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From:   Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Date:   Wed, 19 Oct 2022 22:40:18 +0200
Message-ID: <CAFBinCCyEVbc4N7TUEi=sbLFv7Rc-L=y-h8xBuZK446x1oLc2g@mail.gmail.com>
Subject: Re: [PATCH] arm64: dts: meson: Enable active coling using gpio-fan on
 Odroid N2/N2+
To:     Anand Moon <linux.amoon@gmail.com>
Cc:     neil.armstrong@linaro.org, Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Kevin Hilman <khilman@baylibre.com>,
        Jerome Brunet <jbrunet@baylibre.com>,
        devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-amlogic@lists.infradead.org, linux-kernel@vger.kernel.org
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Hi Anand,

On Wed, Oct 19, 2022 at 7:17 PM Anand Moon <linux.amoon@gmail.com> wrote:
[...]
> > > +&pwm_AO_ab {
> >
> > &pwm_AO_cd not _ab
> >
> No it has a conflict with CPU_B (vddcpu_b) PWM
Uh, you're right. That's probably why the Hardkernel team uses a
software based PWM implementation: [0]
In hindsight they should have used a different pad either for VDDCPU_B
or the fan.

I think the most pragmatic approach (since the "GPIO PWM" driver is
not upstream and I don't know if something like that would be accepted
upstream) is to use a GPIO based fan as you did in your initial patch.
Not sure what others think though.


Best regards,
Martin


[0] https://github.com/hardkernel/linux/blob/c109dec94e7e819554830acfac4b6ed96e230179/arch/arm64/boot/dts/amlogic/meson64_odroidn2.dtsi#L356-L359