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

[Joonas Lahtinen <joonas.lahtinen@linux.intel.com>]

On Thu, 2017-10-26 at 11:32 +0100, 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>

<SNIP>

> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -3193,6 +3193,7 @@ intel_info(const struct drm_i915_private *dev_priv)
>  #define HAS_PSR(dev_priv)		 ((dev_priv)->info.has_psr)
>  #define HAS_RC6(dev_priv)		 ((dev_priv)->info.has_rc6)
>  #define HAS_RC6p(dev_priv)		 ((dev_priv)->info.has_rc6p)
> +#define HAS_RC6pp(dev_priv)		 (false)

Slap a comment at the end.

> +++ b/drivers/gpu/drm/i915/i915_pci.c
> @@ -216,6 +216,9 @@ static const struct intel_device_info intel_gm45_info __initconst = {
>  static const struct intel_device_info intel_ironlake_d_info __initconst = {
>  	GEN5_FEATURES,
>  	.platform = INTEL_IRONLAKE,
> +	/* ilk does support rc6, but we do not implement [power] contexts */
> +	.has_rc6 = 0,
> +

Extra newline.

<SNIP>

> -	if (IS_IVYBRIDGE(dev_priv))
> -		return (INTEL_RC6_ENABLE | INTEL_RC6p_ENABLE);
> +	/*
> +	 * We assume that we do not have any deep rc6 levels if we don't have
> +	 * have the previous rc6 level supporteditself, i.e. we use HAS_RC6()

"supported itself"

Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

Regards, Joonas
-- 
Joonas Lahtinen
Open Source Technology Center
Intel Corporation
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