linux-kernel - Re: [GIT PULL] Thermal management updates for v4.17-rc1

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Date:   Fri, 13 Apr 2018 11:28:56 +0200
From:   Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     Zhang Rui <rui.zhang@...el.com>,
        Eduardo Valentin <edubezval@...il.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux PM list <linux-pm@...r.kernel.org>,
        "Li, Philip" <philip.li@...el.com>
Subject: Re: [GIT PULL] Thermal management updates for v4.17-rc1

On Friday, April 13, 2018 11:19:40 AM Daniel Lezcano wrote:
> On 13/04/2018 11:08, Bartlomiej Zolnierkiewicz wrote:
> > On Friday, April 13, 2018 11:00:43 AM Daniel Lezcano wrote:
> >> On 13/04/2018 10:55, Bartlomiej Zolnierkiewicz wrote:
> >>> On Friday, April 13, 2018 01:39:05 PM Zhang Rui wrote:
> >>>> Hi, Eduardo,
> >>>>
> >>>> On 四, 2018-04-12 at 21:08 -0700, Eduardo Valentin wrote:
> >>>>> Hello,
> >>>>>
> >>>>> On Thu, Apr 12, 2018 at 09:55:19AM -0700, Linus Torvalds wrote:
> >>>>>>
> >>>>>> On Wed, Apr 11, 2018 at 10:08 PM, Zhang Rui <rui.zhang@...el.com>
> >>>>>> wrote:
> >>>>>>>
> >>>>>>>
> >>>>>>> could you please illustrate me what the kconfig & warning is?
> >>>>>> Just "make allmodconfig" and the warning is about a uninitialized
> >>>>>> variable.
> >>>>>>
> >>>>>> Line 304 in drivers/thermal/samsung/exynos_tmu.c if my shell
> >>>>>> history
> >>>>>> is to be believed.
> >>>>>>
> >>>>>>                 Linus
> >>>>> Yeah, this has also passed my local compilation error. Somehow my
> >>>>> gcc4.9
> >>>>> is not catching it. Using an older gcc (gcc4.6) does catch it.
> >>>>>
> >>>>> Anyways, given that the conversion functions are written to cover
> >>>>> for unexpected cal_type, the right way of fixing this is to rewrite
> >>>>> the conversion functions to allow for returning error codes and
> >>>>> adjusting the callers as expected.
> >>>>>
> >>>>> Rui, bzolnier, please consider the following fix:
> >>>>>
> >>>> as it is late in this merge window, I'd prefer to
> >>>> 1. drop all the thermal-soc material in the first pull request which I
> >>>> will send out soon.
> >>>> 2. you can prepare another pull request containing the thermal-soc
> >>>> materials except the exynos fixes
> >>>> 3. exynos fixes with the problem solved can be queued for -rc2 or
> >>>> later.
> >>>
> >>> Could you please just merge the obvious fix from Arnd instead?
> >>>
> >>> [ it was posted two weeks ago and ACKed by me ]
> >>>
> >>> https://patchwork.kernel.org/patch/10313313/
> >>
> >> I'm not sure these are correct fixes.
> >>
> >> The change 480b5bfc16e1 tells:
> >>
> >> "There should be no functional changes caused by this patch."
> >>
> >> but the fix above returns 0 as a default value instead of '50' or '25'
> >> for the 5440 and that impacts the threshold etc ...
> >>
> >> IMO, the correct fix would be to define a default value '50', override
> >> it at init time to '25' if it is a 5440. And then the variable 'temp'
> >> and 'temp_code' get this value in the default case.
> > 
> > It is okay to return 0 because this code-path (the default one) will be
> > never hit by the driver (probe makes sure of it) - the default case is
> > here is just to silence compilation errors..
> 
> The init function is making sure cal_type is one or another. Can you fix
> it correctly by replacing the 'switch' by a 'if' instead of adding dead
> branches to please gcc?
> 
> if (data->cal_type == TYPE_TWO_POINT_TRIMMING) {
> 	return ...;
> }
> 
> return ...;

I'm not the one that added this switch statement (it has been there since
2011) and I would be happy to remove it.  However could we please defer
this to v4.17 and merge the current set of Exynos thermal fixes/cleanups
(they simplify the driver a lot and make ground for future changes)?

Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics