drm/i915/fbc: Fix nuke for pre-snb platforms

The MSG_FBC_REND_STATE register only exists on snb+. For older
platforms (would also work for snb+) we can simply rewite DSPSURF
to trigger a flip nuke.

While generally RMW is considered harmful we'll use it here for
simplicity. And since FBC doesn't exist in i830 we don't have to
worry about the DSPSURF double buffering hardware fails present
on that platform.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200702153723.24327-3-ville.syrjala@linux.intel.comReviewed-by: José Roberto de Souza <jose.souza@intel.com>

drivers/gpu/drm/i915/display/intel_fbc.c

@@ -187,8 +187,30 @@ static bool g4x_fbc_is_active(struct drm_i915_private *dev_priv)
 	return intel_de_read(dev_priv, DPFC_CONTROL) & DPFC_CTL_EN;
 }
 
+static void i8xx_fbc_recompress(struct drm_i915_private *dev_priv)
+{
+	struct intel_fbc_reg_params *params = &dev_priv->fbc.params;
+	enum i9xx_plane_id i9xx_plane = params->crtc.i9xx_plane;
+
+	spin_lock_irq(&dev_priv->uncore.lock);
+	intel_de_write_fw(dev_priv, DSPADDR(i9xx_plane),
+			  intel_de_read_fw(dev_priv, DSPADDR(i9xx_plane)));
+	spin_unlock_irq(&dev_priv->uncore.lock);
+}
+
+static void i965_fbc_recompress(struct drm_i915_private *dev_priv)
+{
+	struct intel_fbc_reg_params *params = &dev_priv->fbc.params;
+	enum i9xx_plane_id i9xx_plane = params->crtc.i9xx_plane;
+
+	spin_lock_irq(&dev_priv->uncore.lock);
+	intel_de_write_fw(dev_priv, DSPSURF(i9xx_plane),
+			  intel_de_read_fw(dev_priv, DSPSURF(i9xx_plane)));
+	spin_unlock_irq(&dev_priv->uncore.lock);
+}
+
 /* This function forces a CFB recompression through the nuke operation. */
-static void intel_fbc_recompress(struct drm_i915_private *dev_priv)
+static void snb_fbc_recompress(struct drm_i915_private *dev_priv)
 {
 	struct intel_fbc *fbc = &dev_priv->fbc;
 
@@ -198,6 +220,16 @@ static void intel_fbc_recompress(struct drm_i915_private *dev_priv)
 	intel_de_posting_read(dev_priv, MSG_FBC_REND_STATE);
 }
 
+static void intel_fbc_recompress(struct drm_i915_private *dev_priv)
+{
+	if (INTEL_GEN(dev_priv) >= 6)
+		snb_fbc_recompress(dev_priv);
+	else if (INTEL_GEN(dev_priv) >= 4)
+		i965_fbc_recompress(dev_priv);
+	else
+		i8xx_fbc_recompress(dev_priv);
+}
+
 static void ilk_fbc_activate(struct drm_i915_private *dev_priv)
 {
 	struct intel_fbc_reg_params *params = &dev_priv->fbc.params;