, 18 May 2022 at 12:49, Krzysztof Kozlowski
> <krzysztof.kozlowski@linaro.org> wrote:
>>
>> On 17/05/2022 20:45, Anand Moon wrote:
>>> Hi Krzysztof,
>>>
>>> On Sun, 15 May 2022 at 15:18, Krzysztof Kozlowski
>>> <krzysztof.kozlowski@linaro.org> wrote:
>>>>
>>>> On 15/05/2022 08:41, Anand Moon wrote:
>>>>> Add runtime power management for exynos thermal driver.
>>>>
>>>> First of all - why? Second, I do not see it being added. Where are the
>>>> runtime callbacks?
>>>>
>>>
>>> To control runtime control PMU, did I miss something?
>>
>> Controlling runtime PM by itself is not a goal. What does it change if
>> it is enabled?
>>
> It means we could have efficient power management for this driver.
> as per my understanding, it controls runtime sleep and improves power efficiency

How? I asked - what is being changed after enabling PM - and you
answered without any specifics. Where exactly is the power saving?
Please be specific, very specific.

> 
>>> I looked into imx thermal driver # drivers/thermal/imx_thermal.c
>>> to enable run-time power management for exynos driver.
>>
>> So you have runtime PM enabled and then what happens? Where is the power
>> saving? Since you did not implement the callbacks, all this should be
>> explained in commit msg.
>>
> Ok, As per the original code, it just registers the SIMPLE_DEV_PM_OPS
> with .pm = &exynos_tmu_pm

And does nothing else, right? No benefits?

> So I have made sure that suspend resume feature works correctly
>  with these changes on SBC Odroid U3 and XU4.

How is suspend/resume related to runtime PM? Are you talking about
system suspend? What do you mean now?

> 
> I will try to look into setting RUNTIME_PM_OPS
> or use UNIVERSAL_DEV_PM_OPS instead of SIMPLE_DEV_PM_OPS
> any thought on this?

Why looking at them? You avoid giving any specific answer, so we are
repeating the same and the same. Just to be sure - maybe I don't see the
obvious stuff, so please explain also this obvious things.

Please come with specifics, because otherwise I see it as a waste of our
time.

Best regards,
Krzysztof