Re: [PATCH v2 4/6] drm/i915/vlv: Remove the enabling of VS_TIMER_DISPATCH bit in MI MODE reg

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

On Mon, Mar 24, 2014 at 11:58:22PM +0530, sourab.gupta@intel.com wrote:
> From: Akash Goel <akash.goel@intel.com>
> 
> Removing the VS_TIMER_DISPATCH bit enable for MI MODE reg for
> Gen7 platform as it is not required.
> 
> v2: Enhancing the scope of the patch to full Gen7 (Chris)
> 
> Signed-off-by: Akash Goel <akash.goel@intel.com>
> Signed-off-by: Sourab Gupta <sourab.gupta@intel.com>
> Tested-by: Chris Wilson <chris@chris-wilson.co.uk> # ivb, hsw -Chris
> ---
>  drivers/gpu/drm/i915/intel_ringbuffer.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> index eb4811a..9983802 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> @@ -599,7 +599,9 @@ static int init_render_ring(struct intel_ring_buffer *ring)
>  	int ret = init_ring_common(ring);
>  
>  	if (INTEL_INFO(dev)->gen > 3)
> -		I915_WRITE(MI_MODE, _MASKED_BIT_ENABLE(VS_TIMER_DISPATCH));
> +		if (!IS_GEN7(dev))

We shouldn't enable this on gen8 either, and while doing that you could
avoid the extra indentation by rewriting it as something like this:
if (INTEL_INFO(dev)->gen >= 4 && INTEL_INFO(dev)->gen < 7)

Also you could add the appropriate w/a note while you're touching the
code:
WaTimedSingleVertexDispatch:cl,bw,ctg,elk,ilk,snb

> +			I915_WRITE(MI_MODE,
> +					_MASKED_BIT_ENABLE(VS_TIMER_DISPATCH));
>  
>  	/* We need to disable the AsyncFlip performance optimisations in order
>  	 * to use MI_WAIT_FOR_EVENT within the CS. It should already be
> -- 
> 1.8.5.1

-- 
Ville Syrjälä
Intel OTC