Re: [PATCH v3] drm/i915: Remove unsafe i915.enable_rc6

[Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>]

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@chris-wilson.co.uk>
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> Cc: Jani Nikula <jani.nikula@intel.com>
> Cc: Imre Deak <imre.deak@intel.com>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Acked-by: Daniel Vetter <daniel.vetter@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.

Daniele
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