linux-kernel - Re: [PATCH] arm64: dts: meson: Enable active coling using gpio-fan on Odroid N2/N2+

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Message-ID: <CANAwSgQ9gJvtdr_r1K0xxrDxQ6aBh5v=pR9aJSxRytia2PSbrg@mail.gmail.com>
Date:   Fri, 21 Oct 2022 10:37:11 +0530
From:   Anand Moon <linux.amoon@...il.com>
To:     Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Cc:     neil.armstrong@...aro.org, Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Kevin Hilman <khilman@...libre.com>,
        Jerome Brunet <jbrunet@...libre.com>,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-amlogic@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64: dts: meson: Enable active coling using gpio-fan on
 Odroid N2/N2+

Hi Martin / Neil,

On Thu, 20 Oct 2022 at 02:10, Martin Blumenstingl
<martin.blumenstingl@...glemail.com> wrote:
>
> Hi Anand,
>
> On Wed, Oct 19, 2022 at 7:17 PM Anand Moon <linux.amoon@...il.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.
>

When I use gpio-fan  I get the following output with gpioinfo
Feature it woks as expected.

$ .sudo gpioinfo
....
gpiochip1 - 15 lines:
        line   0:      unnamed       unused   input  active-high
        line   1:      unnamed       unused   input  active-high
        line   2:      unnamed     "enable"  output  active-high [used]
        line   3:      unnamed       unused   input  active-high
        line   4:      unnamed       unused  output  active-high
        line   5:      unnamed       unused   input  active-high
        line   6:      unnamed       unused   input  active-high
        line   7:      unnamed       unused   input  active-high
        line   8:      unnamed "regulator-tflash_vdd" output active-high [used]
        line   9:      unnamed      "TF_IO"  output  active-high [used]
        line  10:      unnamed   "gpio-fan"  output  active-high [used]
        line  11:      unnamed    "n2:blue"  output  active-high [used]
        line  12:      unnamed       unused   input  active-high
        line  13:      unnamed       unused   input  active-high
        line  14:      unnamed       unused   input  active-high

When I am using pwm-fan using *pwm_ao_d_10_pins* pin is not getting
registered below hence it is not working on my end.

$ .sudo gpioinfo
....
gpiochip1 - 15 lines:
        line   0:      unnamed       unused   input  active-high
        line   1:      unnamed       unused   input  active-high
        line   2:      unnamed     "enable"  output  active-high [used]
        line   3:      unnamed       unused   input  active-high
        line   4:      unnamed       unused  output  active-high
        line   5:      unnamed       unused   input  active-high
        line   6:      unnamed       unused   input  active-high
        line   7:      unnamed       unused   input  active-high
        line   8:      unnamed "regulator-tflash_vdd" output active-high [used]
        line   9:      unnamed      "TF_IO"  output  active-high [used]
        line  10:      unnamed       unused  output  active-high
        line  11:      unnamed    "n2:blue"  output  active-high [used]
        line  12:      unnamed       unused   input  active-high
        line  13:      unnamed       unused   input  active-high
        line  14:      unnamed       unused   input  active-high

Thanks
-Anand




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