drm/i915: refactor FBC deactivation at init

Make sure we deactivate FBC at intel_fbc_init(), so we can remove the
call from intel_display.c. Currently we only have the "enabled"
software state, but later we'll have both "enabled" and "active", and
we'll add assertions to them, so just calling intel_fbc_disable() from
intel_modeset_init() won't work. It's better to make sure
intel_fbc_init() already puts the hardware in the expected state, so
we can put nice assertions in the other functions.

v2: Keep/improve the comment (Chris).
v3: Improve the commit message a little bit.
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1446664257-32012-9-git-send-email-paulo.r.zanoni@intel.comSigned-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>

drivers/gpu/drm/i915/intel_display.c

@@ -15040,9 +15040,6 @@ void intel_modeset_init(struct drm_device *dev)
 	i915_disable_vga(dev);
 	intel_setup_outputs(dev);
 
-	/* Just in case the BIOS is doing something questionable. */
-	intel_fbc_disable(dev_priv);
-
 	drm_modeset_lock_all(dev);
 	intel_modeset_setup_hw_state(dev);
 	drm_modeset_unlock_all(dev);

drivers/gpu/drm/i915/intel_fbc.c

@@ -1038,9 +1038,9 @@ void intel_fbc_init(struct drm_i915_private *dev_priv)
 	enum pipe pipe;
 
 	mutex_init(&dev_priv->fbc.lock);
+	dev_priv->fbc.enabled = false;
 
 	if (!HAS_FBC(dev_priv)) {
-		dev_priv->fbc.enabled = false;
 		dev_priv->fbc.no_fbc_reason = "unsupported by this chipset";
 		return;
 	}
@@ -1074,5 +1074,9 @@ void intel_fbc_init(struct drm_i915_private *dev_priv)
 		I915_WRITE(FBC_CONTROL, 500 << FBC_CTL_INTERVAL_SHIFT);
 	}
 
-	dev_priv->fbc.enabled = dev_priv->fbc.fbc_enabled(dev_priv);
+	/* We still don't have any sort of hardware state readout for FBC, so
+	 * disable it in case the BIOS enabled it to make sure software matches
+	 * the hardware state. */
+	if (dev_priv->fbc.fbc_enabled(dev_priv))
+		dev_priv->fbc.disable_fbc(dev_priv);
 }