Re: [PATCH v1 3/3] dt-bindings: thermal: sun8i: Add binding for D1/T113s THS controller

Conor Dooley
2023-06-11T10:18:46Z

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On Sun, Jun 11, 2023 at 10:53:56AM +0300, Maxim Kiselev wrote:
> вс, 11 июн. 2023 г. в 01:14, Conor Dooley <conor@kernel.org>:
> >
> > On Sat, Jun 10, 2023 at 11:31:03PM +0300, Maxim Kiselev wrote:
> > > сб, 10 июн. 2023 г. в 21:01, Conor Dooley <conor@kernel.org>:
> > >
> > > ...
> > >
> > > > > > > + - |
> > > > > > > + thermal-sensor@2009400 {
> > > > > > > + compatible = "allwinner,sun20i-d1-ths";
> > > > > > > + reg = <0x02009400 0x400>;
> > > > > > > + interrupts = <0 90 0>;
> > > > > > > + clocks = <&ccu 0>;
> > > > > > > + clock-names = "bus";
> > > > > > > + resets = <&ccu 2>;
> > > > > > > + nvmem-cells = <&ths_calibration>;
> > > > > > > + nvmem-cell-names = "calibration";
> > > > > > > + #thermal-sensor-cells = <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?
>
> 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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