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From:   Anand Moon <linux.amoon@gmail.com>
Date:   Wed, 18 Jul 2018 14:54:30 +0530
Message-ID: <CANAwSgRFehdmYZvPL3yD1=Ng_w1Yhtij=nvZEOqkof7zj8fcwA@mail.gmail.com>
Subject: Re: [PATCH 1/5] thermal: exynos: enable core tmu clk on exynos platform
To:     Krzysztof Kozlowski <krzk@kernel.org>
Cc:     Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
        Zhang Rui <rui.zhang@intel.com>,
        Eduardo Valentin <edubezval@gmail.com>,
        Kukjin Kim <kgene@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Linux PM list <linux-pm@vger.kernel.org>,
        "linux-samsung-soc@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>,
        devicetree <devicetree@vger.kernel.org>
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Hi Krzysztof

On 18 July 2018 at 11:47, Krzysztof Kozlowski <krzk@kernel.org> wrote:
> On 17 July 2018 at 22:23, Anand Moon <linux.amoon@gmail.com> wrote:
>> Hi Krzysztof
>>
>> On 17 July 2018 at 17:50, Krzysztof Kozlowski <krzk@kernel.org> wrote:
>>> Hi Anand,
>>>
>>> Thanks for patch.
>>>
>>> On 17 July 2018 at 12:12, Anand Moon <linux.amoon@gmail.com> wrote:
>>>> clk_summary do not show tmu_apbif clk enable, so replace
>>>> the clk_prepare with clk_prepare_enables to enable tmu clk.
>>>
>>> This is not valid reason to do a change. What is clk_summary does not
>>> really matter. Your change has negative impact on power consumption as
>>> the clock stays enabled all the time. This is not what we want... so
>>> please explain it more - why you need the clock to be enabled all the
>>> time? What is broken (clk_summary is not broken in this case)?
>>>
>>
>> Opps I could not explain some more in my commit message.
>>
>> Actually TMU sensor for Exynos process are controlled by so external clk
>>
>> Exynos4412 have VDD18_TS sensor which controls the CLK_SENSE tmu.
>> Exynos5422 have VDD18_TS01 / VDD18_TS23 / VDD18_TS4 sensor which
>> control the CLK_SENSE tmu.
>>
>> So as per my understanding tmu is clk driver which control the flow  PMIC.
>>
>> clk_prepare_enable combine clk_prepare and clk_enable
>> and clk_disable_unprepare combine clk_disable and clk_unprepare.
>>
>> most of the driver prefer clk_prepare_enable and clk_disable_unprepare.
>>
>> clk_summary is just a reference looking point where we could check the
>> clk is enable/disable.
>>
>> what is broken ?
>> I still few more parameter need to tuned to configure the tmu driver.
>
> I am sorry but I am still unable to see what is broken and what are
> you trying to fix. I asked what is broken and you replied that there
> is a sensor, there is a clock, drivers use clk_prepare_enable and some
> more parameter need to be tuned... None of these are answers to
> question - what is broken. How can I reproduce the problem?
>
> Best regards,
> Krzysztof

Basically I use thermal testing.

# git clone https://git.linaro.org/power/pm-qa.git
# cd pm-qa
# make -C thermal check

most of the testcase failed on Exynos5422 but some pass on Exynos4412.

Attach is the software overview from Exynos5422 user manual.

I am not able to explain in deep technically, but I have studied other thermal
driver to draw into conclusion that tmu clk's need to be enabled.

If you feel the we should not enable these clk, them I will drop the
clk_prepare_enable check
and resubmit the changes with better commit message.

Best Regards
-Anand

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