disp: msm: dp: check capability before enabling crc

This is a partial revert of I67ace5c064b2b56d03732a78f334ea6b1b649608 which tries
to enable Sink CRC irrespective of the sink's CRC capability to workaround an
issue with a specific sinks which reports incorrect capability on first plugin.
But this causes some MST dongles to misbehave causing one or both outputs to
be blank.

Change-Id: I70c70db8ac371fe0094a45780216a2518d688a36
Signed-off-by: Rajkumar Subbiah <[email protected]>

msm/dp/dp_panel.c

@@ -3113,15 +3113,17 @@ int dp_panel_sink_crc_enable(struct dp_panel *dp_panel, bool enable)
 	panel = container_of(dp_panel, struct dp_panel_private, dp_panel);
 	drm_aux = panel->aux->drm_aux;
 
-	ret = drm_dp_dpcd_readb(drm_aux, DP_TEST_SINK, &buf);
-	if (ret < 0)
-		return ret;
+	if (dp_panel->link_info.capabilities & DP_LINK_CAP_CRC) {
+		ret = drm_dp_dpcd_readb(drm_aux, DP_TEST_SINK, &buf);
+		if (ret < 0)
+			return ret;
 
-	ret = drm_dp_dpcd_writeb(drm_aux, DP_TEST_SINK, buf | DP_TEST_SINK_START);
-	if (ret < 0)
-		return ret;
+		ret = drm_dp_dpcd_writeb(drm_aux, DP_TEST_SINK, buf | DP_TEST_SINK_START);
+		if (ret < 0)
+			return ret;
 
-	drm_dp_dpcd_readb(drm_aux, DP_TEST_SINK, &buf);
+		drm_dp_dpcd_readb(drm_aux, DP_TEST_SINK, &buf);
+	}
 
 	return rc;
 }