kms/vc4_hdmi: Refuse 4096x2160@60 hdmi modes

These are no reliable without overclocking.
See: #5034

Signed-off-by: Dom Cobley <popcornmix@gmail.com>

drivers/gpu/drm/vc4/vc4_hdmi.c

@@ -1823,6 +1823,11 @@ static int vc4_hdmi_encoder_atomic_check(struct drm_encoder *encoder,
 	     (mode->hsync_end % 2) || (mode->htotal % 2)))
 		return -EINVAL;
 
+	/* 4096x2160@60 is not reliable without overclocking core */
+	if (mode->hdisplay > 3840 && mode->vdisplay >= 2160 &&
+	    drm_mode_vrefresh(mode) >= 50)
+		return -EINVAL;
+
 	/*
 	 * The 1440p@60 pixel rate is in the same range than the first
 	 * WiFi channel (between 2.4GHz and 2.422GHz with 22MHz
@@ -1861,6 +1866,10 @@ vc4_hdmi_encoder_mode_valid(struct drm_encoder *encoder,
 	     (mode->hsync_end % 2) || (mode->htotal % 2)))
 		return MODE_H_ILLEGAL;
 
+	if (mode->hdisplay > 3840 && mode->vdisplay >= 2160 &&
+	    drm_mode_vrefresh(mode) >= 50)
+		return MODE_CLOCK_HIGH;
+
 	return vc4_hdmi_encoder_clock_valid(vc4_hdmi, mode->clock * 1000);
 }