[Intel-gfx] [PATCH v3] drm/i915: Remove unsafe i915.enable_rc6

[David Weinehall]

On Fri, Oct 27, 2017 at 01:57:09PM -0700, Daniele Ceraolo Spurio wrote:
> 
> 
> On 26/10/17 03:32, Chris Wilson wrote:
> > It has been many years since the last confirmed sighting (and fix) of an
> > RC6 related bug (usually a system hang). Remove the parameter to stop
> > users from setting dangerous values, as they often set it during triage
> > and end up disabling the entire runtime pm instead (the option is not a
> > fine scalpel!).
> > 
> > Furthermore, it allows users to set known dangerous values which were
> > intended for testing and not for production use. For testing, we can
> > always patch in the required setting without having to expose ourselves
> > to random abuse.
> > 
> > v2: Fixup NEEDS_WaRsDisableCoarsePowerGating fumble, and document the
> > lack of ilk support better.
> > v3: Clear intel_info->rc6p if we don't support rc6 itself.
> > 
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
> > Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> > Cc: Jani Nikula <jani.nikula at intel.com>
> > Cc: Imre Deak <imre.deak at intel.com>
> > Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
> > Acked-by: Daniel Vetter <daniel.vetter at ffwll.ch>
> > ---
> 
> I think that for execution/debug on early silicon we might still want the
> ability to turn features like RC6 off. Maybe we can add a debug kconfig to
> force info->has_rc6 = 0? Not a blocker to this patch but worth considering
> IMO.

Most of the BIOSes I've seen on our RVPs have had an option to disable
RC6.


Kind regards, David