drm/i915/fbc: Don't set an illegal fence if unfenced

If the frontbuffer doesn't have an associated fence, it will have a
fence reg of -1. If we attempt to OR in this register into the FBC
control register we end up setting all control bits, oops!

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: "Zanoni, Paulo R" <paulo.r.zanoni@intel.com>
Reviwed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20160819155428.1670-2-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/intel_fbc.c b/drivers/gpu/drm/i915/intel_fbc.c
index 37415f96f906eca3e9bfe055e117f72fb04c6d0d..faa67624e1ed734b80b0c0b9734b63c173d9389c 100644 (file)
--- a/drivers/gpu/drm/i915/intel_fbc.c
+++ b/drivers/gpu/drm/i915/intel_fbc.c
@@ -190,9 +190,13 @@ static void g4x_fbc_activate(struct drm_i915_private *dev_priv)
                dpfc_ctl |= DPFC_CTL_LIMIT_2X;
        else
                dpfc_ctl |= DPFC_CTL_LIMIT_1X;
-       dpfc_ctl |= DPFC_CTL_FENCE_EN | params->fb.fence_reg;
 
-       I915_WRITE(DPFC_FENCE_YOFF, params->crtc.fence_y_offset);
+       if (params->fb.fence_reg != I915_FENCE_REG_NONE) {
+               dpfc_ctl |= DPFC_CTL_FENCE_EN | params->fb.fence_reg;
+               I915_WRITE(DPFC_FENCE_YOFF, params->crtc.fence_y_offset);
+       } else {
+               I915_WRITE(DPFC_FENCE_YOFF, 0);
+       }
 
        /* enable it... */
        I915_WRITE(DPFC_CONTROL, dpfc_ctl | DPFC_CTL_EN);
@@ -244,21 +248,29 @@ static void ilk_fbc_activate(struct drm_i915_private *dev_priv)
                dpfc_ctl |= DPFC_CTL_LIMIT_1X;
                break;
        }
-       dpfc_ctl |= DPFC_CTL_FENCE_EN;
-       if (IS_GEN5(dev_priv))
-               dpfc_ctl |= params->fb.fence_reg;
+
+       if (params->fb.fence_reg != I915_FENCE_REG_NONE) {
+               dpfc_ctl |= DPFC_CTL_FENCE_EN;
+               if (IS_GEN5(dev_priv))
+                       dpfc_ctl |= params->fb.fence_reg;
+               if (IS_GEN6(dev_priv)) {
+                       I915_WRITE(SNB_DPFC_CTL_SA,
+                                  SNB_CPU_FENCE_ENABLE | params->fb.fence_reg);
+                       I915_WRITE(DPFC_CPU_FENCE_OFFSET,
+                                  params->crtc.fence_y_offset);
+               }
+       } else {
+               if (IS_GEN6(dev_priv)) {
+                       I915_WRITE(SNB_DPFC_CTL_SA, 0);
+                       I915_WRITE(DPFC_CPU_FENCE_OFFSET, 0);
+               }
+       }
 
        I915_WRITE(ILK_DPFC_FENCE_YOFF, params->crtc.fence_y_offset);
        I915_WRITE(ILK_FBC_RT_BASE, params->fb.ggtt_offset | ILK_FBC_RT_VALID);
        /* enable it... */
        I915_WRITE(ILK_DPFC_CONTROL, dpfc_ctl | DPFC_CTL_EN);
 
-       if (IS_GEN6(dev_priv)) {
-               I915_WRITE(SNB_DPFC_CTL_SA,
-                          SNB_CPU_FENCE_ENABLE | params->fb.fence_reg);
-               I915_WRITE(DPFC_CPU_FENCE_OFFSET, params->crtc.fence_y_offset);
-       }
-
        intel_fbc_recompress(dev_priv);
 }
 
@@ -305,7 +317,15 @@ static void gen7_fbc_activate(struct drm_i915_private *dev_priv)
                break;
        }
 
-       dpfc_ctl |= IVB_DPFC_CTL_FENCE_EN;
+       if (params->fb.fence_reg != I915_FENCE_REG_NONE) {
+               dpfc_ctl |= IVB_DPFC_CTL_FENCE_EN;
+               I915_WRITE(SNB_DPFC_CTL_SA,
+                          SNB_CPU_FENCE_ENABLE | params->fb.fence_reg);
+               I915_WRITE(DPFC_CPU_FENCE_OFFSET, params->crtc.fence_y_offset);
+       } else {
+               I915_WRITE(SNB_DPFC_CTL_SA,0);
+               I915_WRITE(DPFC_CPU_FENCE_OFFSET, 0);
+       }
 
        if (dev_priv->fbc.false_color)
                dpfc_ctl |= FBC_CTL_FALSE_COLOR;
@@ -324,10 +344,6 @@ static void gen7_fbc_activate(struct drm_i915_private *dev_priv)
 
        I915_WRITE(ILK_DPFC_CONTROL, dpfc_ctl | DPFC_CTL_EN);
 
-       I915_WRITE(SNB_DPFC_CTL_SA,
-                  SNB_CPU_FENCE_ENABLE | params->fb.fence_reg);
-       I915_WRITE(DPFC_CPU_FENCE_OFFSET, params->crtc.fence_y_offset);
-
        intel_fbc_recompress(dev_priv);
 }