linux-kernel - Re: [PATCHv2 6/6] thermal: exynos: Add runtime power management for tmu

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Date:   Sat, 21 May 2022 15:22:13 +0530
From:   Anand Moon <linux.amoon@...il.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Bartlomiej Zolnierkiewicz <bzolnier@...il.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Amit Kucheria <amitk@...nel.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Linux PM list <linux-pm@...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>
Subject: Re: [PATCHv2 6/6] thermal: exynos: Add runtime power management for tmu

Hi Krzysztof,

On Wed, 18 May 2022 at 12:49, Krzysztof Kozlowski
<krzysztof.kozlowski@...aro.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@...aro.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

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

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?

>
> Best regards,
> Krzysztof

Thanks and Regards

-Anand