[Intel-gfx] [PATCH] drm/i915/fbc: FBC causes display flicker when VT-d is enabled on Skylake

[Ville Syrjälä]

On Fri, Jun 17, 2016 at 05:39:51PM +0100, Chris Wilson wrote:
> Erratum SKL075: Display Flicker May Occur When Both VT-d And FBC Are Enabled
> 
> "Display flickering may occur when both FBC (Frame Buffer Compression)
> and VT - d (Intel® Virtualization Technology for Directed I/O) are enabled
> and in use by the display controller."

WaFbcTurnOffFbcWhenHyperVisorIsUsed:skl

> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Paulo Zanoni <paulo.r.zanoni at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_fbc.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_fbc.c b/drivers/gpu/drm/i915/intel_fbc.c
> index fddba1eed5ad..e47785467220 100644
> --- a/drivers/gpu/drm/i915/intel_fbc.c
> +++ b/drivers/gpu/drm/i915/intel_fbc.c
> @@ -1230,6 +1230,18 @@ void intel_fbc_init_pipe_state(struct drm_i915_private *dev_priv)
>  			dev_priv->fbc.visible_pipes_mask |= (1 << crtc->pipe);
>  }
>  
> +static bool need_vtd_wa(struct drm_i915_private *dev_priv)
> +{
> +#ifdef CONFIG_INTEL_IOMMU
> +	if (!intel_iommu_gfx_mapped)
> +		return false;
> +
> +	if (INTEL_GEN(dev_priv) == 9)
> +		return true;
> +#endif
> +	return false;
> +}
> +
>  /**
>   * intel_fbc_init - Initialize FBC
>   * @dev_priv: the i915 device
> @@ -1247,6 +1259,12 @@ void intel_fbc_init(struct drm_i915_private *dev_priv)
>  	fbc->active = false;
>  	fbc->work.scheduled = false;
>  
> +	if (need_vtd_wa(dev_priv)) {
> +		struct intel_device_info *info =
> +			(struct intel_device_info *)&dev_priv->info;
> +		info->has_fbc = false;
> +	}
> +
>  	if (!HAS_FBC(dev_priv)) {
>  		fbc->no_fbc_reason = "unsupported by this chipset";
>  		return;
> -- 
> 2.8.1
> 
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-- 
Ville Syrjälä
Intel OTC