[Intel-gfx] [PATCH 4/7] drm/i915/hwmon: Show device level energy usage

[Andi Shyti]

Hi Badal,

[...]

> > diff --git a/Documentation/ABI/testing/sysfs-driver-intel-i915-hwmon b/Documentation/ABI/testing/sysfs-driver-intel-i915-hwmon
> > index 16e697b1db3d..7525db243d74 100644
> > --- a/Documentation/ABI/testing/sysfs-driver-intel-i915-hwmon
> > +++ b/Documentation/ABI/testing/sysfs-driver-intel-i915-hwmon
> > @@ -25,3 +25,11 @@ Contact:	dri-devel at lists.freedesktop.org
> >  Description:	RO. Card default power limit (default TDP setting).
> >  
> >  		Only supported for particular Intel i915 graphics platforms.
> > +
> > +What:		/sys/devices/.../hwmon/hwmon<i>/energy1_input
> > +Date:		February 2023
> > +KernelVersion:	6.2
> > +Contact:	dri-devel at lists.freedesktop.org
> 
> I'm sorry for being late on the review here, and I know that others
> already looked at the date and other details here in this doc.
> So I'm curious why we have decided for the dri-devel mailing list
> and not for the intel-gfx since intel-gfx is the only one we have
> listed for i915 dir in the MAINTAINERS file:
> L:      intel-gfx at lists.freedesktop.org

same question here.

> > +Description:	RO. Energy input of device in microjoules.
> > +
> > +		Only supported for particular Intel i915 graphics platforms.

[...]

> > +/*
> > + * hwm_energy - 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 int
> > +hwm_energy(struct hwm_drvdata *ddat, long *energy)

This function can just be void.

Andi

> > +{

[...]