[Intel-gfx] [PATCH 2/5] drm/i915: Read actual GPU frequency from MEMSTAT_ILK on ILK

[Chris Wilson]

Quoting Chris Wilson (2020-10-21 18:36:00)
> Quoting Ville Syrjala (2020-10-21 14:14:40)
> > From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > 
> > There is no GEN6_RPSTAT1 on ILK. Instead of reading that let's
> > try to get the same information from MEMSTAT_ILK. At least it
> > seems to track MEMSWCTL frequency request perfectly on my ILK.
> > It needs the same invert trick as the request value.
> > 
> > We don't want to put the invert thing into intel_gpu_freq()
> > and intel_freq_opcode() because that would incorrectly invert
> > the min/max/etc frequencies also.
> > 
> > One day someone might want to reverse engineer the formula for
> > converting these numvers to Hz, but for now we'll just report
> > them raw.
> 
> Raw. That'll be a nuisance, but a step forward.

I should note that currently these are only hooked up to the debug
interfaces, and not sysfs, so raw is "good enough" and should not be
user visible.
-Chris