Re: [PATCH] drm/i915/bdw: Disable idle DOP clock gating

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Wed, Apr 02, 2014 at 07:46:37PM -0700, Ben Widawsky wrote:
> It seems we need this at least for the current platforms we have, but
> probably not later. In any event, it should cause too much harm as we do
> the same thing on several other platforms.
> 
> Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
> ---
>  drivers/gpu/drm/i915/intel_pm.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index fa00185..f73f8ca 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -4868,6 +4868,10 @@ static void gen8_init_clock_gating(struct drm_device *dev)
>  	I915_WRITE(GEN7_HALF_SLICE_CHICKEN1,
>  		   _MASKED_BIT_ENABLE(GEN7_SINGLE_SUBSCAN_DISPATCH_ENABLE));
>  
> +	/* WaDisableDopClockGating:bdw May not be needed for production */
> +	I915_WRITE(GEN7_ROW_CHICKEN2,
> +		   _MASKED_BIT_ENABLE(DOP_CLOCK_GATING_DISABLE));

The hsd says you should also disable tcunit clock gating in
GEN6_UCGCTL1.

There's another w/a by the name of WaDisableRowChickenDopClockGating
which seems to be the same thing (apart from the tcunit bit maybe).
You might want to add that w/a note as well.

> +
>  	/* WaSwitchSolVfFArbitrationPriority:bdw */
>  	I915_WRITE(GAM_ECOCHK, I915_READ(GAM_ECOCHK) | HSW_ECOCHK_ARB_PRIO_SOL);
>  
> -- 
> 1.9.1
> 
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-- 
Ville Syrjälä
Intel OTC