drm/i915: Optimize HDCP key load

HDCP key need not be cleared on each hdcp disable. And HDCP key Load
is skipped if key is already loaded.

v2:
  No change. Added Reviewed-by tag.

v3:
  No change.
Signed-off-by: Ramalingam C <ramalingam.c@intel.com>
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/1517609350-10698-6-git-send-email-ramalingam.c@intel.com

drivers/gpu/drm/i915/intel_hdcp.c

@@ -49,6 +49,10 @@ static int intel_hdcp_load_keys(struct drm_i915_private *dev_priv)
 	int ret;
 	u32 val;
 
+	val = I915_READ(HDCP_KEY_STATUS);
+	if ((val & HDCP_KEY_LOAD_DONE) && (val & HDCP_KEY_LOAD_STATUS))
+		return 0;
+
 	/*
 	 * On HSW and BDW HW loads the HDCP1.4 Key when Display comes
 	 * out of reset. So if Key is not already loaded, its an error state.
@@ -542,8 +546,6 @@ static int _intel_hdcp_disable(struct intel_connector *connector)
 		return -ETIMEDOUT;
 	}
 
-	intel_hdcp_clear_keys(dev_priv);
-
 	ret = connector->hdcp_shim->toggle_signalling(intel_dig_port, false);
 	if (ret) {
 		DRM_ERROR("Failed to disable HDCP signalling\n");