Re: [PATCH] drm/i915/fbc: Disable fbc with VT-d also with kbl and cfl

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

On Tue, Sep 25, 2018 at 04:38:03PM +0300, Mika Kuoppala wrote:
> Using fbc with VT-d flickers also on kbl and cfl.
> 
> Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Cc: <stable@vger.kernel.org> # v4.9+
> Signed-off-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_fbc.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_fbc.c b/drivers/gpu/drm/i915/intel_fbc.c
> index 74d425c700ef..a149f08c1b79 100644
> --- a/drivers/gpu/drm/i915/intel_fbc.c
> +++ b/drivers/gpu/drm/i915/intel_fbc.c
> @@ -1275,9 +1275,10 @@ static int intel_sanitize_fbc_option(struct drm_i915_private *dev_priv)
>  
>  static bool need_fbc_vtd_wa(struct drm_i915_private *dev_priv)
>  {
> -	/* WaFbcTurnOffFbcWhenHyperVisorIsUsed:skl,bxt */
> +	/* WaFbcTurnOffFbcWhenHyperVisorIsUsed:skl,bxt,kbl,cfl */

The hsds seem to be saying that this was fixed in kbl/cnl. I guess the
flicker could be due to a different vt-d vs. fbc issue.

Is the chicken bit in CHICKEN_PIPESL in the correct position?

Hmm. Bspec doesn't list chicken bit for glk. That would seem to suggest
that we need this w/a for glk as well.

>  	if (intel_vtd_active() &&
> -	    (IS_SKYLAKE(dev_priv) || IS_BROXTON(dev_priv))) {
> +	    (IS_SKYLAKE(dev_priv) || IS_BROXTON(dev_priv) ||
> +	     IS_KABYLAKE(dev_priv) || IS_COFFEELAKE(dev_priv))) {
>  		DRM_INFO("Disabling framebuffer compression (FBC) to prevent screen flicker with VT-d enabled\n");
>  		return true;
>  	}
> -- 
> 2.17.1

-- 
Ville Syrjälä
Intel