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Date:   Sun, 11 Jun 2023 11:18:34 +0100
From:   Conor Dooley <conor@kernel.org>
To:     Maxim Kiselev <bigunclemax@gmail.com>
Cc:     linux-kernel@vger.kernel.org,
        Vasily Khoruzhick <anarsoul@gmail.com>,
        Yangtao Li <tiny.windzz@gmail.com>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        Amit Kucheria <amitk@kernel.org>,
        Zhang Rui <rui.zhang@intel.com>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Conor Dooley <conor+dt@kernel.org>,
        Chen-Yu Tsai <wens@csie.org>,
        Jernej Skrabec <jernej.skrabec@gmail.com>,
        Samuel Holland <samuel@sholland.org>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Cristian Ciocaltea <cristian.ciocaltea@collabora.com>,
        linux-pm@vger.kernel.org, devicetree@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-sunxi@lists.linux.dev,
        linux-riscv@lists.infradead.org
Subject: Re: [PATCH v1 3/3] dt-bindings: thermal: sun8i: Add binding for
 D1/T113s THS controller
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On Sun, Jun 11, 2023 at 10:53:56AM +0300, Maxim Kiselev wrote:
> =D0=B2=D1=81, 11 =D0=B8=D1=8E=D0=BD. 2023=E2=80=AF=D0=B3. =D0=B2 01:14, C=
onor Dooley <conor@kernel.org>:
> >
> > On Sat, Jun 10, 2023 at 11:31:03PM +0300, Maxim Kiselev wrote:
> > > =D1=81=D0=B1, 10 =D0=B8=D1=8E=D0=BD. 2023=E2=80=AF=D0=B3. =D0=B2 21:0=
1, Conor Dooley <conor@kernel.org>:
> > >
> > > ...
> > >
> > > > > > > +  - |
> > > > > > > +    thermal-sensor@2009400 {
> > > > > > > +          compatible =3D "allwinner,sun20i-d1-ths";
> > > > > > > +          reg =3D <0x02009400 0x400>;
> > > > > > > +          interrupts =3D <0 90 0>;
> > > > > > > +          clocks =3D <&ccu 0>;
> > > > > > > +          clock-names =3D "bus";
> > > > > > > +          resets =3D <&ccu 2>;
> > > > > > > +          nvmem-cells =3D <&ths_calibration>;
> > > > > > > +          nvmem-cell-names =3D "calibration";
> > > > > > > +          #thermal-sensor-cells =3D <0>;
> > > > > > >
> > > > > > >> Is this calibration required, or optional, for the d1?
> > > > > >
> > > > > > Calibration data for the D1 is optional as for the H6.
> > > > > > (But without it, the sensor data will be inaccurate).
> > > > >
> > > > > Okay. Modulo the signoff:
> > > > > Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
> > > >
> > > > Wait, that's not what I meant to say... Clearly turned my brain off=
 for
> > > > a moment. If it is not going to function correctly without the
> > > > calibration data, why not make the calibration data required for the
> > > > d1's ths?
> > >
> > > I don't really know why, but the calibration data is optional for
> > > other controllers.
> > > So I just did it the same way.
> > > Here is explanation comment about it from the driver:
> > >         /*
> > >          * Even if the external calibration data stored in sid is
> > >          * not accessible, the THS hardware can still work, although
> > >          * the data won't be so accurate.
> > >          *
> > >          * The default value of calibration register is 0x800 for
> > >          * every sensor, and the calibration value is usually 0x7xx
> > >          * or 0x8xx, so they won't be away from the default value
> > >          * for a lot.
> > >          *
> > >          * So here we do not return error if the calibration data is
> > >          * not available, except the probe needs deferring.
> > >          */
> >
> > Wait, so if there is no calibration data then this thing will just defer
> > probing, ad infinitum? Looks like everything other than the a33 has the
> > cells in the dts, and the software seems to expect the cells.
> > What am I missing?
>=20
> Not quite. If we don't have a calibration cell in the dts, then we
> just skip the calibration.
> We will only get EPROBE_DEFER if we have calibration in the dts.

Ah that makes a lot more sense, thanks.

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