Re: [PATCHv5 2/5] thermal: rcar_gen3_thermal: Add R-Car Gen3 thermal driver

[Wolfram Sang <wsa@the-dreams.de>]

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Hi Niklas,

thanks for this work!

> +/*
> + * Linear approximation for temperature
> + *
> + * [reg] = [temp] * a + b => [temp] = ([reg] - b) / a
> + *
> + * The constants a and b are calculated using two triplets of int values PTAT
> + * and THCODE. PTAT and THCODE can either be read from hardware or use hard
> + * coded values from driver. The formula to calculate a and b are taken from
> + * BSP and sparsely documented and understood.
> + *
> + * Examining the linear formula and the formula used to calculate constants a
> + * and b while knowing that the span for PTAT and THCODE values are between
> + * 0x000 and 0xfff the largest integer possible is 0xfff * 0xfff == 0xffe001.
> + * Integer also needs to be signed so that leaves 7 bits for decimal
> + * fixed point scaling, which amounts to a decimal scaling factor of 100.
> + */
> +
> +#define SCALE_FACTOR 100
> +#define SCALE_INT(_x) ((_x) * SCALE_FACTOR)
> +#define SCALE_MUL(_a, _b) (((_a)*(_b)) / SCALE_FACTOR)
> +#define SCALE_DIV(_a, _b) (((_a)*SCALE_FACTOR)/(_b))
> +#define SCALE_TO_MCELSIUS(_x) ((_x) * 10)

Spaces around operators everywhere, please.

I wonder about SCALE_MUL; isn't that more like "unscaling" because _a
and _b are already scaled?

And since _b is always a constant, couldn't we simply drop this macro
and simply do _a * _b (with _a being scaled already and _b not)?

Regards,

   Wolfram


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