drm/vc4: hdmi: Add full range RGB helper

We're going to need to tell whether we want to run with a full or
limited range RGB output in multiple places in the code, so let's create
a helper that will return whether we need with full range or not.
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20220120151625.594595-6-maxime@cerno.tech

drivers/gpu/drm/vc4/vc4_hdmi.c

@@ -104,6 +104,15 @@ static bool vc4_hdmi_mode_needs_scrambling(const struct drm_display_mode *mode)
 	return (mode->clock * 1000) > HDMI_14_MAX_TMDS_CLK;
 }
 
+static bool vc4_hdmi_is_full_range_rgb(struct vc4_hdmi *vc4_hdmi,
+				       const struct drm_display_mode *mode)
+{
+	struct vc4_hdmi_encoder *vc4_encoder = &vc4_hdmi->encoder;
+
+	return !vc4_encoder->hdmi_monitor ||
+		drm_default_rgb_quant_range(mode) == HDMI_QUANTIZATION_RANGE_FULL;
+}
+
 static int vc4_hdmi_debugfs_regs(struct seq_file *m, void *unused)
 {
 	struct drm_info_node *node = (struct drm_info_node *)m->private;
@@ -1119,8 +1128,7 @@ static void vc4_hdmi_encoder_pre_crtc_enable(struct drm_encoder *encoder,
 
 	mutex_lock(&vc4_hdmi->mutex);
 
-	if (vc4_encoder->hdmi_monitor &&
-	    drm_default_rgb_quant_range(mode) == HDMI_QUANTIZATION_RANGE_LIMITED) {
+	if (!vc4_hdmi_is_full_range_rgb(vc4_hdmi, mode)) {
 		if (vc4_hdmi->variant->csc_setup)
 			vc4_hdmi->variant->csc_setup(vc4_hdmi, true);