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From:   Krzysztof Kozlowski <krzk@kernel.org>
Date:   Mon, 31 Aug 2020 15:59:08 +0200
Message-ID: <CAJKOXPd+067DywsEJ=5G4NLPfo9+hrun0qvkrYGAsVepCZC3Jg@mail.gmail.com>
Subject: Re: [PATCH 23/33] ARM: dts: exynos: Remove empty camera pinctrl
 configuration in Odroid X/U3
To:     Sylwester Nawrocki <s.nawrocki@samsung.com>
Cc:     Sylwester Nawrocki <snawrocki@kernel.org>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        Rob Herring <robh+dt@kernel.org>,
        Kukjin Kim <kgene@kernel.org>, devicetree@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org,
        "linux-samsung-soc@vger.kernel.org" 
        <linux-samsung-soc@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Denis GNUtoo Carikli <GNUtoo@cyberdimension.org>,
        Simon Shields <simon@lineageos.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
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On Mon, 31 Aug 2020 at 15:57, Sylwester Nawrocki <s.nawrocki@samsung.com> wrote:
>
> On 31.08.2020 12:42, Krzysztof Kozlowski wrote:
> > On Mon, 31 Aug 2020 at 12:35, Sylwester Nawrocki <snawrocki@kernel.org> wrote:
> >> On 8/31/20 10:38, Krzysztof Kozlowski wrote:
> >>> On Mon, 31 Aug 2020 at 10:31, Marek Szyprowski <m.szyprowski@samsung.com> wrote:
> >>>> On 30.08.2020 15:51, Krzysztof Kozlowski wrote:
> >>>>> The camera's pinctrl configuration is simply empty and not effective.
> >>>>> Remove it to fix dtbs_check warning:
> >>>>>
> >>>>>     arch/arm/boot/dts/exynos4412-odroidx.dt.yaml: camera: pinctrl-0: True is not of type 'array'
> >>>>>
> >>>>> Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
> >>>>
> >>>> I think that this was intentional to properly enable support for
> >>>> mem-2-mem mode in Exynos4-IS (FIMC), but I'm not sure what are the
> >>>> default values if no pinctrl properties are provided. Sylwester, could
> >>>> you comment?
> >>>
> >>> Indeed it could be intentional... I see now errors:
> >>> [   33.752203] s5p-fimc-md soc:camera: Failed to get pinctrl: -19
> >>>
> >>> I wonder why getting an empty pinctrl is needed... maybe the driver
> >>> should accept missing pinctrl?
> >>
> >> It might have been better to have the pinctrl properties optional, as there
> >> might be boards without the image sensor attached and FIMC could still be
> >> used in memory-to-memory mode, as Marek pointed out. But it seems too late
> >> now to change that. The binding defines the pinctrl properties as required
> >> (Documentation/devicetree/bindings/media/samsung-fimc.txt) and we need to
> >> keep them in dtses.
> >
> > You can always make a required property optional and it is not a break
> > of ABI. The other way around would be a break. Why then not changing
> > the driver to accept optional pinctrl?
>
> Feel free to send the patch, I would prefer to leave that as is though.
> Is it really suddenly a problem to use an empty property? The pinctrl
> bindings allows it.

The bindings scream:
arch/arm/boot/dts/exynos4412-odroidx.dt.yaml: camera: pinctrl-0: True
is not of type 'array'
so either we should model it differently (not as empty array), update
the driver to make it optional or change the bindings/dtschema. I'll
see how to fix it properly.

Best regards,
Krzysztof