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

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Date:   Wed, 18 Jul 2018 01:53:59 +0530
From:   Anand Moon <linux.amoon@...il.com>
To:     Krzysztof Kozlowski <krzk@...nel.org>
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

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.

>> simplify the enable of tmu_triminfo_apbif clk, also fixed
>> the order of goto error for failed cases.
>
> This has to be split into separate change.
>
> Best regards,
> Krzysztof

Best Regards
-Anand