drm/i915/dp: do not proceed with autotests if we don't ACK them

There is no point in setting intel_dp->compliance.test_type, and
proceeding with the autotests, if we're about to NAK the request. Some
drive-by cleanups while at it.

v2: look at the ACK bit, as the result may also contain
    TEST_EDID_CHECKSUM_WRITE

Cc: Manasi Navare <manasi.d.navare@intel.com>
Reviewed-by: NManasi Navare <manasi.d.navare@intel.com>
Tested-by: NManasi Navare <manasi.d.navare@intel.com>
Signed-off-by: NJani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1484931846-25390-1-git-send-email-jani.nikula@intel.com

drivers/gpu/drm/i915/intel_dp.c

@@ -3985,45 +3985,42 @@ static uint8_t intel_dp_autotest_phy_pattern(struct intel_dp *intel_dp)
 static void intel_dp_handle_test_request(struct intel_dp *intel_dp)
 {
 	uint8_t response = DP_TEST_NAK;
-	uint8_t rxdata = 0;
-	int status = 0;
+	uint8_t request = 0;
+	int status;
 
-	status = drm_dp_dpcd_read(&intel_dp->aux, DP_TEST_REQUEST, &rxdata, 1);
+	status = drm_dp_dpcd_readb(&intel_dp->aux, DP_TEST_REQUEST, &request);
 	if (status <= 0) {
 		DRM_DEBUG_KMS("Could not read test request from sink\n");
 		goto update_status;
 	}
 
-	switch (rxdata) {
+	switch (request) {
 	case DP_TEST_LINK_TRAINING:
 		DRM_DEBUG_KMS("LINK_TRAINING test requested\n");
-		intel_dp->compliance.test_type = DP_TEST_LINK_TRAINING;
 		response = intel_dp_autotest_link_training(intel_dp);
 		break;
 	case DP_TEST_LINK_VIDEO_PATTERN:
 		DRM_DEBUG_KMS("TEST_PATTERN test requested\n");
-		intel_dp->compliance.test_type = DP_TEST_LINK_VIDEO_PATTERN;
 		response = intel_dp_autotest_video_pattern(intel_dp);
 		break;
 	case DP_TEST_LINK_EDID_READ:
 		DRM_DEBUG_KMS("EDID test requested\n");
-		intel_dp->compliance.test_type = DP_TEST_LINK_EDID_READ;
 		response = intel_dp_autotest_edid(intel_dp);
 		break;
 	case DP_TEST_LINK_PHY_TEST_PATTERN:
 		DRM_DEBUG_KMS("PHY_PATTERN test requested\n");
-		intel_dp->compliance.test_type = DP_TEST_LINK_PHY_TEST_PATTERN;
 		response = intel_dp_autotest_phy_pattern(intel_dp);
 		break;
 	default:
-		DRM_DEBUG_KMS("Invalid test request '%02x'\n", rxdata);
+		DRM_DEBUG_KMS("Invalid test request '%02x'\n", request);
 		break;
 	}
 
+	if (response & DP_TEST_ACK)
+		intel_dp->compliance.test_type = request;
+
 update_status:
-	status = drm_dp_dpcd_write(&intel_dp->aux,
-				   DP_TEST_RESPONSE,
-				   &response, 1);
+	status = drm_dp_dpcd_writeb(&intel_dp->aux, DP_TEST_RESPONSE, response);
 	if (status <= 0)
 		DRM_DEBUG_KMS("Could not write test response to sink\n");
 }