Re: [Intel-xe] [PATCH v6 4/5] drm/xe/hwmon: Expose hwmon energy attribute

[Andi Shyti <andi.shyti@linux.intel.com>]

Hi Badal,

[...]

> +/*
> + * xe_hwmon_energy_get - Obtain energy value
> + *
> + * The underlying energy hardware register is 32-bits and is subject to
> + * overflow. How long before overflow? For example, with an example
> + * scaling bit shift of 14 bits (see register *PACKAGE_POWER_SKU_UNIT) and
> + * a power draw of 1000 watts, the 32-bit counter will overflow in
> + * approximately 4.36 minutes.
> + *
> + * Examples:
> + *    1 watt:  (2^32 >> 14) /    1 W / (60 * 60 * 24) secs/day -> 3 days
> + * 1000 watts: (2^32 >> 14) / 1000 W / 60             secs/min -> 4.36 minutes
> + *
> + * The function significantly increases overflow duration (from 4.36
> + * minutes) by accumulating the energy register into a 'long' as allowed by
> + * the hwmon API. Using x86_64 128 bit arithmetic (see mul_u64_u32_shr()),
> + * a 'long' of 63 bits, SF_ENERGY of 1e6 (~20 bits) and
> + * hwmon->scl_shift_energy of 14 bits we have 57 (63 - 20 + 14) bits before
> + * energy1_input overflows. This at 1000 W is an overflow duration of 278 years.
> + */
> +static void
> +xe_hwmon_energy_get(struct xe_hwmon *hwmon, long *energy)

can we call it rather xe_hwmon_energy_update() as this is not
sending anything, but just updating the energy values.

Anyway...

Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com> 

Andi