[PATCH 2/3] drm/i915 Do not write in removed FBC fence registers

[José Roberto de Souza]

From: Radhakrishna Sripada <radhakrishna.sripada at intel.com>

Platforms without fences don't have FBC host tracking and those
registers are marked as reserved in those platforms.

v2: checking num_fences to write to FBC fence registers (Ville)

Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
Cc: Matt Roper <matthew.d.roper at intel.com>
Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan at intel.com>
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
Signed-off-by: Radhakrishna Sripada <radhakrishna.sripada at intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi at intel.com>
Signed-off-by: José Roberto de Souza <jose.souza at intel.com>
---
 drivers/gpu/drm/i915/display/intel_fbc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/display/intel_fbc.c b/drivers/gpu/drm/i915/display/intel_fbc.c
index 3a9e41e93ebf..fa8fca1a6b7c 100644
--- a/drivers/gpu/drm/i915/display/intel_fbc.c
+++ b/drivers/gpu/drm/i915/display/intel_fbc.c
@@ -320,7 +320,7 @@ static void gen7_fbc_activate(struct drm_i915_private *dev_priv)
 			       SNB_CPU_FENCE_ENABLE | params->fence_id);
 		intel_de_write(dev_priv, DPFC_CPU_FENCE_OFFSET,
 			       params->crtc.fence_y_offset);
-	} else {
+	} else if (dev_priv->ggtt.num_fences) {
 		intel_de_write(dev_priv, SNB_DPFC_CTL_SA, 0);
 		intel_de_write(dev_priv, DPFC_CPU_FENCE_OFFSET, 0);
 	}
-- 
2.25.0