[Intel-gfx] [PATCH v2 3/3] drm/i915: Ensure the HiZ RAW Stall Optimization is on for Cherryview.

[Ville Syrjälä]

On Tue, Jan 13, 2015 at 12:46:53PM -0800, Kenneth Graunke wrote:
> This is an important optimization for avoiding read-after-write (RAW)
> stalls in the HiZ buffer.  Certain workloads would run very slowly with
> HiZ enabled, but run much faster with the "hiz=false" driconf option.
> With this patch, they run at full speed even with HiZ.
> 
> Increases performance in OglVSInstancing by about 2.7x on Braswell.
> 
> Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>

Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
also for the remaining two patches.

> ---
>  drivers/gpu/drm/i915/intel_ringbuffer.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> Split, as requested by Ben.
> 
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> index 0df15a4..23020d6 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> @@ -846,6 +846,11 @@ static int chv_init_workarounds(struct intel_engine_cs *ring)
>  			  HDC_FORCE_NON_COHERENT |
>  			  HDC_DONOT_FETCH_MEM_WHEN_MASKED);
>  
> +	/* According to the CACHE_MODE_0 default value documentation, some
> +	 * CHV platforms disable this optimization by default.  Turn it on.
> +	 */
> +	WA_CLR_BIT_MASKED(CACHE_MODE_0_GEN7, HIZ_RAW_STALL_OPT_DISABLE);
> +
>  	/* Improve HiZ throughput on CHV. */
>  	WA_SET_BIT_MASKED(HIZ_CHICKEN, CHV_HZ_8X8_MODE_IN_1X);
>  
> -- 
> 2.2.1
> 
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-- 
Ville Syrjälä
Intel OTC