Re: [PATCH 04/16] drm/i915: set ILK_DPFC_FENCE_YOFF to 0 on SNB

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

On Fri, Aug 14, 2015 at 06:34:09PM -0300, Paulo Zanoni wrote:
> The doc is pretty clear that this register should be set to 0 on SNB.
> We already write y_offset to DPFC_CPU_FENCE_OFFSET a few lines below.

Bspec says:
"Restriction : The CPU fence is always programmed to match the Display
 Buffer base, so this offset must be programmed to 0 to match. 	DevSNB"

We definitely don't program the fence to match DSPSURF, so it's not very
clear that this is really the right thing to do. I suppose it depends on
how the Y offset in the SA register interacts with this one. I never got
around to fixing the Y offset stuff in my FBC efforts, so I've not tried
it on real hardware and so I have no sure answer here.

> 
> Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_fbc.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_fbc.c b/drivers/gpu/drm/i915/intel_fbc.c
> index 9ffa7dc..f7be9ab8 100644
> --- a/drivers/gpu/drm/i915/intel_fbc.c
> +++ b/drivers/gpu/drm/i915/intel_fbc.c
> @@ -216,7 +216,12 @@ static void ilk_fbc_enable(struct intel_crtc *crtc)
>  		dpfc_ctl |= obj->fence_reg;
>  
>  	y_offset = get_crtc_fence_y_offset(crtc);
> -	I915_WRITE(ILK_DPFC_FENCE_YOFF, y_offset);
> +
> +	if (IS_GEN5(dev_priv))
> +		I915_WRITE(ILK_DPFC_FENCE_YOFF, y_offset);
> +	else
> +		I915_WRITE(ILK_DPFC_FENCE_YOFF, 0);
> +
>  	I915_WRITE(ILK_FBC_RT_BASE, i915_gem_obj_ggtt_offset(obj) | ILK_FBC_RT_VALID);
>  	/* enable it... */
>  	I915_WRITE(ILK_DPFC_CONTROL, dpfc_ctl | DPFC_CTL_EN);
> -- 
> 2.4.6
> 
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-- 
Ville Syrjälä
Intel OTC
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