linux-kernel - Re: [PATCH 1/5] thermal: exynos: enable core tmu clk on exynos platform

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Date:   Wed, 18 Jul 2018 08:17:50 +0200
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     Anand Moon <linux.amoon@...il.com>
Cc:     Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Zhang Rui <rui.zhang@...el.com>,
        Eduardo Valentin <edubezval@...il.com>,
        Kukjin Kim <kgene@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Linux PM list <linux-pm@...r.kernel.org>,
        "linux-samsung-soc@...r.kernel.org" 
        <linux-samsung-soc@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel <linux-kernel@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>
Subject: Re: [PATCH 1/5] thermal: exynos: enable core tmu clk on exynos platform

On 17 July 2018 at 22:23, Anand Moon <linux.amoon@...il.com> wrote:
> Hi Krzysztof
>
> On 17 July 2018 at 17:50, Krzysztof Kozlowski <krzk@...nel.org> wrote:
>> Hi Anand,
>>
>> Thanks for patch.
>>
>> On 17 July 2018 at 12:12, Anand Moon <linux.amoon@...il.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