From 765e7cd9a6fd488c6575a5e7952e5d7d3ac87520 Mon Sep 17 00:00:00 2001
From: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Date: Fri, 6 Mar 2020 10:58:33 -0800
Subject: [PATCH] drm/i915/display: Do not write in removed FBC fence registers
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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@intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200306185833.53984-2-jose.souza@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 010b1107671fa..2e5d835a9eaa8 100644
--- a/drivers/gpu/drm/i915/display/intel_fbc.c
+++ b/drivers/gpu/drm/i915/display/intel_fbc.c
@@ -321,7 +321,7 @@ 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);
 	}
-- 
2.30.2